The Morkovin hypothesis (1962) explained

23:31Basically, I just adjust the parameters for density and I adjust the parameters for turbulence or sorry for temperature >> and I'm going to get the turbulent effects that I get at high moach. Okay, this is a non-trivial statement. Okay, because what it's assuming is the essential physics at the at the high scale at the at the vehicle level is going to be very similar, >> right? It's saying all I have to do is adjust some parameters and I'll get the right physics. There's nothing like weird that's happen in between. I if it's raining outside, I can just put on a raincoat and I'm fine. Like I there are no other derivative thing like the addition of a single item that is

24:13trivial. >> Yeah. Yeah. Yeah. That is that Yeah. Yeah. I can just adjust some parameters, right? It's not the rain is like acid rain that's going to melt my rain coat and kill me and all this other stuff, right? Right. You know which which is which is like it is it is it is filling in in it's not in it is saying that the this maps in both domains in a way that what we're saying is that is a big deal that we're saying that it >> we're saying that yeah we're saying that there's some there's some trivial transformation >> that can scale the compre the really complex yes >> compressible stuff >> into just a couple knobs. >> Yeah. Into just a couple of knobs. Right. And and why that matters is

24:54because like right now we have simulations, >> okay, >> that deal with this kind of stuff, okay? They're called computational fluid dynamics. They basically churn physics equations in a computer and tell you how the air is going to flow around an object going at a certain speed, given the air density, given the temperature, and things like that. Formula 1 people do it all the time. >> This is what video games use for like water. >> Yes. >> You know, like water animations in your Uncharted 4 or whatever. >> Yeah. Exactly. >> They need to use models like this. >> They they use models like this and like people at aerospace companies use probably more sophisticated models, but at the end of the day, at the end of the day, it's just like it's it's resting on this hypothesis, right? Because there's

25:34two ways to do it. There's a direct nu numerical simulation called DNS. That's the gold standard. Okay. >> You're basically solving Navier Stokes for like tiny tiny little packets of of space. >> Okay. >> And you're and you're getting really granular with it. >> Yep. doing a direct numerical simulation for something like an airplane. We don't have the computation. >> I was going to say like we barely have the computation for me to get an image of me making eggs in the morning out of Chachi BT let alone this multi-point. >> Yeah. This is like imagine every single little part of air that's interacting with every other little part of air, right? How many how many supercomputers are there that you're going to like rent time on? >> Correct. to like deal with every single

26:17iteration of your design. It's not going to work. >> The the point is classical computing does not really have the horsepower to do like physicsbased or physics level models without getting to supercomputer scale. >> Exactly. Yeah. Yeah. And there's not that many supercomputers in the world, right? Like there's not one like just here. >> Right. Right. >> Right. And then and then the other so what what we usually do is we use something called a computationally cheap RANs. It's called Reynolds average Navier Stokes. It's basically a way to like blur out >> a lot of the physics. So on the left you've got direct numerical simulation. Yes. >> And on the right you've got the Reynolds

26:57average simulation. You can see that it's kind of a blurred out version >> Yes. >> of the direct numerical simulation. So it's giving you a good enough answer. >> Yes. >> Okay. >> Yes. But here's the thing. Every single one of those simulations, especially when you're trying to go into this Mach 5 and beyond level, it's assuming explicitly Marovven's hypothesis. >> Okay. >> Which is that the physics up there is basically equivalent to the physics down here >> up to a certain scale factor that we can calculate. >> Mhm. >> Okay. >> Mhm. >> The key thing is this. No one's actually like done the work.