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-   -   Surface Pressure Osciallation (https://www.cfd-online.com/Forums/fluent/69605-surface-pressure-osciallation.html)

kawamatt2 October 28, 2009 10:40

Surface Pressure Osciallation
 
I am simulating flow around a wind turbine blade section. The Reynolds number is quite high (3e6) and as such i am using a turbulent model. I am none too familiar with turbulence theories but have been using the k-omega with a turbulent kinetic energy calculated via k=(3/2)(Ti*U)^2 and specific dissipation from k/w<=Re .

I am searching for a steady state solution to compare with some experimental results. The simulation runs and converges fine and lift data is roughly 5% low compared to the experimental data. Where i'm having issues is on the surface pressure distributions. I'm getting some checker boarding on the top leading edge of the airfoil and i can't figure out why. Below is an element plot of the pressure contour and i have circle the checker boarding.

http://i5.photobucket.com/albums/y18...ureContour.jpg

Here is a picture of my grid. I built the grid in such a way that for the first 1% of chord away from the airfoil i used a structured grid and then progressed to an unstructured grid. Also a closeup of the mesh near the airfoil. I am using a Y+ of about 14 here. I have tried from 20 down to 4 with the same oscillating surface pressure results.

http://i5.photobucket.com/albums/y18...verallMesh.jpg
http://i5.photobucket.com/albums/y18...loseupMesh.jpg

Here is a plot of the surface pressure compared to the experimental data i have. You can see the squigles at the top leading edge of the airfoil.

http://i5.photobucket.com/albums/y18...essurePlot.jpg

Anyone have any ideas on how to get rid of these. I have read about the Rhie and Chow technique of discretization and i and assume fluent can use this. I must be using the wrong solver or have a parameter set wrong. Also this is an incompressible simulation.


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