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applying time variable rotation to spherical cavity

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Old   June 28, 2014, 10:19
Default applying time variable rotation to spherical cavity
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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
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Old   June 29, 2014, 06:17
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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?
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Old   June 29, 2014, 08:29
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Quote:
Originally Posted by ghorrocks View Post
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).
thx for your reply
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Old   June 29, 2014, 19:33
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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?
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Old   June 30, 2014, 07:41
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Quote:
Originally Posted by ghorrocks View Post
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:
theta(time) = (1/2)* (deltatheta*(1+tanh((2*thetadot*(time-t0))/deltatheta)))
deltatheta, thetadot and t0 are known constants


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Old   June 30, 2014, 08:48
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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.
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