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skd May 25, 2006 14:22

Moving wall
 
Hi,

I'm going to make a wall move in fluent and I'm not sure which method I should use. I have thought of two methods:

1) Create a UDF using DEFINE_GRID_MOTION and then hooke it to the right zone in the dyn.mesh zones panel. The motion will then be specified with the x and y displacements,

2)Create a UDF using DEFINE_PROFILE and then hooke it into the wall velocity section in the b.c panel. The motion will then be specified with its x- and y velocity.

-Are there any differences in performence between these two methods?

-I know you can loop over the nodes in method 1, but can you do that with method 2? or is only a face loop possible here?

-Are there any differences in using a face loop compared to a node loop if the entire wall is set to have the same displacement/velocity?

Please help me with this!:)

Thanks in advance!

skd

chankhar May 27, 2006 14:08

Re: Moving wall
 
you can make wall move at the boundary condition and don't work with udf chankhar

skd May 28, 2006 03:42

Re: Moving wall
 
hi, can I use the method I described in alternativ 2? skd

skd May 28, 2006 06:39

Re: Moving wall
 
I have tried to make the wall moving in the b.c panel, by selecting moving wall and components, but it will not work... Could you please help me with some tips? Thanks! Skd

Luca May 29, 2006 03:26

Re: Moving wall
 
if you use the bc panel you can add only a tangential component to the wall velocity (refer to the user guide). Luca

Fabrice June 8, 2006 01:46

Re: Moving wall
 
Hi,

with a DEFINE_PROFILE UDF, you will set only the boundary velocity of the wall, but you will not make it move and so your results shouldn't be correct. You should use a DEFINE_CG_MOTION macro to make your wall move and use a dynamic mesh. Let me know if you succeed in implementing a dynamic mesh because I've got big troubles in my model (negative cell volumes are detected after a few iterations). Thanks.

skd June 8, 2006 05:25

Re: Moving wall
 
HI,

I have managed to implement a moving wall using a define_grid_motion macro. I have also used the define_cg_motin macro to move some other things. It is very important that you have adjusted the dynamic mesh parameters correct. And it requires a very small time step size! For one of the moving things my time step is 1e-5 and it only works with the coupled implicitt solver, but I don't know why. Hope this gives you some idea for what you can check!

You should use remeshing and smoothing,but you probably know that:)

skd

skd June 8, 2006 05:28

Re: Moving wall
 
HI,

I have managed to implement a moving wall using a define_grid_motion macro. I have also used the define_cg_motin macro to move some other things. It is very important that you have adjusted the dynamic mesh parameters correct. And it requires a very small time step size! For one of the moving things my time step is 1e-5 and it only works with the coupled implicitt solver, but I don't know why. Hope this gives you some idea for what you can check!

You should use remeshing and smoothing,but you probably know that:)

-skd

skd June 8, 2006 13:27

Re: Moving wall
 
HI,

I have managed to implement a moving wall using a define_grid_motion macro. I have also used the define_cg_motin macro to move some other things. It is very important that you have adjusted the dynamic mesh parameters correct. And it requires a very small time step size! For one of the moving things my time step is 1e-5 and it only works with the coupled implicitt solver, but I don't know why. Hope this gives you some idea for what you can check!

You should use remeshing and smoothing,but you probably know that:)

skd

skd June 9, 2006 04:53

Re: Moving wall
 
HI,

I have managed to implement a moving wall using a define_grid_motion macro. I have also used the define_cg_motin macro to move some other things. It is very important that you have adjusted the dynamic mesh parameters correct. And it requires a very small time step size! For one of the moving things my time step is 1e-5 and it only works with the coupled implicitt solver, but I don't know why. Hope this gives you some idea for what you can check!

You should use remeshing and smoothing,but you probably know that:)

skd


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