Aerodynamics: Recirculation Zone Wake and Speed

[aero5682]

How does speed effect the recirculation zone and wake for supersonic and hypersonic speeds? Does it get longer, wider?
Also this is for a blunt body like apollo reentering

 

[boneh3ad]

Speed is not directly relevant. Mach number and Reynolds number will be the most important parameters. You might start there with your search.

 

[aero5682]

I thought I had searched for mach number, apparently I hadnt searched mach number or reynolds numbers effects on it. It seems like subsonically and transsonically mach number and reynolds number increase the length of the recirculation zone, and supersonically and hypersonically decrease the length, but nothing I found was very clear on it

 

[boneh3ad]

You'll just have to keep up the search. I don't know any of the details of wakes like that to give you any answers here. I just know the basic parameters that govern it.

 

[aero5682]

Ok, thanks. Ill move it to aerospace and see if anything comes up

 

[boneh3ad]

I meant to do your own independent research on it. Search Google scholar and look for papers. You likely won't find that answer by asking on here. It's fairly niche.

 

[aero5682]

Yeah it seemed like it. I don't think I am going to find it here. And I will be looking on google scholar and stuff. But it doest hurt to ask. I thought there might have been some well known rules like recompression shock angles or pressure differences or something, or mabey it was some well known thing, but it doesn't seem so

 

[boneh3ad]

There probably are rules of thumb at least to some degree, but the area is so specialized that it's not something that would typically be taught in any undergraduate fluids course or really any graduate courses. It's the sort of thing a researcher would learn from reading papers while conducting their research rather than in a classroom. Shoot, I even teach compressible flow courses and I don't know the answer to this off the top of my head. All I can tell you is that the inviscid phenomena like the shock angles are going to depend pretty much exclusively on the geometry and the Mach number, and the viscous phenomena like unsteadiness in the wake are going to be based on the Mach and Reynolds numbers.

 

[aero5682]

Hmmm, I wonder if since the recompression shocks and those shear layers seem to sort of bound the wake in, if calculating those angles might help, but the unsteadiness in the wake might effect it too. Looks like I have some research to do