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-   -   Negative Shear? (http://www.cfd-online.com/Forums/fluent/29072-negative-shear.html)

Mark November 13, 2001 10:53

Negative Shear?
 
Hi

I'm currently running a Fluent simulation of a turbine stator.

When plotting the wall shear stress Fluent reports that the wall shear stress is negative at some places (especially the suction side). Can somebody please explain this to me? Does this mean that the wall shear is of opposite direction to the velocity in the cell closest to the wall? Is this physical? Or are the wall functions pulling my leg?

I'm running the case with the realizable k-epsilon model and non-equlibrium wall functions, The case is compressible and subsonic.

Regards

Mark


Rob December 26, 2001 16:05

Re: Negative Shear?
 
Mark,

Negative shear stress at some points along a surface generally indicate reversed flow. This happens most often in a region where the boundary layer has separated off of a surface. In your case, negative shear is very commonly found in the separated region of an airfoil shape, which is usually found on the suction side of the airfoil. I hope this helps some.

Rob


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