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Old   July 18, 2011, 15:02
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SamboReal
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Hello guys,
I have a questions depending on adjointShapeOptimizationFoam. Did anyone of you already used it?.
I runned the tutorial but I can not identify that he is improving the geometry.
I didn’t changed anything in the tutorial!
Can someone help me?

Thanks
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Old   July 18, 2011, 16:42
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?????????????
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Old   July 19, 2011, 00:32
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Masashi Ohbuchi
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Hi,
You can plot contour of alpha. I suppose this means plugged space for drag reduction.

And following presentation gives adjoint method for optimization.
http://www.openfoamworkshop.org/6th_...ers_slides.pdf
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Old   July 20, 2011, 09:45
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Thank you very much.
Do you may no, where I can find some more information about that?
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Old   August 25, 2011, 09:55
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Nick Gardiner
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Hi

Can you explain what the alpha stands for? And in the slide show linked to above, is L the same as lambda in the solver?

Thanks
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Old   October 20, 2011, 14:15
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David Boger
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Hi Nick,

You've probably answered your own questions long ago (or given up entirely), but no, the L in the slides refers to the cost function that is to be optimized. The purpose of the equations is to calculate the gradient of the cost function with respect to the porosity (alpha) in each cell. Once the gradient is in hand, the alpha field is updated by moving in the direction of the gradient (steepest descent). The lambda in the code controls the step size taken along the gradient; i.e., the step size for the steepest descent method.

Hope that helps,
David
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Old   September 10, 2012, 20:29
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Erkan
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Hi guys,

i am also new with openfoam. Unfortunatelly the above links are not working .
Is there any other document where too have a look on the equations?

Checking the .c file and trying to understand the equations is very difficult.

thanks

Last edited by uwsa; September 10, 2012 at 23:15.
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Old   October 24, 2012, 12:06
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Hello to everybody,

has someone already tried to solve shape optimization for an alternative cost function like flow uniformity?

As far as I understand, the current implementation tries to reduce total pressure loss.
Has someone a starting point for me to change this or add something?

Thanks in advance,
georg
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Old   October 25, 2012, 04:12
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Hi Georg,

Some references which present additional cost functions:

Othmer, C., Th. Kaminski, and R. Giering, Computation of topological sensitivities in fluid dynamics: Cost function versatility, Proc. ECCOMAS CFD, Delft, 2006
http://www.wire.tu-bs.de/mitarbeiter...ad_eccomas.pdf

and

Othmer, C. (2008), A continuous adjoint formulation for the computation of topological and surface sensitivities of ducted flows. International Journal for Numerical Methods in Fluids, 58: 861–877. doi: 10.1002/fld.1770
http://onlinelibrary.wiley.com/doi/1....1770/abstract

regards,
Sylvester
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Old   October 26, 2012, 06:16
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Hi Sylvester,

thank you for the references.
I did not know the first one yet.
Some more stuff to read!

Honestly, I have some difficulties to identify the definition of the cost function within the solver.
Can you help?

Best regards,
georg
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Old   October 26, 2012, 08:24
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Hi Georg,

That is because the cost function is not defined in the solver, but in the boundary conditions. In this case they are 'adjointOutletPressure' and 'adjointOutletVelocity'.

regards,
Sylvester
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Old   October 26, 2012, 11:12
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Sylvester, you´re right!
I found the explanation within the papers.
Thanks for your pointer!

Unfortunately, this does not solve my problem completely.
Maybe I just do not see the wood for the trees.
I am still puzzling around the translation of the cost function, e.g. pressure loss, into the correct boundary conditions!

Any hint is helpful!

Best regards,
Georg
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