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Problem with rotational mesh deformation: Part II

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Old   November 3, 2004, 06:34
Default Problem with rotational mesh deformation: Part II
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I'm getting no where with this problem so I have to ask for help again. I have modified my test case slightly to simplify it.

I busy playing with the mesh deformation functionality in CFX 5.7.

I've set up a simple test problem as follows:

The origen of the coordinate system is in the exact centre of the fluid domain. The idea is for the flap to rotate around the coordinate system origen to present a varying obstruction to the flow.

I have named the cut out "flap" and specified its motion explicitly using CEL. In the Flap boundary condition mesh motion dialog I have set "Specified displacement" and used two CEL functions "XDisplacement" and "YDisplacement" for the X and Y displacements respectively.

I then defined these as follows:

AngleAmp = (30/360)*2*pi [rad] To = 1[s] Angle = AmpDeg*(t/To)[rad] XDisplacement = ((x*cos(Angle))-(y*sin(Angle)))-x YDisplacement = ((x*sin(Angle))+(y*cos(Angle)))-y

It's dead simple ... the flap is supposed to rotate 30* around the origen in 1 second.

The mesh outline at time 0:

The mesh outline at time 1.0s:

As you can see the rotation is correct i.e. 30* but the flap has "shrunk" down in size.

Any suggestions as to where I'm going wrong?!

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Old   November 3, 2004, 08:21
Default Re: Problem with rotational mesh deformation: Part
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Oh lord ... how could I have been so dense!

Nevermind I've spotted my mistake

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Old   November 4, 2004, 04:05
Default Re: Problem with rotational mesh deformation: Part
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hi tia, i 've got a quite similar problem with a rotating flap. can you tell me wether you made your mistake with the CEL- expressions or was there an other source for this "shrinking flap"

thanks in advance

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