A young engineer is designing a 1500 watt hair dryer and hopes to sell it on the open market. He or she calculates, using science and a lot of testing, that the outlet conditions for optimum hair drying occur with a temperature and velocity of 50 degrees Celsius in 20 meters per second respectively. Any hotter or faster than that, despite doing a better job of drying, might cause the customer to burn themselves or their hair, which the legal department suggests is a bad thing. The engineer assumes that under normal conditions, the ambient air will be about 22 degrees Celsius and 100 kPa. Because of the stagnant condition of the ambient air and the large size of the intake, the inlet velocity will be negligibly small. Additionally, the body of the hair dryer will be well insulated so as to avoid the whole burning the customer thing. Determine first the mass flow rate of the air through the device, that's how much mass flow rate this can process while consuming 1500 watts, and accomplishing the change in kinetic energy and enthalpy required. Secondly, determine the volumetric flow rate at the outlet of the device, and thirdly, the diameter of the outlet which would yield optimum hair drying conditions. So the first thing I'm going to do is draw an approximate diagram and indicate what I know. So I know conditions at the inlet of the device, and I know conditions at the outlet of the device. I'm going to treat the internal mechanisms as two separate steady flow devices. First a fan, which I'm assuming handles all the change in kinetic energy, and then an electric resistance heater. I'm assuming the fan handles all the change in kinetic energy, and the electric resistance heater handles all the change in enthalpy. Now, of course, in reality it's a little bit more complicated than that. They aren't going to be that exclusive of one another, but this is sort of like when you're analyzing kinematic motion and you figure out the path of a projectile by considering the x-axis and the y-axis individually. It's not as though it actually traverses only the x-axis and then the y-axis, but breaking it apart into pieces allows you to analyze one piece at a time and bring them together. In the same way, if we assume all the change in kinetic energy happens in the fan and all the change in enthalpy happens in the heater, then we end up at the same result. By treating the work input to the fan as going directly into kinetic energy, we are also accounting for any pressure increases that are actually converted back into kinetic energy inside of a nozzle, say, at the end of the shape of the hairdryer. If we draw a control volume around the entire thing, it eventually becomes kinetic energy regardless of which individual conversions happen within the internal mechanisms. Since we're assuming 100% operating efficiency, essentially, it doesn't matter how many conversions occur. Does that make sense? Excellent. So since I have two study flow devices here, I am going to indicate a state point between them, and that gives me the ability to analyze the fan and the heater individually if I want, but I can also draw a control volume around the entire body. So I have electrical power input to the fan mechanism, and I have electrical power input to the heater. Now, I know what you're thinking. You're thinking, but John, surely the heater should be a heat transfer in, right? Well, it depends on how you draw your control volume. Since I'm drawing my control volume around the body, that means that the energy is crossing my boundary in the form of electrical work. If I drew an energy balance around the heating mechanism itself, then it's entering my control volume in the form of heat transfer. Since both of them are energy rate inputs in my energy balance, it doesn't really matter whether I call it a W or a Q, because it appears as the same term anyway. Then I know the power input of the fan and the power input of the heater have to sum together to 1500 watts. So I'm assuming the velocity at state one is pretty close to zero, from the words, negligibly small. Now, of course, the velocity at the inlet can't actually be zero, or else there would be no mass flow rate. What we're saying here is that the velocity is so close to zero that when we calculate the kinetic energy at the inlet, we're saying a small number squared relative to the outlet velocity squared is basically zero. Another way to think about it is that the kinetic energy at the inlet actually still came from the fan. The fan is pulling the air, so if you expand your control volume out far enough, you're actually grabbing stagnant air. So the change in kinetic energy happens as a result of the fan anyway. Next, we are assuming the temperature at the inlet is about ambient conditions, which we were told were 22 degrees Celsius, and that the pressure is about 100 kilopascals. At the outlet, we have a velocity and a temperature, and then we can assume the pressure at the outlet is still about ambient conditions. Then at state two, the temperature at state two is going to be assumed to be essentially T1, because we're assuming only kinetic energy is increased across the fan. We're assuming all the enthalpy increase happens across the heating element. Similarly, we're saying V2 is approximately equal to V3. Remember, state two doesn't really exist. It's the intersection of the Y and X components of my projectile motion. I have the option of setting up a mass balance and an energy balance around a control volume on just the fan, around a control volume on just the heater, or around everything all at once. In the interest of really exploring the example problem to the best of our ability, why don't we try it both ways? So first we'll analyze the fan and the heater together, and then we'll analyze them individually. So I will call control volume control volume one, just the fan control volume two, just the heater. And maybe I'll color code that to make it a little bit easier to see. So blue control volume is control volume one, red control volume is control volume two, and then green maybe. Green control volume is the whole kit and caboodle. For those mass and energy balances, we're going to be setting up a simplification that looks pretty consistent. So let's just talk through our assumptions one time. First of all, we are assuming steady-state operation. The fan has been running long enough to reach steady-state. It's not as though we are analyzing the hairdryer being turned on initially. We're saying it's turned on. It has been running long enough that it has reached steady-state conditions. I could add to that that it's an open system, even though that's unnecessary, because that's not really a simplification we're making. The universe is open systems that we simplify in certain circumstances to closed or isolated systems. Next, I'll assume that the air is ideal. So I can use ideal gas properties for the air. Then I can explicitly say change in kinetic energy across control volume two is zero, and the change in enthalpy across control volume one is zero. That's what allows me to write these properties at state point two. That's not a very good-looking CV. Let me try that again. I'm going to assume the changes in potential energy are zero regardless of how you look at it. And then I will also explicitly assume that there is no power output and that the device is adiabatic. The assumption of adiabatic comes from the phrase well insulated. I was told that the hairdryer was well insulated, which means I'm neglecting any heat transfer through the body of the hairdryer. So with that set of assumptions in place, I can start my control volume analyses. So I will set up three parallel mass balances and energy balances, one on control volume one, one on control volume two, one on control volume three. Beginning with control volume three, for no reason in particular other than that's what I had said first. I have a mass balance and an energy balance. The mass balance starts with change in mass of control volume three is equal to the mass entering minus the mass exiting. The energy balance similarly begins with delta E on control volume three is equal to energy entering minus energy exiting. Because I have steady state operation, it's going to be most convenient for me to divide everything by dt or rather derivate everything with respect to time at which point I have dm dt is equal to m dot in minus m dot out. dm dt is zero because it's steady state and nothing can change with respect to time, including the mass of the control volume. Similarly on the energy balance, I will divide everything by dt, which again is really just derivating with respect to time at which point I have dedt, which is zero. Again, that's the energy of the control volume and that's zero because of assumption number one is equal to e dot in minus e dot out. Therefore the mass flow rate entering has to leave. I only have one inlet it's state one. I only have one outlet it's state three. So I can say m dot one has to be equal m dot three which I can just call m dot for simplicity's sake. Then on the energy balance, I can write e dot in is equal to e dot out. I can clear a little bit more space for myself by scooching over the mass balance. It is the technical term scooch and then I'm going to write e dot in as its full list of possibilities, which is e dot in plus work dot in plus the sum in of m dot theta because it's an open system. Any dot out could be q dot out could be work dot out and it could be the sum out of m dot theta because I have adiabatic operation. I can neglect the heat transfers because there's no opportunity for work output. I can neglect work out. That leaves me with power input power input plus the sum of all the mass full rates entering. There's just one eight state one times theta one. Remember that theta consists of enthalpy plus kinetic energy plus potential energy on the exit side. I have the sum of all the mass full rates exiting of which there is one eight state point three times theta three theta is enthalpy plus specific kinetic energy plus specific potential energy. Then I neglect changes in potential energy because of assumption number four and I'm going to factor out the mass full rates by bringing this term over to the left, excuse me, over to the right at which point I have the mass flow rate through the hairdryer multiplied by h3 minus h1 plus specific kinetic energy three minus specific kinetic energy one. Therefore the mass flow rate through the fan, excuse me, through the hairdryer can be written as the power input divided by h3 minus h1 plus specific kinetic energy three. Remember specific kinetic energy is one half times velocity squared. So I can write that as v3 squared over two minus v1 squared over two. I can figure out delta H because I know the properties of state one and the properties of the state three. I can figure out the change in specific kinetic energy because I know the velocity of state three and the velocity of state one. Velocity of state one by the way is just zero and the power input was given 1500 watts. Therefore if I take 1500 watts divided by the specific change in enthalpy plus the velocity at the exit which was 20 meters per second squared divided by two and account for the units I will eventually get a mass flow rate. That's the result of the mass balance and energy balance on control volume number three. Since I'm going nowhere near control volume order let's consider control on two next. Control volume two was red and on control volume two I'm going to start with a mass balance and an energy balance. The first couple of steps are going to be identical from control volume three so I'm going to duplicate those over and in fact while I'm at it I will duplicate those over to control volume one as well. One was blue and I can go through and change all the subscripts. This is one, this is two, that was this is TOO not this is TWO. This is one also. This one, however, is two, TWO and this one is two. So as a result of the mass balance on control volume two I can say that the mass flow rate entering control volume two which is m dot two has to equal the mass flow rate at the exit which is m dot three. Similarly I will just abbreviate that as m dot. The energy balance on control volume two could consist of the same terms because it's still an open system. So I will duplicate those over as well. The only difference being that when I'm considering just the heating element I don't have to account for any changes in kinetic energy. Furthermore to clarify a little bit I will call this power input term the power into the heater. So the change in kinetic energy across the heating element is zero and therefore the power into the heating element itself is going to be m dot three times h three minus m dot two times h two because it's the same mass flow rate. I can factor out the mass flow rate and write that as m dot times h three minus h two. Two control volumes down. One more to go. The mass balance on control volume one has one inlet. It is state point one. It has one outlet. It is state point two. Therefore I can write m dot one is equal to m dot two. It's the same mass flow rate which I can abbreviate m dot. For the energy balance on control volume one I can write that in much the same way. Except this time I don't have any changes in enthalpy because I'm assuming all of that happens in the heater. Furthermore I will call this power input the power to the fan and then I have power to the fan. It is equal to m dot two k e two minus m dot one k e one which is just m dot times k e two minus k e one which is v two squared over two minus v one squared over two. And just like on control volume three the velocity of state one is zero. So I can simplify this down to just m dot times v two squared over two. So I have a power input to my heater. Of the mass flow rate through the heater times the delta h. And I have the power input to the fan as the mass flow rate through the fan times v two squared over two. And then because I know that both of those power terms have to come from the electrical socket they must sum together to 1500 watts. We are assuming perfect efficiency and that power factor doesn't exist. So I could combine these together and write this as 1500 watts is equal to the power input to the fan plus the power input to the heater. And then make the substitutions power input to the fan was m dot times v two squared over two. Power input to the heater was m dot times h three minus h two. I could simplify this by factoring out the mass flow rate at which point I would have v two squared over two plus h three minus h two. And then if I wanted to simplify it all the way down to parameters that I was given directly I could recognize that v two is the same as v three and write this as v three squared over two and that h two is equal to h one. Therefore this would be h three minus h one. And look we have the same equation if I solve this for the mass flow rate I would have mass flow rate times excuse me mass flow rate equal to 1500 watts divided by v three squared over two plus h three minus h one. Look it's the same. How neat is that? I think it's pretty neat. So regardless of which method we use to approach the problem we end up at the same result. And I think that we have effectively stalled as much as possible. Now we actually have to start doing math. For that I will jump on to a new page. And then just for simplicity sake I will copy this equation over. So on page two I can actually get to calculating things. The first thing I want to find is the mass flow rate. For that I'm going to have to actually evaluate a delta h. I know v three. I know the power input. I know v one is zero. So all I have to do is evaluate delta h. And I am home free to calculate the mass flow rate. For my evaluation of delta h remember that I have three options. The first option is to look up the h's in my property tables and subtract them directly. The second option would be to determine how the specific heat capacity of air changes as a function of temperature and evaluate it by using the definition for cp which is dh dt for ideal gases. Remember that when we're talking about changes in enthalpy of an ideal gas it is cp dt because that's defined with respect to enthalpy. It has nothing to do with the pressure being constant or not constant. H goes to p, u goes with v. The udt is cv. Harry Potter ultraviolet. If I knew how cp varied as a function of temperature for air I could evaluate that integral and I could make it even easier by assuming it didn't change. In that case when I write dh is equal to cp dt and I integrate both sides and I can delta h on the left. If I assume cp is constant it comes out of the integral then I'm left with cp times delta t. That's even easier. So option one, look up h's and subtract them. Option two, I try to be a little bit organized about this. Option two, I guess that's actually h3 not h2. Option two would be to look up cp as a function of t and integrate option three is to assume the specific heat capacity doesn't change at which point it comes out of the integral. So those are the options that I could do. The real question is what I should do. Option one would yield the best answer under these circumstances. Option two would yield a pretty good answer. Option three would yield a worse answer. But I recognize that I have an ideal gas. I'm making a lot of simplifications for this problem. Like for example assuming that there's no heat loss and that all the energy conversion happens perfectly. Those simplifications end up with uncertainty in our answer that is much, much bigger than the difference between any of these options. As a result I might as well use the fastest one which is option three. But in the interest of character building and since we have effectively infinite time on the internet let's do all three shall we? Yeah I think that sounds like fun. So for option one I want to look up h1 and h3 using my property tables. For that I recognize that I actually have ideal gas properties of air on table a22. So I will jump over to table a22 and I can look up the enthalpy for a given temperature. Remember that for ideal gases u and h are only functions of temperature. So h1 will be the enthalpy of air at T1 and T1 was 22 degrees Celsius. 22 degrees Celsius plus 273.15 is going to be 295.15. You can verify that with a calculator just because I don't really trust my mental math at the moment. Yep 295.15. And in my ideal gas property tables I see that I don't have 295.15. I have 295. Now because I don't have an exact value the best thing to do would be to interpolate. Now 295.15 is like close enough to 295 to probably be okay with using 295. But you know I think in the interest of character building we should actually evaluate that interpolation. So what I'm going to do is take 295.15 minus 295 I'm going to divide that by 300 minus 295 and that's equal to the enthalpy at 295.15 which is what we're looking for minus the enthalpy at 295 which is 295.17 divided by the enthalpy at 300 which is 300.19 minus the enthalpy at 295 which is 295.17. And we're looking for x and we get 295.321. So h1 is about 295.321. We can repeat the same procedure for the enthalpy at t3. That was 50 degrees Celsius if I'm not mistaken. Yep 50. So we want 50 degrees Celsius. 50 plus 273.15 is like 323.15 I think. But let's double check that with the calculator 50 plus 273.15. Hey look at that. Surprising everyone the mental math was correct. So we find 323.15 surely we have a direct row for that. Oh man we don't. Oh no I guess we have to interpolate again. Well luckily for us this is a good opportunity for character building. So 323 that doesn't start with a two. 323.15 minus 320 divided by 325 minus 320 is equal to the thing that we're looking for. Nope that's not an equals command calculator. Keep up. The thing that we're looking for minus the enthalpy at 320 which was 320.29 divided by the enthalpy at 325 which was 325.31 minus the enthalpy at 320 which was 320.29. We're looking for x and we get 323.45 so 323.453. Let's use all those decimals just to be as certain as we possibly can be. So with h1 and h3 we can subtract the two if my calculator cooperates 323.453 minus 295.321 and we get 28.132. So our delta h using option one came out to be 28.132. For option two we are going to have to try to figure out a correlation between cp and temperature for ideal air. For that I can look at table A21. So table A21 gives me lines of best fit for the specific heat capacity divided by the molar gas constant for a variety of gases as a function of temperature. So I would have to solve for the molar cp by multiplying by the universal gas constant and then evaluating that integral. That seems like fun. So assuming that I remember to go in and speed that up you guys can see that I just copied over the constants these coefficients for air. Remember that these are not actually the constants the value given in the table is beta times 10 to the third so in order to write beta in our equation we actually have to write 1.337 times 10 to the negative third. Likewise for gamma instead of writing 3.294 we write 3.294 times 10 to the negative sixth. So with this fourth order polynomial I get an approximate function for cp of air as a function of temperature. We can integrate that in order to plug that into our delta H. But for that integral I would yield the molar specific heat capacity which means that I would get the molar specific enthalpy. So in order to actually write the mass specific heat capacity I have to take the molar specific heat capacity and divide it by the molar mass of air which means that I'm actually going to be taking the universal gas constant 8.3 and 4 divided by the molar mass for air which I can get from table A1. On table A1 I see that it's 28.97 and then I'm multiplying that by this function to get the mass specific heat capacity. So when I do that integral I can bring out the molar specific gas constant and the mass constant for air and I will get out a delta H term. Excited? I'm excited let's do some calculus and by we I of course mean let's make my calculator do some calculus for us. So if I pop up my calculator and I write out front I have come on calculator parentheses you can do it out front I have 8.314 kilojoules per kilogram kelvin excuse me kilojoules per kilo mole kelvin divided by 28.97 kilograms per kilo mole which will yield a result in kilojoules per kilogram kelvin and then I'm multiplying that by let's grab an integral we're going to integrate this lovely function 3.653 plus the quantity 1.337 times 10 to the negative third e negative 3 negative 3 much more better times temperature which is I'm going to call x for now x there we go much more better plus 3.294 3.294 e negative sign not minus times x squared plus negative 1.913 oh man did I remember the right negative let's jump out to that first term did I write negative or did I write I didn't write anything man okay negative sign not minus sign much more better look at all those negatives then over here I have negative 1.913 times 10 to the negative ninth negative sign not minus sign 9 times x carat 3 beautiful plus 0.2763 e to the negative sign 12 time x to the fourth that's my entire function close front see we are integrating with respect to x and we are integrating from 22 degrees celsius which remember that when we looked at these correlations what we are talking about is temperatures in kelvin so even though it doesn't really matter when we're talking about linear temperature differences it might matter in the exponentials here so I will write that is 22 plus 273.15 and then 50 plus 273.15 and we get nothing cool did I integrate with respect to 22 how did that happen come on calculator I don't want to integrate with respect to 22 I want to integrate with respect to x much more better okay calculator if you would be so kind we get 28.1295 and even the calculator thinks that we have questionable accuracy awesome so delta h of 28.1295 kilojoules per kilogram now option two is a lot of work it's actually more work than option one and it's less accurate because it's using a line of best fit I don't think that option two is really ever useful when we're talking about ideal gas properties of air if we actually want to be accurate we will use the actual enthalpies if we are approximating we will assume the specific heat capacity is constant option two is trying to be unnecessarily precise with an approximate method and I don't think it's worth our time to even try so on an exam with me at least I will never ask you to compute a delta h or a delta u using option two but if you're curious about how that would work now we've done it okay now for option three we're assuming cp is constant and we are going to look up the cp value for air on table a 22 no on table a 20 for air at a halfway point between 22 and 50 I see halfway between 22 and 50 is going to be like 37 here let's let the calculator do the math we get 36 that's more like it 36 plus 273.15 the halfway point between 20 and 50 is going to be 309.15 therefore we should be using a cp value of air at 309.15 no you could probably make an argument for the fact that we're approximating anyway we might as well just grab 300 instead of 309.15 but unnecessary precision is the name of the game at the moment I can evaluate an interpolation here by writing 309.15 minus 300 divided by 350 minus 300 is equal to the thing that we're looking for minus the value at 300 which is 1.005 divided by the value at 350 which is 1.008 minus the value of 300 which is 1.005 and we get we we get 1.00555 0.00555 and again this is more accurate than I would expect you to be on an exam if you were taking one of my exams it would be totally fine to assume the cp of air is constant at 300 because it's the closest row that you have since you're approximating anyway might as well just approximate there's no point in being that precise about an approximate method but you know we're really exploring all of our options here therefore delta h would be that cp value that we just calculated 1.00555 kilojoules per kilogram kelvin multiplied by our temperature change between states 3 and 1 which is going to be 50 minus 22 degrees celsius cancels kelvin here because the temperature change in degrees celsius is the same as the temperature change in kelvin I mean you could think of it like we can add 273.15 to both of these and we'll still get 38 or whatever I mean since we're here and we have infinite time we might as well just try that 50 minus 22 is 28 28 not 38 well done on the mental math john this is why we have a calculator and then 50 plus 273.15 minus 22 plus 273.15 see we still get 28 that's why degrees celsius and kelvin cancel when they are a temperature difference so 1.00555 times 28 value gives us 28.1554 1 no 28.1554 so being real extra accurate yielded a delta h of 28.132 being very approximate gives us 28.155 a difference of 200 ish that's well less than the amount of error that we introduced by other approximations that we made throughout our solution again things like the assumption that we have perfect energy conversion that we have no losses whatsoever that there is no heat transfer out through the nacelle body of the hairdryer all of those are going to affect our answer way more than two hundredths of a kilojoule per kilogram which is why in these circumstances it would be downright encouraged to just use this value but you know sometimes worth looking stuff up in tables just to be extra certain as a result of having this number already we might as well just use it if you were doing this on an exam you could totally use this value or better yet you can actually just grab the cp value at 300 which is 1.005 and ignore that extra interpolation just for funsies here that produces a value of 28.14 so you could totally use 28.14 instead of 28.132 but you know what we have the number let's use the number now I'm plugging that into our mass flow rate calculation which I almost forgot we were doing it's been so long since we talked about it we can take 1500 watts and divide that by 28.132 plus the velocity at state three which was 20 meters per second yes 20 meters per second I'm going to square that and divide by two so I'm going to write 20 squared meter squared per second squared divided by two then I recognize that I need to add that two kilojoules per kilogram therefore I'm going to want to convert from meter squared per second squared to kilojoules per kilogram to do that I'm going to start with kilojoules and work backwards a kilojoule is a thousand joules a joule is a Newton times a meter and a Newton is a kilogram meter per second squared Newton cancels Newton joules cancels joules kilograms cancels nothing meters and meters cancel square meters second squared cancels second squared leaving me with kilojoules per kilogram so therefore if I take 28.132 plus 20 squared divided by 2000 I will get the denominator of this calculation generally speaking I am a proponent of doing arithmetic as few times as possible so I would probably continue to do the unit conversions after this resulting sum but just to make it a little bit easier to follow let's do it as two separate steps so I'm going to calculate just the denominator first 28.132 plus 20 squared 20 carat two divided by 2000 and we get 28.332 so we are taking 1500 watts divided by 28.332 kilojoules per kilogram and we are looking for an answer in kilograms per second because that's what part a is asking us for therefore we need to write a kilojoule is a thousand joules and that a watt is a joule per second joule cancels joules kilojoules cancels kilojoules watts cancels watts leaving me with kilograms per second so now I'm going to take in my calculator if it cooperates 1500 divided by 28.332 times 1000 and we get 0.053 look at that part a done done now part b asks for the volumetric flow rate at the outlet of the device for the volumetric flow rate we are going to involve the mass flow rate that we just calculated and a density term mass flow rate can be expressed as density times volumetric flow rate so because we're looking for volumetric flow rate we can take mass flow rate and divide it by density you could also think of that as taking mass flow rate times specific volume because specific volume and density are reciprocals of one another the density is going to come from our ideal gas law pv is equal to mrt remember this is the mass specific gas constant which is the universal gas constant divided by the molar mass so I can write density which is mass divided by volume is equal to pressure divided by gas constant times temperature and then in the interest of doing arithmetic as few times as possible I'm going to make all of these substitutions symbolically specific gas constant for air is equal to universal gas constant divided by the molar mass of air universal gas constant comes from the inside of the front cover of our textbook and is 8.314 kilojoules per kilo mole kelvin and the molar mass of air comes from table A1 which is 28.97 kilograms excuse me 28.97 kilograms per kilo mole so when I make this substitution for my volumetric flow rate I'm going to write this as that shiny new mass flow rate from part A divided by pressure times gas constant times temperature so I had what was that in 0.052944 you know just to be arbitrarily precise kilograms per second and then universal gas constant was 8.314 kilojoules per kilo mole kelvin and we're dividing that by molar mass which was 28.97 kilograms per kilo mole and then we are multiplying by temperature since we're talking about the volumetric flow rate at the outlet we're talking about the volumetric flow rate with the mass flow rate at the outlet and the density at the outlet which means that we're using the pressure at the outlet and the temperature at the outlet since the mass flow rate is the same everywhere it doesn't matter but it does matter for temperature and pressure the temperature at the outlet was 50 degrees celsius I'm pretty sure yeah and then the inlet temperature was 22 the outlet pressure and the inlet pressure are both 100 kilopascals so 50 plus 273.15 kelvin divided by 100 kilopascals now kilomoles cancels kilomoles kilograms cancels kilograms kelvin cancels kelvin or kilojoules and kilopascals to cancel I need to expand them a little bit a kilopascal can be expressed as a kilonewton per square meter and a kilodjoule can be expressed as a kilonewton times a meter kilonewton cancels kilonewtons kilodjoules cancels kilodjoules kilopascals cancels kilopascals I have cubic meters in the numerator I have seconds in the denominator which is a volumetric flow rate but remember the problem wants an answer in cfm which is cubic feet per minute so we have to convert from cubic meters into cubic feet and from seconds into minutes so first I can find the conversion for length one meter is 3.2 808 feet so I will write one meter 3.2 808 feet and then I will cube everything one cubed is one meters cubed cancels cubic meters and cubic meters and then I need the seconds to become minutes but there are 60 seconds in one minute seconds cancels seconds and then just to be consistent here I will write a cfm is a cubic foot per minute so that minute cancels minutes and cubic feet cancels cubic feet leaving me with cfm so zoom out a little bit here man that's going to be hard to see with a calculator okay well we can suffer through calculator if you would please turn on we have 0.052944 times 8.3 that's 8.314 multiplied by 50 plus 273.15 multiplied by 3.2 808 cubed multiplied by 60 and we are taking that entire numerator and dividing it by 2 8.97 multiplied by 100 multiplied by one cube which is one and I get 104.033 now where to write that I do a little bit of cleaning here scooch this up again technical term then I can write the volumetric flow rate at the outlet and write the volumetric flow rate at the outlet is 104.033 with part b done I can calculate part c for that I will go to a third sheet of paper part c wants to know what the diameter of the outlet should be so I have a velocity at the outlet I have a volumetric flow rate at the outlet I can use that information to calculate a cross-sectional area which if I have a circular outlet means I can calculate a diameter so my volumetric flow rate can be expressed as average velocity I can denote an average velocity as opposed to the velocity at any point if we were talking about a more representative velocity profile at the outlet it would be a little bit higher at the center and a little bit slower toward the edges but we're calling velocity here an average and then we are multiplying by cross-sectional area we can express the cross-sectional area of a circle as pi over four times diameter squared and then I can write that as velocity squared times pi times diameter squared divided by four I know the velocity at the exit it's 20 meters per second I know the volumetric flow rate at the exit it's 104.033 cubic meter excuse me cubic feet per second cubic feet per minute I know pi I know four so diameter is just going to be the square root of four times volumetric flow rate divided by velocity at the exit times pi so we could go back into our volumetric flow rate calculation and get rid of the conversion at the end to imperial I mean we could just knock off those two components at the end which were 3.2808 cubed n 60 or we could handle that unit conversion backwards or we can actually just substitute in the equation that we use to calculate volumetric flow rate in the first place inside of this calculation it doesn't really matter which method we use theoretically if I kept track of enough decimal places they should all be equivalent but just to be representative of the sort of work that someone might do if they had a limited amount of time on an exam and they had already calculated a volumetric flow rate in cfm let's do the unit conversions from cfm back to whatever it is we need to get an answer in inches so I have four I have 104.033 I was 104.033 John 3 3 and then with that I could put my calculator away for a moment and that was cubic feet per minute and I'm dividing by the velocity of the exit which was 20 meters per second I'm going to go double check that 20 meters per second and I'm going to divide by pi and then I'm going to perform whatever unit conversions I need so that when I take the square at the end I get inches out so in order to get inches out as the answer for diameter I need everything under the radical to be inches squared so I need to get cubic feet times seconds per minute times meters to become square inches so first of all I recognize that one minute is 60 seconds at which point minute cancels minute seconds cancel second next I represent one foot as being 12 inches and then I cube everything perhaps square everything is a little bit easier yeah because we have the conversion from meters to feet yeah let's do that square everything one square is one inches squared is what I want to get to square feet cancels two of the three feet in the cubic feet on the left and then I write one meter is 3.2808 feet which again comes from this conversion on the inside of the front cover and then meters cancels meters square feet and feet cancels cubic feet and I have square inches so when I take the square root of a quantity in square inches I will get out an answer in inches so calculator if you would be so kind I will write that as 4 times 104.033 times 12 squared all divided by 20 times 60 times one square inches is one times 3.2808 and then I take that entire quantity raised to the one half power and I get 3.9 let's double check that all of our numbers appear four appears 104.033 appears 12 squared appears 20 appears 60 appears 3.2808 appears awesome so for diameter at the outlet it should have 3.9 inches in diameter and that's everything we need to answer the question


Okay, it's actually not that strong. OH GOD IT'S GON- HELLO EVERYBODY AND WELCOME TO EMPIES IN THE UNDERGROUND WHERE TODAY There is a new whole ant species, the fire ants, and we're loading up medium because I've already tried to- Well, I've learned from you past mistakes that hard is always too hard and to never do that first time So we do medium this time So this is the first time we've had a new ant species since the leaf cutters And I cannot wait to see what this has in store for us. So here we are, oh look the queen's so small! Oh, that's so cute So we have missions actually so we got to collect 50 food. Now this was mainly for the games con Or games com. I always call it con, like convention, but it's not, it's com So we've got to get 50 food Let me just put all me and son get that food. So what's interesting about a Fire ants is that they can um Traverse water they're one of the only ant species that can and to do this they link their bodies together And something about fire ants and maybe ants in general But definitely fire ants is they're kind of coated in a substance. I don't know what it is actually They're water resistant So they make a ball or a bridge or whatever and they literally just float on the water It's just so crazy. You see I think that it's in the amazon where they are Um, they're probably all over the place Basically, but they they sort of move nests depending on the the flooding and stuff That's so crazy. I love that. That's so cool So we need to build a soldier chamber and we need to build a oh god Do I want to do I want to go that way?  Am I doing it wrong this whole time? Probably let's be there Uh, so let's go 40 40 Jesus. Well, at least we've got one Uh, we'll put him in there And another one and that should be Oh, I could do another one go on then. I how much are they to hatch the uh They're four for the hatch. So I do have enough for 812 So I should be good and then we'll put them also on that And what I want to do is just scavenge down here. We got a little bit there And I mean we can go up to the top. There's a lot of things to do there to get There's some what now question marks usually mean woodlouse. So Water drains. Oh my god. Okay. Um, right. So build a drop off food chamber Okay, you know The food chamber. Where do we want the food chamber? I kind of want it to be like this way Have some food tiles in here. However. We don't really have too many. Oh god.  That's right fire and sting. That's why they're called fire and sorry I forgot guys. Yeah fire ants are known for their incredibly painful stinger Um, this feels like you're on fire basically So there we go and now all we need to do is dig to the surface So we've done all the checklist and what is about to drain? What does what I mean? Lord knows We're about to find out. Um danger is what that means Oh my god, look at all the buggies. Oh, that's right. We can we can sort just uh Okay, so the water's draining now. What does it reveal? Not much, but I am wondering Oh Oh, there's big beetles. I don't know if I like those big beetles if I've got to be honest Do want to go up that way? That seems like a lot of death. That seems like a lot of death. Let's dig Let's dig out this way. Let's dig what these are. If these are wood louse, then we're all good If it's something killer We're screwed. Um, there's something big over there too, but this really seems to be my my safest bet is to go for whatever this is Let's find out. What is it survey says? Loads of free food brilliant. Okay Let's just uh build our food towels up a little bit. Oh, I can't wait to see these guys traverse the Out of the water. This is gonna be great. Okay. There's nothing outside Wait, where do they all go? And I guess you can go out here and kill this guy. I think he's probably worth food So I don't see why not may as well.   Yeah Stingies, yeah Beautiful is there another one out Yes, there's another one go grab that one get the free food Oh, there's workers in here Turn back You're too small. Oh, they have like a really strong initial hit So they're probably like weaker overall and bites and stuff But they're probably really decent an initial hit. I like that I like it a lot. So I don't know what this is. I don't know if I want to know what that is But I like the free food we just got out here So when this makes a flood it'll be interesting to see what happens So I'm not gonna dig it all the way out because I want to make a bridge. Oh look.  They've killed all of us We're all dead. Everybody.  We need we need to gain upon numbers a little bit build up the numbers Right now go now get your revenge Yes Initial hits strong strong are we enough this? Oh, no that no the toxic the toxic spot. Yeah, we got it. We got it. We got it. We got it. Yeah, they're all dead Look at all those How do we oh, I guess we can get over there, but then there's a lot of attacking things So this is where we get all our food. This is how we do it Okay, okay, so grab these as well. We need these Oh, this is cool. I can't wait to see the bridges. So we're getting some food. We're getting some food back That's right. Look at that though Look at that. Okay. Let's see if we can make some bridges. Oh god. No. What is that? I do not like the looks of that. Oh you're gonna do it Oh, they are Okay, they cost a lot and That's all they do. Will they stay there? Did they have enough? Oh, I like it, but I don't have enough so can you guys go back? Whoopsie daisies. Okay, right. Oh, well, we're gonna have to dig in a little bit and just see what this is I do have enough for a couple more though. I'm gonna be honest.  I'm not gonna get any more just yet in case This is quite bad Whatever these are Nah, they're fine. The workers are dead though. The ants must. Yes. Yes. The initial stings Beautiful. Okay. We lost one. That's fine There you have it. Oh, yes I want to get it. Look at this. Look at all this. This is gorgeous I want it all although I want to be a bit careful of whatever this is No, I don't I don't know if I want to go around food stores are full Okay, we can upgrade these I mean, I guess I can just dig out a little bit more and add Add a couple more food stores as well Right flood's gonna happen in a short period of time. So we don't need to worry about that more Yeah, I got two more. We'll get two more. I kind of you know what we should just get workers Workers are probably way better at making a bridge. No I wonder if you can go to this side Like all the way to the right if you have enough ants. I bet you can Uh, so what's the next thing we could go for? Okay, okay Let's try whatever this is. Hopefully this isn't an ant colony Oh, it's gonna take a while to dig there. I don't know if this is a really good idea. This might be a better one Uh, we'll find out though. We're gonna we're gonna put them in a little choke area here Okay, here we go. Ah, they're fine. Yeah, it's easy peasy beautiful choke point Yeah Look at them. Just die I think because once they attack a new enemy then they instantly do their their like initial attack again and Ho Ho Ho Jesus That was beautiful Uh, what are you doing? Uh, what what are you doing? Hello? Hello? Hello, you're coming into attack me. Oh dear. Oh god. What are you? Are you a bombardier beetle?  Oh god. It's got the boiling spray Oh, yeah, it is a bombardier beetle. That's what they can do They have like a certain sack inside them which like super heats liquid And after all that they gave me no food. Thank you. Thank you so much Um, okay. Well with that in mind, let's dig out this We're gonna have a lot more workers and I'm gonna put them the workers can form the bridges. Hopefully I think Otherwise I've just wasted a lot of food.  Oh god, we're gonna lose. Oh, no. Oh no Um, oh no No, I didn't realize it was gonna be that tough. Ah for god's sake I didn't realize it was gonna be that quick. Let go place it. Yes workers Put that down. We need more food. Yes Here we go. Here we go. This is how we do it. This is how we do it. Do not engage. Do not engage with the enemy Leave leave them to engage. Do you do attacking my queen?  Okay. This is all right. This is all right. The queen could take some hits. It's fine She's built for it Um We're gonna get there. We're gonna get there.  Oh, that's good. We made it brilliant Okay, now everything else go outside attack him kill them all I do want to go this way. There was a bombardier bill there, but look at all the prize Prizes But we could go this way I suppose Although it's gonna take a lot to get over there. I think uh, we have a lot of food a lot of food Um now you guys can attack. Okay, see if you can do this way and also you guys go that way too Because if you can both make this stuff that would be perfect if you can make the bridge There's no bombardier bill over here at the moment and there's a lot of prizes to be had So let's have a look. Come on I'll work. Yes. Yes. Yes Bridge complete escape to the promised land zero out of oh, I'm gonna go over this way. That's the promised land Okay, right. So it doesn't make much sense. I can't I don't think I can extend over here Well, you know, I'll give it a shot. I'll give it a shot. See if I can One there and one there. Okay, so the floods. Yeah, we're not gonna make it. We're not gonna make it Okay, everybody back everybody back. I mean you do wait and wait for those guys to go back. Oh, you do Okay, good. So they they programmed that in good. Otherwise, it wouldn't end up with a an island of stranded ends Um, with that being said I have a lot of attacking ants now I think I can probably go And get some of these dangerous beasties in here now. In fact, what about this? Do you think that's just two of the big Beetley beetles, do you think? Hmm I'm also wondering if when the flood goes out or whatever Um, because there's two bombardiers here if they're gonna come in and attack me And I think they probably will there's three actually So I've been the chances of that happening is really high Um, but we're gonna go in here And there's two big ones there too So we'll see we'll see what's this way now It would be great if I played this before because then I'd know exactly what was waiting what was lying in wait So now they can cross and the bombardier beetles are probably gonna make a beeline towards me We'll see. Hopefully they hopefully I can clear out whatever this is in time Please don't be too bad. Please don't be too bad. No, it's good. It's good. It's not even the green beetle, man Not even the green beetle Yes Surround him Oh, oh the problem the spray the spray is kind of deadly. Oh, they are making their way over to me I do see him. So once this is killed. Yeah, okay Uh, green beetles. Oh, sorry.  No get in you fools.  Don't don't let them build up Don't let these bombardiers build up, please Oh the sprays. Okay. That's too dead. Oh I like how this guy doesn't have any uh Like extra special sound effects for his a attack All right, there we go. We lost quite a few but uh, not too bad. Not too not too shabby not too shabby not too shabby I've got 95. I've got plenty of workers. In fact, I will put them all on working duty Anyway, just to get the eggs prepared for when these guys inevitably die because they will So we need to get ten ants over here to the promise land. I think that's what that means It doesn't say that that's the promise land, but I'm assuming that's what it means There's one almost dead. There you go.   They're almost dead and it's cost me almost everything I've got pretty much Um, so yep, there you go. Yep.  It's not too bad. It could actually be a lot worse Um, and you know what is I'm actually going to send out these little workers over here to just grab the little buggies Yeah, you don't attack. That's fine and you attack and you attack. Okay. Just grab these little guys. Yes Grab them That was a free 25. That was That was beautiful. Okay.  Oh Yeah, there's other things you can attack. Yeah, go get that. Oh always. Is it coming in? Yes, do the spray on one if you do the spray on one, that's perfect I don't mind doing that and then we completely surround them. Don't do it again Yeah another hundo beautiful Yes, grab all the free food Right, we need to upgrade our food tiles as well. I'm just realizing this I don't know if I can upgrade That'll do probably wasted a bit too much on that but that's okay. That's okay. We're doing good And my phone is buzzing like there's no tomorrow. I like that. I like that All right, and there's bomb dear Beatles over here now as well as the promise line We really need to get over there though and then they can go over this way because I don't know what this is This I don't know what that is either But this could all be food and if it is food perfect That's really gonna help me out. Oh, they're just mystery meats. Oh brilliant. Yes. Take it all take it all. Yes Um, really, I just need numbers. I don't know if I want to upgrade Um too much of the answer if I'm gonna be honest Because I need the numbers for the bridges to reach These guys unless these are the promise lines. They might be the promise lines And then I might get another thing afterwards Goodies. Oh look some beans. Oh brilliant Yes, go take it all.  Uh military ants Food stores are full. Well, not for much longer. Don't worry. Yeah. Look at that. Oh beautiful beautiful Beautiful. I'm sure they're way better at level two and stuff because that obviously their initial sting will do loads more damage um But Oh, is everything going and no the floods Okay, but how many bombardiers do I have three four? I got five bombardiers to beat. Okay, so next time Next time we're good We're really good. Um How many one two three there's two from over here if we can go out and meet them ahead of time That's way better for us because they're probably gonna all meet us around about the same point So we're gonna yeah, it looks like they probably would meet us around by the same point So if we just go and kill this guy before the other one like sort of joins up Yep, there we go Oh, there it is. There it is. There's death. There is death All right, they're all dead. Can we can we get up there? Oh, we can't we can't get up there.  Whoa Yay That's brilliant. Did they do their uh electric stuff? I'm sorry. They're the acidy butts Oh my god And because they killed each other it actually has food for me Oh, that is really good. I don't know what happened there. They obviously just didn't like each other. Oh, no, there's the 15 Okay, I'm trying to think right if I get on the land here with all my ants and then try and cross Before the flood that might be better for me. Yeah I'm gonna I'm gonna go up here And see if I can do that And then I'm gonna I'll see if the workers can build the other bridge So I'm gonna I'm gonna predict this so ants everybody come up here Don't get flooded. I mean technically You should survive, but I don't know if the games programmed that way. So we've only got that that and That left to excavate down here Oh, he would be worth a hundo he would be worth a hundo But I'm kind of okay. I want the big prize. I don't know where he's going.  Here's the flood. We're probably gonna lose this and I think Oh, we didn't perfect. Okay. Okay guys build a bridge build the bridge Build the bridge across Here we go. Yes. Yes Come on.  This is wonderful And now that we've done that we can make more Now that we know this works and I'm just gonna I'm just gonna dig this all out man Just gonna dig this all out then we might yeah Not looking too hot for the workers. They've got stuck out here. Unfortunately. Oh, there's one coming back. Okay. Okay. Okay. Okay Guys guys. Yeah. Yeah. I mean we killed a lot and maybe we'll maybe we'll get at some point But we need to kill all this stuff And we're running low. We are running low. Um Come on. Oh, no. No, there's loads of food here. There's loads of food. Come on. We can do this Oh, no, I got so much food that was I kind of worked and it kind of didn't So workers, I want you to go over here and go that way And then all of the the big Killer ants can make the second bridge And we've already got so much food over there man So much food and we should be good now because we just got a lot of food So all the workers are gonna make their own little bridge here.  That's good.   They haven't made it yet Come on guys. Where are you all? Here we go. There we go. There we go. There we go Right go in a huge killing spray and grab everything in fact no longer fight just grab food and go just grab food and go As quick as you can right we got 40 odd seconds I don't know what's gonna happen when the flood leaves because they're just gonna float down right?  Perfect. Yes We got 30 seconds. It's just we just don't have the numbers there We need more workers to just do the bridges That's what we need and then once we do that we'll be able to oh take it all So this isn't the promised land because we have made it there otherwise so Right, okay, and that should be enough To put everybody over there and extras. Yep. Yep Right the flood's gonna drop down the battle has begun. Yeah Oh did they just die? Oh, they don't know what to do He didn't know what to do. Oh, okay.  So you and stay out here Um workers. Oh wow we got 30 now sweet Right if only these guys attacked each other now that would be perfect And we need to grab all this food, but we can't it's just gonna go waste it. Yep. Yep. Let them waste Let them waste. Yes. Yes. They're spraying and they've all missed everything Yeah, now we're going now moving for the kill. Like hopefully they won't be able to do it again Yes Yes That was the tactic. That's how you do it. Just don't don't go to attack them. Just run around They'll spray kill maybe one or two and then you're golden. Okay. So while we're here Uh doing absolutely bugger all Uh, we may as well Dig out Um, how do we get in this one is oh this way we'll go here tomorrow's the day guys tomorrow The day they will rule the day Yes. Yes. Yes. Yes. Yes. Yes. Yes. I like I like the lord.    Oh, there he is. He's working it. He's working it. Right.   So i'm not too worried, but I will Put these guys on on that bridge duty So they'll build it first The uh the attacking force can go and just sweep the area. You know just do a good deep clean Perfect perfect I don't really need like there's nothing too big here that I need more Or like I don't know uh the higher levels.  No, there we go. Okay. Let's get over here We're gonna make it we're gonna make it. Yeah, we made it. We just made it. We just made it Oh god, there's too many of them. There's so many of them. Oh, I don't like it Hold hold hold here. Hold here guys. Well, maybe we can maybe we can just slowly whittle them down I think I think we can we just slowly whittle them down Yeah, the two and although we're losing we're losing food pretty pretty quick here although here we go We're doing good. We're doing good. Yes kill them. Yes Perfect now massacre all of them and get the food. Oh, yes. Okay.   You're good. There's one thing left over here But he's just a little grub we're getting a lot of food though.  You made it. Yes. Yes And we've lost a few And they've just instantly died and that that one that's like no and then he died. Oh, that's interesting. That's how that works Okay, okay everybody here Um, I think you can be shoved back onto nest duty because there's a lot of Things to take care of and we've got a whole crud ton of Bombardier beetles to take care of Right. Um, oh this is gonna be tricky. So how how are we gonna do this? How are we gonna do this because there's a crud ton of them?  We're gonna run past them. They're gonna do the volcanic Whatever and the food stores are full.  There's so many of them Yep, if you can get them turned around that's perfect. You just don't want them like facing everybody What do you do get out of here? This isn't your fight Okay, I think we're gonna win this we're gonna win this but my god That was tough. That was freaking tough. Right. We definitely need more numbers. We need more numbers Oh another one. Oh another three hundred. I'll take it How many how much do you need to get over here? You must need the biggest bridge in existence My god, they'll also release whatever this is because we need whatever food that can give us to Oh god, there's more of them.  Scavenging is going good. Okay. Here we go. Look at all the food over there What is some of the floor? I didn't even realize and they're coming out.  Oh, it's just those bugs. Oh, that's fine That's okay. I think I think we can probably take them out Okay, we're going for the we're going for the place we normally go to they're gonna take a while to get to our area And I don't think I've got anything to worry about at the moment with those guys So kill that bombardier Workers if you can go that way Yep. Bombardier killed Another bombardier. Oh no. No. No. No. Oh, that was nasty. That was nasty Right, okay, we're gonna any any red ants you can go that way Yeah, because they're gonna be quite deadly if they especially if they get to the queen It's gonna cost us a little bit more time to do this But we need to we really need to we're not gonna get those guys back But there should be enough in here just to kill these guys I think everything's assigned to attack except for the nests, which is fine because you don't really want the nest Ness wants to attack and that should be them done He's got just just a one dude there. Look at that. Look how many workers you need.   Okay. Do we kill a bombardier be like I think we did. Oh, no. He's he's he's over here. That's fine That's fine. Okay. Here we go.  We finally made it. We're getting so much food. Oh, thank god. Yes Oh, this feels good. I'm gonna need a lot of food stores A lot of food stores. Yeah, I'll upgrade those and oh thought that was a spider on my leg. Hello Yeah, that's it. They were taking care of completely there. We're gonna have so much food now All right, so I will add one two three four five six seven eight and then if we kind of grade That's a three. There should be a couple of threes coming out of this now Once they go oh, look at all that food. Look at all the food man That's crazy. We've got too much food. Oh my god. Yes. This is it. This is what I've been leading to I love it. Look at the little babies and then how many soldiers it takes in comparison. Yep I think that needs probably needs a little bit of balancing, but you know, it's all right. Oh, they are attacking each other Yeah, look at them. Ha ha Beautiful wait what more How many chambers do you want? Okay? There seems to be like a conga line of the bomber bills just attacking each other apparently Which I'm I'm all for I don't really mind about that Yes, go grab the food if you can I don't know if you can grab the food because it definitely doesn't look like you're grabbing the food If you go up here to defend that would be great. Oh, no, they've got it. They got it Right. Okay first Bombardier beat one two three four five six seven I'm not worried at this point. I've got so much food that you can just run in and die I'm like a general in world war one No, no thought for the poor poor lives that will be lost Because we've definitely well won that that cannot be said for the generals really I kind of want to make for this area now too I wonder how many ants we need in order to get to the other side then Ooh, that'll be I mean look at all this look at all this that just needs excavating out. Look at all that Get it Where is the promise land escaped to the promise land zero 10 ants if that is the promise land I think we can do it. I think we can get there It didn't tell me what it was. I just thought it was this bit over here. Oh, no, that is a oh my god Okay, yeah, we're gonna need a lot where we're gonna need a lot I didn't even realize it was all the way over there. I don't know if we could do that No, you will join this way. Yes. Look at them. Look at them go like a well oiled machine Although they're kind of being held up a little bit. That's a little bit of an issue. Yeah, come on. Come on guys You got this. Yes Lay siege to the babas beautiful Ah gorgeous gorgeous Oh Bombardier be it'll appeared. That's all right. That's all right. We can take care of that I kind of like seeing everything it doesn't look as appealing that looks way more appealing. That's so cool Now when you have the health bars, it's like kind of cheating Oh, it just melts them. Absolutely melts them. We need more More I need more Okay, where that was a bit excessive, but you get the picture We're gonna lay siege to all of this Go away.   No, don't oh you're gonna die Once they start going back. That's it.  Oh no There's so many Bombardier beetles. It's unfair They're gonna get they're gonna get acid shot. I get oh god I can't look I can't look at it. I mean, but we're not doing too bad. They keep on being born So that's good, but Oh It's horrible. Can you imagine some of your face melted? Oh No, no, no, no, no, no. No, thank you. All right. We're starting to get a lot more We don't have too many actually we've got everybody doing nest duty. So There's a lot of workers doing that. So we should be all right. Yeah, look at that. Look at that. We're almost there and Hello, just your neighbor your friendly neighborhood fire and colony just keeping your numbers in check Yes That's gonna be a lot of food. That's gonna be a lot of food and that's everything and whoo. Yes Wow So we basically got everything that was there So the next place to go to is over here and to scavenge this little area as well Wow, I don't know if we're gonna be able to do it though In time. I don't think so. Yeah, we haven't got we haven't got enough time We haven't got enough time to get over here And if we do they're not gonna bring back any everybody go here and scavenge out the final bit of food That's it. Look at all this. How many do I have 142 bloody of these things? So we're only gonna be attacked by one bombardier beetle ready.   Oh god. Well, I guess if it means It's not too bad. And what was over here? Oh, nothing. Nothing was over there.  There's just scavenge it all I'm gonna split it. We're gonna have we're gonna take care of this. We're gonna have one there One far among sent trail that one far among sent trail there and then So nothing's gonna get out as soon as the flood comes everything's gonna be killed immediately And then we're just gonna make a break for it.  I think v is that but we can only do when it's flooded and this is it This is our break for freedom Except for that guy that guy's dead. I'm so sorry What was it that? I'm so sorry. I don't know where it is. Oh no They're taking damage. They're running away like no And there you go. Okay, so in 50 seconds We need to get 10 ants to the promised land but Judging by my 142 plus workers. I think we're gonna be good Okay, I'm gonna set them here. I'm gonna set those guys here and see we got what? 50 53 53 ants That are gonna come about here and try and go across. We'll see how far we get with 53 And then we've got another 52 which will double it and then a 37 And then we've also got workers if we need to make it like if we're really struggling for ants We've always got workers to chuck right Okay, I'm waiting V go Go v go go go go go go No do definitely attack I want to see this is 50 odd 50 odd ants. I'll let them go Right, so another 50. Oh my god. We do need a lot We need a lot. Um Okay, what happens when we put every ant in there? Let's see every ant now Except for the ones working on the nests Is gonna go Right, let's have a look. Let's see how far we get we need 10.  I don't think it's gonna happen But they're gonna make a break for it. They're doing their best Come on Come on ants How far can you go? Yes, come on colony. We're gonna make it to the other side Aren't we though? I hope so. Oh, I don't know. I don't know Nah, I think we're just too short Damn it. How many more do we need?   I thought it would have been You know, it's not bad. They did they did a good. They did really good making this work this mechanic Wait, why they go over this way? There's no one over here. Damn it. They're all over there You fool And now we've got no food because everybody's dead brilliant There we go So that's all new stuff and then we've got a crud ton of bombardier beetles to take on So let's get this over with Maybe we need 200 has begun.  Yes There you go. See that's how you do it. That's how you do it Just dig it all out man. Dig it all. We might need it all There we go. I don't know how many how many freaking aunts I need. Look at this Look at all of this. This is the most of my aunts. I think I've ever made. Oh my god.  I lost a lot. I lost a lot of aunts. Okay, which one's gonna have the most now Who's gonna be the most prosperous of these islands? Right because I got I got mine covered with these entrances. So anything that comes out I get But which one's gonna have the most by the looks of it. It looks like this one maybe This one's only got a couple of bombardiers on it or one bombardier at the moment. That's got two That's got three. We've only got one here. So may as well go for this one and Hmm Yep, we'll definitely go for this one. We're gonna make it. We're gonna get as many as we can here Grab them. Grab them and go. Why is it so satisfying? Why do I love seeing little insects die? Because I got a couple of them up. Yeah, I mean Right, what's gotten it? Oh, that's always so big That one where we're going there next.  Did they kill one? I think I think they might have broken it up.  Yes now get them They're not so promised land, but still the promised land for food and there is oh my god. There are so many there There are so many. Why is there so many? I don't like it. I don't want it to be this many At one line two line Three line and fill that bit in Yes Yes, and then all the food we're gonna get from this Oh Oh, yes. Look at all the booty. I mean each one's like 25. So four of them and that's a hundred Oh, yes. Oh, yes gorgeous Oh When you could carry more I mean the workers would be good, I suppose But we need the workers for this because there's a lot of nests to sort of manage So 47 workers sounds about right Now do we go over here or do we just let them slowly kill each other? Which seems to be what they're doing. I think we let them just kill each other I mean, yeah, that looks tempting, but It'd be so cool if you go from that island to that island and skip this part That would be awesome But I bet you can't do that.  Let them fight They're basically just chasing the weakest one and then they do a couple of bites to them And then that guy's chasing that one who's doing a couple of bites It just becomes this conga line of ones attacking the other. That's good though I like that might be because it's a medium difficulty was hard difficulty They probably wouldn't and I would have definitely have died Oh, no, that one's getting completely surrounded right. I got 202 now I'm gonna make another line and another line and another line and Another line although I'm not connect those two up. I'm gonna keep that separate just in case So now they're going to attack me I think yeah now they're going to attack me Right remember men what the strategy is That could all the prettys look at them all tactic is to run past them.  Yes Gorgeous yep They're gone. Okay run past run past run past now attack go There is a lot of them though, so Oh, wow we up We're doing I mean I'm not seeing the death because I don't want to I don't want to click it Nope, we're doing good. We're doing good. That was actually maybe even a positive trade-off Yeah Not bad not bad now do we Try it. Do we try it again? We got 221 And this time if it doesn't look like it's going that way I will put Um, do I still have the thing over here? Don't have the pheromone trail. Do I I will put um the other ants to just go and Eat one of these colonies. Yep. There's a hundred and what about this way? I know. Yeah, so wait. We're doing good.  They're all going they're all going Everybody should be coming over to this segment even you guys And workers and the 40 workers come on come on 221 There's definitely enough right There has to be look everyone's everyone's coming up. Come on everyone join the cause for the bridge for the bridge I think we might be able to do it Maybe yes, come on. Yes. Come on.  It takes a lot of time To get to that side. Yes We're almost there Come on Come on come on How many ants do we need? Yes. Yes. Yes more ants Five ants have made it um Oh god, we need four more. We need four more I'm sending out there the ones who work in the nursery go for it. Make a break for it Don't attack anything. We just need to get to the promised land. Is there one more? Why are you leaving the promise there we go? We did it. We did it. Yes My beauties They made that me like oh, that's probably about that why that long Something it's probably like an arms length. Maybe right. I'd say it's probably like an arms and look at them go They left to a new colony Victory for solensis in victor. Oh, I like that name.  That took me an hour Well guys, if you've enjoyed that video leave a like and until next time I'll see all your beaver babies later. Oh, bye-bye


Well, welcome everyone. This is July 25, 2022. It's Jenkins governance meeting topics for today include news. Action items. Blue Ocean admonition. Embeddable build status plugin from last meeting. CDF updates if Oleg joins us and forum and community topics if Gavin's available. Any other topics that need to go on the agenda. Okay, then let's go back to the, the top of the agenda so by way of news, the next long term support release release candidate is due out on Wednesday with release two weeks afterwards thanks to Alex Brandis as our release lead. He's been the release lead for the last two long term support releases thanks very much. The upcoming conference, the Southern California Linux Expo in Los Angeles at the end of this week. Kosuke will be speaking and Alyssa and I are also speaking. Basel noted that Jakarta mail migration is in progress Basel what would you like to tell us about that. We just landed earlier this week or last week and the important thing to note for users is that they need to update some plugins and lockstep with each other. And those are indicated in the release notes. So, if you want to pull up for example the mailer plugins release notes, you should be able to see the messaging that we put in place. If you see that section that says related plugin releases, it's a little bit further down. But that, that gives you an example of, you know, these three plugins need to all be upgraded at the same time. That's an important note for users. And if it's actually more than just those three if you go back to the JIRA epic there's, there's a handful of them but those three are the most most popular ones. There's there's some additional for example I fixed up the SAML plugin and a mail watcher plugin, but those are installed on 2% of installations so they're not as common. The one thing that I would want to note in this meeting is that the disk usage plugin is kind of in a, in an odd state, so I didn't touch it, but that one could use a volunteer if someone is, if someone cares about using this plugin. The reason I didn't update it was that releases are currently blocked because there is, there is a security vulnerability that is on the main branch that has not been released. So the security team blocked future releases to prevent that vulnerability from ever being released in the first place. So if someone, so basically fixing this plugin up is is more involved than, you know, just submitting a pull request or adopting it there's some there's some additional catch up work that needs to be done, which I didn't volunteer myself to do. But if anyone is interested in using this plugin. I don't think it's going to work with the Jakarta mail migration. And I don't think any changes can be made to it until these security issues are dealt with. So that that would be a great example for someone to volunteer pick this up if they're using this. But other than that, I think we're in good shape with this migration. So, thank you well and Bruno Bruno and I are actually doing a session at DevOps world tutoring people as part of a workshop on how to adopt a plugin. We may pick this one as one of our candidates just to use as part of a lab exercise. So it's, that's an interestingly complex one. I don't know what the vulnerability is on the main branch. So, it might be a very simple one, like reverting one commit. So it might be a complicated one. I don't, I don't have access to the security tickets. So I didn't, I wasn't able to read it. There is a link to the ticket, which is private. So I think whoever whoever wants to take this on might might benefit from being able to read that ticket so that they know what they're dealing with. Well, and that that knowledge should probably then inform do I want to adopt it or not because if I'm not an active user of it then adopting it and saying I'm going to pick up a security fix, maybe more than they're ready to do. Thanks, good guidance. Buzzel anything else. No. All right, thank you. Action items. We've got a bunch that I have to sadly report I've made no progress on, and it'll probably be that way for at least another two or three weeks just for all the things I've got to do. Any questions with me now this one, the last one that we had put on last week, Gavin Morgan create a proposal to hire a writer. I think we may have a solution here that may address it I was hoping to have Gavin here but I wanted to highlight this at least to show people what. So Gavin's concern was that the ocean is not being actively maintained. It's not being not being actively enhanced. And because it's not being actively enhanced. That makes it difficult for people who arrive new to Jenkins and are then surprised. Oh this thing that's described in lots of places is not getting more enhancements. Certain fixes are being applied and security fixes are being applied when selected. So what Kevin has done as he's created a standard admonition to put on the page. And it says this kind of thing here, an info block that says blue ocean is not receiving further functionality updates. It will continue to provide pipeline visualization but will not be enhanced further. For me this was, and Gavin has seen this and said yeah that seems reasonable. Others are welcome to comment on the poll request encouraged to do so just wanted to be sure you're aware. Now what this this standard text or some variant of it will appear on most of the blue ocean pages like right now it appears on creating a pipeline and on dashboard, it appears on Activity View. So that users who are reading will see that status as they're working through their reading. Any comments or concerns there. All right, I think I think it looks great it's it's really good to be transparent about the status so I think the message is great. And I agree with that now I like. I did like the docs office hours Asia segment said hey, could we refine the message so that when we're talking about pipeline editor, we don't, we don't do as much to mention stage view but we mentioned specifics for pipeline editor and that's, that's I think we'll work with Kevin on separately. It's, it's I think it's an interesting idea of are there variations we should use for each of those pages that will make the message clearer. Great. If nothing else on blue ocean let's go on to the next topic then. Last, last time we met we had an item, an action item raised that the embeddable build status plug in bundles of was bundling a proprietary font. It's not allowed to be redistributed. And so it was violating the Jenkins terms for Jenkins plugins. And so what we did two weeks ago we said we'll set a two week clock. If no one adopts the plug in within two weeks we will cease distribution of that plug in because it's violating the terms. And in the in that intervening two weeks, it's been adopted and a release has been delivered that removes the proprietary font. Thanks special thanks to Basel for highlighting how to do that change. It was actually a very simple change based on his guidance, and the plug in now has a few more tests thanks to his guidance. So, release is done. It is still on CI Jenkins.io and better maintained than before. I think most of the credit goes to you mark for picking it up because I think that was that was very kind of you to adopt this very rarely used plugin. In this case I admit it was it was guided self interest. I didn't want the infra team to waste the time removing it. And so that's a that's a terrible reason to do it but it was cheaper to adopt it than it was to go through the process of removing it from all the infrastructure. Oh legs not here so I'm going to drop the updates from CDF and forums and community topics. I had two or three topics that I thought might be worthwhile, even without Gavin here. So, if you're okay with that. There is a discussion right now on a vendor site. What Gavin has proposed is a let's create a site called vendors dot Jenkins dot IO. That is a place where companies that provide support services or sell products based on Jenkins or etc could do place their information so that others can find it. Right now what we have as an outdated wiki page that points to vendors that are absolutely no longer active. So here's what his current prototype looks like. And what you see is we've got two vendors, a hypothetical vendor here that he created, and a less hypothetical vendor here that I created some rough data for now the data is not correct on these but the, the sampling is intended. Or the layout is an idea and what this gives then is a link here to more information about the vendor and a link to their support site, or a link to their website. The idea being, okay, this way. This is much better than let's do the search for Jenkins commercial vendors on the wiki page. And here it is this one is how it currently looks today. Actually, and Evelina you may recognize one or more of these, these names. Well, it's kind of a historical name. Exactly. Right. And, and that's what this page is sort of the, the historical wow it's not been touched in five plus years. And so it's so badly out of date that this is going. I would expect it was not touched for 20 years. Sorry, that's just a joke. I just wonder like how, how do we decide who ends up there, because as you pointed out, I know a company that I believe should be there or to, but do we have some criteria. Actually, any company that would like to place themselves there we would encourage them to submit some sample data so we can test drive it. Because that way we, we get a sense. Right now my, my, my scope is limited because I don't know all the companies that are providing products. And so I provided data but if you are aware of someone that would be willing to provide data, the data format is actually quite simple it's a little yaml file. And so, so it's, you can see the yaml file that I provided is someplace further down here. Here's the here's the yaml file that Gavin did. And here's the yaml file that I did this one. And if, if, if you've got a vendor that might be interested in being included we would love to have sample data from them. Okay, and then where do they send it. And if they just post it right here as a reply just like I did in this threat. Okay, and then because the companies I'm talking about the consulting companies that I know have consultants are really really good at Jenkins so that's kind of thank you looking for. Okay, exactly. And I, and I think that is, that is very well aligned with what Gavin's looking for what, what, what started his conversation about this was, Hey, we get people who ask questions on jenkins.io that are well beyond what a person who is doing this for nothing would do, but if we could point them to consultants to organizations that offer services for for fee. They may be able to get the answer they need. And the community can benefit overall because we're not just having people expect commercial grade support from a bunch of volunteers. Right, I, I don't work with these companies anymore but I'll drop them a message and direct them to the threat so they can just take care of that if, if they think it's the right fit, I mean I'm sure it is but I'm not a good job. Well, that would, that would be a great thing if you could just share a pointer to them saying hey, here's this thing that's being assembled.  Thank you. All right, so next topic was that there is a new. There's a there was recently a series of 25 plus pull requests that were merged into Jenkins core to begin the process of getting us eventually ready to enable content security policy. So content security policy, here's the, the video segment is linked that talks about what it is, how it works and why we're doing this. We're still quite, quite a ways away from being ready to enable it, but it will be, it was promoted in last year's Hacktoberfest will be promoted again in this year's Hacktoberfest, and we hope work will continue so that the day will come when we can consider enabling content security policy on Jenkins core, and thus prevent a whole bunch of cross site scripting attacks with a single configuration. So, so just be aware of that it's no no action required yet from plug-in maintainers because it's most important that we get core ready first. And so Daniel Beck who's doing much of the work and vatic felonie the security officer are both making people aware without telling any of the plug-in maintainers oh you must do something right now it is just in core, and it's intentionally being done in a way that 100% compatible. Alright, so last item I had was on github comment ops. And I have to admit I am I'm really pleased with this the ongoing discussion talks about a technique that Tim Jacob has added for Jenkins core and several repositories that allow a, a comment to perform operations that normally are only allowed for maintainers like labeling a pull request or removing a label, or asking for reviewers by name. I found this to be at least for me personally quite helpful, because it means I can submit a pull request, and in the text of the pull request if I just put slash reviewer. K Martens 27, it will ask for Kevin to be a reviewer if he's got merge permission on that repo. So, very, very nice capability. Any other topics we need to go over today in governance meeting. Okay, I'll take that as an end. Thanks very much.