Optimizaed angle of Attack

[hosseinnegahban]

Hi Professor He,

I had a question regarding angle of attack variable in DAFoam. I am running a 2D optimization case with having trailing edge morphing. Optimization is done, and the Cd is minimized, however, the angle of attack changes considerably for example it changes from 3 degrees to 0.313. Is it normal ? Because when I run a simple simulation in openfoam with AOA= 0.313 without optimization, the drag is lower than the optimized drag.

I would appreciate if you help me with this question.

Here is the attached opt_IPOPT results and the script below shows the variation of angle of attack which has changed from 3 degees to 0.313 degrees.
opt_IPOPT.txt

[friedenhe]

What are the CD and CL from the DAFoam optimization? And what are the CD and CL from the "simple simulation in openfoam with AOA= 0.313 without optimization"?

[hosseinnegahban]

For the optimization case the initial AOA= is 3 degrees and CL=0.44147 (constrained) and optimized Cd= 0.010466 and the optimized AOA =0.313

For the simple simulation without optimization, AOA= 0.313 and CL= 0.16396 and Cd = 0.009126

[friedenhe]

Comparing two designs' Cd is only meaningful if they have the same lift.... If you set AOA=0 degree, you get an even lower drag...

[hosseinnegahban]

How about Cl/Cd comparison? When I compare the Cl/Cd of the two designs the optimized one is 42 and the simple one 18. Is this comparison logical?