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Applying time derivative as a dirchlet boundary condition

Posted Mar 1, 2013, 7:11 a.m. EST 5 Replies

Rahul Kishor Semiconductors
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Hi,

I need to apply the time derivative of a displacement created in a piezomaterial as the velocity for a fluid boundary.....

Could someone please let me know as to how this can be handled in COMSOL....Eagerly waiting for your reply.....

Thanks in advance!!

Regards,
Rahul Kishor
Nanyang Technological University,Singapor
5 Replies Last Post Aug 11, 2015, 10:35 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 Mar 2, 2013, 2:54 a.m. EST
Hi

check the internal variables of COMSOL, you have the ut and utt, implicit derivatives of the dependent variables.
But you can also couple via u (displacements) on the boundaries, no ?

--
Good luck
Ivar
Hi check the internal variables of COMSOL, you have the ut and utt, implicit derivatives of the dependent variables. But you can also couple via u (displacements) on the boundaries, no ? -- Good luck Ivar
Rahul Kishor Semiconductors
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Posted: 1 decade ago Mar 3, 2013, 11:10 p.m. EST
Hi Ivar,

Could you please let me know as to what "coupling via u displacement" means...Is it similar to what I have done- ie
v= dU/dt , where v is the fluid velocity and U is the displacement of the piezomaterial......


When I set the above condition and compute.It throws the error-"Pointwise constraints for time derivatives are not supported."


Thanks,
Rahul Kishor
Hi Ivar, Could you please let me know as to what "coupling via u displacement" means...Is it similar to what I have done- ie v= dU/dt , where v is the fluid velocity and U is the displacement of the piezomaterial...... When I set the above condition and compute.It throws the error-"Pointwise constraints for time derivatives are not supported." Thanks, Rahul Kishor
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Mar 4, 2013, 1:15 a.m. EST
Hi

but on which "entity" are you applying your velocity ? It looks like you do it on a "point", COMSOL has only derivatives on boundaries, as most edges and points/vertex are singularities the the FEM math sens

--
Good luck
Ivar
Hi but on which "entity" are you applying your velocity ? It looks like you do it on a "point", COMSOL has only derivatives on boundaries, as most edges and points/vertex are singularities the the FEM math sens -- Good luck Ivar
Rahul Kishor Semiconductors
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Posted: 1 decade ago Mar 10, 2013, 11:21 a.m. EDT
Hello Ivar,

I have applied it along the boundary wall (interface between the fluid and the piezoelectric domain)......ie I have set in the "wall" - a moving velocity with the x component as ut and the y component as vt (where u and v are the dependent variables or the displacements in the pzd domain)......

Is there some workaround for it?

Regards,
Rahul Kishor
NTU, Singapore
Hello Ivar, I have applied it along the boundary wall (interface between the fluid and the piezoelectric domain)......ie I have set in the "wall" - a moving velocity with the x component as ut and the y component as vt (where u and v are the dependent variables or the displacements in the pzd domain)...... Is there some workaround for it? Regards, Rahul Kishor NTU, Singapore
Andre
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Posted: 9 years ago Aug 11, 2015, 10:35 p.m. EDT
Hi Rahul,

Did you get to solve this issue?

Thanks!
Hi Rahul, Did you get to solve this issue? Thanks!

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