[gunnersnroses]

Is it possible to use a multi-grid idea to initialise the flowfield in SU2? What I want to do is say 1000 iterations on a coarse mesh to quickly get the general flow field and then have this interpolated onto a finer mesh to resolve the details.

Would the FULLMG_CYCLE multi-grid option do something similar?

Thanks

[fpalacios]

Hi Mike,

Exactly, that is more or less the idea of FULLMG. Starting from the coarse levels the solver adds more grid levels as it converges the solution.

Best,
Francisco

[gunnersnroses]

Thanks for replying, I've been trying to use it but it repeatedly fails " !!! Error: SU2 has diverged. Now exiting... !!! " before even completing a single iteration. I'm using the below settings for a supersonic/hypersonic case, could you possibly advise on some settings? Below is what I've been using so far.

Also could you please provide some details as to how it determines when to interpolate onto a finer mesh?

Thanks

% -------------------------- MULTIGRID PARAMETERS -----------------------------%
%
% Multi-grid levels (0 = no multi-grid)
MGLEVEL= 2
%
% Multi-grid cycle (V_CYCLE, W_CYCLE, FULLMG_CYCLE)
MGCYCLE= FULLMG_CYCLE
%
% Multi-grid pre-smoothing level
MG_PRE_SMOOTH= ( 2, 1, 1, 1 )
%
% Multi-grid post-smoothing level
MG_POST_SMOOTH= ( 0, 0, 0, 0 )
%
% Jacobi implicit smoothing of the correction
MG_CORRECTION_SMOOTH= ( 0, 0, 0, 0 )
%
% Damping factor for the residual restriction
MG_DAMP_RESTRICTION= 0.7
%
% Damping factor for the correction prolongation
MG_DAMP_PROLONGATION= 0.7

[fpalacios]

MG is the kind of algorithm that when works is great... but it is difficult to make it works (in general) and this is not a problem of SU2.

Unfortunately your application doesn´t fit very well to a MG algorithm with, as you can guess, because of the interpolation to coarse (or very coarse grids) are not able to capture very localized features (like in hypersonic of source term dominated problems).

The basic recommendation is to start with a typical setting (V cycle) reduce
MG_DAMP_RESTRICTION= 0.5
MG_DAMP_PROLONGATION= 0.5
and the CFL number.

Cheers,
Francisco