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June 24, 2014, 16:37
#2
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Thomas D. Economon
Join Date: Jan 2013
Location: Stanford, CA
Posts: 271
Rep Power: 7
Hi,

Thanks for a great question. The type of continuous adjoint formulation in SU2 takes advantage of shape calculus in order to find analytic expressions for the surface sensitivity. This is done assuming small perturbations in the local normal direction alone, without loss of generality. Tangential and normal components can be taken into account (and have been in previous work), but this is not necessary.

Hope this helps clear things up,
Tom

p.s. Don't forget that finite differencing is prone to truncation/subtractive cancelation error.. it can often take a few tries to find the appropriate step size. It is typical that we find some discrepancy between the two gradients.
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November 17, 2017, 08:59
#3
New Member

Kemas Zakaria
Join Date: Nov 2017
Posts: 1
Rep Power: 0
Quote:
 Originally Posted by economon Hi, Thanks for a great question. The type of continuous adjoint formulation in SU2 takes advantage of shape calculus in order to find analytic expressions for the surface sensitivity. This is done assuming small perturbations in the local normal direction alone, without loss of generality. Tangential and normal components can be taken into account (and have been in previous work), but this is not necessary. Please see the attached description of how we compute gradients using projection for some more information. Hope this helps clear things up, Tom p.s. Don't forget that finite differencing is prone to truncation/subtractive cancelation error.. it can often take a few tries to find the appropriate step size. It is typical that we find some discrepancy between the two gradients.

Dear,

I am a new user in using SU2 and right now i want to use the surface sensitivity computed by SU2 to calculate the gradient of the objective function with respect to my own design variables. From the image attached in your reply, can you explain more in detail about the term deltaSi ("area of the surface control volume surrounding node i").

Any reply would be highly appreciated
Best regards,
Kemas

 November 22, 2017, 06:37 #4 Member   Zeno Belligoli Join Date: Sep 2013 Location: Delft, The Netherlands Posts: 52 Rep Power: 6 Hi Kemas, I think reading the first 2-3 chapters of Thomas Economon's dissertation will give you all the info you are looking for for the mathematical insights of the SU2 adjoint formulation. Best, Z

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