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-   -   Mesh Displacement Normal to the Wall (https://www.cfd-online.com/Forums/cfx/97911-mesh-displacement-normal-wall.html)

 Juliet February 28, 2012 08:33

Mesh Displacement Normal to the Wall

Hi Everyone,

Do you know how to impose the mesh displacement normal to each node in Ansys CfX v.13 ? The wall I'm trying to displace is quite irregular. I've the distance by which each node should be displaced , but I want to impose the movement normally to each one of the nodes. I could only select a general frame of reference for the wall, but this would not give me a refined enough displacement.

Hope you can help me!

Cheers

J

 ghorrocks February 28, 2012 18:05

You might be able to define this using the surface normal variable. Look in the CFX Reference manual for the available list of variables and hopefully you can use the surface normal variable.

 Juliet February 28, 2012 21:46

Hi Glenn,

Thank you so much for your prompt reply! The surface normal variable I managed to find in CfX Pre was : Normal Area in the X,Y,Z direction. I used this to specify the Mesh Displacement in the x direction as : Specified Displacement X --> 4[mm^-1] * Normal Area X (where 4 is just an arbitrary constant].

However, my solver crashed with this error : "Normal area vectors are only available at boundary face centers or integration points".

I also tried the other variables in CfX Pre which seemed similar to the one suggested by you, which are : Normal X and Normal Vector. I still got the same error.

Do you know what I am doing wrong?

Thank you so much for your help!!!

J

 ghorrocks February 29, 2012 06:53

Looks like the normal areas are not available at the nodes. This makes things trickier. I cannot think of a simple way of doing this.

 stumpy February 29, 2012 10:34

I thought that might happen. You can try making a vector Additional Variable equal to Normal X/Y/Z, then base your expression on the Additional Variable instead. This may make the data available at the nodes (but my best guess is that it won't work). There's no other solution I can think of, unless you can describe your surface with an equation.

 MikeD123 April 18, 2012 16:50

Hi Juliet,

Just wondering if you ever found a solution to your problem? I am attempting to solve a moving boundary problem, where the boundary is displaced in the normal direction at each point/node (this vector value changes across the boundary). I encountered the same problem as yourself when attempting to use the Normal X, Normal Y command. I also attempted the suggested procedure of assigning the Normal X variable to an algebraic additional variable, however this gave the same error as before. I think it maybe possible to retrieve some information using user-fortran routines, have you come across this at all? I have little experience in this area so it would be a lot to learn only to find that this approach was just as fruitless.

Regards,

Michael

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