# Questions regarding Discrete Adjoint Solver

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April 19, 2021, 11:21
Questions regarding Discrete Adjoint Solver
#1
Member

Join Date: Jun 2020
Posts: 30
Rep Power: 5
Hi,

I tried simulating the Test case of Onera M6 using the SU2's discrete adjoint solver. I am new to the implementation of the sensitivity solver and trying to analyze the results generated from the implementation, and have the following questions-

1. What is the difference between the Surface_Sensitivity contours generated by surface_adjoint.szplt and surface_sens.szplt? Which ones are usually used for representing the sensitivity of the objective function wrt to design variables?

2. What does FINDIFF_STEP in of_grad_cd.csv represent?

I'm using v 7.1.1. I have attached the config file and gradient results as well.

I appreciate any inputs! Thanks!
Attached Files
 of_grad_cd.txt (10.3 KB, 5 views) Adjoint_Onera_M6.txt (29.0 KB, 3 views)

Last edited by Daaman; April 21, 2021 at 15:51.

April 24, 2021, 06:25
#2
Member

Ole Burghardt
Join Date: Mar 2016
Location: Kiel, Germany
Posts: 60
Rep Power: 9
Hi,

Quote:
 Originally Posted by Daaman 1. What is the difference between the Surface_Sensitivity contours generated by surface_adjoint.szplt and surface_sens.szplt? Which ones are usually used for representing the sensitivity of the objective function wrt to design variables?

The first is the adjoint solution (from which sensitivities are derived, it's the objective function sensitivity w.r.t. flow solution), the latter is the objective function sensitivity w.r.t. surface mesh coordinates including mesh deformation, i.e. surface mesh coordinates as design variables.

Quote:
 Originally Posted by Daaman 2. What does FINDIFF_STEP in of_grad_cd.csv represent?
FINDIFF is used for finite differences, adjoints don't use it.

Best, Ole

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