[bhuve]

..HI!...in ,y problem i want to update pressure ,temperature and velocity at boundary outlet.its a unsteady problem with set of equations...can you please tell how to update at outlet boundary.

[ngj]

Hi

If the value at your boundary should be uniformly distributed, then you should be able to use "timeVaryingUniformFixedValue" otherwise you probably need to do some programming.

Search the forum, because several threads deal with the timeVaryingUniformFixedValue.

On the other hand both specifying pressure and velocity at the outlet-boundary sounds to me like specifying the solution you are after, except if the flow is supercritical, of course.

Best regards,

Niels

[bhuve]

HI!...Neils
thanks,..i m tring with code for nozzle throat ,probably probelm is there for appropriate BC.can you tell that at nozzle throat ,what should be the boundarary condition for perturbations for pressure, temperature and velocity these are to be updated with time.
..thanks

[ngj]

Hi

What the boundary conditions should be is problem-dependent, thus I cannot help you based on your informations.

Usually the velocity is specified at the inlet with a zero gradient in pressure and at the outlet the pressure is set to zero and having a zero gradient in the velocity. With respect to temperature it depends on the problem.

Best regards,

Niels

[bhuve]

hi!!...thank you,
in problem i have to set dv/dz=0; where, z is axial length. v is transverse velocity.
I have a code in which i wrote..
label nozzlethroatPatchID = mesh.boundaryMesh().findPatchID("nozzlethroat");
fvPatchVectorField& nozzlethroatu = U.boundaryField()[nozzlethroatPatchID];
forAll(nozzlethroatu,i)
{
#include"nozzlethroat.H"(in which equations are written for p.T,u)
nozzlethroatu[i]=vector(....updated u components from equations.)
}
problem is how to specifiy dv/dz=0;??
can anyone plese replly.