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Prescribed mesh velocity

Posted Feb 1, 2012, 3:35 a.m. EST Mesh Version 4.2a 2 Replies

Jerry Lucas
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Hi everyone,

in a prescribed mesh velocity, if i want that a boundary has a free prescribed mesh velocity in x direction i have two options:

vx no write nothing

or

√ vx u

if i change the coordinate system, how can i to do the same?

One way will be

vt no write nothing

but the other?

√ vt ??????

Thanks you

JL
2 Replies Last Post Feb 1, 2012, 8:21 a.m. EST
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Feb 1, 2012, 5:17 a.m. EST
Hi

I'm not 100% sure I catch you.
A prescribed displacement or velocity unchecked = free motion no restritions

If checked = 0 the mesh is fixed, if = u (u or u_solid from solid, it's a displacement) then the mesh is driven by the other physics.

If its = u (u or u_fluid from CFD) it's a velocity.

U remains along the coordinate direction x so you need to redefine your variables to project them into the global coordinate system. this can be done via a coordinate system i.e. sys2.r ... or its inverse see coordinate in the doc

--
Good luck
Ivar
Hi I'm not 100% sure I catch you. A prescribed displacement or velocity unchecked = free motion no restritions If checked = 0 the mesh is fixed, if = u (u or u_solid from solid, it's a displacement) then the mesh is driven by the other physics. If its = u (u or u_fluid from CFD) it's a velocity. U remains along the coordinate direction x so you need to redefine your variables to project them into the global coordinate system. this can be done via a coordinate system i.e. sys2.r ... or its inverse see coordinate in the doc -- Good luck Ivar
Jerry Lucas
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Posted: 1 decade ago Feb 1, 2012, 8:21 a.m. EST
Hi Ivar,

you are helping a lot in the conplicated model that i am developing.

I will reformulate by question:

i have 2 physics: lanimar flow and moving mesh. The gravity force deform the drop.

in one boundary i have inplemented prescribed mesh velocity. I have change the coordinate system from global coordinate system to boundary system 1. So, i have to write the velocity for tangential and normal direction.

In case of normal velocity (from a distance of 30e-3 has velocity and after no)

(u*nr+w*nz)*(R>30e-3)+0)*(R=<30e-3)

I have doubt in case of tangential velocity. I want to be it free motion until (R>30e-3). After, 0.

Any idea?

Thanks
JL

Hi Ivar, you are helping a lot in the conplicated model that i am developing. I will reformulate by question: i have 2 physics: lanimar flow and moving mesh. The gravity force deform the drop. in one boundary i have inplemented prescribed mesh velocity. I have change the coordinate system from global coordinate system to boundary system 1. So, i have to write the velocity for tangential and normal direction. In case of normal velocity (from a distance of 30e-3 has velocity and after no) (u*nr+w*nz)*(R>30e-3)+0)*(R=30e-3). After, 0. Any idea? Thanks JL

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