[ugurtan666]

Dear SU2 users,

I am using SU2 7.1.1 for an external flow problem 0.5 Mach at sea level. I have obtained steady results with decreasing relative residuals up to 4 levels by JST central scheme with artificial viscosity.

However, steady state convergence is not possible for upwind schemes (I am mostly trying AUSMPLUSUP2 btw). Although I have obtained converged aerodynamic coefficients and stable flow contours, residuals stall after one order of reduction from farfield initial condition.

I have read Venkatakrishnan's paper (Convergence to Steady State Solutions of the Euler Equations on Unstructured Grids with Limiters) and I came to this conclusion:

The limiters are wiggling i.e. the cause of stalling residuals. As the coefficient of Venkatakrishnan decreases, residuals are getting better but it is still less than 2 order of magnitude.

I have some thoughts which I listed below but it would be pretty good to hear some advices from you!

1) I have prepared a fully structured mesh to check the effect of limiters on mesh type, but I am not sure if it is gonna work.

2) I have tried to use LIMITER_ITER to freeze limiter values after oscillations around quasi-converged aerodynamic coefficients starts but solution crashed.

3) I need to understand the effect of VENKAT_LIMITER_COEFF. In his paper, Venkatakrishnan achieves better residuals by increasing coefficient K whereas I have achieved better stability with decreasing VENKAT_LIMITER_COEFF in SU2. It would be nice if there is any document/paper etc. to get information about the VENKAT_LIMITER_COEFF in SU2.

4) Beyond all, I want to perform a DES analysis in SU2. In my opinion, JST is not a good choice with its diffusivity. For that reason, I wanted to use an upwind scheme in DES study but I need to be sure that the effect of wiggling limiters is minimal during data collecting stage in DES.

Nevertheless, my DES experience is limited so I want you to know that I am open to read different views, comments, paper advices, documents etc.

Thank you very much for your patience and your time!