Urgent: Unsteady 3-D supersonic cavity flow
 

Dear all, I am a Master student. Since last 3 months I am trying to solve 3-D supersonic cavity flow problem. The problem I am facing is that shear layer over the cavity is not moving or showing movement as time progress. Inside the cavity, there is no variation in pressure, hence no change in vortex inside the cavity. I could get bow shock at the right corner of cavity. I have tried lot of options i.e. different grid sizes, all the turbulence models available in fluent including LES.

Can anyone please comment on why am I not getting variation in pressure inside the cavity as time progress? Please help me..

with regards, Min-Sung Kang

Re: Urgent: Unsteady 3-D supersonic cavity flow
 

Hi there, I'm not that familliar with what you actually expect from cavity flows, but usually if I have flow characteristics that I am not capturing when I'm doing transient simulations, it is because my time step is too big.

Do you have any idea on the physical time scale of the variation of flow structure that you are expecting in your cavity flow simulation? I mean if the expected frequency of pressure variation is very high, that means the timescale is very small (even more so at supersonic speeds!!!). Try to ensure that your time step is at least a third of this value to be able to capture this flow characteristtics.

Hows the convergence on your simulation so far?

axisymmetric cavity queries
 

hii...currently i m working on supersonic axisymmetric cavity flow...i have done unsteady pressure measurements wid time step of e-07 n e-09. with the former i m not getting the desired frequency n wid the latter i m not getting the mean surface pressure plots though i got the frequency...i have tried wid 80*100 cells on cavity of depth 3mm n length 4 mm for both the cases ...plss somebody suggest some soluton plss

Hi

Did you see shear layer oscillation?