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Flow over rotating sphere

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Old   August 11, 2009, 04:57
Default Flow over rotating sphere
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mistry
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Hi all
i want to do analysis of flow over rotating sphere.problem is:

to specify rotating domain in CFX Pre i found when i specify sphere as solid domain it is not giving be rotaion option when i specify fluid domain it only gives me option how to solve problem...

secondly i think SST model is best for the selection any suggestion?

how to specify FSinterface... here

Please guide me.
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Old   August 11, 2009, 09:16
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Glenn Horrocks
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Hi,

Assuming you are modelling flow over a rotating sphere with a known velocity then forget about solids, rotating domains or multiple domains. Just have a single domain with the sphere cut out of it. To impose the sphere rotation give the sphere walls a tangential velocity. I think the easiest way to apply this velocity is using a CEL expression to give velocity on the sphere surface as a function of XYZ location - this is easy providing the sphere location is known and the rotation rate is known.

As for which turbulence model is best - that depends on what you are trying to get out of the model and what Reynolds number and Mach number you are running at. SST is a good general purpose one but there are cases when it is not appropriate.

Glenn Horrocks
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Old   August 11, 2009, 10:02
Default Rotating sphere
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mistry
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Sir,
Really your quick reply energied me do continuous work on CFD...

may i get any hint how to specify rotational velocity using CEL on sphere surface. my idea is to specify inlet region velocity need to specify.

My inlet velocity is 3 m/s and diameter of sphere is 1,1.5 m ,rotational speed 100rpm,150,200 and want to study pressure,velocity distribution on outer surface.

please Guide me.
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Old   August 11, 2009, 20:07
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As I said, it is a pretty basic CEL expression to give the sphere a rotating wall. You should be able to derive the expression yourself once you understand the basics of CEL. Have a look in the tutorial examples for some examples of how to use CEL.

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