Flow over rotating sphere

csmistry · August 11, 2009, 04:57

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.

ghorrocks · August 11, 2009, 09:16

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

csmistry · August 11, 2009, 10:02

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.

ghorrocks · August 11, 2009, 20:07

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.

Glenn Horrocks

August 11, 2009, 04:57	Flow over rotating sphere	#1
csmistry Member mistry Join Date: Apr 2009 Location: India Posts: 69 Rep Power: 17	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.

August 11, 2009, 10:02	Rotating sphere	#3
csmistry Member mistry Join Date: Apr 2009 Location: India Posts: 69 Rep Power: 17	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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August 11, 2009, 09:16		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	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

August 11, 2009, 20:07		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	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. Glenn Horrocks