And we're back. What's up everybody drew here that anxiety guy.com. What's up, Billy? Hello Billy the anxiety Jedi cross from anxiety United Decaffeinated decaffeinated this time. Yes, Billy is days five days without caffeine. I'm impressed and feeling good Feeling more awake feeling more alert, but I thought caffeine was supposed to have the alert and awake You know the side effect of it, but actually stopping it has had a completely different effect I don't know whether it'll continue. That's me next week. We're gonna call it it. I'll be drinking like Espresso And espresso with a Red Bull Just just intravenous drip right into the arm. Mm-hmm. Yeah, I'm not a caffeine guy I can't do caffeine it upsets my stomach to if I drink too much that's bad for you I thought I'd give myself another chance. We was on about it last week with the lifestyle choices and that yeah I thought there's nothing, you know caffeine is not a good thing. So Let's see all these steps. I'm taking every week by the end of the year Yeah, you're fine. You're gonna be like running marathons the British Olympic team British moms maybe if they bring darts in maybe that's the only one I could probably keep I heard they're gonna do that Yeah, just I read it on the internet. So it must be true Go to me just a quick Caffeine or a related story the gym that I used to go to I switched gyms a while ago And there was a guy you see all the time and you could tell he he was every once in a while You would see that he was he had anxiety issues for sure I talked to him one day and he's that panic attack sometimes in the gym except that he would go to the gym He's only like hardcore guys hardcore, you know, and you go to the gym and he would drink a pre-workout So any people listening may understand what a pre-workout is these stupid drinks and powders and stuff You buy in supplement stores and this the pre-workout It's just jam-packed with caffeine and like beta alanine, which is another like major stimulant and he would wind up It would literally make half his face numb, which is a known side effect of beta alanine. So people have a slight out It's not dangerous, but so this guy would have had serious anxiety problems And he would hop himself up on this pre-workout. I remember thinking man. Why are you doing that to yourself? Gotta get the pump man Wow, all right more power to you brother Yeah, I was gonna kick it a scene like I haven't seen him in a couple years since I switched gyms, but anyway Okay, before we get off topic too much today, we're gonna continue our discussion of exposure therapy and Jackie if you are listening, which I know you are we're gonna answer your question now Which I promised we would do last week, but then we got sidetracked as we were ill and talked about that Yeah, yeah, how you feeling this week anyway, I'm good my ears still a little plugged But you know it is what it is. I'm improving. I'm good. Good. No sniffles Good. That's what I like to hear. We survived. Yes. We did survive contrary to like Yeah, you know whatever pop in that popular opinion, but What your brain may have been telling you we have survived. So let me go into my inbox. I want to look at Jackie's Message that she had sent me essentially the question was we talked about exposure if anybody hasn't watched sort of our first Discussion of exposure you should do that episode 13. Was it 13? Yeah Well, we should it was just kind of an overview of what exposure is and especially what to expect out of it You know having good expectations going in but Jackie brought up a good question after we published that video and that was How do you make progress with tasks that you can't really practice every day? And she specifically talked about flying like getting an airplane and flying It's not like you could just decide to jump on a plane and fly around, you know every day to practice it So so she she asked, you know, how do you deal with that? You know, how do you do things? How do you practice things that you can't necessarily practically practice? Practically practice. So we'll talk about that a little bit and it just I think an extension of the whole exposure situation.  Why am I arms tired? It's a good question the oh, here's Jackie's question just taking me long to get it up She says my question is related to recovery I find I am doing pretty well with my small stuff such as food shopping shopping lines out to eat traffic Etc. Etc. However, things I can't get a lot of exposure on such as going to the dentist or the doctor or flying in an airplane I find I wish I could practice the Stuffins I must censoring out of these things and beat them But I have no opportunity since they tend to be once or twice a year things. That's how she's asking, you know How do you do that? So I'll talk about those are good things like going to the dentist going to the doctor It's not things we do all the time. I'll talk about flying specifically because yes, I have been flying again and Here's the general answer to that question that we can maybe dig a little deeper And I don't know if you have a few of these as well, but for me I mean, I've always I have never been a fan of flying I have flown but I don't like it I've never really liked it Actually, I kind of like it now. It's crazy that sounds and I'll tell you how that happened I mean, so if I go back to my worst anxiety days and when there was some agoraphobia there and it was difficult Just get out the door the idea of getting on a plane and flying somewhere I mean, you might as well told me to go to the moon, you know It wasn't in the realm of possibility in those days or it didn't seem like it was anyway and it's not like I was able to practice flying because I really only started flying again in the last year and What I could say is the exposure work that I did and getting to the point where I could live a pretty normal life Even though I wasn't flying at all because I didn't I didn't really need to Plus I was still sort of hanging on to that phobia. I don't want to I don't like it. I'm afraid of it When the time come when the time came and I said that said I have to start doing this because I'm not going to be stuck here in New York forever. I got to actually be able to do it It was I'm not going to say it was super easy, but it became really easy and it's just because of the spillover So in improving my overall anxiety situation and working on just getting out the door back in 2008 2009 To where I am now living a pretty normal life. It became easy to tackle that task Just because of the spillover from everything else that I've worked on We talked we talked about it on the list that I made didn't I with the five things remember when I reached the fifth And I was able to do that. Yep It had a rebound effect and I was able to do so much more it opened up so many more doors because it's not the task That you're challenging. It's the feelings. Isn't it once you start to accept that you feel like that? That's exactly right. Yeah, yeah, that's exactly right So in the end what you start to learn as you go through this process of Exposing yourself to the things that make you anxious is it's not the task like you said It's not the supermarket or in Jackie's case the traffic or driving for me. It was driving It's not that it's how you feel when you're doing it. So when you learn not to care sunlight shining through again There will have an angel as a guest in the next Yeah So Yeah, it's all right. No big deal. I would say that for me When you when you use your exposure to learn The reason why you do exposure is not so much you can get back to the supermarket. Although you need to go to the supermarket It's so that you can learn to not care, right? I'm gonna reiterate that and people say well We'll expose your make my panic go away Ultimately it will but that's a secondary step first is you will learn not to care whether you panic or not Yeah, so for me when I was time to get back on an airplane and start flying around which now I've done quite a bit of in the last six or eight months Especially this year is you know what maybe I'll have a panic attack on the plane Or maybe I won't but I don't care or in that's the difference. Okay. Yeah. Yeah, right exactly So so that's how that works and I think the same thing with going to the dentist or the doctor things You don't normally do to have any of those that you know You're talking about your five things you got to the point where I could do this What else what else happened? Well, they were really trivial the five things for me They were small things like post box walk into the local shop the supermarkets stuff like that But there's one thing that really sticks out and when you because you mentioned this question last week And it was my wedding so that obviously that's something that you can't do well. I suppose you can The build up to the wedding was probably Something along those lines, you know the anticipatory anxiety the build up for months in advance And it's just how do you get through that? But the the simple answer for me was that I just did yeah, and it was it was easier than I anticipated And I think that's probably a huge part of the battle with these things is just how bad you imagine that it's gonna be But when you actually go and do it It's never as bad as you thought it was gonna be that's true The anticipation sometimes makes that worse. I will tell you I keep using flying as an example because it's my example, but When it got to the point for me to actually do that I had I think maybe a couple of weeks sort of notice like all right That's it. This is book doing this and it was The anticipation wasn't as bad and I think again because my ability to deal with anticipatory anxiety had also been greatly improved by all the previous work that I had done and You know it matters and then what I would definitely say is even then even then How do you practice things you can't necessarily practice? I did it virtually so when I was ready And it's okay. The flight is booked. That's it or even just before the point of committing like I'm gonna do this I Spent a whole lot of time and you know the internet is an amazing resource I didn't buy like a fear of flying course or anything like that But there's a ton of people on YouTube who are flying aviation enthusiasts who take their their cell phone and record Takeoff and record landing and I must have watched a hundred different videos of people who had record record a takeoff It's my least favorite part. Yeah, what it did was it desensitized me to oh the noises. This is normal This is normal. This is gonna happen next This is gonna happen next and as soon as I will it was able to go through my head the steps of like We're gonna taxi. We're gonna turn we're gonna stop we're gonna accelerate We're gonna lift off the ground this this gear is gonna come up We're gonna turn based on you know, which way we're going Well, I was able to watch other people do it a lot by the time I got on that plane I was very nervous, but I Knew what to expect already and I was just this is normal. This is normal. This is normal This is normal and it went much better than I ever thought so When I did that I think my ability to actually Virtually practice flying by watching other people do it and acclimate to that was there's no way I could have done that in 2009 or 2000 I could have never done it Yeah So so many of your skills will improve as you do your exposure in the small stuff It will begin to lead to larger and larger things Mm-hmm. So that's what the only way that you can actually know whether you're ready to do it Is by actually doing it in the end. Yes. Yeah, yeah in the end And so I think one of the things that I would definitely say is for the tests that you really can't practice because you don't do them all the time You know do the best you can and as you're working on your other things and you become more Resolent and more able to learn and even process cognitively as opposed to having to do it because when we're in the beginning stages You could think about going to the post box all you want. Did it really help you go to the post box? You had to actually just do it right to post that letter myself, right? But but in the end as we get better and better at these things you will make improvements sometimes just by visualizing As you know that resolute so you build that skill set so that helped me a lot Remember work. I worked worked on visualization stuff visiting relatives before my old therapist like we sat down we imagined How it was gonna go right and just made things go nicely And just kept working on it. Yeah, and that helped in it. Yeah. Yeah, definitely when I went there I was able to picture how it was going in the visualization right and bring bring that to reality now instead of the horrible Images that I'd been making in my mind, you know, so rather than sitting there worrying about what's gonna happen get there and then think about that It was the other way around the therapist had you visualize a good trip to go. Yeah. Yeah Yeah, and then you were able to just play that script out Exactly, which is great and I think that comes that skill. That's a good skill to learn I can remember back, you know when you and I kind of first met and you knew the struggles I was going through I actually got in the car one morning and drove To the office that I had at the time that building and I remember having my little point-and-shoot camera on the dashboard And I didn't I didn't speak I did it in silence and I just I videotaped it I recorded it and I didn't post it anywhere I didn't share it with anybody and I kept that on my phone and I would watch that video again and again and again And it was me kind of being able to sort of walk myself through that trip Which was literally like an eight or nine minute trip. It was so short But it was hard, but in those days I hadn't built up that Resiliency yet and my skill set was still wasn't it was still building those things. So it helped, but it didn't help that much But as I get further down the road those things help more So you just get more and more capable as you do more and more of this work So maybe you're not Jackie maybe to speak to Jackie directly Maybe you're not going to the dentist But when you go to the supermarket or you stretch yourself beyond the supermarket and take a trip to a movies or something Go see a movie in a different town. They've been at that it will actually help you get to the dentist in the end So I think that's the answer.  This is fine I can get to the school I can get to the to the post box I could get to my office like you can't if you just stop there then your progress kinds tends to stop Yeah, yeah, yeah, so I mean I was thinking I was I was thinking about the flying thing And then there may be so many different things like when I think about flying if we're on the subject of flying It's not just the the flying. In fact, I'm not really scared of the prospect of flying It's it's the like the check-in the queues the amount of people at the airport getting to the airport And then obviously being enclosed on a plane with no escape They're the kind of things that I would imagine so it's not really a fear of being up in the air, right? It's more a fear of those things that I already associate with my anxiety wherever I am So it's not specifically flying for me. Okay. Well, actually that's good because along the lines of this Conversation as you work on those things. Yeah. Yeah, that's why I would imagine that if I can deal with standing in a queue in a Supermarket, it's no different to standing in a queue checking in 50 million fags in my suitcase Cigarettes in the US. Yeah, sorry. It's like a panicky now. Whoa.  I admit there's no magic thing that's gonna make that somehow easy I suppose it's wherever you're at with your anxiety So whatever's making you if it's a hundred yards down the road and that's bringing anxiety then work on that exactly Yeah, because it's that feeling of anxiety that we've got to try and get past Yeah, so it doesn't matter how far you can go or wherever it is It's when you reach that point of anxiety and panic That's what you need to try and work towards isn't it it is it is and as far as the nuts and bolts of how it works It's it's a I Try and generalize it like it's intent. It's time and then distance for me. Wow. What is going on over there? It's like somebody turned a floodlight on That's amazing But what for me when I was working on driving for instance I had to learn that the formula was not so much distance but time Like time, you know, what's the best way to put it the phone is like time under load if you will So I would be able to get in the car and say okay.  No, that wasn't a I would try that and it would be really rough to do That so what I what was more effective to me was I'll stay in that half mile radius and I'll just go for time Because even that half mile would get challenging after 10 minutes, you know, I would want to return back home So it was time and then when I get comfortable I would increase the distance and then increase the time again and when that was okay Then it would increase the distance. So it that's this is it's an incremental thing And you have to actually do it and it doesn't matter what you start at It might just be standing in front of your the front door of your house For 30 seconds if you can't manage to get yourself off the sofa then just go into the next room for 30 seconds It doesn't matter what it is. It doesn't matter what the task is and as you get better at that task It's going to carry over to the next task Yeah, yeah I think something with what you just said about having like the distance thing When I was doing the walking during May when I was going for a walk every day I don't always feel more edgy when I sort of reached the halfway point So when I was furthest away from home sure that became an issue So I agree with what you say if you can keep base it on time So being out of the house because that is enough because I mean there's times where I can just sit out front in the car and feel On edge. Yeah, so it's just a case of sitting there and riding it out, right be on edge You know if you but but it's important for us to I think say that it's not we don't mean white knuckle your way Right, there's a difference if you're feeling yeah, yeah, maybe edgy in the car. It has nothing to do with like just Grinning and you know great yourself. Yeah, that's that's not it you have to learn to just really do the opposite which is the You know just just let it be there and don't fight it and relax and Then in a way, it's all about learning to be soft in the face of the onslaught as opposed to being hard in the face Of the onslaught, I think that's probably one of the most difficult things to get your head round, especially in the moment Yeah, it's completely the opposite of every what every cell in your body wants to do Yeah, you want to brace you want to fight you want to push back, but really you have to learn to be soft and And Yeah, so that we could do a whole discussion on that I think yeah, yeah, so Anyway, I think that's that's the very long-winded answer to Jackie's question the things you can't I think we had something to do with table tennis So yeah, so I don't know if you have anything you would like to add to that or your own personal experiences And well, I've never flown or I have flown but I was probably about seven years old when I did I didn't have anxiety Issues and it was good and I enjoyed it and everything was great The world was a good place. Yeah, so that's it get your back into plane flight here in New York We'll go have a beer. Well video that it's gotta be done. It would that will happen one day my lad is desperate to go to America So well, you're always welcome come on over. I'm coming tell them I said it. What's okay Let's talk a little bit for a second about your What you think your and you know to answer this question it just seems like a good discussion to the extension to the discussion but When do you get to the point where you feel like okay? I'm good enough and then you stop Do you have examples of when you have done that? This is enough like I think probably with that with a list of five I know I keep going back to it But the list of five things like the fifth with the supermarket and when I reach that that was kind of But it honestly really felt like it was enough like I was going to like theme parks taking the kids We're going out for dinner Every other day or whatever going shopping. There was just there was still anxiety I'm not gonna say that there was never anxiety because there was right and like in the queue for the checkout There was still anxiety, but it just didn't bother me I was at that point where it just didn't matter anymore. Yeah, but there was obviously still limitations But I mean we were even talking about going abroad like going to France for Holidays and stuff like that. So the fact that I was even talking about it That means that I'd reached a good place Yeah, but then it was like it was about three years ago I think my wife's grandma died and that was what really Knocked me back. I don't know why it was just major stressful And that's what started in the very first place was a stressful Experience so I don't know just major setback and then I just I've just basically had to start again From the bottom the only difference this time being that I Feel more disheartened because I've already had to do it once and it's like well if I do it all again And then some something else happens You know, there's always that in the back of my mind Even though I know it's worth doing it now. Yeah, it's just like it takes a bit more of a drive To actually try and do something Hmm and so that stressful event I mean, yes, it had stress and emotional stress and everything which can certainly trigger anxiety did it Did you retreat when that happened? Yeah, yeah majorly. So didn't do it. Yeah, I just stopped doing anything. Yeah, yeah, right So there you go So yesterday I was telling you before we went live. I had a discussion with somebody on Facebook That sort of revolved a little bit around that theme. That's another thing we talk about probably for a whole episode one day That retreat, you know, so it's part of exposure when you're having your bad days and you want to retreat backwards I'm not gonna do it today That's a it's a bad idea.  I'm not trying to just say that sort of stuff, but It's retreat is a bad idea when it comes to exposure. It's a bad idea Yeah, no, it really is. Yeah, I think if I give anything to this podcast I am the evidence that that is not a good thing because that's what I've always done Like you stuck it out You went for it and you gave it everything and you just kept on doing it the persistence part Yeah Whereas I got to a comfortable place where there were still limitations Right, and then something else happened set back and I'm back down there and now I've got to do it all again Yeah, but that's the thing I'll do it and I'll like go out for breakfast a couple of weeks ago And I ain't been out since I've been I've been out I take my son to college like three times a week, but that's just driving and I've never really had an issue with that Yeah, but like, you know, I'm back there But I think what at least in my own experience what winds up happening is I don't mean to imply that you have to spend the every day for the rest of your life out doing crazy Stuff you don't but there comes a point where when you keep pushing it and doing it again and again and again and again No matter how you feel no matter what the day wasn't about how crappy that day was Sooner or later you get to the point where you almost don't have to do that anymore and you will maintain that that level You know at least I found that so even in a setback like the setback didn't put me back to ground zero again Because I had spent the time to really cement that progress in a way because it's a tenuous progress And I find that sometimes people when they're doing their exposure work will you know be really and I love success stories I love to get those messages. Hey, I made it to whatever we went to the movies list I haven't been to the movies in two years. I love those. Those are great But it doesn't mean that you're now continually able to go to the movies You better go again tomorrow night if that's a goal in the next night or the next night You spent a fortune on movies, but I think the point is it the progress can be quick But you really have to keep cementing it It's like anything else learning to play the guitar or whatever to keep practicing those scales again and again and again and again Even when you think you have it, you don't have it.  Yeah Yeah, that's the difficult part. I think that's the part that I've always struggled with it's Why do that when I can sit here and play FIFA? Yeah, and it's comfortable. EastEnders exactly and it's comfortable But you know and I remember those days and it is comfortable and sometimes even these days It's comfortable, but you will get to the point where you could take a day off like regular people do like I'm just I'm tired I'm not feeling well. I'm exhausted. I'm taking today off lock yourself in the house play FIFA all day And it's just the same thing that regular people would do.  So Anyway, it was worth throwing out there as part of I think answering this question And so it's all about just doing the work again and again and again over and tenaciously And then it will spill over and then for Jackie You'll be able to fly or you'll be able to overcome that problem much faster than you think you would yeah. Yeah So that's that's that I mean you want to move on to some how long we've been going man Let's see here. We've been going for 25 minutes. You want to take some comments like we usually do. Oh, yeah All right, let me get my glasses on so I can see you again. I'll take mine off Spannering the works I Um, I got a lot of good comments. We were talking about episode 14 Right, so let's see The health anxiety health anxiety. Yes Yeah, feeling ill. Well, actually here's a question that I got Let's talk about Bella Donna for a second. I think she's commented on yours too sometimes Nice name Yes, we will she talked about you guys touched a little on obsessive thoughts I think that would be a really great topic for an entire video. It's a huge part of anxiety We should probably schedule that. Yeah. Yeah. Yeah. So yes, we will do that. Thanks for that comment Let's talk about a comment that I got from Philip. Hey Philip Hydro have really bad anxiety panic attacks. I'm at the point where I'm pretty much housebound and this was in response to episode 14 Thankfully, I have savings, but that will come to an end at some point So this is a big question and again probably worthy of its own episode So if you have any opinion or suggestion on working from home at least until I get a grip on my life I would really appreciate it I heard from previous episodes that Billy works from home What kind of work does he do I'm supposed to if it's not an impediment you want to take that a little bit I know people so he I guess they have noticed that you have said that you work from home So about about eight years ago I decided to just give something to try and like the only thing I could really think of I like using computers and that's all I just went down the web design route route route. I'm being American for a minute. Wow So, yeah, I just I self-taught web design just started using different software putting things together Started advertising it locally just like friends family doing a few websites here and there for people and then started getting paid off it and Hey presto, that's where we're at now. That was like eight years ago. So there's many different things that you can do I mean, there's whatever it is that takes your fancy, I guess I would always say something that is actually interesting to you because that's you don't want to be bored And like although works not supposed to be fun really although Drew's having fun at work right now. Look, I'm having a great time I work. Yeah. Yeah, I'm technically working right now, but that's it That's why I did web design found something that I'm interested in something that I wanted to learn more about and just rolled with it And just see where it goes FYI ewebs EW right ewebz Okay, add me on the PlayStation Network. My username is ewebs. By the way, Billy's really good at it, too So for somebody self-taught and you're really good job with those websites. Yeah, check it out So that yeah, so that's what you don't say start your own business from paying money. You're like super discount For any anxious sufferers. So That's cool. So that's what Billy has done. He's very good at it, too So I applaud that so I'll tell you how I answered Philip though for those of you who are not reading the comments This is I guess kind of typical of me. I said, hey, Philip That's a good question in the bottom line is what I essentially told him was yeah, don't don't do that. So And and maybe we could talk about that a little bit So you built a reasonably successful little home business doing web design and you've done some really nice sites I've seen I don't know how much money you've made or not made that's irrelevant, but you were able to do that We can all say that I think When I was at my worst when you and I first met You know, I was I had the privilege or the luxury of UL of me being able to run my business a Lot of the time from my home That in retrospect was a tremendous mistake. I would 100% agree Yes, it was a tremendous mistake. So as much as it seems like let me just get my bearings I'll work at home for a while while I'm getting my act together. Yeah Working from home isn't getting it doesn't doing anything for to get your act together Yeah, yeah, it in my I'm gonna speak to my own experience here That was retreat and it was a huge huge huge mistake So I struggled and was stuck for much longer than I really had to be because I took advantage of that luxury and said, okay I could just you know, I could just sit at home Well, I mean when all this first started I probably worked full-time for about three years And just made it through every day. He didn't really help doing that But I know that it certainly didn't help when I stopped. That's the point Yeah, so, you know, I'm I weren't getting any worse when I was working full-time for somebody else I was doing what I had to do every day and I was getting through every day So I probably would have eventually learned that it didn't really matter whether I was having anxiety or not because I'm still surviving Right, but then I made the choice to just I just jacked everything in and did nothing for probably about six months And then I felt like a bum I was like claiming on the social and stuff and it was horrible and I didn't want to feel like that Yeah, and that's why I took the step to do something myself, but I know that it weren't The right decision definitely not. I mean, I still I look now for full-time jobs, but it's just like I Just can't see how I could I wouldn't want to let a company down Very like phoning up every Wednesday Thursday Friday. Yeah, it's Can't come in today. Yeah, you know what I mean? I have the thoughts that I know that it's not the right thing to do Yeah, but I've got myself into such a habit now like eight years in seven eight years in I Couldn't do it any other way now, but that doesn't stop me from actually expanding maybe getting an office, you know Yeah, I think I'm going to work because that's Yeah, yeah, just getting out of the house. Yep. Yep, and I think that's a huge deal So I think if you read my comment those of you follow along and Philip I'm talking to you I know it seems kind of harsh to say that but but I don't I think it's a big mistake to really look at that whole thing Well, I'll just let me just rest here. Nothing happens when we sit still, you know, we've talked about this There's no like immune response that makes your anxiety better when you rest it doesn't Rest is masking it. It's just retreating from it and it just makes it harder And what I found is that when I would work at the house, I Would it was I was still almost white-knuckling my way through the day There's two that two points I want to make about that number one was I was always worried that the phone would ring Or something would happen that would cause me to have to go I remember you remember some of those days, right? I'm gonna actually remember in our first little group that we had sharing video of that like oh my god You're like I actually have to go to the data center now and do something And it just turned it into this giant mountain of like this seems oh my god Because I was retreating from it and I would spend all day worried that something would come up That would force me out of that home office and that was difficult And I think the other thing that it did in the end was It would have been it's easy for me to say just get out there and keep working and like you said you worked full-time for quite Some time and you just got through the day you just you just did what you had to do to get through the day I think your approach would be different now Like you know more now and yeah, it's it's not about just white-knock. I mean just maybe I had another two hours I can grit my way through it, you know The approach is different and it yeah, definitely and I learned that it was a different approach I couldn't just go out there and just just to be tight and brace all day long and just I just got to make eight hours Just gonna make it as it wasn't that it Yeah, you would have a different approach now. I think so when I say Philip specifically and anybody thinking about this No, don't work at home get out there get out there is good advice, but get out there in the right way Yeah, yeah, I was gonna say like that's not to say don't work for yourself. Oh, no, don't base it at home Yeah, or don't don't use that. Yeah, I mean look there's a lot of really great home base at home base business I'm not saying yeah, do that. Yeah, I'm saying don't do that because you feel like well Let me just retreat back to my home while I figure this out. Yeah. Yeah, it's not Don't use your career accommodating your anxiety. That's exactly right That's exactly if it happens to be a home-based business great But then you better get your rear end out of your chair and out of the house doing other things Three and four times a day while you're doing a home-based business when I sort of about a year into after I'd started I'd go I'd have like a call and I'd go and meet Clients I'd have to go to their offices and then like over the past Probably two three years since my latest setback really. Yeah, like That doesn't happen anymore. I went through a phase of getting them to come to me and now it's like if somebody asked for a meeting now Sorry, yeah, I can't do your job find somebody else. That's what that's honestly what kind of happens It's like if somebody wants to meet me now, I always try and get out of it So I've got myself into that now I dig myself into these holes and then I have to go through the process again to get myself back out of it And it's I know the mistakes.  Oh hardly hardly And I think that's um, yeah that first decision that says I'm not taking this meeting And I can remember very clearly getting to a point that it helped It helped me start to move forward to a certain extent because I remember very clearly thinking like this is not okay Like I can't call myself a business owner and entrepreneur and all these things and Retreat from that like I'm missing out on a lot of opportunities because I was in the same boat Like that's a good project, but it's 35 miles away. So I can't yeah, I don't want to get involved in that like that Yeah, I just I started getting angry at that like I'm not I can't do that So that helped that helped kind of get me going. So that's the answer to that You want to do another one from that I have real quick. Yeah, this is Bob I'm in no rush. No rush. Okay. We these are turning into marathons, but that's okay. People seem to be watching Bob writes for me, this is about the health anxiety thing for me It starts with a sensation a shooting pain stomach pain jaw arm chest pain palpitations Shortness of breath and dizziness that leads me to wonder. Is this a heart attack? Nothing else or how how it cannot be sometimes Else this can go on for days after the initial sensation, but we'll be revolving in my head wondering what it meant It can also start with a thought like today is the day I have a heart attack Mm-hmm, and if this thought this thought will rotate for days on and leading to large degrees of couch hugging anxiety So he doesn't really ask a question. It's more of a comment and Bob. Thanks for sharing that Does that sound familiar to you at all help anxiety wise Yeah, 100% yeah, that's usually what it is It's a sensation or a feeling like I mentioned to you my legs have been aching Yeah, the last couple of days. I don't know whether that's a caffeine withdrawal thing. We're like that's been on my mind 100% it's been on my mind. It's like what if what if it is something What if I'm not get I'm not getting like super anxious about it, but it's there Yeah, it's in the back of my mind, and it's like we've said a thousand times It's probably experience that's not making me go over the edge. Sure, you know But if it's something new if it's a new sensation whatever it is it does it plays on your mind 100% even if it only happens once and it doesn't happen again. Yeah for a few days No question. It's gonna be like what if what if and I think that plays to the whole we talked about it in episode 14 It's the health anxiety thing is so much I mean it revolves so much around cognitive work as opposed to the physical exposure work And that kind of leads to Jenny's question from yesterday So which method is best for getting rid of anxious and fearful thoughts Quieting the mind or replacing negative thoughts with positive ones And my answer to that was it's both those are those are both skills that you have to learn and you will use them both and I think at first replacing like in the case of the health anxiety The what if learning to replace the what if with some other thought is probably the easier skill to learn at first But as you go down the road you could actually get to the point where you take that what if just let it go out and just have think nothing And what I mentioned to Jenny is both they're both the right answer Just I would say probably yeah, if you start with the replacement thing You'll probably reach a point where you yes just to acknowledge Whatever it is and then you can just let it go rather than the need to replace it So I'd probably start with replacing. Yeah, and replacing could be exhausting. It could be tiring But you're right You'll get to the point where you acknowledge it and you won't need to replace it anymore like You know, you don't even think about it anymore. He comes in and goes. Yeah So both are good skills that you have to learn and that were my comments Those were my comments on episode 14 that came in. I'm almost fading into the background. Look is that so bright You're gonna wind up in another dimension if the light gets any brighter anybody that watches this video You'll have to wear glasses and put like some Lens on the one side So funny Sorry, that's all right. So I'm kind of out of things at the moment I think that's it. Those are kind of the comments that I got set between now and you know this weekend last Yeah, I was just reading I got nothing. Wow. No love for billy I think there was a few comments But most people make um Funny remarks on mine. Maybe they see me as the class clown, which I don't mind I'm happy with that.  Did I did I mention the heart this week? Oh, no, did I mention that nope This is my son because he started college He got like a gift pack thing like an introductory and he got a stress Squeezy heart and he gave it to me. So that's pretty cool. Very impressive Anybody wants one they can have this one I don't have any five thousand dollars five thousand dollars. You could will you sign it at least autograph it? Oh, yeah, hell, yeah So, oh, I know what we wanted to mention when this video gets published Yes, yes, what it's took us like how long I know I just well the heart reminded me so when when we publish this video because we record on Thursdays and then we upload on Tuesdays and it will be what day will that be? It will be the 10th Tuesday the 10th and it's world mental health day I wonder who that who does that it's like through the world health organization has declared that I'm so really sure but it's another pointless day Really yesterday was national boyfriend day in the u.s. Really really? What's your thoughts on the on the days that they do because they do it over here Like we have a mental health day and now we've got world mental health day Do you think it's worth doing my comment is always like every day is mental health day for me Kind of kind of I know we've touched on this before and we'll probably do an episode on social media Which will tie into that, but we have a long list of topics to cover on this podcast We need to start writing them down. We should we should instead of making them up five minutes before we go live So my thought on world mental health day. It's not a like it's not inherently a bad thing I guess it's not a bad thing. I just don't I always hate that awareness thing Like oh, we need awareness. Well, okay awareness is fine And and I would say this if you want awareness of your mental health issue And and it is anxiety or agoraphobia or whatever it is that we're talking about panic disorder And you want awareness of that let that awareness Be so that the people in your life can cheer for you and like support you while you're doing the work to recover I can't stand it and I'm talking just specifically about the topic that we're on which is anxiety disorders Right. I'm not talking about people who are suffer from multiple personalities or yeah psychoses I don't like it when awareness is all about accommodate me. We need awareness people need to know how hard this is No, they don't they just need to know that you're working on it So like I I'm just and I know I'm harsh when I say that but we don't I don't want awareness People don't need to know that it's this will knock you to your knees like yeah, it will but so what get up You know get off your knees. Damn it. So I just don't like the whole awareness thing. I don't I don't we're not going to find a cure that this is we're not trying to raise money to find a cure Like we know what the cure is already just to do it So that's it. Yeah. Yeah for people like you and me. That's what it should be It should be awareness of treatments maybe maybe improving improving access to treatments. That's the World world improving access to mental health treatments day That's a mouthful. That's a big hashtag. Twitter's going to 280 characters. So that's okay. We can do it We need that to hurry up I think one thing that would be great. You know what I'd love more awareness of we should probably spend a little bit more time Here in the u.s. At least when you're going through school You're in like middle school and you have health class and you'll learn about like sexually transmitted diseases and dental hygiene and exercise and diet and it's a cursory review I think because it seems like they should do it in the schools But even a couple of days on mental health would probably be huge To understand what anxiety is that it's normal every human being feels it. What's anxiety? What's depression? What do you do when you start to feel that way? It would go a I think a very long way if somebody just had three days of middle school That they could maybe remember and like oh, yeah, I remember when mr. Green told me this Yeah, as opposed to completely bewildered and not knowing what it is and and running, you know to pills and A lot of people are campaigning for it They're campaigning for it over here to bring it into schools and that and they should just you know Like especially when the numbers are rising they are rising they are rising So I think it's good, especially here. We just had another unfortunately another mass shooting in the us In Las Vegas. It's horrible. And when that comes up aside from the gun issue, which that's not a topic for us But you know, it always also leads to discussion of mental health issues because invariably that becomes a thing Well, it's not about gun control. It's about mental health and maybe that's true I don't know but and then we you know, we talked about a little bit But I don't know like just a little bit education would probably help people who are in our position a lot I would say so. Yeah, so you're not starting from dead zero. So that's my thought on world mental health day Don't know Take it or leave it. Yes. I'm waiting for world peanut butter day. I can get behind that one Oh, I'm allergic to peanuts. Oh, no, I'm not. Oh, no, you're not you might be in the time Yes, it takes to open the lid Because that was it I commented and said I mean I I said in the last one for people to leave there are rational fears And nobody did nobody. Oh, that's rough. I'll give you one when I was really really at my worst I used to have this irrational fear of being the first person to drink out of like another milk the first milk carton Right. Yeah. Okay. Like because what happens if so in case it was contaminate bam That's exactly right, which is completely and utterly ridiculous.  Yeah, another thing for me was like insect bites I don't know if you if you ever had that where you picked up an insect bite and this one could be malaria For sure. You never know. You never know. You never know. Well, there's got to be some mosquito here right now carrying malaria Zika virus You know what if we let those stuff those things take hold you would just sit in the house like wrapped in bubble wrap all the time You know, that is what it is I think I think we have exhausted our topic for today and our comments. We've been at it for 44 minutes That's pretty good. Seems about right for us. Yeah. Yeah So what to figure out we're going to talk about next time of as always if you guys are watching on youtube either channel Comments and questions are always welcome. Yes. Hit my website that anxiety guy calm hit billy's website Anxiety united.com. Did you didn't you just say that? Did I say that? Either way that anxiety guy calm anxiety united.com you'll find us all the same just open anxiety You'll find us somewhere tweet at us tweet at us facebook us. Whatever you want to do I'm busy. I'm playing fifa this week. Oh, he wants to join me. All right, so I'll tweet at me billy will be very busy The new fifa came out. He's a little bit preoccupied. Yes I'll put in one little shameless plug if you do find me on facebook facebook.com slash that anxiety guy There's also This was just on a whim. We were talking about it before I went on we were went online Yes, I started a discussion group to go along with the podcast just because Like you can I didn't even know what's the thing on facebook And we're up to 40 members or so and there's some pretty decent discussion Yesterday, we had a little thread going about positive stuff like tell us here. Let's share success stories So if anybody wants to pop over there, everyone is welcome to join Where is it facebook.com facebook.com slash that anxiety guy? I'll link the forum the discussion group also in the video description In case anyone wants to pop in everybody's welcome. I'm not selling anything. Just it's a place to chat How much? Yes And that's it all right, so we will be back again next week. We are done. We're out of here. Well done young man Oh, yeah We'll see you guys next week. Ta-da. See you Let me just awkwardly stop the recording


OK, Dickinson was a little bit handicapped tonight because their libero was the setter for the first two. So they were adapting to that. But I thought that our block was terrific on their outsides, who are both very, very good players. And we got on those nice long serving runs because the serving was excellent. We didn't give it back to them. We made them earn it. And we got a lot of momentum. And it went in our favor. Closing out that third set was a little bit of grit. Dickinson switched their setter, played, and they played a lot better. And we just had to stick to it and finally put that last ball down. Lauren Davis put that last ball down to end it.


on San Francisco, 40,000 security professionals talking about how to keep the bad guys out, especially with IoT and 5G coming right around the corner. Joined by a many-time CUBE alumni. Always great to catch up with Mark, Mark Denon-Covin from Trend Micro. What's your title now? BP Cloud Research, is that good? BP Cloud Research, that's good. Welcome. Thank you for having me, I appreciate it. So it's always good to see you've got the booth. You guys always have kind of the craziest, wackiest booths. I was wondering if you fell out of the rocket ship and that's how you butted your arm. That's definitely a better story. So I think we can go with that or transport or malfunction. Something like that would be a much better story than the sad truth. OK. So you've been coming to this show for a while. We see all the AWS events. How has the evolution of Cloud and the ongoing expansion of Cloud kind of changed the game in the world of security? Yeah, I think Cloud has enabled us to a lot of things that we've been trying to do for a long time. And so we've talked about enabling granular security throughout the enterprise for years. And it's always been hard because we've had a lot of different vendors, a lot of different systems. When we moved to Cloud, it's getting a lot more homogenized and everything's accessible via an API. So we're seeing a lot of maturity in that space where people are embracing that fact and starting to enable some things that we've been trying to do like that solid identity and access management that's been really difficult in the enterprise. It's far simpler in a Cloud space. That's interesting because the other factors is all these things are now all connected via APIs, right? And there are a whole lot of SaaS applications in the enterprise. So the attack surface is growing significantly. And then as was pointed out in the keynote this morning, a lot of people work from home. They plug in their Nest. It's just growing very, very quickly. So how do you look at some of these challenges? Yeah, and it's funny because it's significant. And you look at IoT alone, right? There's billions and billions of devices that are being connected. And those devices themselves aren't necessarily so much of a threat that we did see that this year with the Marais, Botnet and some massive DDoS attacks. But it's the data that's going in the back end that's more of a danger to consumers. And we see that with SaaS services as well as a security practitioner. You lose the ability to apply the traditional controls that we're used to. And now you're relying on your service provider to do that for you. But it's still your data. So you're sort of forced to strike this balance of making sure you're leveraging the controls and options the provider has, but also looking out for things like, you know, people affecting the data going in and sort of manipulating and gaming the system more. And I think you ever mentioned and they said that this morning, too. Right, right. The other thing they said this morning is that every company has at least one person that's trying to connect with the Nigerian prince who's going to click on the... Well, he needs money. He needs money, right? You've got to give him a little money. So, I mean, it's funny. As far as we've evolved, you know, every, you know, my wife would say, oh, I got this weird email for like, don't click it, don't click it. Yeah. It's the same old techniques. It is. And, you know, as this, I've been doing a lot of research in serverless security lately and that's driven me to a really weird question because it's a collection of services where you don't have the ability to apply any controls directly. And it sort of started me down this path of what does security mean? And it ties to what you were saying in that at the end of the day, users need to be able to use these systems. And sort of a pet peeve of mine is we tell people not to click on these links, but that's the sole purpose of a link is to be clicked on. So, we need to find a better balance of educating people and giving them the context in which to make these decisions and having better reputation systems and better automated controls so that they don't have the option of clicking or not clicking. They just never see bad links in the first place. Right, that's a good strategy. The other theme that's coming out over and over is really collaboration within the ecosystem here to share facts, share knowledge, share data so that you can pick up patterns faster. You can see, you know, it's really the same thing over and over and over and really being kind of the co-opetition which is what makes Silicon Valley, Silicon Valley. It is, and it's nice to see it increasing. I think it's gaining pace and we're not just seeing it with the vendors, we're also seeing it where competitors in different industries are getting together. So, a lot of financial CISOs are collaborating because they're shared, they have a common enemy and they realize they can't beat them alone. So, if they're sharing threat intelligence amongst themselves, that they all sort of win because if one of them goes down, you know that attacks come into the next door, you know, the next day and we're doing the same thing in the vendor space where we're being more open to collaboration. We're sharing research analysis, you know, where a lot of vendors are launching bug bounty programs, you know, responsible disclosures becoming a little more standardized. So, not only within the community of vendors, but also within the research community. I think the more we talk, the better off we are because we see it in the underground where criminals are selling services to each other. They go, don't worry about setting up a botnet, Jeff, I'll rent you one. So, that Mirae botnet of IoT devices, we found that available for sale. You could lease it for 7,500 US would get you almost a gigabyte of DDoS attack. And, you know, that's a really low barrier of entry for criminals. We need to make sure that we're making it easy for defenders to defend against that kind of thing. Still, my favorite is the fake ransomware. I didn't actually put ransomware on your machine, but I told you I did. So, go ahead and send the money to the Nigerian guy. And I promise I won't turn it on. Well, and so that one's one of my favorites, but also sort of the super evil one that we saw this year was, okay, I've encrypted your files and I'll give you the key, not for money, but if you encrypt two of your friends. So, the pyramid scheme in spreading the attack. And that one was just super evil because it's mainly the social side. Like, what kind of guy are you? Are you going to encrypt, you know? Which friends get it, right? Exactly, you know. What's at the bottom of the list on Facebook. Yeah, but ransomware is a great example of the attackers realizing that they can do this at scale. They can be insanely profitable because even if you don't think you have a lot of valuable data, you probably got personal photos and videos that are really important to you. And if you're not taking basic preventative steps like backing up or patching your systems, then they're going to be able to get 500 bucks out of you. And that doesn't sound like much, but when you multiply that times, you know, 50, 60,000 people, because they just need to click a button or add people to a list. That's a huge amount of cash that's flowing in their coffers. Right. The other big change in scale that keeps getting talked about here is government, you know, kind of backed cyber issues. Yeah, the nation state. The nation state, thank you. Totally changing the game again as we talked about off air. It's good to know who you're fighting with. At least you can see them. But at the same time, the scale of resources that they can bring to bear, significantly bigger. Yeah, and that's the challenge. If you're not a nation state against a nation state, you know, it's David versus Goliath without a good ending. Yeah, without the rock.  You know, but it is, there is some advantage in knowing your adversary, especially when you're talking about, you know, nation state versus nation state because everybody's got signature moves they've got go to work, you know, and you can kind of track them over time. And we've seen that with some research available, which is a great example of, you know, community participation, places like Mandiant sharing information, you know, we do it at Trend Micro, a bunch of the community players share like, hey, we found this APT. We're associating it with, you know, probably a nation state, we're not sure who, but even the government, DHS just had a great release on Grizzly Step, which was a very specific campaign done, but very detailed analysis, which we didn't see that three years ago. So helping people out to understand what they're up against. And if you're, you know, a smaller enterprise or even a larger enterprise, you might not have the resources, but you can still take steps to make it harder. Right. And that's sort of the name of the game, make it harder so that you get a better chance at protecting your data and at least being aware when you have been breached. All right, Mark, I'm going to give you the last word before we sign off here. What are your kind of priorities for 2017? What, you know, we talk a year from now. Yeah. What are we going to talk about that you guys worked on this year? Yeah, hopefully, you know, a lot of the same, we're still pushing hard in cloud security around servers and containers. But a lot of my personal research has been pushing more towards teams and security professionals and what we need to do to adjust to be educators in the space, as opposed to being a silo team that's just telling you, saying, hey, you really should do this better. And I think that's a space that, as an industry, we're working up to that we have the expertise and we need to make sure the rest of the business gets it too. I love it. We've heard about Big Date all the time. It's a team sport. Security's a team sport too. It is. It's a great way to put it. All right, Mark, you and the COVID, I'm Jeff Frick. You're watching theCUBE, we're at RSA downtown San Francisco. Thanks for watching.


We were looking at waves on shear flows where we had analyzed the Kelvin-Helmholtz instability as a model for wind wave generation. We had found that the model predicts a threshold wind speed where at least one wave number is on the threshold of instability and the threshold wind speed was about 650 centimeters per second. We had mentioned that this is not a good enough model because experimental observation actually shows that both on the field as well as in the lab shows that the threshold wind speed is much lower and is about 110 centimeter per second. We now go on using the same dispersion relation. We will now look at even simpler model which is the Helmholtz instability of a vortex sheet. So I have put here the full dispersion relation once again and now we are going to do a number of simplifications. In particular we are going to say that we do not have two separate fluids. So the density of the upper fluid and the density of the lower fluid are the same. So rho u is equal to rho l is equal to rho. So we just have a single fluid. So consequently also do not have any surface tension. So t is equal to 0. If we substitute these simplifications into the full dispersion relation then the dispersion relation simplifies to that. Note that setting rho u is equal to rho l l eliminates the gravity term. There is no surface tension and consequently the what is inside the square root is always negative. You can see that this term the first two terms inside the square root are 0 and this term is always negative. There is a negative factor outside and then the negative minus 1 multiplies a square. So that is always positive and consequently this term that I have encircled in yellow is always negative. Note that this is inside the square root and the first two terms are 0 because of these two approximations that we are making. So we are saying that there is only one fluid. So there is a single density and there is no surface tension. So that sets both the first two terms inside the square root to 0 and we are left only with the third term which is negative. So consequently we find that there is always instability. So the dispersion relation now simplifies to that expression. The real part of the dispersion relation gives us the phase speed and it is telling us that if you put a perturbation k the real part of the phase speed tells us the speed with which the disturbance propagates and it is the average of the two velocities. And you can see that there is an imaginary part also and the imaginary part actually depends on the difference between the two. So as long as uu minus ul is greater than 0 or even less than 0 the difference is not equal to 0 you will always have instability. You can see that if uu minus ul is greater than 0 then one of those plus minus there is a pair here will produce instability and if uu is less than ul then the other will produce instability. So either cases as long as there is a difference in velocities between the two streams we are going to get an instability. So let us understand this instability a little bit more in particular because now we are dealing with a single fluid there is no interface as such. So what does it mean to have a difference between velocities between the two streams? So for that it is useful to take the to take the to consider the special case where uu is equal to u and ul is equal to minus u. You can see that the difference so u let us say is greater than 0. So this is what it would look like you know. So look at the picture on the left.  So these are line vortices. So this is my way state velocity. So in 2D it would look like this. So I have a 0 line that is equal to 0. And then the fluid at the top is moving with a positive u velocity capital U which is greater than 0. The fluid at the bottom is moving with negative u velocity. So it is equal and opposite velocity. So this is u and this is minus u. So you can see that this is in this particular limit it is easy to understand the physical mechanism of this instability. And what I have indicated at the figure at the top are basically line vortices. These are point sources of vorticity and you can see that I have driven I have drawn them in a way such that they induce a vorticity field which is they induce a vorticity which is clockwise. So you can see that this will induce a velocity field which will be exactly this. So the fluid at the top will be moving with a positive velocity and the fluid at the bottom below the z is equal to 0 line will be moving with a negative velocity and there will be a jump in the derivative of velocity. The derivative of velocity the z derivative velocity is related to the vorticity. So you can see that there is vorticity at z is equal to 0 but nowhere else. And so this is this line which I am indicating here in red is basically what is known as a vortex sheet. Note that so this is a vortex sheet and I have drawn this sheet in 3D here. It is not inconsistent to assume vorticity although analysis has been inviscid irrotational. Note that the vorticity is confined only to the sheet in the base state. So only the vorticity is at z is equal to 0. There is no vorticity anywhere else. So in this case the vorticity is like a delta function which is present only at z is equal to 0. So it is a very singular distribution of vorticity and we are interested in asking the question that if we perturb this sheet of vorticity using a Fourier mode of wave number k then what happens to the sheet of vorticity.  So this is telling us something very interesting this is telling us that any wave number any k basically grows. So all modes are unstable all Fourier modes are unstable and this is basically related to the growth rate. The imaginary part of omega will give me the growth rate and that is proportional to k into u the imaginary part of omega is actually equal to plus minus k into u. So one of them will actually grow. So you can see that this is what is predicted by this model and this is telling us that if we put a sheet so let me draw if you put a vortex sheet and if you perturb it so let me put a Fourier mode here and this is telling that if you put a Fourier mode here then independent of the wave number of the Fourier mode every Fourier mode grows in time and all Fourier modes are unstable. So all modes are unstable. Is it possible to understand the physical mechanism of this instability? Yes. So for that recall that we have chosen our line vortices to have a clockwise sense in the base state. So I am going to draw the line vortices and in 2D they appear as points. So that is the sense of vorticity. Now when I take this vortex sheet deform it in the shape of a cosine wave or a sine wave and that is indicated in blue here then let me draw the line vortices in the perturbed state and so on. Now you can see that in the perturbed state so you can think of this as a vortex sheet which is seeing a base state induced by itself. So this is the base state induced by itself. So in a linear approximation you can think of this as this base flow, this vortex sheet will be carried by the base flow. So there will be a tendency of the base flow to advect the vorticity towards these kind of points. You can see that from the picture that the vorticity will be advected towards the points which I have highlighted in red. Note that I have highlighted the alternate zeros of the Fourier mode. I have not highlighted consecutive zeros. In the consecutive zeros so this is the other zero which I have left out. So this is a point towards which vorticity is advected and this is a point away from which vorticity is advected. This is an effect of the base state velocity profile on the vortex sheet and the effect is that that the vorticity is advected towards the points in red and away from the points in black. This causes an excess of vorticity at the points in red and a deficit of vorticity at the points in black. Note that the way I have drawn it this clockwise sense of vorticity by the right hand rule is a negative vorticity. So this causes a negative excess of vorticity at the points in red and a deficit in vorticity at the points in black. So we have now I am going to use another color. So at the place in red we have a net excess clockwise vorticity. At the points in black we have a net deficit negative vorticity. So at the points in red we have a net excess negative vorticity. At the points in black we have a net deficit negative vorticity. A net deficit of negative vorticity is equivalent to a positive vorticity. So you can see that this thing in green that I have drawn will actually lead to a velocity profile which will give which will cause the amplitude of the vortex sheet to increase. Whereas at the points in black there is a net deficit of negative vorticity that is equivalent to having a there is a net deficit of negative vorticity that is equivalent to having a positive vorticity. So it will be like that. And this is also going to cause the amplitude of the vortex sheet to grow. So at alternative points we have this mechanism where alternative points have an excess of vorticity and again alternative points have deficit of vorticity and both of this lead to growth of the vortex sheet and consequently the instability which is predicted here. You can see readily that this mechanism is not specific to any Fourier mode. This will operate for any Fourier mode although the growth rates depend on the wave number of the Fourier mode. Consequently this mechanism operates for all Fourier modes and thus all Fourier modes are unstable. With this background it is now also possible to understand why did we get only a band of unstable wave numbers in the Kelvin-Helmholtz model when we had two different fluids. This particular analysis is the Helmholtz instability of a vortex sheet where there is only a single fluid. So there is no contribution from gravity, no contribution from surface tension. But suppose we applied the same model that we had done earlier for two different fluids and we had found that there is a band of wave numbers indicated here in green which are unstable. So now it is possible to understand why we have only the specific band of wave numbers which are unstable. You can see from the vortex sheet instability model when we have only one fluid that all Fourier modes are unstable. Now suppose we have two different fluids the vortex sheet would also predict the same thing that all Fourier modes are unstable. However now we have surface tension and gravity also. Because of surface tension there is a penalty to be paid in terms of surface energy because of gravity there is a also a penalty to be paid in increasing the potential energy of the system. Recall that we are looking at when we are looking at the Kelvin-Helmholtz model we have had found instability when the heavier fluid was below and the lighter fluid was above. So we are looking at a statically stable configuration. So start from the Helmholtz vortex sheet model where all Fourier modes are unstable. If we put in gravity to them then it puts a penalty on gravitational potential energy. Remember that wave numbers or wavelengths which are sufficiently long are strongly affected by gravity. So consequently at very large lambda or very small k we expect gravity to have a stabilizing effect. So this is shown up here in this figure. Similarly at very small wavelengths where surface tension is becoming important there is a surface tension penalty to be paid on the Helmholtz vortex sheet model. So consequently not all wave numbers are unstable when we put in surface tension and gravity. Sufficiently long waves are stabilized by the presence of gravity in the model. Sufficiently short waves are again stabilized by the presence of surface tension in the model. It is only in these intermediate regime of wave numbers where gravity and surface tension are roughly of the same strength which cannot overcome the instability of the vortex sheet model where this instability of the or the Kelvin-Helmholtz instability is to be formed. And so consequently this is a rough physical explanation for why only these band of wave numbers are unstable. These band of wave numbers are basically coming from the Helmholtz vortex sheet model whereas the ones which have got stabilized are stabilized either because of surface tension or because of gravity. So this is what we wanted to discuss about the Helmholtz instability of a vortex sheet. It is physical understanding of why all wave numbers are unstable and then what happens when we put surface tension and when we put gravity into the model and why does it cause some wave numbers to stabilize while others continue to remain unstable. There are let us ask what are the engineering applications of this. There are many engineering applications I will mention only two of them. Firstly the Kelvin-Helmholtz model is of great relevance in understanding slug formation in gas liquid to phase flows. I have mentioned this in my introduction to the course that this is relevant to oil transport in pipelines where water can be used as a lubricant. So I have plotted here for example a situation where we have a co-flowing situation where we have gas and liquid flowing in a channel the gas is at the top the liquid is below the line in yellow indicates the interface between the two in the base state. One can do an analysis of this and this also becomes unstable and waves are formed and these waves can become large amplitude waves and the liquid can actually go and occupy the entire cross section of the channel. So I have indicated this here and this is what is known as a slug. So you can see that the liquid has gone and occupied part of the entire cross section of the channel. There can be wave breaking also which leads to aeration and formation of gas bubbles in the channel. So this is a liquid slug with gas bubbles in it. This is very important. This is a troublesome feature in the industry and consequently one needs to study. There have been a lot of studies. The formation of slugs can cause oscillations in the volume flow rate and which in turn can also lead to pressure fluctuations as well as cause damage to equipment. So it is of industrial relevance to understand the origin of slug formation and its relation to waves and instability in gas liquid to phase flows. I have outlined two papers here. Those of you who are interested in understanding more about this can go and read these two papers. One of them is a very recent study. The second area where many of these things find obligations, the Kelvin-Helmholtz instability in particular finds applications is mixing in the ocean. So if you are interested, you can go and read this paper which is a nice introduction to how Kelvin-Helmholtz instability leads to mixing in the ocean. You can go and read this paper. Also look at figure 2 in this study where there is a nice demonstration of the Kelvin-Helmholtz instability. There are many such demonstrations on the internet. So one typically takes a tube of finite cross section and which are closed at the two ends and then you have a light and a heavy fluid which is in static equilibrium. And then if you suddenly turn or tilt the tube or the channel, then you can see that those regions in which I have indicated in hash in black and in purple, you can see that the black region was originally occupied by the heavy fluid. The purple region was originally occupied by the lighter fluid in the base state. However now because the interface has to remain horizontal. So the interface was earlier the yellow interface here and after the tube is suddenly tilted, the interface will become like that in blue. So you can see that those hash regions will have to be exchanged. So there will be heavy fluid which will occupy the region in purple and there will be light fluid which will occupy the region in the hash region in black. This effectively causes a net flow in this direction. So the lighter fluid moves from left to right, the heavier fluid moves from right to left and this causes instabilities to develop on the interface. There are nice pictures of visualization of these instabilities and how they lead to mixing in that thin layer between the two fluids. This is of great relevance of mixing in oceans. You can read more about it in this paper. So now it is a good time to summarize what we have covered so far in the second half of this course on interfacial waves. So we started with waves on a free surface. By free surface I mean those analysis where the density of the upper fluid was neglected. If we neglect surface tension then we had said pressure to be equal to 0 at the free surface. So that is why it was a free surface. We looked at capillary waves. We looked at capillary gravity waves. The important feature here was that there was no velocity in the base state. We looked at two approximations the deep water and the shallow water approximation. We had also found that the dispersion relation in both the approximations and in the general case of finite depth we had also found the dispersion relation for both capillary as well as capillary gravity waves. We have looked at what simplifications happen to the dispersion relation in the limit of deep water as well as shallow water. Recall that the deep water limit is one where the depth of the base state pool is much much greater than the wavelength of the perturbations which are placed on the free surface. The shallow water limit is the opposite limit or it is also known as the long wave limit. We then went on to waves on an interface where we model the density of both the fluids and we found corrections to the dispersion relation both in finite depth as well as in deep water when we took into account density of both the fluids. We looked at initial conditions which involved a single Fourier mode. We also looked at a continuum of Fourier modes which we called as the Cauchy Poisson problem. We have discussed the Cauchy Poisson problem in some amount of detail. We have in particular looked at the Cauchy Poisson problem in Cartesian as well as in cylindrical base state geometries. In Cartesian base state geometries when we looked at the continuum of Fourier modes we required use of Fourier transforms and eventually our answers were written as inverse Fourier integrals with the integrand containing the Fourier transform of the initial condition. We also looked at some asymptotic features of those integrals using the method of stationary phase. In cylindrical geometry we used the counterpart of the Fourier transform namely the Hankel transform. Here also we use the method of stationary phase. Recall that using this method led us to the concept of group velocity or the velocity of the amplitude of the envelope. Now subsequently we looked at perturbations on a fluid cylinder which went on to another base state geometry which was cylindrical. We looked at waves on a fluid cylinder which we modeled as being infinitely long in the axial direction. We replaced it with a gaseous cylinder where there was a gas inside and liquid outside and we ignored the we considered treated it as a free surface problem and we only solved for the liquid outside and assuming the gas inside to be exerting constant pressure. We also looked at thin films on a solid rod. In all the three cases of this problem we found instabilities as well as stable base states which were stable to certain perturbations as well as unstable to certain other perturbations. Recall that the criteria for which wave numbers are unstable remained the same for all the three. In this particular case we ignored the in this all the three cases fluid cylinder gas cylinder as well as thin film on a rod we ignored gravity and these were pure capillary waves or pure capillary perturbations. We then moved on to studying perturbations on spherical geometries. In particular we looked at perturbations on a liquid sphere here too the restoring force was only that of surface tension and we looked at liquid spheres we also looked at vapor bubbles the two limits and we in particular we looked only at shape oscillations. We did not allow the volume of the sphere to change. This was done using Legendre polynomials. We have looked at Legendre equation as a part of this analysis. Next we went on to the next level of complication where our base state did not contain any velocity but was time dependent. In this case we had a pool of liquid which was being shaken up and down with a certain amplitude and a certain frequency. Here also the base state in the base state the interface is flat the pressure field is hydrostatic but the effective value of the acceleration due to gravity becomes a periodic function of time. A linearized analysis led us to the Matthew equation. We looked at Floquet analysis we understood the Floquet theorem and using the Floquet theorem derived earlier in the course we analyzed the Matthew equation and we found that there are tongues of instability where the response of the free surface to perturbations can be oscillatory and it can grow in an exponential manner. In particular we found that there are these harmonic tongues and sub harmonic tongues. Harmonic was when the oscillatory the frequency of the oscillatory response was the same as that of the forcing frequency. Subharmonic was where the oscillatory the frequency of the oscillatory response was one half the forcing frequency. So this was this led us to Matthew equation Faraday waves and Floquet analysis. Next we looked at waves on shear flows. This is the last topic that we covered. Here we looked at a dispersion relation which was rather complicated. We looked at various limits of the dispersion relation. In particular we found that if we one limit of the dispersion relation reduces to all the problems that we have studied earlier or in other words the problem number 1 waves on a free surface or waves on an interface. Then we also looked at Rayleigh-Taylor instability where we exchanged the heavier fluid with the lighter fluid. So the heavier fluid being above and the lighter fluid being below we found is expectedly unstable. However the interesting feature here was that that some of the modes can be stabilized by the presence of surface tension. We then looked at waves on shear flows where the base state actually had a velocity and there was a velocity discontinuity at the interface. So this is what we mean by shear. So we looked at the Kelvin-Helmholtz instability and we found that the Kelvin-Helmholtz instability even when you have a heavier fluid underlying a lighter fluid it still predicts an instability. There is a band of wave numbers which are unstable when the difference between the speeds of the two streams exceeds a certain threshold. We use that for analyzing the minimum speed at which wind can form waves on a calm body of water and we found that it gives a prediction which does not agree very well with experiments. Next we try to understand the Kelvin-Helmholtz model a little bit better by looking at Helmholtz instability of a vortex sheet. Here we said that we do not have 2 fluids. We have a single fluid phase and then there is only a single density and consequently there is no surface tension and so the first 2 terms inside the square root of the discriminant drop-off and we are left with just the third term which turns out to be negative. So here we found that all Fourier modes are unstable. We looked at the physical mechanism of this instability and that physical mechanism when we went back to the Kelvin-Helmholtz model using this understanding of the physical mechanism we could also understand why only a band of wave numbers are unstable in the Kelvin-Helmholtz model. In each of these problems that I have listed and that we have covered so far we have also highlighted specific engineering applications. There have been a large number of varied engineering applications of everything that we have studied so far. I have also given you pointers to the literature for those of you who are more interested in studying making a deeper study of specific topics. So, so far we have covered all of this and the common theme that runs across all the 6 points that I have just summarized is that that each of them have been linearized analysis. So far we have not covered any interfacial wave problem or any free surface wave problem which is nonlinear. All our problems so that we have studied so far have been linear problem. We now go on to the, we will now go on to the last part of this course where we will do a nonlinear problem. We will look at something called a Stokes wave and we will find what does nonlinearity, what are the new features that nonlinearity brings on to a free surface wave. We will use the Linsted-Poincaré technique that we had studied earlier on in this course for understanding or for analyzing the nonlinear pendulum. We will find application of the Linsted-Poincaré in analyzing the Stokes wave and finding out the amplitude correction to the dispersion relation. We will do this in the next video.


Hey everyone. So up until this point in fatigue, we've basically been talking about how to determine what the limit for our stress is under fatigue, under a fatigue situation. So anytime that we have cyclic loading, loading that's applied on and off or positive negative kind of any sort of fluctuating loading. And that's great. That's the first step. We need to figure out what the limit is. The next step then is to be able to take the stress that is actually applied to our part and compare it against that limit so that we can know if we're predicting failure or not. And there's another basic graphical tool that we'll use for that called the constant life fatigue diagram or sometimes called the Goodman diagram, which helps us kind of visualize what's going on and all the things we need to consider. So first I just want to talk about this idea that there is alternating loads. And the easiest example is probably the paperclip being bent back and forth. If I take my paperclip, don't have one, but if I take my paperclip, which we'll pretend is this pen, and I bend it back and forth, if I look at a spot on the top of the pen, it's going to be in compression and then tension and then compression and then tension and then compression and then tension until it in theory fails. And in that case, I probably as long as I'm going, you know, the same amount of force up and down, I probably am going to have a cyclic loading centered on zero, right? And that may be the case for a lot of problems or it may not be the case. There's nothing that says that the the average of my cyclic load has to be zero. So in this this plot that's on the screen, that's kind of what we're seeing is that, you know, I might have a mean stress or whatever that mean stress might be, it might be zero or it might be something else. And then I have an alternating stress. And, you know, in a standard sine wave, you know, we're probably familiar with amplitude and all of these sorts of things. The stress can go up and down. And it may or may not cross zero, depending on the relationship between the mean and the alternating stress. So those two things need to be known in order to kind of fully understand what's happening. And in the plot on the right, we can see that the mean stress is greater than the alternating stress, such that the stress never crosses zero, right? It's always, in this case, positive or intention. And this could be an example where we have, you know, more than one loading at the same time. So I might have a part that's being pulled, while also being cycled this way, in which case I may never cross below zero, even as I compress the top by bending it this way. If I'm also pulling, I may never actually drop below zero and put it in compression. So those two things kind of have to work together to help us understand what's going on. So once we know our mean and alternating stress for a situation, then we can employ this constant life fatigue diagram to kind of understand our situation. So this is an example of what that constant life fatigue diagram might look like. And basically all we do is we're pulling information from our SN curve, such as that 10 to the third cycle that I talked about, or limit that I talked about, and our endurance limit, which we usually say is, you know, 10 to the six. So anything there and above would be our endurance limit. And I've plotted those here and said that anything, those values slope down towards the ultimate strength on this tension side of the mean stress. And that gives me kind of this converging plot of blue lines that all meet at the ultimate strength, because nothing's going to exceed the ultimate strength. We're not going to exceed that and still have our part survive. So that is important to consider. And then we have a dashed line here plotted, I guess, dash dotted line, which has limits at the yield strength on both axes, and then connecting those lines. And the reason for that is that we can't exceed the yield strength, right? Yield generally comes from static loading, but if we exceed the yield strength, we're still going to yield, even if we have this cyclic dynamic loading. So we still have to kind of keep that in the back of our mind. So as you might imagine, we can, for any situation, as long as we know the mean and alternating stress, say I have a data point here that represents how I'm loading my part, I can say, okay, well, that's safe, right? It doesn't exceed any of these lines that represent my limits. This is safe, you know, for an infinite number of cycles. Now, and kind of interesting thing is I can, if I would were to dash in a line through that point from the origin, I could actually use this line as sort of a calculation of my safety factor. My safety factor is really a metric that says, you know, how close am I to failure? So if this is where the first failure would occur, if I'm interested in infinite life, then my safety factor is going to be the ratio of how far I've gone or how close I am to that dot over that total distance. Now, if infinite life isn't my interest, maybe I only need my part to last 1,000 cycles, then my failure point is out here. And I have a whole new scenario, right? I have a much higher safety factor if I'm not not very close to that part. So great. That gives me a good understanding of, or at least visually, graphically of what I'm looking at. And I can do that comparison. And this slope of this line is, you know, just the relationship between so rise is the alternating stress, run is the mean. And it gives me that relationship between what this looks like graphically, and then, you know, the mathematical equation. So if I know that slope, I can go ahead and write equations of these lines if I wanted to, and set them equal to each other and find where their intersection point is. And that would tell me, you know, what I'm looking at in terms of what I would expect for failure under these criteria.  What that limit is, that's the limit on my stress. And then I look at my mean and my alternating stresses and plot them on the chart alongside my limit and do that comparison point. So am I exceeding my limit? Or am I not? So I kind of have the two sides that I have to figure out, what is my stress? What is my fatigue limit? And once I do that, I can, I can calculate what's happening for my part. All right, thank you.