Simulate a micro valve with fsi

FrankW · July 13, 2011, 05:52

Hi,

i try to simulate a micro valve with cfx. My first results of a simple 2D design are bad, because the mesh is distorted on the flap tip at the gap. I have tested many settings at the Mesh Deformation->Mesh Stiffness and i get not really a good deformed mesh. How can get i a good deformed mesh? The goal is to simulate a 3D model of a valve and if does'nt work in 2D i thing there is no chance to get a good 3d model. Has anyone a idea to modify the Mesh Stiffness so that i get usable mesh.

regards
Frank

stumpy · July 13, 2011, 10:05

Try the expert parameter 'meshdisp diffusion scheme = 3'

ghorrocks · July 13, 2011, 20:38

I would us a GGI to connect the two regions. Then the outer region does not move (or at least not much), and the inner thin region can deform without constraint of the outer region. This will be much easier than thrying to get mesh motion to work across both regions together.

FrankW · July 14, 2011, 03:45

Hi,

@stumpy The expert parameter does'nt work. I've seen no effect of this to the deformed mesh.

@glenn What do you mean with inner and outer region? Can you make a sketch. I've defined one subdomain under the flap without meshmotion.

ghorrocks · July 14, 2011, 08:56

How does this look?

Fluid6.jpg

u22 · February 14, 2013, 04:21

Hello all!

I am trying 3d FSI simulation with CFX 14, it crashes cause negative element is formed (see pic.). Setting meshdisp diffusion scheme 3 not avoid that error... How to get fixed wall mesh to "slide" along Y direction (but Z must be fixed) and to follow Y displacement of mesh on "Moving wall" side?

ghorrocks · February 14, 2013, 05:01

Split your fluid domain into 3 joined fluid domains like this, as shown by the orange lines:
fix.jpg

Give the vertical line the same X displacement as the piston, and the horz one the same vertical displacement. Then your mesh will stay nice and orthogonal.

u22 · February 18, 2013, 08:55

Thanks for the tip, Glenn!

I divided domain into 3 sub-domain. But I did not get how to give to points at stationary wall same displacement as moving wall for corresponding directions.
"Give the vertical line the same X displacement as the piston, and the horz one the same vertical displacement."

I have to use CEL ? Or set some specific conditions at subdomain or walls, like "mesh motions = unspecified"

ghorrocks · February 18, 2013, 17:21

On second thoughts this is trickier than I originally thought - I do not know how to specify one dimension but leave another dimension unspecified. I cannot see how to do that. But it would be nice if you could do that, it would make a number of motions simpler to specify. Sorry if I mislead you.

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July 13, 2011, 10:05		#2
stumpy Senior Member Join Date: Apr 2009 Posts: 531 Rep Power: 21	Try the expert parameter 'meshdisp diffusion scheme = 3'

July 13, 2011, 20:38		#3
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	I would us a GGI to connect the two regions. Then the outer region does not move (or at least not much), and the inner thin region can deform without constraint of the outer region. This will be much easier than thrying to get mesh motion to work across both regions together.

July 14, 2011, 03:45		#4
FrankW Member Frank Weise Join Date: Mar 2009 Location: Germany Posts: 55 Rep Power: 17	Hi, @stumpy The expert parameter does'nt work. I've seen no effect of this to the deformed mesh. @glenn What do you mean with inner and outer region? Can you make a sketch. I've defined one subdomain under the flap without meshmotion.

July 14, 2011, 08:56		#5
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	How does this look? Fluid6.jpg

February 14, 2013, 05:01		#7
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	Split your fluid domain into 3 joined fluid domains like this, as shown by the orange lines: fix.jpg Give the vertical line the same X displacement as the piston, and the horz one the same vertical displacement. Then your mesh will stay nice and orthogonal.

February 18, 2013, 08:55		#8
u22 Member Anthony Nitski Join Date: Aug 2009 Location: Earth Posts: 35 Rep Power: 17	Thanks for the tip, Glenn! I divided domain into 3 sub-domain. But I did not get how to give to points at stationary wall same displacement as moving wall for corresponding directions. "Give the vertical line the same X displacement as the piston, and the horz one the same vertical displacement." I have to use CEL ? Or set some specific conditions at subdomain or walls, like "mesh motions = unspecified"

February 18, 2013, 17:21		#9
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	On second thoughts this is trickier than I originally thought - I do not know how to specify one dimension but leave another dimension unspecified. I cannot see how to do that. But it would be nice if you could do that, it would make a number of motions simpler to specify. Sorry if I mislead you.