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-   -   Problem with rotational mesh deformation: Part II (http://www.cfd-online.com/Forums/cfx/20771-problem-rotational-mesh-deformation-part-ii.html)

NymphadoraTonks November 3, 2004 06:34

Problem with rotational mesh deformation: Part II
 
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: http://www.imagedump.com/index.cgi?pick=get&tp=145367

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: http://www.imagedump.com/index.cgi?pick=get&tp=145367

The mesh outline at time 1.0s: http://www.imagedump.com/index.cgi?pick=get&tp=145368

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?!

TIA

NymphadoraTonks November 3, 2004 08:21

Re: Problem with rotational mesh deformation: Part
 
Oh lord ... how could I have been so dense!

Nevermind I've spotted my mistake :)


Ben November 4, 2004 04:05

Re: Problem with rotational mesh deformation: Part
 
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

Ben


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