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Flow over sphere at high Re

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Old   August 20, 2012, 23:19
Default Flow over sphere at high Re
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I am trying to do a 3D RANS simulation of flow past a sphere at high (up to 1,000,000) Reynolds. I am going to be trying to get data from this for a number of different turbulence models. But let's just stick to k-omega for now. I am also trying to check how well a snappyHexMesh solution will compare to a structured grid solution.

A few questions:

I am having difficulty coming up with a structured 3D sphere by using blockMeshDict -> Does anyone have any idea how to do this? I may post a separate question in the meshing forum.

We are trying to determine the coefficient of drag using a k-omega model (k and omega boundary conditions attached) at Re = 1M and were unsure about what conditions to implement on the sphere to control the surface roughness. Currently we are producing results with drag approximately double the expected for a smooth sphere and suspect that roughness is being introduced that we do not understand and cannot control.

Some people on forums say that nut and nuTilda are used for k-omega and some say they aren't, which is correct and what is an appropriate boundary condition to specify a smooth surface if they are indeed required?

Also, At the moment we are just using the default discretisation schemes for simpleFoam (attached in fvSchemes file).

Thanks for any help



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