Thanks, everyone, for joining this conference. These are the most important events that the Center for Open Science is associated with because our mission is really to support communities and catalyzing change themselves and the participation by you as a collective body is a critical part of how it is that we can engage the broader community that isn't present on ways that we can continue to improve and enhance the quality of the research that we do and support and try to translate into practice. What I'd like to spend my time talking about today is really a stage setting for what might be conceived of as the ultimate goal of this community action to try to reform and improve research practice, which is to make the research that we produce, that we share, that we translate into policy or practice itself trustworthy. That's something that we can count on, that we understand and can calibrate the confidence, represent the uncertainty, remove the bias, maximize the generalizability or at least understand the boundaries of where things generalize and don't and have the research community, the researchers and the research suppliers all be accountable to that evidence to the extent possible. So what I'd like to do in talking about that big picture long-term objective of improvement and reform is give a couple of examples of public trust of researchers in different scenarios and argue that these small scale examples provide an object lesson for advancing trustworthiness of research more generally. A common perception of the end goal of achieving public trust is for researchers to ultimately be confident, be certain and be correct in the claims that they make. Thereby, if they achieve that, they've earned the public trust and research findings, what they produce, by demonstrated of their authoritativeness. We know what we're talking about, trust us. That I'm gonna argue is the wrong way for us to think about what is the end goal for achieving trustworthiness. Instead, I'm gonna argue that making research trustworthy and ultimately earning that public trust is best achieved if we think of the end goal as helping researchers be humbled in their claims, calibrated with the quality of the evidence and consistently truth seeking. And so let me illustrate what I think the implications of public perceptions of researchers, in that case, versus the alternative way that we might conceptualize, trust and trustworthiness of researchers. And I'll do that by summarizing the results of a survey of almost 5,000 US adults that we did in my lab several years ago, Charlie Ebersole and Jordan Axt were co-authors on this work. And what we did was we presented very simple scenarios of here as a researcher that did this thing, how much do you think they are competent, their ability? How much do you think they are ethical as researchers? And how true do you think their findings are? And so we had those three outcomes, the first two being about the trustworthiness of the credibility of the researcher, the last one about the actual truth value of the findings that they produce. And we wanna see what happens when different situations emerge of researchers' behavior, what drives the perceptions of researchers' ability and ethics and how is that associated with whether they are correct, whether their findings are true findings, at least in the context of reliability or replicability. So I'm gonna summarize the results in this graph and what I'm showing here is the baseline question. So a first question that we asked, researcher X, Brian, found an interesting result and I published it. And then people rated on a scale of how, what do you think of Brian's ability? What do you think of his ethics, given this is all you know, and how true do you think the finding is? So if all you know is that I found this result and published it, we get a baseline rating which is anchored here at zero. So whatever the response, individual response was, was put at that midpoint. And then we provided additional information and then we'll ask them those same questions, what's their ability, what's their ethics, how true is the finding to look at how it changes against that baseline. So for example, I found an interesting result and published it and David succeeded in doing an independent replication. Now rate me on how my ability, my ethics and whether my findings are true. And what you see here is that if, what you now also know is that David succeeded and replicate my findings, respondents saw me as more having more ability, stronger ethics and the truth of that finding, that it's a real finding was stronger compared to just knowing that I found a result that was interesting and published it. So they are responsive to evidence of replication and that has implications both for their perceptions of truth and their perceptions of my ability in ethics. What if instead David fails to replicate my finding? Well, what occurs is what you would expect perhaps which is they perceive decline in T compared to the baseline of the truth of my finding well, that makes sense, fail to replicate. So if that's all I know, then I think it's less likely to be true but they also perceive that I am some slightly less ethical and have less ability than if they had only known that I had found something and published it. With just these two scenarios, we might think or conclude that our reputations, ability and ethics are tied fundamentally tied to whether we're right or not, whether we find true things or false things. If we find false things, then we have poor reputations. If we find true things, then we have strong reputations. But let's look at a few different wrinkles in what other kinds of scenarios might occur. So I found an interesting finding result and published it. David fails to replicate it and I say, well, David did it wrong. His result is not valid. He doesn't know what he's doing. If that is the scenario that occurs, then respondents are similarly responsive to the truth value being lower as if it was just failed to replicate. My criticism does not say, oh, well, he must be right, David must be wrong. But also I lose some reputation on both perceived ability and perceived ethics for laying in that criticism. Of course, it doesn't mean you just have to criticize it. I could have instead say, oh, David failed to replicate my finding. And then I looked at his methodology and I agree. And I, oh, geez, maybe I was wrong. That result might not be correct. Respondents are responsive to that. The perceived truth of that finding goes down even a little bit more. Wow, they're both saying that maybe that original finding isn't reliable. But the perceptions of my ability and my ethics go the opposite direction. So compared to the baseline of just knowing I found something and publish it, David fails to replicate it and I agree, is actually associated with people perceiving my ability as even higher than the baseline and my ethics is even higher. So even though now the only additional thing is that they found out some evidence that I might be wrong, my ability, perceptions of my ability and ethics actually go up because of the way that I responded to that new evidence. Now, that doesn't only happen if I just give in and agree anytime someone fails to replicate my finding they'll say, well, they must be right. I can productively examine that. So David fails to replicate my finding. And then I say, that's weird. Huh, and I start some new research to try to figure out why I found it this way and David found it that way. If that's my response in this scenario, the perceived truth of the finding actually goes up a little bit even though the only new evidence is that it failed to replicate. And that might be because the perception of my actions in response lead to perceptions that I have even higher ability than any of the other scenarios observed and that my ethics are even higher. So that productive engagement with findings as they are observed, respondents are very responsive to that and adjusting their perceptions of the reputation, the credibility of researchers accordingly. Now, instead, we may not even have David involved at all. I might have just done additional follow-up research and failed to replicate my own finding. And then I published that too saying, well, I got it that one time, I didn't get it this time. In that scenario, the effect on the perceived truth of the finding basically changes just like it would when David fails to replicate my finding. But because I went ahead and published that, there is a positive impact on the perceptions of my ability and the perceptions of my ethics. And of course, that's not the only way that I might respond when I fail to replicate my own result. I might say, oh, well, I failed to replicate it but I did that second study terribly and so I'm not gonna publish it, I'll file draw that. If I do that, the baseline reaction is that the truth value is even lower. Boy, he's trying to hide stuff or something, right? I'm really not gonna trust that finding and the perceptions of my ability and ethics tank in comparison to just publishing my failure to replicate. And of course, a final type of reaction might be, I'm not even gonna follow up at all. I got my publication, I'm gonna move on and do other stuff. And in that scenario, also the perceived truth and the perceived ability and my perceived ability and ethics decline as a consequence. So when we look at this in aggregate, what we can see is that US adults appreciate that findings are uncertain. They recognize that those results could be wrong and they do not judge researchers ability and ethics solely on whether they were right or wrong. But rather on how they pursued the truth. So look especially at these three results where the belief in the finding and the perceptions of the researchers ability and ethics do not track each other if the researcher demonstrates that commitment to finding the truth even in the face of contradictory evidence. And what's remarkable is that in all three of those situations compared to the baseline at zero, there is now less evidence that the finding is true but more perception of the original researcher having more ability and more ethics. Even though the only additional thing about the evidence is that there probably or might be wrong. That's remarkable responsiveness to style how researchers approach their work. And so what I think the narrow implication of that is is that researchers are trusted more for a commitment to getting it right over being right. And then there is from those examples that are just about replicability something more broad that I think we can conclude about trustworthiness in general. And that is that the trustworthiness of research is more about the process of doing research than about the outcomes. The outcomes are findings from research will always be the basis for distrust because science sometimes presents us with unwelcome evidence. Evidence that challenges what we want to be true because of our ideology, our financial interests, our personal commitments or other was that's always gonna happen. And it will always be the basis for accusations of lack of trustworthiness. I don't like your findings David. So therefore I don't think you are likely to be trustworthy. And if our aim is to end that type of accusation in the broader public, we're in a fight that's unwinnable but it's the wrong fight. When someone receives unwelcome evidence from science what do they try to criticize? They try to criticize the process. Respect for science is high because people know that science has been successful in the past but they also know that it isn't perfect. It's subject to biases like everything else. It's subject to personal interests that we have as researchers that bring to it. It's subject to all the kinds of things that present in real life evidence that isn't quite aligned with the truth. So when I get unwelcome evidence from the world of science that I don't like I'm gonna be motivated to find flaws in the process of the research behind the evidence so that I can dismiss it. So our broader project is not to cater to ideology but rather to recognize that the outcomes are going to be contentious and the best opportunity that we have as a research community is to enact the behaviors that address those areas of process that could justify a critic's response to I shouldn't trust this because the process was bad. So what are those different aspects of behavior that we as a individual researchers and as a community can take on to make research more trustworthy? A first dimension is accountability. Are the researchers accountable to being trustworthy? Did I go through IRB approval? Did I acknowledge any conflicts of interest that I might have? Did I provide a positionality statement for how it is that I am interacting engaged with this work? Did I disclose my funders? Did I credit all of the contributors to the work? Another dimension is is the research assessed can it be evaluated? Is it a valuable? Did I share my research plans? Did I share my data, my code, my materials? Did I show all of the outcomes of what I did? That doesn't mean that it's true. It doesn't mean that it's replicable, but it does mean that you can check and that evaluability is an indicator of trustworthiness on its own, even if it's not an indicator of validity or generalizability or anything else. Has the research been evaluated? Has it been assessed? Has it been reproduced? Has it been shown to be robust? Has someone replicated it? Has it gone through peer review? Has it been engaged in the scholarly discourse and been debated and critiqued than everything else that occurs? Is it well formulated? Does the research take relevant knowledge and perspectives into account? Is it based in the existing literature? Is it informed by theory and provided a sequence, a logic, a rationale for what the expectations of this work is given the understanding that currently is present in theory or otherwise. Is it representative of and generalizable to the population in which one tries to infer it? Does it, did it include the stakeholders that are affected by the research? Does it engage in participatory research with those communities that might be impacted to help inform and shape what the questions are? Does the research control bias? Does it promote accuracy and validity? Does it use validated measures, blinding, randomization, preregistration, all of the types of actions that are a ways to address bias in the research process itself? And does it work to reduce error, promote precision and reliability, attention to sample size, using reliable measures, power analysis, et cetera? And finally, do the claims match the evidence? Is it calibrated? Does it represent the uncertainty of where it is compared to the conclusions that we're interested in drawing versus what the evidence justifies? Does it identify limitations? Does it pursue alternative explanations? Does it identify the constraints on generality that are known or potentially unknown? And are the conclusions aligned with the evidence? So that's a lot of things, but it is the lots of things that we are constantly engaged in to try to say as is the work that we're doing, work that we think can earn trustworthiness and then ultimately will earn the public trust. One of the challenges that we face and the reason that we have meetings like this is not just to improve our own skills and abilities and ideas for how we can do those various behaviors, but also with the recognition that this is a systems challenge, that it's not just us individually that have to start to enact these behaviors, but how is it that we reform the reward system, the training models, how it is that people are engaged with this as a collective effort in our field and in science more generally. And the general conclusion that I take from a lot of this work is that a core basis for science being trustworthy is because it has mechanisms in the ideal instantiation that lead to it not trusting itself and to constantly be questioning with that openness to potentially being wrong humility with that calibration of really interrogating where it is that the claims are aligned and misaligned with the evidence and that is always looking to find the truth in the best way that we can so that science serves the public interest in the way that we all aspire it to do. So thanks again for coming to this on conference for being part of this effort to improve ourselves and our communities and I'm excited to see what will come out of it over the next couple of days. Back to you, David. Brian, there was a great question in the Q&A feature. I think I know the answer to it, but I want to see if I'm wrong. You're using me as a straw man for the competent or the incompetent replicator of your work. In the research itself, I believe you used researcher X or researcher Y. Monica asks if you're using a particular person's name like David, it's obviously it's commonly associated with white males and all the assumptions that go along with that. So just a little clarifying question on that study there. Yes, thank you for that. You are my favorite straw man so I appreciate your willingness to step in that regard. It is you are correct that in the actual research we avoided any names at all. We used variable labels X and Y and otherwise to just try to decontextualize those factors, which I think that Monica is quite right that if we had varied names that there might be different impacts depending on assumptions that people bring to trustworthiness of people based on things that get inferred by name in terms of social identity and otherwise. So thanks for that. I'm gonna open it up to any other questions that come in through the audience right now. As folks who are typing those in, I'll take the moderators prerogative and start the Q&A session. Brian, given the trustworthiness implications of everything that you've kind of seen today or you've seen forever but described today. What are the, I think a lot of folks are gonna chime in on this as the particular context with education research comes where there are unique challenges with direct replications and a lot of it comes down to questions of, well, how much can the different contexts account for the different results and what are the implications of that? Given that different contexts are always going to occur, what are the implications for how you see replications being potentially useful in education research? And I'll ask kind of a similar question tomorrow when we have a special guest from the National Center of Education Research who are really tackling this question directly in the context of education, but what's your perspective on this from what you've seen in conversations and different disciplines? Yeah, thanks for that. It's a really important question. And for me, the starting point in thinking about the role of replication for establishing trustworthiness and understanding of phenomena is rooted in a phrase that you said which is given that there isn't an exact replication. There is no such thing as exact replication. Some things feel closer to exact because, oh, that's a paradigm we can do again and it feels very mechanical and it even might be automated or it might not be obvious why it would vary across different samples or settings. But there is no such thing. Every time we conduct a study that's different than, it is different than the prior study that we conducted. If it's done on the same people, those people are different. If it's done on different people, the people are different. History has inevitably changed, time has passed. So no matter the circumstances, the replication is not the same event as the original study. So given that, what is the role of replication in helping us understand the phenomena? What it doesn't do is tell us precisely why or how the original findings were observed. That's an historical event and we can't go back and make that happen again. We can question its credibility. We can question its certainty as an event that occurred in the past. But we're not ever revisiting it in any formal way. The replication is new evidence and additional evidence about the phenomenon. So what I think the role of replication really is is to confront our current understanding with additional evidence to either challenge that interpretation, create occasions for theoretical innovation. Oh, we observed it there. I did a replication where given our understanding of the phenomenon today, we thought we would observe similar evidence. We didn't observe similar evidence. Now what? Either we've found a boundary condition unwittingly, something is different that matters, even though I didn't know that there was something that different as matters. Or the original finding is less robust than we had originally thought. So maybe it doesn't actually occur ever or even except under the most constrained circumstances. Or there may be something in the implementation of that replication study that we didn't realize was suboptimal, that could have been realized by somebody else or even nobody realized, but now we have to identify is suboptimal about it. All of those possibilities are opportunities for theoretical innovation, meaning better understanding of the phenomenon that we're pursuing. So when we set up those conditions for I expect to observe similar findings as before, whatever the domain, it provides a chance to one generalize if we do see similar findings. Oh, these are different occasions. We now have a broader understanding or evidence base that this occurs under different circumstances, change in sample setting, history and otherwise. Or it provides an opportunity to question and start to do that iterative search for potential boundary conditions or a weakening of the understanding such that it wasn't as promising as we initially thought. So thanks for that. Yeah, that's great. The floodgates have opened for questions. So read a few as they come in and we'll answer them live. Monica asked a follow up about your research. Did you ask participants at the end and visualize what the researcher in the examples looked like? Oh, there's some classic research on that that is, you know, a draw scientist that I love that original work that shows a lot of implementation of stereotypes very quickly. We did not be a great follow up to give these scenarios, especially to see if some of those stereotypes end up manifesting differently depending on the researcher's behavior before you have anything about their social identities. Somebody should do that. Monica, if you don't, somebody else do it, please. That'd be really cool. So thanks for that. I can just imagine what the least trustworthy scientist looks like. There could be some fun stereotypes in there. He's not wearing a badges shirt. I guarantee it. Yeah. I hear about ability to publish replication. Shannon asks, did you find that publishers are more or less willing to publish replication research? Seems like there could be another barrier to having opportunities to establish trust. Also any room for researchers to conduct their own replications. Yeah, great question. And of course, this is part of that systems challenge, which is if the ways in which we get the rewards we need to advance our career publication don't actually encourage or accept the things that would produce trustworthy science, then we're never going to solve it individually because it has to be solved as a system. And the devaluing of replication research has been a longstanding problem and is still a challenge in many domains. Attitudes among publishers are shifting to some degree, not comprehensively, but there is more openness to replication research in some pockets now than there was before. But there also are opportunities to lower the barrier to entry to trying for replication. And from our perspective, the best opportunity for that to lower the risk for individuals to pursue replication is to propose them as registered reports at journals. And the reason that we advocate for this is because if the work is just to do the design work and submit that to the journal of journal that accepts registered reports, then you don't have to do all the work of conducting the study and only then to find out that journals are not interested in it. Instead, you present, this is what we want to do, this is why we think it's important to replicate this finding and this is how we're gonna do it. We have found in just in anecdote data, a lot more willingness for editors to consider replication studies in that context because it's a lot easier to see without the present of the evidence, whether it's succeeded or failed, that, oh, this is something that is uncertain when we really should have some more evidence about it. The other advantage of using registered reports for replication is that because people have skin in the game, if you're replicating my findings, I want my findings to be true, I'm ego involved in my findings. And so if I know the results and they're not looking good for me, I'm gonna find problems in your methodology and say, oh, this is all the reasons it was terrible. If I see the results and they are favorable to me, then I'll say, oh yeah, it's a great study, you should publish it. With registered reports, me being pro that finding and David being against that finding, neither of us know what the outcomes are gonna be. So we will peer review to maximize the quality of the test because we both believe that it's true or not true depending on our preexisting points of view. And so registered reports actually, I think ease the means of publishing and then the ultimate rigor and diagnosticity of the findings because people have to engage with the design prior to knowing the outcomes. So that went a little bit off what you were asking, but thank you for that question. It's great, great issue to tackle. Johnny asks, do you think that any of these findings and trust and then scientists and researchers might have changed over the past few years since the COVID pandemic? I don't wanna think about it, it's a good question. No, great issue to raise. And in fact, I'm on a National Academy of Sciences Strategic Council, it's called about trust. And I can't remember the name. Trust is in the title of what the Strategic Council is all about. And Skip Lupia is also on that and he finished a review to document what are the actual changes in trust and science over time? And Pew data and other data show remarkable resilience in trust, the public trust in science over the past 70 years, up until maybe about 10 years ago. And the challenges that and trust in science is among the most trusted of all of the other things. So even as trust in government and Congress in other things have declined, trust in science maintained. Trust in science has started decline over the last several years, but the surprising thing is that it's not declining at a rate different than the decline in trust in any other institutions, Supreme Court, Congress, military, et cetera. Trust in all of them are declining at about the same rate, suggesting that rather than COVID or more general issues in lack of trust of science being unique to science, it's more of a pervasive challenge of lack of trust in expertise in institutions that maintain and have responsibilities for whatever area of practice of humanity they're engaged in. And that's a huge problem, but the point is it's not a problem that's unique to science. It is about institutions and expertise more generally. Just putting in some links to the relevant. Oh, thank you for coming. Content they put in that Pew study. Brian asks, Brian Cook asks, what are your thoughts about the future impact of the OSTP memo? And this is a great qualifier game changer or just rearranging the deck chairs. Thank you, Brian. It is a game changer. And for context for those that are not familiar with the memo, this came out while Alondra Nelson was serving as intern director of OSTP and had been in the works for a few years. And the basics of the memo are to require open access, direct all federal agencies that fund research to develop policies that require open access of research articles with no embargo. So upon publication and to require the agencies to develop policies for open data, whether the data are supporting a published article or whether it's data that did not end up getting published but was funded by federal research. So on those dimensions, open data and open access, the OSTP memo is a game changer. It will instantiate those policies for 30 billion, whatever huge amount of money is spent yearly by US federal agencies on research. It will also increase the likelihood that other national governments will adopt similar policies and there are others that are even further ahead than the US. So a lot of action in Europe has actually made it easier for action in the US to occur. And other UNESCO is also now advancing and advocating for these types of actions globally and lots of nations have signed on to that. So this is super important, but of course it doesn't solve some of the problems about rigor and reproducibility because sharing the papers and sharing the data are retrospective. If all of the research had low rigor from the outset, all's that sharing the paper and sharing the data is gonna do is expose how bad the research is. It isn't gonna solve the actual credibility and trustworthiness other than improving transparency. So it is a part of the solution and there's still a long way to go to get to the full scale of the solution. But even at the national level, there are steps that are occurring that really address rigor and reproducibility. In fact, the general accountability office in the US issued a report that really have, this is not a directive report. It's more of an analysis and recommendations, but it really leaned into, we need to improve rigor, we need to improve replicability. Here are the solutions that are worth looking at at scale, preregistration, registered reports, all kinds of stuff. It is really impressive report for sort of keeping that, the bar moving up on open science practice on a national scale. And I should note, if you're interested in these questions, Laura Naomi is here in an attendee and she'll be presenting from the National Center for Education Research tomorrow on their perspective and their findings for how the OSTP memo will be affecting the Department of Education. So stay tuned for more insight into there. Let's see. Matt Makle asks, some fields have made more systematic change than others to become more trustworthy. Do you feel there's a generalizable secret sauce to bringing about this type of systematic change? Do you think that there are any big field specific problems or different cultures between disciplines that reduce likelihood of having that general formula? Great question. Thanks, Matt. I think that there is a general strategy that works, but how it's translated into tactics and implemented is field dependent. And the general strategy is what we propose and promote as our theory of change that lots of others use in similar or variations for trying to reform the cultures that they're in. And the base idea is that there isn't, you have to take a systems level approach and appreciate that these are not just individual challenges and that there are lots of agents in the distributed decentralized system of science that all need to shift in order for actual behavior change to start to scale and to be sustainable. And so the baseline that I think is widely applicable comes out of the long history of social behavioral research that looks at how do you change behavior and how do you change cultures? And that is at base, you need to have technologies that make it possible to do the new behaviors, do open science. You have to integrate those behaviors with people's daily workflows to make it easy to encourage adoption of those behaviors. You have to, like this meeting is doing, work on the norms within those communities to make visible the champions of open science, their activities to indicate to others that this is a thing that one can do that are doing and are actually becoming more popular in our field, are valued by our field. You have to work on the rewards. What gets published? The earlier question, how can you get a replication published? If journals aren't open to that, then it's gonna be very hard to promote replication as an individual practice because the reward systems are misaligned. I can't get funded, I can't get published. Why would I do that thing? And you have to work on the policies like the OSTP memo is directing. But you can't do any, just one of those things, all five of them, make it possible, make it easy, make it normative, make it rewarded, make it required, are all interdependently required to for successful sustained culture change. Cause if you just implement a policy and you don't do the normative work in the community to have buy-in, train people how to do it, how to do it well, get them to see the value of that behavior, then they'll treat the policy like a bureaucratic burden. This is just something that NIH tells me I have to do. Okay, I'm gonna do that. In fact, I'll assign it to somebody else just to get it done and fill out that dumb paperwork to post the data. Who cares if it's usable or useful? It's not what I'm here for. It's just a thing that the government makes me do. Whereas if the normative work has been done, if the technology is there that makes it easy and guides you through doing it, then I'm much more likely to say, oh, this is good practice. And it just so happens that my funder also agrees that it's good practice certifying that. And so I'll do it well. So as a general principles, I think that model of behavior change is widely applicable. How to instantiate it in this context requires a lot of on the ground tactical thinking. Who are the agents of change? Where is a beachhead available where we can start with change here and then expand across the community? Where are there areas of resistance versus just complacency? Cause let's not start with areas of resistance. Let's start where people are ready to champion it, try it out and see if all of those objections that are very normal, ordinary, reasonable objections, whether they actually occur so that we can adapt the solution for this particular context and then bring it to scale. So thanks for that, Matt. Sandra asks a follow up question on the trustworthiness study. Who is the sample population? U.S. adults, I believe, but was there any variation, do you see any variation between lay public or scientific community within that? Yeah, great question. Yes, it was a general sample of U.S. adults. The sampling companies claim that they're representative, but they were not. I don't call them representative cause I don't trust the sampling companies enough to say that. So, but they were a diverse cross-section of U.S. adults. We have done the studies with members of the scientific community, much smaller sample. So the estimates are much more uncertain, but the findings are quite consistent. The one place where they differ is in a substantial way is in data that I didn't show in those slides, which is about rewards. Who's more valued? A researcher that is boring but reproducible versus a researcher that is exciting, produces exciting findings, but that aren't reproducible. And so we had U.S. respondents and scientific researchers answer questions about which one is valued more. The boring findings but reproducible, creative, exciting findings, not reproducible. And the general public thought that science was more sensible and valued reproducibility more than scientists themselves think, say, no, no. The person that's doing exciting stuff gets rewarded more, even if none of their stuff is true. So that's one area of difference. That paper, I think I've provided a link. We can provide a link in the chat to the paper and the slides and you can look at that data. So thanks for that. Shelby asked, are there negative trustworthiness effects on the journals or on the platforms that shared original studies after publishing a study that failed to replicate? Not that I know of systematically, but I certainly have seen individual instances where someone is so mad about a replication of their result that didn't work, that they blame anybody that's associated with it. The original researchers, they're terrible. The journal and the editor, why the heck did they publish this? What's this funder doing questioning my research? Don't you know who I am? Kind of reactions. So that has occurred, but it's so unusual that it's memorable. It's like, oh yeah, I remember that crazy guy who reacted all this way. So I think the baseline is, no, this is everybody recognizes that replicability is just part of how science works. And yeah, there is contentiousness around the edges, when especially as we are, see it as an unusual event. But places, areas of science where replication has been done more and become more common, that heat declines very rapidly because it's easier to recognize this is part of ordinary science. This isn't an unusual thing that is done to target, although some people do have a bone to pick and do target things. So that does occur. But if it's done well and done broadly, then it is normal and even a compliment to researchers for someone to try to replicate their findings. But of course it doesn't feel great to not have a finding replicate. We're not gonna get rid of that. We like our findings. I think we have time for one more question. There are a couple more in the chat that we'll document, but I'm going to go to John Whitmer's ask, can you speak about some of the underlying cultural values required for this type of behavior change? It strikes me that there are some deeper values or commitments that come before we can move to tools and technologies. That is a great point. And in fact, in that theory of change that I described, there's a presumption that there are idealists and champions that want to do these things, that do value these behaviors. And the positive story there, and we have the Open Scholarship Survey, I'm sure we can share some slides on education research community. The positive story is that most of the behaviors that you would associate with open science and the underlying philosophical commitments are much more widely endorsed by research communities, including the education research community than people even perceive that they're endorsed. There is a challenge of pluralistic ignorance where we think that our communities are less supportive of open science practices than they are because we don't see others doing those practices. But when we survey as representatively as possible, we find broad endorsement of almost all of the behaviors and at very high levels, very little active resistance. When there's resistance, it's more like, I don't know, sort of in the neutral zone. So that suggests that the opportunity for change is real in the sense that people have the values that are aligned with the behaviors and the barriers to adopting them are, I don't know how to do it, I don't know where to do it. I'm not rewarded for doing it. I don't see others doing it. I'm not sure why I would do it. If you can address those practical barriers, here's where you can do it, here's how you can do it. Here's evidence that others in your community are doing it. Oh, and in fact, now here's a funder and a journal and even your institution starting to reward it. Now you're gonna get quick adoption because those value, it's an opportunity for me to say, oh, I've been wanting to do this. I just haven't had any of these things in place. So great, I'm on board. It's aligned with my values. In fact, I feel better about the culture of science now that it is more, it's rewarding me for the values that I bring to the science in the first place. Brian, thank you for that. We do have more questions and I took a note of them and so we'll share those around, but for everybody who participated, thank you. Thank you, Brian, for sharing your thoughts. As folks leave this plenary session, you'll go back into the virtual lobby and the next round of sessions will be starting in just a few minutes. So please enjoy and I'll see you later today and tomorrow as well. So thank you, everyone. Thanks, everybody. Love the questions, really appreciate it.


From the Alaskan wilderness to the swamps of Appalachicola, from the Rocky Mountains to the Arizona desert, America's national forests are home to some of the most biologically diverse and economically important landscapes in the world. These ecosystems are under the management of the USDA Forest Service. About 200,000 miles of rivers and streams wind through this terrain. Waterways are critical habitat for fish and other aquatic organisms. But for every mile of waterway, there are nearly two miles of roads. And where the roads and waterways intersect, there are culverts and problems. Many of these stream crossings now function as dams that prevent the passage of fish and other organisms. The challenge for forest managers is to find ways to break the barriers in these critical habitats. For aquatic life, survival is, literally, a matter of getting across. Everywhere we've looked at every national forest unit, we have found problems. Usually we go to a forest or look and people aren't even aware of some of the problems. We used to look at roadstream crossings as basically an engineering problem. Today, however, though, it's the health and diversity of our watersheds is the issue. And we're really needing to look at it from an interdisciplinary approach using the best science as we move through this. On the Wachita National Forest in Arkansas, Forest Service biologist Mel Warren and Rich Standage are checking to see if repairing a stream crossing has restored the habitat for some of these fish. How you doing, Rich? Fine. Rolled a couple darters. So we've definitely got them in here where we didn't have them before we fixed the culvert. So it's working. They've found that about half of the stream crossings here are accidental barriers to passage. But with this one repaired, there's one less barrier. And the fish can utilize it now work. They had been cut off for maybe 20 years before of not being able to make it up into that tributary to spawn. Streams like these have little or no game fish. But many think that aquatic passage at this level is a priority despite limited funding. In my estimation, we're not doing anything close to what we could be doing and we should be doing for these crossings. Well, in North America, we have over 800 species of fishes. Most of these are non-game fishes. The majority, well over two-thirds, are non-game fishes. Many of these non-game fishes are affected by barriers to passage. And all these fishes function there to help process matter in the streams and on the downstream end to help produce productive fisheries for the sport fishermen. About one-third of non-game fish are threatened, endangered, or of special concern. These fish share ecosystems in complex ways with other creatures such as mussels. A mussel the size of your hand can filter about a quarter of water per hour. They're sedentary animals. The only way they can disperse is by means of the fishes on which their larvae live for a brief period before they metamorphose into adult mussels. So most of their movement is concentrated in this larval stage as they hitchhike on fishes. And so barriers to passage could limit the distribution of freshwater mussels in stream systems simply by limiting the fishes that are able to cross through those barriers. Nearly three-quarters of North America's mussels are threatened, endangered, or of special concern. Almost half of the native crayfish are in the same situation. The highest concentration of aquatic species at risk is in the southeast, but all regions of the country are affected. And nearly 70% of these at-risk species are in the national forests. As a matter of fact, most of the species that are threatened, endangered, or sensitive occur in streams from medium-sized rivers to these headwaters. Aquatic organisms need access to places that provide escape from unfavorable conditions like high or low flows or temperature shifts. They'll move upstream to find desirable spawning habitats. Certain fish in any species tend to be pioneers and move into new waters to utilize new habitats. It's also to get to new food sources to escape predation. In Montana's Lolo National Forest, engineer and hydrologist Tracy Silty studies the movement of aquatic species. Research tells us that adult trout can swim for long distances of one to three feet per second. Now the dace species, even at maximum speeds, can only sustain one to two feet per second. So the swimming capabilities of different species can be very different, and this is a very important consideration. Aquatic organisms evolved under certain water velocities and flow depths. When these conditions change markedly, species can be stressed or killed. Standard culverts function much differently than the streams that they become part of. The water velocities inside of culverts often exceed the swimming capabilities of most adult trout and typically are far beyond what most juveniles can sustain. During dry seasons, the depths within the culvert can become so shallow that most aquatic organisms can't get through the pipe. Under natural conditions, the irregularities along the stream margins, the bottom and the sides create slow velocity areas and resting places for fish and other aquatic organisms during storm events. And then when flows go low, they create little passageways. The big question with all of this is how do we duplicate the stream through the road crossing? In the Falls Creek drainage of Alaska's Tongass National Forest, Tracy Silty has teamed up with hydrologist Mike Furnas to inventory crossing problems. Historically, crossings were about providing safe travel and sometimes passage for adult, anadromous fish. And we didn't pay a lot of attention to the juvenile life stage, to other species, to stream processes or watershed linkages. Stream crossings first became an issue for the Forest Service in the days of steam locomotives, but the number of crossings has grown dramatically since the automobile. The engineer's toolkit for crossings that weren't bridges consisted of steel and aluminum culverts, sometimes corrugated, sometimes not. Concrete low water crossings, concrete box culverts, and going back to the old railroad days, culverts made out of wood. Over time, perspectives on stream crossings and the aquatic creatures that depend on them have changed. Over the years, we've learned a great deal about engineering and hydrology and biology, and we now understand why these organisms need to move and how to provide for that in our designs. Mike Furnas helped develop fish crossing, a software tool to test whether fish can pass through the expected range of flows in a culvert when other, more expensive solutions are impractical. The best way is usually a bridge, but often a bridge isn't feasible. And where it isn't, the best solution is what we call stream simulation. And we do that by matching the width and the gradient and the stream bottom to what we find in the stream so that we have a seamless connection between the stream and the culvert. And to an aquatic organism, the culvert, the crossing, looks just the same as the stream does. In the short term, simulated culverts cost more than standard culverts. But over their design life, they actually save time and money because they reduce maintenance costs associated with chronic problems and total failures. They're also sized properly for flood events which optimizes road safety and minimizes erosion and sedimentation to the streams. Culverts can cause what are known as backwater effects at the inlet. They can allow debris and sediment to deposit, eventually plugging the culvert. This can cause a domino effect of crossings that fail during large storm events, washing out roads and adding more sediment to streams. There are also significant hidden costs of poorly designed crossings. When you start adding up how much of the watershed is functionally cut off to aquatic organisms, the importance of providing passage is clear. Well, obviously we can't fix all the problems at once, and so we'll have to set priorities. Now culverts have a lifespan of 25 to 30 years, so there'll be plenty of opportunities to replace with passable structures as we go. But we'll have to make sure, particularly away from the arterial roads and in the upper reaches of watersheds, that we don't miss something that needs immediate attention. We can't afford to have a barrier accidentally isolating a genetically distinct population, increasing the risk of extinction. Extinction is a major concern in the Pacific Northwest, where most clusters of at-risk salmon, steelhead and sea-run cutthroat are found. In the Loxacellway drainage of the Clearwater National Forest, a multidisciplinary team is taking on problem crossings. The majority of our spawning and rearing habitats for salmon, steelhead, resident trout occur in the smaller tributaries of the larger streams, and basically by eliminating the barriers that we have, namely culverts, we can increase habitat access to those habitats exponentially. The Battle Creek culvert has actually been known to be a barrier since 1979 when one of the original Clearwater National Forest fish biologists identified it as a problem. The Battle Creek feeds into the Loxacell River, the Loxacell River feeds into the Clearwater River, the Clearwater feeds into the snake, and eventually into the Columbia River. So the fish populations that we have here are part of the big Columbia River basin. What we do here can affect populations overall. From the beginning to the end of construction, the entire project took approximately six months. The Idaho Transportation Department paid for the installation of these culverts. The Forest Service identified the problem and assisted with design and permitting. The Nespersh Tribe assisted with engineering and funding for the project. This area that we're in right now is an aboriginal territory for the Nespersh Tribe. And the Nespersh Tribe has hunting and fishing treaty rights in this area. And in order for those rights to be meaningful, we have to have healthy populations of wildlife, we have to have healthy populations of fish. And so we approached the Forest Service on working collaboratively on restoration activities. One year after restoring passage, this partnership is paying off. I did a spawning survey up the stream and found evidence of bull trout spawning, which hadn't been seen in a while for about 50 years. And just last spring, two steelhead were actually seen in the Kirk spawning. Great. Repairing barrier crossings is now a group effort across the country. Forest Service personnel are joining with other federal and state agencies, with tribes, local highway departments, conservation groups, landowners and others. To do this important work. Mobilizing our resources to address passage barriers, really to sew the landscape back together, crossing by crossing ought to be a priority at every level of the agency. Under the Endangered Species and Clean Water Acts, we're responsible for ensuring free passage of native aquatic species in the waterways of the National Forest System. Not only is it the right thing to do, but I believe we face substantial biological, legal and credibility risks if we fail to redeem our stewardship responsibilities to these resources. These access corridors, they're the true wealth of our nation. That's how we provide the standard of living that is so important to Americans. Along with that standard of living and the quality of life, though, is our interrelationship with our environment. And Americans want to have that relationship with the out-of-doors. They want to protect other species. They want that quality of life.


What's going on everyone? Sam here with Layton Sports Cards ripping one box of 2021 Top's Chrome Platinum Anniversary Baseball Hobby for Michael G. So good luck here, Michael. One Chrome autograph per box is what we're looking for, so see what we got in here. Pull the 52 mantle short print so those things are money. What's up, Lane? Morning, morning. This is Sugo Tyler O'Neill on the Refractor. I feel like he was a rookie left shithead. Maybe it was 120. Tennis just in turn. We got Joe Morrigan on the Refractor for the red school one there. Call of Famer, one of the best second basemen to ever play the game. 11 spring air. We got Mike Brasso is going to be the Aqua Wave. So you get like one or two of these a box, I would say. A little bit of a short print there. And the Grom Refractor. Nice. We've got the Gold Wave Giancarlo Stanton. That is 43 out of 50 for the Yanks. Nice one there. Congrats on that one, Michael.  I love the color that comes out of this. The numbered stuff. So nasty. We've got Ria Muto, Chris Walker, Smith. Ozzy Smith is a Padra. Pedro, there's Lonnie Smith on the back as well. Call of Famer is in that one. A couple of Red Sox legends. D-Train, love that Dantro Willis is in this. We've got Blue Mini Diamonds. It's going to be Dalton Sheppri's. That's a rookie for the Ace. 84 out of 199. Congrats on that one again, Michael. Nice little card for you there. Always good to pull some numbered rookie stuff. Another Widener. Got a Babe Ruth on the back as well. Pretty slick card there. Stockus. Our X-Fractor is going to be a rookie of Christian Javier. Not too bad. You get one X-Fractor for box as well. Nice one. Always good to pull a rookie out of that as well, which is pretty cool. There's Luis Garcia. A couple of rookies on the back. Iglesias, Will Clark. Roy Oswald is going to be your auto. What a throwback. 136 out of 199 on the refractor.  Astro legend, Philly legend, Dodger legend. Man, I loved Prime Roy Oswald. He was like must watch TV when he was pitching. So sick. Congrats on that one, Michael. A little bit of mid-2000s nostalgia for you. Edwin Incarnacion on the refractor. Timmy Reigns. Keegan Aiken rookie. A senior Starling Marte on the refractor. Still has a Marlin in that one. Mitch White rookie. Some extra card in there. So he'll probably be zipped. Not zipped, but he'll probably be one less. That's Whitey Herzog, manager on the aqua wave. We're seeing there is a little bit of a queue right now. If you're to order it now, it'll probably be about an hour to an hour and a half before it gets ripped. But if you buy one, it will go today. It's just not going to be right off the rib. Colomé on the rookie. We do have pretty good amount of orders ordered this morning before we got in. Tyler Zuber, Edgar Martinez, Hall of Famer refractor there for the Mariners. Jojo Romero, Scott Kingery, Peterson. There's our pack that only had three, but there's a Christian Pochette rookie in there. Not bad. Brian Garcia, Youth Darvish. Got a couple packs left here for you, Michael. Open more Willie Maze, Tommy Lestella, Jonathan Stiever. There's a William Contreras for the Braves and Blake Taylor. That'll do it for your box there, Michael. Congrats on the hits again, buddy. We'll get them right out to you. Appreciate it as always.


Now, we look at Mach number. Mach number as all of you know is very useful when we look at high speed flow. Ernst Mach was, so here is an example of the effect of high speed flow on the pressure acting on the surface. So what is happening here is there is a condensation of atmospheric water vapor due to the differences in the pressure. We will study about it little bit. So Mach number as we all know the ratio of the flow stream velocity, ambient speed of the moving vehicle and the speed of sound under those conditions. So you have a ratio of local flow velocity and the sonic speed in that medium. It is a dimensionless number because both of the parameters have the same dimension and it determines the behavior of the fluid when the velocity is more than the A, when Mach number is more than 1 then we have a huge effect of this Mach number. So let us have a look at very briefly. At higher speeds approaching the speed of sound the exact relation between the speed of the aircraft and the speed of sound becomes very important. It is called the Mach number usually shortened to M. This is how it is calculated. This aircraft has flown 6 tenths of a mile in the time the sound wave traveled 10 tenths of a mile. It is flown at 6 tenths of the speed of sound in the same atmospheric conditions. That is it is flown at Mach 0.6. This aircraft is flying at Mach 0.9. So if the shock, if the sonic. At higher speeds. The sound speed and the velocity of the aircraft match then by the time the sonic wave arrives the aircraft will also arrive and the Mach number will be equal to 1. Let us look at this significance okay. So essentially what is happening is that when Mach number increases not beyond 1 but even beyond 0.3, 0.4 when it goes beyond 0.3 you start seeing that the density of the air does not remain same and the air starts getting compressed okay. So the local density of the air changes and there because of that the force acting on the aircraft is not the same. So if you apply the conservation of momentum then it can be very easily shown that rho v dv is equal to minus dp the minus sign showing that if this increases this decreases and vice versa. Similarly, if you assume acentropic flow and I will define acentropic flow very soon in that condition it can be shown that the relationship gamma dp by rho is valid. So using these two quantities one can derive further an expression which says that dp that is change in the pressure is equal to gamma RT times b rho. Now if you remember gamma RT basically represents root of gamma RT is speed of sound. So, gamma RT is speed of sound square a square okay and a is basically what m into v okay correct. So, you can use that. So, I will repeat the same thing again. So, dp is basically gamma p by rho dp p by rho is gamma RT okay.  This is not to be derived or not to be really memorize or something this is just tell you the link that Mach number gives us between velocity and density. That is the whole purpose of this small derivation. Mach number is a link for example if Mach number is 0 then density is 0 change in density is 0. If Mach number is equal to 1 then dv by v is equal to d rho by rho therefore that change in the velocity and change in density are related. So, if Mach number is less than 1 then you know it is a very small number because it is a square. So, let us say Mach number is 0.1. Now it will be 0.1 square times dv by v which can be neglected. So, that means it will almost be equal to 0 in which case d rho by rho equal to 0 in which case density remains constant. It does not remain constant but it is almost constant. As the Mach number keeps on increasing the link between the change in density with velocity becomes prominent. So, when Mach number is 1 the change in the density is change in velocity. At Mach number more than 1 the factor becomes m square. So, this is the significance of Mach number. We do not take Mach number just as a ratio for no reason. This is the real reason because it gives you a link up between velocity and change in the density. So, what is the history of Mach number this gentleman. He was born in 1948 and he was a physicist and he was the first person to actually study and quantify the effects of high speed flow on a body. Before Mach number there were bodies flying at very high speeds. For example, bullets have been there for many years but he was the first person to photograph a bullet. I will show you. So, here is Ernst Mach. He was the first to understand the principles of supersonic flow and this is the photograph taken from a very interesting paper on history of high speed flight. So, notice there is a hyperlink there. So, there is a paper by the same JD Anderson whose book we are following. There is a von Karman Memorial lecture in the year 2000 given at the aviation sciences meet an exhibit which happens once a year every year. So, in that you normally have some invited lectures. So, he was an invited speaker in that and he spoke about the history of high speed flight. And in that I have taken this picture from there. This is the first photograph of a bullet taken by a scientist to understand the flow around the bullet. You can clearly see that ahead of the bullet there is something, behind the bullet there is something and we have those two vertical lines. We will talk about that in the next slide. So, for those who are interested in little bit of history this is a paper and I am going to upload this paper also on Moodle. It is a fascinating paper. It is a historical piece. It talks about what happened, how did it happen, who said what. You will not find equations too much here, but you will mostly find statements about what happened, what were the problems faced and how this thing all came about. So, I will be sharing it on Moodle. It is a very interesting read. On the left hand side you have a more recent photograph of a bullet. And this particular photograph has been taken using the technique of Schlieren photography. So, here you do not see those two vertical lines and this particular photograph is you can see it is much more clearer. But fundamentally it is the same. The two photographs are doing the same thing. They are trying to capture the flow field around a bullet. This particular photograph by Mark was presented in this very outstanding paper. Look at the date is very old 1887 that is when he is able to study. So, what did he do? Basically he showed the existent of shock waves and he photographed the shock waves formed by the bullet. Same photograph. So, you notice in the nose there is a strong shock wave which is also curving in the nose and then it is tapering back on the back. Then there is a weaker shock waves at the aft end of the bullet because the end of the bullet is not flat. It is having some shape, some conical kind of a shape. So, therefore there are going to be weak shock waves created at the end. Those of you who will study aerodynamics in the courses that follow especially when you study high speed aerodynamics, you are going to study about the phenomena of strong shock waves, bow waves, weak waves, mark waves, etcetera. And these two vertical lines are not anything physical. These are the lines made by the trip wires that triggered the camera which was used by Mark to record this photograph. So, we should ignore those two vertical lines. Many people have a wrong idea. It is a vertical shock. It is not a shock. It is not a it is not a normal shock. It is just the lines made by the trip wire. Yes. What does a shock wave mean? Good question. What does a shock wave mean? I am tempted to answer the question, but I would request you to wait till the next capsule in which you discuss shock waves. We will discuss about them. Right now we are talking about little bit of historical thing. Today's talk is mainly about introduction to three scientists who are solvers in fluid mechanics. So, we will talk about shock waves in the next in the next capsule. Just bear with me for a few more days you will get the answer there. Okay. Let us go ahead. This is a technique that is used to obtain the photo called as a shadow graph, which is different from much later. So, light was passed through this particular and there was a reflection on the film plate and then those film plates created shadows and those shadows are what you are seeing. Now, the important thing is this so for the moment let me just tell you that these lines are basically called as shock waves. What they are? How they come? We will come in the next few lectures, but basically the effect of the shock waves is to create changes in temperature and in the air flow. This is another beautiful picture of a bullet. This time the bullet has a base and notice that the angle of the shock wave in both the pictures are not the same. So, this angle is a function of the flow speed as we will see very clearly. So, with this we now start defining the regimes of Mach number. So, there are different flight regimes based on the Mach number. Typically, we consider up to 0.3 as low Mach number. Then you have subsonic flow 0.3 to approximately 0.7 or 0.8. From 0.8 to 1.2 we have transonic flow which encompasses sonic conditions, but because we take a small margin before and after 1 and call it as transonic flow, then we have supersonic flow. Technically speaking, flow at Mach 1 will be sonic flow. Then we have hypersonic flow which starts normally from Mach number 4.5 or 5 and goes up to around 10 to 11 and then you can have hyper-velocity flow. So, very soon we will have a look at examples of vehicles that operate in various flow regimes. So, in subsonic flow small turbo piston drop aircraft, I would like people to identify the aircraft. Is there a question there? Can somebody identify this aircraft? Yes? Spitfire. Spitfire. Very right. It is a super marine spitfire. A distinct aircraft which is distinguished because of the shape of the wing. If you notice the shape of the wing is elliptical. There is a reason for that which we will study in the next class about. When we talk about lift generation, we will understand why this aircraft is good because it has got an elliptical wing platform. We will also study why you need not make it like this to make it good. So, this kind of aircraft which fly in subsonic flow are generally ones with very slender wings and rounded features. So, they belong to the subsonic regime. There are a few other examples of aircraft which are falling in this particular category. Mostly these are low speed aircraft. Generally, turbo prop, piston prop, they normally fall in this category. I am not saying that all of them fall in this category. I am just saying that generally low speed aircraft are the ones which are flown by propellers. Okay. Then go to transonic flow. In transonic flow, the example that I have chosen is to show you the creation of shock waves on top of the wing. I do not know why the video is not clear. You can notice there is a small thin line here. This line is actually air. This photo was taken from the window of an actual transport aircraft. And you can see there is a line of air which is adhering to the wing. This is the sonic line. The flow behind this is at a Mach number higher than 1 or I am sorry not higher than 1. This is the transonic flow line. So, this shows that the flow is transonic. So, it is the reason that divides the flow between subsonic and supersonic. The aircraft is flying at a transonic speed, Mach number 0.8. But the acceleration of the flow over the wing has led Mach number to be towards the sonic Mach number. So, this is transonic flow regime 0.8. And most aircraft in which we fly long distances, for example, Airbus A350 or Boeing 748, they are all transonic flow. They all operate in transonic flow regimes. The typical cruise Mach number will be 0.8 for these aircraft. Alright, let us look at supersonic flow. This is a very interesting video. And you have to also you have to see and hear. If the plane is coming, this is over a ship, condensation of and you hear the plane after it has crossed you. It means it is supersonic because the sound came to you after the plane crossed you. This is called as the supersonic fly by. And the clouds that we saw on the plane were basically the condensation. So, supersonic flow is more than around 1.2 Mach number up to around 4 Mach number. And the two examples of aircraft which can fly supersonic are our own HAL Tejas and the Boeing F-18 Super Hornet, which is the one that you saw in the fly past. Yes, the clouds condensation can happen even before you break the sonic barrier. Basically, the condensation takes place only when the pressure drops. But if you notice here, there is an angle at which the clouds are attached. So, that is an indication of the fact that it has gone supersonic. Even if you look at a subsonic aircraft, you can see condensation sometimes depending on the weather conditions. So, the conditions and pressure is not an indication of sonic or supersonic flow. But the condensation pattern of this type which shows a special, this is actually a Mach cone as I will talk about in the next few slides. So, that becomes visible because of condensation. No, no, no, no, no. Condensation occurs only if the atmospheric conditions are such that there are large concentration of water molecules present. Let us say just after rain. This is a very good season to see condensation, the rainy season. So, it is not that every time it will happen. This is, this is you know, natural flow visualization. It happens when there are conditions that allow it to happen. It is not going to happen always. So, do not assume that every time an aircraft goes supersonic, there will be some cloud like this. No, you can have, I will show you some videos of flight of supersonic aircraft without condensation visible. Let us go to hypersonic flow. This is a hypersonic air breathing vehicle launched from an aircraft. Of course, you cannot measure the velocity because you do not know whether it is hypersonic or not, but you have to believe. So, the rocket motor is fired after it is released from the body. So, we are also developing a vehicle like this called as the HSTDV. DRDL in Hyderabad is working on that project and there is quite substantial progress in that our department is very actively involved in the project through some studies which my colleagues are doing. So, an example is X-43 scramjet which is a supersonic ramjet. We will have one lecture especially on engines and the other example is the Boeing X-51 Wave Rider which is an example of a hypersonic aircraft. Let us go to hypervelocity flow. This kind of a flow is encountered only by missiles and spacecraft. So, this is a video of a rocket which is launching a satellite in space. Only these kind of vehicles are able to be subjected to hypervelocity flow. For example, the Pathfinder and the ULA Delta both of which Pathfinder is basically a missile and ULA Delta 4 is a rocket used to launch satellites. So, that is why now there is nothing like hyper supervelocity flow beyond Mach number etcetera. There is no demarcation beyond that. Normally any Mach number beyond 11, 12 we say it is super is hypervelocity flow. Yes. Sir, sonic boom also exists in this? Sonic boom will exist everywhere and anytime you exceed sonic velocity. But the boom may not be heard because it may be dissipated or because of weather conditions because of the altitude. So, the sonic boom is a phenomena which is I will come to that in the next few slides. Let me just go there then you will be able to understand it but little bit better. So, scramjets operate at around Mach number 10. This is the highest speed aircraft known to human beings. Missiles operate between Mach number 3 to 5 normally and then you have these rockets which go to much higher Mach numbers. The space shuttle for example encounters Mach numbers of 20 during its flight. Then there is something called as Mach waves. What are Mach waves? As you can see Mach waves are essentially locus of the intersection of the sonic waves released by an aircraft as it proceeds. Now since the aircraft is flying higher than speed of sound that is why these the sonic waves the sonic waves are behind the aircraft and they coalesce together and this particular the angle that is created by the intersection of these is called as a Mach wave. So, this happens only when the velocity is more than the velocity of sound and the repercussion of this is they create a sudden change in the density and temperature and also the load or the stress which is acting on the body. So, as the velocity of the shock wave increases this Mach waves become at a steeper angle and their amplitude also increases. So, now let us look at formation of shock waves. This is a picture which shows you that when the velocity is more than velocity of sound when V is more than A or in this case it is called as V A. So, as I showed you in the previous video the locus of these particular lines. So, the wave fronts are lagging behind the source in a conical region and the edge of the cone is called as a shock wave. So, this is the answer to your question. The shock wave basically is the edge of the cone which forms a wave front and this particular angle of this shock wave is directly a function of the speed of the object. So, as we will see now. So, this is a stationary sound wave at any point of time there is a sound source and the center and at p equal to 1 unit you have 1 circle, 2 units, 3 units, 4 units you have these concentric circles. If the source starts moving at a speed that is lower than the speed of sound then you will have still concentric circles but you will find that the gap between them is more on the back and less in the front because the object is also now moving. Okay. So, what will happen is because there is a compression in the front the frequency at which sound emanates is going to change and on the back because there is an expansion the frequency this is called as Doppler effect and this particular effect is used. When the body moves at a speed more than the speed of sound then this is what happens. So, wave crests are going to overlap and you have a large amplitude shock wave. So, the red lines are basically almost tangential here it is parallel to a tangent for improved clarity but basically the line that is tangential to all these blue lines is the shock wave. Okay. There are 3 or 4 types of shock waves. The first one is a normal shock wave. This is like a front which moves. This particular kind of shock wave occurs in front of blunt bodies at the in the central region. The next one is an oblique shock wave. This happens mostly on bodies which are having a very sharp point. So, from the point at an angle there will be the shock waves and this angle beta will depend upon the flow mark number. You also have curved shock waves. So, this is an example of sonic boom. The sound which you hear is sonic boom. So, why are you hearing a sound? And also remember if you see the sound is coming after the plane has gone. It is not overhead. The plane is ahead of you and then the sound comes to you. That means the plane is somewhere there. It has crossed me and then the sound is coming to me. Now, for you it is only a sound right now. But there are many instances in which this particular pressure wave can break the windows, window glasses. There are examples at when military aircraft are practicing near the air bases. There are many, many situations in which the people nearby complain breakage of window panes, shattering of window panes. That is because of the sonic boom. And if this is happening above your house routinely every day, then you will start getting serious complaint from it. So, let us look at sonic boom. In this particular photograph, we actually see three different mark cones. The one which is just behind the canopy. Then we have one which is little bit which is on the tip of the wing and then one on the tail. So, it is a loud noise and it happens because of the constructive interference or the cohesion of the waves. We will see it and essentially it is a pressure difference which comes down. So, if you notice if there is a plane flying, there will be one shock wave from the nose and one from the rear portion. They both are going to hit the ground if you are at a sufficiently low height. If you are at a very high altitude, then the shock, the sonic boom may be attenuated. It may not reach or the pressure may fall because of the losses in the atmosphere. But if you fly supersonic at say 100 meters from the ground, then there is a very good chance that the bow wave and the tail wave are going to hit the ground and create this end shape pattern which is the sonic boom. So, as the aircraft flies over a terrain at low altitude at supersonic speeds, you have this horseshoe type area of influence on the ground. So, this is a plane at supersonic speeds. You have a conical pressure wave front which is the mark cone and that conical front is hitting the ground and moving along. So, this creates a parabolic boom carpet. So, any and everything that is on that on the ground along that horseshoe type ground interference pattern, they are going to be affected by the sonic boom. So, now the Mach angle or the angle at which the shock wave is inclined at a particular speed is a function of the speed. So, you can see very straightforward relationship exists between this Mach angle mu and the velocity v and sonic speed a. So, basically sin of mu is going to be a by v and therefore, sin mu is 1 by m. So, mu is sin inverse 1 by m. So, as Mach number m increases the value of mu will reduce. So, by looking at the shock by looking at the by looking at the Mach or by the numerical value of the Mach angle, you can actually figure out at what Mach number the aircraft is flying. It gives you a kind of a visual indication of the speed. Now, let us do little bit of calculations regarding the shock. First of all, we must look at and understand what is meant by an isentropic flow. It is a flow which is reversible and we assume that there is no entropy loss. It is an assumption. It is very difficult to get in real life any flow where there is no loss in entropy. Entropy is a disorder which continuously increases. But for a theoretical calculation purposes or ignoring the loss in the change in the entropy, you can assume the flow to be isentropic. So, if the flow is isentropic, the benefit for us mathematically is that the changes in the variables are small and gradual. They are small and gradual which means the functions are continuous and differentiable. That is how it helps us. So, the creation of sound waves can be assumed to be an isentropic process. It happens slowly and the changes in the variables are very small. So, for example, if you take if you take a simple nozzle where you have a chamber which contains a fluid, let us say air at pressure Pc, temperature Tc and density rho c, it proceeds, it encounters. There is one section where the condition is subsonic. You have pressure P, T and rho and there is a area A, area cross section A. And then as it goes and comes back, we have a full recovery. If we assume it, this is an assumption, then the flow is isentropic. So, through a nozzle, the flow can be considered to be isentropic. So, if it is a process isentropic, then in the TS diagram, it is a straight line. There is no change in S because no heat is added to flow and there is also no energy transmission because of friction. This is only an assumption. In real life, it is very difficult to get such flows. Just a detail. So, the idea is we want to define something called as total pressure. So, in this particular example, you see a tube in which there is a fluid flowing at some flow rate, velocity is V and when you connect the wall of this particular tube to pressure line, there is some pressure acting because of the atmosphere, sorry, at the at the inner surface at the border. That pressure is the static pressure. So, you can see it pushes the fluid column to some value. But when you insert a tube at the center or down below, then the pressure is higher. That additional pressure is the dynamic pressure which is there only because of the fluid flow. It is actually half rho V square. So, the total pressure would be the static pressure which is there even in the at the at the edge. That means where you assume there is no flow at all plus the pressure because of the flow.  And the entire half MV square of the particle, the entire kinetic energy particle will be utilized just to create pressure. There will be no losses, no friction, no heating. If we assume it, I keep on repeating. If we assume it, then we have total pressure. In reality, the total pressure that we get is less because of losses. So, this is possible only in the isentropic process. So, therefore, P total will be P static plus P dynamic. Another example, you have on top of fluid. And then if you apply Bernoulli's at A and B, where A is just before in a cylinder, in a container, there is some pressure A and B is just inside the pipe outside. And then you put a pressure measuring device which is measuring the pressure. You will find that at B, the pressure is P naught inside the pressure is P and the velocity is V. So, the P naught is going to be the pressure P which is the static pressure plus half rho V square depending on the velocity at which the fluid is coming out. So, there P is static pressure and rho V square by 2 is dynamic pressure. So, with this you can get the value of V. So, this is a very simple way of measuring velocity using the incompressible Bernoulli's equation by measuring the pressure difference at the two places. This principle is used to measure the velocity. Similarly, we have a concept of total temperature. Again, it will be static temperature but here we have to bring in the effect of Mach number. So, we use thermocouples to measure the total temperature. So, it is a sum of the static temperature and the dynamic temperature again in the same manner as the pressure. So, how do you get the relationship? It can be shown. I do not want to prove it and I do not want you to also worry about it. We are not into fluid mechanic calculation. We are into introduction to flight. So, our purpose is to get a general overview of how things are going to be happening. So, right now it is sufficient for you to assume that the total temperature T is going to be static temperature plus depending on the specific heat and the Mach number. So, this will tell you that as the Mach number increases, there is going to be a problem. Is there an issue? It should. Yes, I am glad that you observed it. The minus 1 should not be there. Thanks for pointing it out. So, from this you can get P by P naught as a ratio of T's with gamma upon gamma minus 1. So, that is all. That is the total pressure. We come to an end on today's class.


Near some weekend, River's governor says he will start campaigning for his preferred presidential candidate in January. Now, since losing out in the presidential primaries of the People's Democratic Party, there has been a crisis in the party over calls for Iotcha Aiu to step down from his position as national chairman of the party amid the crisis, the integrity group inclusive of five PDP governors, Wike, Shea Makide of Oyo State, Samuel Orton of Benwe, Okesey, Piazu, Ovapia, and Ifan Yuguayu of Inugu were formed. All five governors have exempted themselves from the campaign of Atiku Abu Berger, the presidential candidate of the PDP for the 2023 elections. People whom do we vote for? So all of you who have been in suspense, who have been saying all kinds of things, are dissing me words, generally what has come, generally what has come. Not only will I tell them where they will vote, I will move from state to state and why they should vote for the people that they should vote for. Nothing will happen. So all of you appearing on television, abusing me, don't waste your saliva again, generally what has come, generally what has come.  All those of you who are telling Nigerians, you used to have 40 shoes, you have to have 50 wristwatches, time has come to convey those shoes and wristwatches to vote. Not because, not because, it's not to adhere on the podium and raise your shoe high and raise your wristwatch high, time has come to convert you to vote.  If they vote for PDP, they vote for corruption. Wait, all the force will reply. But then Nigerians, with this thing you said, have fun. What do you see standing now? Is it the same PDP or any?