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-   -   Why Q-criterion does not show the gradients on whole surface? (https://www.cfd-online.com/Forums/main/230182-why-q-criterion-does-not-show-gradients-whole-surface.html)

mazhar16823 September 11, 2020 12:25

Why Q-criterion does not show the gradients on whole surface?
 
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Hi everyone,

I have performed steady state simulation for a wind turbine blade using STARCCM+. Now, I want to demonstrate the velocity gradients on the blade. Although, I have created an isosurface and Q-Criterion by varying the isovalue from 50 - 1000, but I see that gradients are represented on half of the blade and half blade is taken away. Actually, I want to compare my Q-criterion with the reference Q-criterion from Large eddy simulation. Could you please suggest how to fix this issue - I want to have the gradients all along the blade surface. You can see in the figures, for LES gradients are represented on the whole surface whereas in my case I don't get them throughout.



Thanks for your time.

FMDenaro September 11, 2020 13:37

Quote:

Originally Posted by mazhar16823 (Post 782593)
Hi everyone,

I have performed steady state simulation for a wind turbine blade using STARCCM+. Now, I want to demonstrate the velocity gradients on the blade. Although, I have created an isosurface and Q-Criterion by varying the isovalue from 50 - 1000, but I see that gradients are represented on half of the blade and half blade is taken away. Actually, I want to compare my Q-criterion with the reference Q-criterion from Large eddy simulation. Could you please suggest how to fix this issue - I want to have the gradients all along the blade surface. You can see in the figures, for LES gradients are represented on the whole surface whereas in my case I don't get them throughout.



Thanks for your time.




In no way you can compare the steady state simulation to the instantaneous LES field. You must do a time averaging of the LES fields and then compare them.

mazhar16823 September 11, 2020 13:51

Quote:

Originally Posted by FMDenaro (Post 782600)
In no way you can compare the steady state simulation to the instantaneous LES field. You must do a time averaging of the LES fields and then compare them.


Thanks for your kind input.I am trying to represent the velocity gradients on the whole blade surface using RANSE; Is not it possible? Since there is void on half of the blade. I have varied the velocity scale and Isovalue for the Q-criterion as well.


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