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January 29, 2014, 23:08 
Surface_Sensitivity variable in surface_adjoint file

#1 
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Tommy Chen
Join Date: Mar 2011
Location: University of Michigan
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Hi Stanford guys
I have run a continuous adjoint computation of the RAE2822 airfoil in the test cases. In the surface_adjoint.dat file and the surface_adjoint.csv file, I found that the surface_sensitivity variable is a one dimensional scalar instead of a 2D vector? Why is the surface sensitivity of 2D airfoil scalar instead of vector ? Many thanks 

January 29, 2014, 23:41 

#2 
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Tommy Chen
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So is this 1D surface_sensitivity variable the absolute value of the 2D gradient vector?
If then , what is the variable that difines the direction of the gradient? 

January 30, 2014, 01:58 

#3  
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Francisco Palacios
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Quote:
In this link your will find a good reference of the implementation https://adl.stanford.edu/papers/AIAA..._March2012.pdf Anyway, the computed sensitivity is with respect to displacements in the normal direction. So it is always an scalar... e.g. how change the drag of the aircraft when you move a point on the surface in the normal direction to the surface. Best, Francisco 

January 30, 2014, 09:41 

#4  
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Tommy Chen
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Quote:
Thanks Francisco, So if the swept angle of the wing or the span and chord length of the wing are also design variables,which leads to the change in the plan form, then the normaltosurface sensitivity is still all that we need to calculate the gradient of the objective function ? 

January 30, 2014, 21:14 

#5  
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Francisco Palacios
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Quote:
Best, Francisco 

January 30, 2014, 21:22 

#6  
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Tommy Chen
Join Date: Mar 2011
Location: University of Michigan
Posts: 96
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Quote:
So actually I can use all the normaltosurface sensitivity and the normal vector (the absolute value of which is the surface element area) to project the gradient to any other design variables developed myself. 

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