domain size for 3d external aerodynamics
 

Hi all,

I was told to make some runs on the sub-transonic regime for a 3d "cone-like" shape. I'm building a parabolic shape domain from which I will subtract the "cone" and I was wondering how big this domain should be...I mean, in the tutorial on compressible external flow in fluent TG the domain is several times the chord of the profile long and high. In my case, this will lead to a very huge domain. Any hint on the minimum domain extent and/or shape for such a case? I'm not expecting great shock waves by the way...

Thank you in advance.

Edi.

Re: domain size for 3d external aerodynamics
 

It should be at least 5 chords in EVERY direction. 10 is better, especially downstream if you have a bluff trailing edge on your body.

Actually, if you had strong shocks you could get away with a smaller domain forward of the shock because the fluid isn't affected by (doesn't "see") the body until it reaches the shock... so you could have estimated the shape of the Mach cone, and you would've only had to extend the domain a little bit forward of the cone (1 or 2 chords... possibly less, but that gives you some room if you miss-calculated the mach cone or some room for Fluent to vary the Mach cone as it reaches a solution).

The problem is that you have to get the BC away from the influence of the body, and in subsonic regimes, this could be a very large area compared to the body, including the upstream direction. 5 to 10 chords is a good rule of thumb. Once you have a solution, then you can analyze the results and possibly try a smaller domain.

Hope this helps, and good luck, Jason

Re: domain size for 3d external aerodynamics
 

Thank you very much. It was helpful.

Edi.

3-d low Re flow analysis
 

Hi,

I am simulating a UAV of almost 2m wing span. what should be its ideal domain size to get comparable cl and cd values?

I am trying to reduce the computation time...:mad:

Thanks in advance:)