CFD Online Logo CFD Online URL
Home > Forums > Software User Forums > SU2

RANS discrete adjoint oscillating

Register Blogs Members List Search Today's Posts Mark Forums Read

Like Tree3Likes
  • 1 Post By wallym
  • 2 Post By pcg

LinkBack Thread Tools Search this Thread Display Modes
Old   August 12, 2019, 05:56
Default RANS discrete adjoint oscillating
New Member
Pablo Garrido
Join Date: May 2019
Location: Netherlands
Posts: 7
Rep Power: 6
pgdelaserna is on a distinguished road
Hi all,

I am using the discrete adjoint solver based on the RANS equations (with SA as turbulence model) to obtain the surface sensitivities embedded in SU2. My issue is that, even though I achieve a reasonable convergence of the direct problem (where I reduce the residuals about 5 orders of magnitude and the residual plots are smooth, with no oscillations towards the end), the discrete adjoint is oscillating.

For the direct problem, I have used JST as the convective numerical method, with MUSCL flow activated and VAN_ALBADA_EDGE as slope limiter. Now, my questions are:

1. For the discrete adjoint problem, do I also have to activate MUSCL_ADJFLOW, as I have used MUSCL scheme for the flow solution?
2. Does necessarily the convective numerical method for the adjoint problem need to be the same as the one used for the flow? (e.g. if I've used JST for the flow, do I need to use JST as well for the discrete adjoint).

Any help related to how to avoid oscillations in the discrete adjoint residuals is much appreciated

Thanks in advance!
pgdelaserna is offline   Reply With Quote

Old   August 19, 2019, 12:07
Senior Member
Wally Maier
Join Date: Apr 2019
Posts: 123
Rep Power: 7
wallym is on a distinguished road

Thanks for your question. My suggestion for you would be to try and converge your direct problem even more to get a better discrete adjoint solution.

To answer your questions, these options are only required for the continuous adjoint formulation (both in 1 and 2). So messing with these wont affect your solution.

pgdelaserna likes this.
wallym is offline   Reply With Quote

Old   August 20, 2019, 04:43
New Member
Pablo Garrido
Join Date: May 2019
Location: Netherlands
Posts: 7
Rep Power: 6
pgdelaserna is on a distinguished road
Hi Wally,

Thanks for your help! I did not know that those options were only for the continuous adjoint. But indeed I noticed that did not make any effect on my results if they were or not activated.

I will take into account your advise and try and converge better the direct problem.

pgdelaserna is offline   Reply With Quote

Old   August 25, 2019, 04:32
Senior Member
Pedro Gomes
Join Date: Dec 2017
Posts: 465
Rep Power: 13
pcg is on a distinguished road
Hi Pablo,

JST is a central scheme, it does not use MUSCL reconstruction.

For best convergence of the discrete adjoint everything should be consistent, otherwise you are linearizing around an unconverged solution.

From a mathematical stand point the discrete adjoint should converge better if you increase the CFL, and if relaxation becomes necessary use RELAXATION_FACTOR_FLOW in the range 0.5 - 0.8.
JST results in relatively hard linear systems so BCGSTAB+ILU are your best bet, the former to avoid using too much memory.

Kaanytk and pgdelaserna like this.
pcg is offline   Reply With Quote


adjoint, residuals, su2

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Discrete vs Continuous Adjoint solution variable: Scaling/normalization issue? asitav SU2 2 November 21, 2018 19:11
Problem with Discrete adjoint based on RANS SumanVajjala SU2 3 July 31, 2018 05:36
Discrete Adjoint giving garbage values Manish Kumar Mishra SU2 1 March 7, 2018 15:35
Shape optimization doesn't converge - Adjoint log file JPBLourenco SU2 Shape Design 0 December 11, 2017 08:41
Discrete Adjoint Euler Computation doan.nak SU2 2 June 6, 2014 04:01

All times are GMT -4. The time now is 00:08.