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-   -   Cfl_adapt (https://www.cfd-online.com/Forums/su2/238847-cfl_adapt.html)

Speng October 6, 2021 16:58

Cfl_adapt
 
1 Attachment(s)
In the TestCases\turbomachinery\transonic_stator_2D case I'm trying to run with CFL_ADAPT turned on. I've changed the cfg to what's shown below (files is also attached) but when I run it AFAICT the CFL isn't adjusted at all. Am I missing something.

Also apparently periodic BC and multigrid aren't compatible currently what are useful ways of improving convergence? For this particular case I tried ramping the exit static pressure which had a noticeable positive impact.

% Courant-Friedrichs-Lewy condition of the finest grid
CFL_NUMBER= 40.0
%
% Adaptive CFL number (NO, YES) Default is NO this example changed to YES with appropriate CFL_ADAPT_PARAM
CFL_ADAPT= YES
%
% Parameters of the adaptive CFL number (factor down, factor up, CFL min value, CFL max value )
CFL_ADAPT_PARAM= ( 0.5, 1.2, 20.0, 100.0)

ari003 October 7, 2021 05:34

Quote:

Originally Posted by Speng (Post 813746)
In the TestCases\turbomachinery\transonic_stator_2D case I'm trying to run with CFL_ADAPT turned on. I've changed the cfg to what's shown below (files is also attached) but when I run it AFAICT the CFL isn't adjusted at all. Am I missing something.

Also apparently periodic BC and multigrid aren't compatible currently what are useful ways of improving convergence? For this particular case I tried ramping the exit static pressure which had a noticeable positive impact.

% Courant-Friedrichs-Lewy condition of the finest grid
CFL_NUMBER= 40.0
%
% Adaptive CFL number (NO, YES) Default is NO this example changed to YES with appropriate CFL_ADAPT_PARAM
CFL_ADAPT= YES
%
% Parameters of the adaptive CFL number (factor down, factor up, CFL min value, CFL max value )
CFL_ADAPT_PARAM= ( 0.5, 1.2, 20.0, 100.0)

Just a quick question, if you specify the freestream pressure and temperature then automatically from ideal gas law freestream density is computed. Dont you think specifying the freestream density is simply redundant? Also the density through ideal gas law is around 7.

Speng October 7, 2021 13:24

The config file is from the SU2 developers; the only thing I've changed is the adaptive CFL settings. This is a turbomachinery analysis of a high pressure turbine nozzle so the boundary conditions are set separately so I doubt the freestream conditions are relevant/important.

pdp.aero October 7, 2021 15:27

This might help:

REF_DIMENSIONALIZATION= FREESTREAM_PRESS_EQ_ONE

Speng October 7, 2021 18:33

Quote:

Originally Posted by pdp.aero (Post 813844)
This might help:

REF_DIMENSIONALIZATION= FREESTREAM_PRESS_EQ_ONE

That didn't make the CFL vary.


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