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Writing a CEL expression for y position at a specific timestep

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Old   March 27, 2019, 17:40
Default Writing a CEL expression for y position at a specific timestep
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Nick Thomas
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I am creating a deforming mesh and my equation for the motion is dependent of the starting position of a surface. Is there a way in CEL that I can use this value (the y position of every point on a cylinder at t=0) in a transient simulation? In other words, the y position of the cylinder will be changing but I only want to use its original position as a constant in my expression.
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Old   March 28, 2019, 03:57
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It should be possible but I still got some understanding problems. Is this a rigid body motion or do you actually deform the cylinder?
CFX gives you several options to perform mesh deformation. Lets say you want to displace the cylinder points by 1mm per timestep, you can use relative mesh displacement, which applies the deformation relative to the last timestep.
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Old   March 28, 2019, 07:38
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The initial coordinates (Initial X, Initial Y, Initial Z) are available via CEL, say

MyDispX= Initial X + ....
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Old   March 28, 2019, 13:48
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Quote:
Originally Posted by Opaque View Post
The initial coordinates (Initial X, Initial Y, Initial Z) are available via CEL, say

MyDispX= Initial X + ....
Thanks, that does the trick!

However, I am trying to use the Y coordinates at every node on a surface so that displacement is unique to each node on the wall. The cylinder moves at a constant velocity and then is displaced back to the start, but I am hoping each bit of the wall will relocate once it reaches a certain point. In other words the cylinder wall will be split during the displacement process. Is this possible? Trying "Initial Y@Cylinder Walls" does not work.
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Old   March 28, 2019, 14:08
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Not sure what you are trying to do.

Recall expressions have local context, i.e. if you are evaluating

MyDisp = Initial Y + 2 [cm]

on the Cylinder Walls, I assume the expression is also used under Cylinder Walls where

BOUNDARY: Cylinder Walls
BOUNDARY CONDITIONS:
MESH MOTION:
Option = ...
Displacement = MyDisp
END
END
END

There is no need to refer to the location, it is IMPLIED.

Perhaps I need better context of what your goal is
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