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Boundary Conditions on a Sphere

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Old   December 6, 2012, 06:34
Default Boundary Conditions on a Sphere
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Vasileios Sassanis
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Pals,

i want to apply a BC for velocity on a sphere. I want the velocity ALWAYS to be tangent on the faces of the sphere and never,during the solution, going through its surface.

Does anybody know which BC i should apply?
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Old   December 7, 2012, 04:42
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Tom Fahner
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Hello VSass,

It depends whether your sphere should be moving (movingMesh) or if it is only rotating in a stationary point. I am assuming it is the latter, in that case you can use:

rotatingWallVelocity

If it is the former:

movingWallVelocity

Depending on the choice you may need to set some other parameters that describe the motion.

Regards,
Tom
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Old   December 7, 2012, 04:47
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Vasileios Sassanis
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Thanks Tomf,

i have a fixed sphere so i guess i sould work with the rotatingWallVelocity.

Good day to you
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Old   December 7, 2012, 07:44
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Bernhard
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I am not sure what you are trying to model, but you could also consider slip as boundary condition.
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Old   December 7, 2012, 10:46
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Vasileios Sassanis
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Bernhard,

i have a hybrid sphere seperated in two boundaries, upstream and downstream, and this hybrid sphere is located inside a farfield which is also spherical and we suppose it is far away from our hybrid sphere. I am trying to solve the Navier - Stokes equations in the hybrid sphere using icoFoam,but Courant number keeps crashing no matter what time step i apply. I now work on modified icoFoam in order to keep e.g. maxCo=0.7,but i want to be sure that the crash is not due to boundary conditions.
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