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-   -   Meaning of non-physical points ... (https://www.cfd-online.com/Forums/su2/127947-meaning-non-physical-points.html)

 deeps December 27, 2013 02:56

Meaning of non-physical points ...

Hi All,

I had few queries regarding SU2 terminology. :confused:

1. Several times I encounter this msg: The solution contains n non-physical points. What does this refer to ?

2. How are the residuals defined? Lets say the value at some iteration for variable 1 is -3.4567. What does it indicate? Does it mean log_10 (Var1_i iter/ Var1_ i-1 iter)?

3. Has anyone tried using 2 level Multigrid? How to decide optimal child/parent ratio for a given grid?

Would appreciate your response.
Thanks,
Deepanshu.

 fpalacios January 11, 2014 23:05

Non-physical points means that after the solution update the density is negative.
Su2 computed the L2 norm of the residual and plots the Log10 of the value. In other words a value of -12 means that the residual is 10^-12.
To set the optimal parameters of the MG is an art. when you have convergence issues do not forget to reduce:
% Damping factor for the residual restriction
MG_DAMP_RESTRICTION= ____
%
% Damping factor for the correction prolongation
MG_DAMP_PROLONGATION= ____

Best Regards,
Francisco

 deeps January 13, 2014 01:20

Meaning of non-physical points ...

Dear Francisco,

Thank you for your inputs.

Deepanshu.

 momo_sjx January 14, 2014 18:51

Set Multigrid=0, the non-physical points can be removed.
It works sometimes for me.

 deeps January 29, 2014 02:04

Thanks Sean for your inputs.

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