# applying time variable rotation to spherical cavity

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 June 28, 2014, 10:19 applying time variable rotation to spherical cavity #1 New Member   Join Date: Feb 2014 Posts: 5 Rep Power: 4 Hi everybody I want to apply this time variable rotation to a spherical cavity in CFX 14.0. theta(t) = (1/2)*(deltatheta)*(1+tanh((2*thetadot*(t-t0))/deltatheta)) deltatheta, thetadot and t0 are known constants. I'm a new user to CFX. I would really appreciate if you guide me through the process. thx

 June 29, 2014, 06:17 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 12,638 Rep Power: 98 Your equation is simple to do as a CEL expression. What do you mean you want a time varying rotation in a spherical cavity? Can you post an image of the motion you want to use?

June 29, 2014, 08:29
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 Originally Posted by ghorrocks Your equation is simple to do as a CEL expression. What do you mean you want a time varying rotation in a spherical cavity? Can you post an image of the motion you want to use?
The domain is a spherical container which 60% of its volume is filled with water.
I want to rotate the container around its axis (z axis for example) according to the formula given (theta as a function of time, which is obviously corresponds to a non-constant angular velocity rotation).

 June 29, 2014, 19:33 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 12,638 Rep Power: 98 That did not look like an image to me. And then do you apply the rotation as a tangential velocity to the outer walls of the container?

June 30, 2014, 07:41
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 Originally Posted by ghorrocks That did not look like an image to me. And then do you apply the rotation as a tangential velocity to the outer walls of the container?
Here is the picture of my domain with motion shown by arrows. as it seems, its a pure rotation around Y axis. the angular velocity is a function of time. gravity acts in -Y direction and 60% of the sphere volume will be patched with water.
first of all is applying the desirable angular velocity through :
Details of Default Domain Default >> Boundary Details >> wall velocity>> option (rotating wall)>> inserting a CEL Expression
enough or should I use dynamic mesh?
and what is the proper CEL expression?
here once again the angular position as a function of time:
deltatheta, thetadot and t0 are known constants

 June 30, 2014, 08:48 #6 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 12,638 Rep Power: 98 No need for moving mesh. The Default Domain Default >> Boundary Details >> wall velocity>> option (rotating wall) method you describe will be fine. You just need to transcribe your function into a CEL expression - this is trivial, your function looks like it will convert straight to CEL with little modification. ayousefi likes this.

 Tags cfx 14, rotational flow

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