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-   -   Is my Dynamic mesh setup correct? (http://www.cfd-online.com/Forums/fluent/106902-my-dynamic-mesh-setup-correct.html)

cfd seeker September 12, 2012 03:31

Is my Dynamic mesh setup correct?
 
4 Attachment(s)
I am trying to simulate flapping motion of the wing using Dynamic Mesh. I have setup the case in Fluent but I have some doubts and questions regarding it. I am uploading the pictures which will show the dynamic mesh setup. Kindly tell me is it correct? The problem consist of a domain around the wing, symmetry plane, wing and fluid zones. Few questions......

1. I have declared domain(farfield) as "Stationary" zone as shown in pic1. Is it correct? how to set value of "Cell Height"(shown by a question mark in pic1)?

2. Fluid is set as "Deforming" as shown in pic2. Is it correct? values of the "Zone Parameters" will be taken from "Zone Scale Info" as shown in pic2? right?

3. S1020 is the name of wing which will be given motion using a DEFINE_GRID_MOTION udf and S1020 is set as "User Defined" as shown in pic3 is it correct? how to set value of "Cell Height"(shown by a question mark in pic3)?

4. Symmetry plane is set as "Stationary" as shown in pic4 is it correct? how to set value of "Cell Height"(shown by a question mark in pic4)?

Also after the finalization of UDF I will use full structured hexa mesh for this problem. For this purpose in Dynamic mesh I will only use "Smoothing" and "Layering" for mesh update? am I right kindly comment? I cannot use "Remeshing" as it only works for unstructured meshes? right?

nimbus1947 September 13, 2012 23:25

What i am about to you tell you works for unstructured tetrahedral mesh.

1. Cell Height is the ideal height based on which Fluent calculates whether to split or collapse cells.
Ref:https://www.sharcnet.ca/Software/Flu...ug/node396.htm
2. Use DEFINE_CG_MOTION for the motion of wall.
Ref:https://www.sharcnet.ca/Software/Flu.../udf/fludf.pdf
3. Symmetry plane should be set as deforming.
4. Farfield -> Stationary ? -- Not required
fluid -> Deforming? -- not required

aerosjc September 14, 2012 23:27

1. Farfield not necessary to be stationary. I never set a certain value for the cell height. I just keep the original value. It's ok for my case.
2. Fluid not necessary to be deforming. So, do not need to worry the zone parameters.
Leave them alone.
3. You should refer to the UDF manual for more infomation about DEFIEN_GRID_MOTION and DEFINE_CG_MOTION. In fact, you should use DEFINE_CG_MOTION to define the motion of your wing. And, you should set "Rigid Body" for your wing.
4. I think the symmetry plane may be better to be set as deforming.
5. I don't know whether you want to rotate the wing a big angle, say 45 degrees, or not. Smoothing is available for small degrees. I hold an opinion that layering is not suitable for your flapping case. Remeshing is designed for big degrees or big displacement movement. Actually, I do not know how to move the structural mesh for a big displacement. If you make it, please tell me how. :)

cfd seeker September 15, 2012 14:27

:confused:
Quote:

Originally Posted by aerosjc (Post 381877)
1. Farfield not necessary to be stationary. I never set a certain value for the cell height. I just keep the original value. It's ok for my case.
2. Fluid not necessary to be deforming. So, do not need to worry the zone parameters.
Leave them alone.
3. You should refer to the UDF manual for more infomation about DEFIEN_GRID_MOTION and DEFINE_CG_MOTION. In fact, you should use DEFINE_CG_MOTION to define the motion of your wing. And, you should set "Rigid Body" for your wing.
4. I think the symmetry plane may be better to be set as deforming.
5. I don't know whether you want to rotate the wing a big angle, say 45 degrees, or not. Smoothing is available for small degrees. I hold an opinion that layering is not suitable for your flapping case. Remeshing is designed for big degrees or big displacement movement. Actually, I do not know how to move the structural mesh for a big displacement. If you make it, please tell me how. :)

Quote:

2. Fluid not necessary to be deforming. So, do not need to worry the zone parameters.
Leave them alone.
Are you sure about this :confused:...I guess fluid region will get deform once wing will flap, we check on Smoothing, Layering and Remeshing in order to smooth, layer and remesh "Deformed" portion of the mesh in the FLUID zone, isn't it? your comments

cfd seeker September 15, 2012 14:32

Quote:

4. I think the symmetry plane may be better to be set as deforming.
I am not sure about this? any body else can clarify it please....

Quote:

3. You should refer to the UDF manual for more infomation about DEFIEN_GRID_MOTION and DEFINE_CG_MOTION. In fact, you should use DEFINE_CG_MOTION to define the motion of your wing. And, you should set "Rigid Body" for your wing.
We can use both Macros but ifact Define_Grid_Motion is more better than Define_CG_Motion

aerosjc September 19, 2012 05:15

I agree with you on the idea that the fluid region will deform once the wing will flap. But I think that the setting of smoothing, layering and remeshing is doing this job, so we do not need to set the " deforming " option. This is my opinion.

aerosjc September 19, 2012 05:17

I remember the macro DEFINE_GRID_MOTION is for your mesh motion, instead of your wing motion. my opinion.

cfd seeker September 23, 2012 03:50

Quote:

Originally Posted by aerosjc (Post 382503)
I agree with you on the idea that the fluid region will deform once the wing will flap. But I think that the setting of smoothing, layering and remeshing is doing this job, so we do not need to set the " deforming " option. This is my opinion.

I confirmed it from a very experienced user that for this problem zones will be defined as fallows....
1. Farfield to set as "Stationary"
2. Symmetry also as "Stationary"
3. Fluid to define as "Deforming"
4. Wing to set as "Rigid Body" once you use DEFINE_CG_MOTION macro

aerosjc September 23, 2012 05:51

ok, but I also made a success without your 1, 2, 3.

cfd seeker September 23, 2012 06:07

Quote:

Originally Posted by aerosjc (Post 383187)
ok, but I also made a success without your 1, 2, 3.

Strange because I also confirmed it from the posts in other forums. Have you compared your results with any benchmark case?

aerosjc September 23, 2012 07:58

Could you give me some cases for confirmation? Many thanks!

cfd seeker September 24, 2012 12:10

Quote:

Originally Posted by aerosjc (Post 383194)
Could you give me some cases for confirmation? Many thanks!

you mean Papers or my case and data files?

cfd seeker September 24, 2012 12:13

Quote:

Originally Posted by aerosjc (Post 383194)
Could you give me some cases for confirmation? Many thanks!

http://www.cfd-online.com/Forums/flu...volume-3d.html
Read this thread

Vidit Sharma December 16, 2012 10:37

Hi All..

Sir,
I am trying to rotate a 2D box or a 2D cup structure in Fluent using smoothing and remeshing. I am using tri mesh and as mentioned in Fluent Manual I am using smoothing and remeshing and also set the remeshing parameters from mesh info tab given in the remeshing menu. But the problem is that when i start simulation and it goes to first time step Fluent display "Updating mesh at time level N..." and here it stops and it happened alot of time and even waiting after a whole day it didnt worked. I also tried time step size from 0.01 to 0.000001 but it still show this problem.

Can you plz help in this case?

Thank u in advance

akshaymanikjade January 26, 2013 15:01

you pls check your dynamic mesh parameter properly.....if have proper idea to set or no then let me know so will help in this regard..:)


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