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Old   April 22, 2014, 21:59
Default mesh displacement in CFX
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Mal
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I want to know the displacement of a particle in one certain direction,for example direction Y,so i use the motion mesh.But there are two kinds of displacement:Total Mesh Displacement Y and Mesh Displacement Y.If i want to know the motion trail of a particle in direction Y,which one i should refer to?Namely,what is the difference between the two kinds of displacement?
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Old   April 22, 2014, 23:12
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Glenn Horrocks
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I suspect you are getting confused between all the different displacements.

"Mesh Displacement" and "Total Mesh Displacement" refer to the motion of the MESH during a moving mesh simulation. It has nothing to do with the fluid flow or the motion of particles.

The variable "velocity" is the velocity of the FLUID.

Neither of these variables tell you anything about the motion of a particle.
If you are using lagrangian particle tracking then I think it is "Particle velocity".
If you are using eularian particle models then you will have to do some work to extract the particle motions - maybe a streamline of the particle phase velocity field.
If you are doing a rigid body simulation then it is in the rigid body variables.
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Old   April 27, 2014, 03:21
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Quote:
Originally Posted by ghorrocks View Post
I suspect you are getting confused between all the different displacements.

"Mesh Displacement" and "Total Mesh Displacement" refer to the motion of the MESH during a moving mesh simulation. It has nothing to do with the fluid flow or the motion of particles.

The variable "velocity" is the velocity of the FLUID.

Neither of these variables tell you anything about the motion of a particle.
If you are using lagrangian particle tracking then I think it is "Particle velocity".
If you are using eularian particle models then you will have to do some work to extract the particle motions - maybe a streamline of the particle phase velocity field.
If you are doing a rigid body simulation then it is in the rigid body variables.
Dear Glenn Horrocks,
Thanks for you reply.
I am using motion mesh for processing the simulation of the vortex-induced vibration for a cylinder.Now,i want to know the displacement of cylinder during the VIV, so i create a monitor particle on the center of cylinder,then i monitor this point I create when CFX is on solving.The question is that I have monitor the "Mesh Displacement" and "Total Mesh Displacement" for the user point, however i don't know which one is the real displacement of the point.Namely,what's the difference of the "Mesh Displacement" and "Total Mesh Displacement".
At last,I attached three graphic for this problem.
Kind regardsviv.JPG

mesh disp Y.jpg

total mesh disp Y.jpg
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Old   April 27, 2014, 06:37
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It depends on how you have set it up, but Mesh displacement will probably be the change in mesh position from the last time step, and total mesh displacement is the absolute position of the mesh. The total mesh displacement is the integral of the mesh position.
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