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Moving Interior Wall in cdf

Posted May 15, 2012, 12:25 p.m. EDT Fluid & Heat, Computational Fluid Dynamics (CFD) Version 4.2a 4 Replies

fhtagn
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Hi,

I am studying pipe flow, currently in 2D.

I have placed a rigid interior wall, making a certain angle with the direction of flow, inside the pipe. Ideally, I would like it to rotate 'freely' around its first edge (see picture, the red point would be the axis). As of now, I am only using the Laminar Flow module.

By freely, I mean subjected to the flow. How can I achieve this?

1) the freely rotating axis
2) make the mesh follow the interior wall

I am reading this www.comsol.com/support/knowledgebase/970/ and looking for examples.

Thank you

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4 Replies Last Post May 15, 2012, 4:03 p.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago May 15, 2012, 1:38 p.m. EDT
Hi

I'm not sure COMSOL 4.2a allows you to simulate a thin wall like that (may be, perhaps someone else has managed) because for a FSi you need from, my knowledge, a domain (a surface in 2D). But you can make it thin and I would end it with two half circular ends to allow a better meshing and fluid separation (avoid right angle corners in CFD but also ACDC ...). Then to give a rotation axis, one way is to make a hollow cylinder and apply a roller structural BC or apply a weak equation to enforce a rotation

--
Good luck
Ivar
Hi I'm not sure COMSOL 4.2a allows you to simulate a thin wall like that (may be, perhaps someone else has managed) because for a FSi you need from, my knowledge, a domain (a surface in 2D). But you can make it thin and I would end it with two half circular ends to allow a better meshing and fluid separation (avoid right angle corners in CFD but also ACDC ...). Then to give a rotation axis, one way is to make a hollow cylinder and apply a roller structural BC or apply a weak equation to enforce a rotation -- Good luck Ivar
fhtagn
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Posted: 1 decade ago May 15, 2012, 3:53 p.m. EDT
Thank you for your reply

> But you can make it thin and I would end it with two half circular ends to allow a better meshing and fluid separation (avoid right angle corners in CFD but also ACDC ...)

Yes, maybe that will have to do (and thank you for the tips). I have used fillet (the circular ends, right?) and it bends the obstacle nicely. However, I want the obstacle to be rigid, so I guess I'd have to mess with the Young modulus. And add a constraint to a point?

I found this: www.comsol.com/community/forums/general/thread/15286/#p41764

Can someone point me in the right direction? My obstacle's movement will also come from an external ODE, I "just" don't know how to move the obstacle mid simulation.
Thank you for your reply > But you can make it thin and I would end it with two half circular ends to allow a better meshing and fluid separation (avoid right angle corners in CFD but also ACDC ...) Yes, maybe that will have to do (and thank you for the tips). I have used fillet (the circular ends, right?) and it bends the obstacle nicely. However, I want the obstacle to be rigid, so I guess I'd have to mess with the Young modulus. And add a constraint to a point? I found this: http://www.comsol.com/community/forums/general/thread/15286/#p41764 Can someone point me in the right direction? My obstacle's movement will also come from an external ODE, I "just" don't know how to move the obstacle mid simulation.
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago May 15, 2012, 3:56 p.m. EDT
Hi
you could try with the Rigid Connector on your structural domain, that will enforce it to be "rigid"

--
Good luck
Ivar
Hi you could try with the Rigid Connector on your structural domain, that will enforce it to be "rigid" -- Good luck Ivar
fhtagn
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Posted: 1 decade ago May 15, 2012, 4:03 p.m. EDT
Again, thank you.

(had just found this www.comsol.dk/community/forums/general/thread/13559/#p36289)

Another day, another thing to explore in COMSOL...
Again, thank you. (had just found this http://www.comsol.dk/community/forums/general/thread/13559/#p36289) Another day, another thing to explore in COMSOL...

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