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 colopolo August 12, 2011 01:07

dynamic mesh problem

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Dear All,

I have some problems about making dynamic mesh.

I made boundary layer mesh near the rigid body with the quad mesh and outside of quad mesh is consisiting with trimesh.

I would like to rotate the plate with quad mesh ( i.e. the quad mesh around the plate is not modified and only remeshing outside of the quad mesh)

But I have no idea how to do that. I did use spring-based smoothing and it works for small angle rotation.

The attached figure is what I want to do.

 zxin August 15, 2011 04:05

Just a guess, Can you rotate the boudaries instead of the plate?

 Doginal August 15, 2011 12:43

Hello Colopolo

This is something similar to what I have been working on. If you use fluent then i am not sure if i can help as i am using CFX.

My first suggestion is to move away from mesh deformation. Trying to rotate large angles with a deforming mesh is bound to create highly skewed elements. My suggestion is to break the domain into two parts, a rotating area and a stationary area. The rotating area would have to be circular and would have the plate inside. With this inner area, you can rotate the mesh without it deforming.

In CFX this can be done 2 ways (to my knowledge). First is by setting two different domains with the inner domain being a rotating domain. You would then define your interface to be a transient rotor stator and set the rate of rotation.

The second method is to use a moving mesh. In this case you would define a subdomain as the inner domain and specify the motion of the mesh. This thread can be used as a good reference on how to do that: http://www.cfd-online.com/Forums/cfx...g-domains.html

Best of luck and let me know if you have more questions

 colopolo August 15, 2011 19:44

I will work on your way in this week.

By the way, do you have any idea about it using Fluent?

Because, currently I am comparing the results of this case (harmonic rotating plate with +-2 degree, like as plate flutter analysis) with Fluent and Ansys (FSI).

Have a good day

 Doginal August 15, 2011 21:32

Sorry i have no advice if your using Fluent. I dont have any experience with it. With that being said, a 4 degree overall rotation does not seem large enough to warrant using a separate domain.

 colopolo August 15, 2011 22:53

As your mentioned, 1st method is similar to Moving reference frame in Fluent. Through your experiences, what about the results of simulation?

The 1st method is in a good agreement with some experimental results comparing with deforming mesh method?

which way is good one do you think?

 sail August 16, 2011 02:06

shure, it can be done. you just have to call the structured part and the unstructured part of volume with different names, than in the dynamic meshing panel of fluent you give the movement to the valvle and also to the structured part, but taking care to set the latter as "passive".

then you'll have to play with the spring factors and remeshing parameters to have something not too skewed.

 colopolo August 16, 2011 02:11

Thank you.

First, the edges between structured part and unstructured pare, are defined by interface? or what b.c do I put the 4 edges in Gambit?
Second, I used profile file to rotate pannel. in this case, do i only define structured part using profile? how about the unstructured part?

Quote:
 Originally Posted by sail (Post 320198) shure, it can be done. you just have to call the structured part and the unstructured part of volume with different names, than in the dynamic meshing panel of fluent you give the movement to the valvle and also to the structured part, but taking care to set the latter as "passive". then you'll have to play with the spring factors and remeshing parameters to have something not too skewed.

 sail August 16, 2011 18:26

Quote:
 Originally Posted by colopolo (Post 320200) Thank you. First, the edges between structured part and unstructured pare, are defined by interface? or what b.c do I put the 4 edges in Gambit? Second, I used profile file to rotate pannel. in this case, do i only define structured part using profile? how about the unstructured part? I appreciate your help. ^^
has been a while since i havent' used gambit, but anything similar to internal should do the trick. you don't have to use interfaces.

about your second questions, you just specify the motion profile for the valvle and the structured domain. the unstructured is left undefined (the solver take care of it. ) you might just set the most external bc as static in the dynamic mesh setup.

there are lot of well-done tutorials on this subject all across the internet. google them.

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