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g-wagon November 20, 2011 23:13

Ask about how to set up geometry and mesh for moving mesh case
i'm newbie..i want to do dynamic analysis for my butterfly valve case 2D problem, as in real case i want to make a motion for my valve so i have to use moving mesh methode in FLUENT but i don't know how to set up geometry and mesh in GAMBIT for such case like this, please help me what i have to do first, here is my model

-mAx- November 21, 2011 14:05

in your case, moving mesh (remeshing in fact) will be treated within FLuent solver.
So no need to do something in Gambit.
BUT I would suggest you to switch to sliding mesh.
Create a circle surrounding your butterfly valve and split your domain with the circle.
Because of sliding mesh, you need to create interfaces: your disk (valve included) will rotate and you need interfaces for interpolating data between rotor and stator.
FOr that: copy and translate anywhere your disk. Delete the original disk.
Assign remaining circle (stator-edge) as interface.
Assign also circle (rotor-edge from copy) as interface
Translate back your disk (rotor).
Now your 2 surfaces are disconnected and your rotor will be able to rotate free.
You can mesh both
Check tutorial on sliding mesh for set up in Fluent

g-wagon November 22, 2011 03:02

i just want to make a sure max, does my picture below right max??surface with two interface and then connect it in FLUENT

-mAx- November 22, 2011 04:21


-The interface has to be the full circle.In your case interface1 &2 belong to the same.
You will not able to see both interfaces separately since they are superposed.

-Then you may try to change your circle radius for preventing small angles as it seems you have in your picture (circle & top edge are tangential and will generate skewness problem). Try a very small change in radius (tolerance) just for creating a gap between entities

g-wagon November 22, 2011 04:26

okey i understand max what you want to talk about, the important things to create two interface between stator and rotor then connect it , right? okey max, thank for your assistance. owh max can you help me with the UDF? :)

-mAx- November 22, 2011 04:30

No you don't have to connect them. You need to couple the interfaces but lately in Fluent.
forget UDF with me... ;)

g-wagon December 15, 2011 03:44

hi max
how much surface i should have for this geometry??is it two?just the stator and for the rotor?

-mAx- December 15, 2011 03:55

at least 2.
Same topic here:

g-wagon December 15, 2011 04:08 have my own geometry based on your guide, here is my geometry, is it correct??

-mAx- December 15, 2011 04:53

I don't see your pictures

g-wagon December 15, 2011 08:03

-mAx- December 15, 2011 08:55

yes but your circle (interface) is too big.
Thus you will have mesh issue especially where the circle is tangential to your pipe.
So reduce the circle radius

g-wagon December 15, 2011 08:57

okey i got it max..thanks max. now my problem is to define the angular velocity for that thing using UDF

g-wagon December 20, 2011 01:41

hi max.. would you tell me about procedure for simulating this in fluent using sliding mesh approach and then tell me what should i do when i want to use UDF for the motion in this simulation using sliding mesh, thanks

-mAx- December 20, 2011 03:16

Prior to the sliding mesh, I would test if the interfaces are ok.
Juste define grid interfaces, and compute with your inlet velocity.
If everything is ok (understand fluid flows through the interfaces), then you can switch to sliding mesh.
Just enable dynamic mesh and set your angular velocity to your rotor domain. Since it is sliding mesh, no mesh option is required (smoothing, remeshing or layering).
For time dependant angular velocity, you can use UDF (maybe profile), but I am not so experienced in this field

g-wagon December 20, 2011 03:26

the first plan i want to use sliding mesh for this dynamic analysis, i have prepared with the geometry as you taught me last day.. this day when i'm trying to do the simulation i could not fix for the motion especially because i cannot input my UDF in sliding mesh approach.. based on your words, i can use dynamic mesh approach... is there any change in geometry preparation when i use dynamic mesh??or still be rotor and stator as you said,

-thanks a lot-

-mAx- December 20, 2011 03:36

dynamic mesh literally means dynamic update from mesh, but in you case you don't need to update your mesh since they are disconnected.
Understand you can rotate your rotor zone without any effect on stator mesh (thanks to interfaces)
Basically now you only need to define your rotor domain as rigid body, and defined a angular velocity.
Then you can preview the mesh motion, and you should see your rotor domain rotating

g-wagon December 20, 2011 03:46

so the first thing that i've to do is...checking the dynamic mesh parameter in fluent right??

-mAx- December 20, 2011 03:58

go to define/dynamic mesh/zones...
select your rotor zone, define it as rigid body, and set your angular-velocity.
I don t remember if you have to set your velocity in dynamic mesh panel, or in the boundary condition panel (you have to try)
(I don't have Fluent, I am basing on User Guide)

g-wagon December 20, 2011 04:05

i think you wrong max, we have to enable the dynamic mesh parameter and then we go to dynamic mesh zone :D

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