Aerodynamic optimization : how to eliminate stalling wings ?

pinkerthoms · February 10, 2020, 10:23

Hi guys,

I'm actually working on the optimization of a leading edge of a morphing airfoil (single-element airfoil).
This optimization is done by varying its geometry for an angle of attack higher than the stall angle and therefore, some of the airfoils you get lead to stall.
However, once the stall is reached, value of the lift coefficient oscillates (i.e. RANS simulations of the airfoil don't converge) and sometimes, once the maximal iterations number is reached, the simulation stops while the lift coefficient is the highest.
Consequently Ansys thinks that this kind of design points are good … But they are not !

I can't find a way to "eliminate" those airfoils in the optimizer. I already tried to use an average lift coefficient but Ansys doesn't accept it as an output parameter.
I also thought about using residuals as output parameters (and eliminate airfoils for which residuals are above a certain limit) but I can't find a way to do this.

Can someone help me ?

Thomas.

vinerm · February 10, 2020, 11:10

You didn't mention which optimizer is being used; is it the optimization tool within the Fluent or is it based on DOE in the WB?

pinkerthoms · February 10, 2020, 11:24

Quote:

Originally Posted by vinerm

You didn't mention which optimizer is being used; is it the optimization tool within the Fluent or is it based on DOE in the WB?

Thank you for your answer and sorry for the lack of information.
I am using the one based on DOE in the WB.

vinerm · February 11, 2020, 05:06

No experience in WB

February 10, 2020, 10:23	Aerodynamic optimization : how to eliminate stalling wings ?	#1
pinkerthoms New Member Join Date: Feb 2020 Location: Belgium Posts: 4 Rep Power: 6	Hi guys, I'm actually working on the optimization of a leading edge of a morphing airfoil (single-element airfoil). This optimization is done by varying its geometry for an angle of attack higher than the stall angle and therefore, some of the airfoils you get lead to stall. However, once the stall is reached, value of the lift coefficient oscillates (i.e. RANS simulations of the airfoil don't converge) and sometimes, once the maximal iterations number is reached, the simulation stops while the lift coefficient is the highest. Consequently Ansys thinks that this kind of design points are good … But they are not ! I can't find a way to "eliminate" those airfoils in the optimizer. I already tried to use an average lift coefficient but Ansys doesn't accept it as an output parameter. I also thought about using residuals as output parameters (and eliminate airfoils for which residuals are above a certain limit) but I can't find a way to do this. Can someone help me ? Thomas.

February 10, 2020, 11:10	Which optimizer	#2
vinerm Senior Member Vinerm Join Date: Jun 2009 Location: Nederland Posts: 2,946 Blog Entries: 1 Rep Power: 36	You didn't mention which optimizer is being used; is it the optimization tool within the Fluent or is it based on DOE in the WB? __________________ Regards, Vinerm PM to be used if and only if you do not want something to be shared publicly. PM is considered to be of the least priority.

February 11, 2020, 05:06	Apologies	#4
vinerm Senior Member Vinerm Join Date: Jun 2009 Location: Nederland Posts: 2,946 Blog Entries: 1 Rep Power: 36	No experience in WB __________________ Regards, Vinerm PM to be used if and only if you do not want something to be shared publicly. PM is considered to be of the least priority.

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