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-   -   SU2 Discrete Adjoint Error!!!! (https://www.cfd-online.com/Forums/su2/220585-su2-discrete-adjoint-error.html)

vishu343 September 12, 2019 19:13

SU2 Discrete Adjoint Error!!!!
 
Hello All,


I am trying to verify sensitivity of Discrete Adjoint against Finite differences for tutorial case ONERAM6 (SU2 version 6.2.0).


I have plotted dCd/dX (Change of drag coefficient against change in one coordinate of FFD box like delx = 0.001).




In this case, what I see is that at trailing edge of the wing, values differ significantly compared to Finite difference and in other words, Discrete Adjoint seems to be matching with Continuous Adjoint and there is no clear benefit of using Discrete Adjoint in this case.



Would anybody shed some light on such issue or anybody might have experienced something like this!


Thanks a lot!

pcg September 15, 2019 07:22

Are you using the sharp corner filter option?

vishu343 September 15, 2019 08:50

Hi, Thanks for your reply.

No, I am not aware of it (sharp corner filter option). What is that actually! Does it affect discrete adjoint sensitivity.

Thanks.

pcg September 16, 2019 06:48

It is a limiter for the sensitivities in areas where geometry changes very rapidly, it avoids numerical issues but it could explain why you see a mismatch close to the trailing edge.
The name of the option is SENS_REMOVE_SHARP, by default it is off so if you don't see it in your cfg file it is not being used.

Have you checked the FD value you get is (more or less) independent of the perturbation you use?

cfdjetman October 15, 2019 19:55

I've posted my question here


https://www.cfd-online.com/Forums/su...tml#post747133


Could you someone help with this issue.


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