[of_novice]

Hi,

I'm new to CFD and OF (v. 4.1) as well as to C++. I'm using the twoPhaseEulerFoam solver to model a pressure driven flow of air and a liquid through a simple geometry by letting the inlet static pressure be higher than the outlet static pressure. In the prgh input file, I use the prghPressure BC for inlet and outlet:

inlet
{
type prghPressure;
p uniform 2e5;

outlet
{
type prghPressure;
p uniform 1e5;


This works well and gives a flow that looks realistic to my untrained eyes. However, now I want the inlet static pressure p to be time dependent, where it increases linearly from 1e5 up to 2e5. I'm thinking that the uniformFixedValue BC could be used somehow, but if I replace prghPressure with this BC, this fixes prgh instead of p, which gives the wrong solution.

Perhaps I should also mention that in the input file p (which I don't quite understand the need for if p is already given in the prgh file), I use the default BC:s for the fluidisedBed tutorial:

inlet
{
type calculated;
value $internalField;
}

and

outlet
{
type calculated;
value $internalField;
}

Any help would be highly appreciated.

[jherb]

I think you have to create a new boundary condition (e. g. name it prghPressureTimeDependent) which adds the capability of uniformFixedValue BC to the prghPressure BC. Look at the differences between fixedValue and uniformFixedValue to see what you have to add to prghPressureTimeDependent.

Another possibility might be to use groovyBC.

[of_novice]

Originally Posted by jherb

I think you have to create a new boundary condition (e. g. name it prghPressureTimeDependent) which adds the capability of uniformFixedValue BC to the prghPressure BC. Look at the differences between fixedValue and uniformFixedValue to see what you have to add to prghPressureTimeDependent.

Another possibility might be to use groovyBC.

I've actually tried to go that route (creating a new BC), but since I'm completely new to C++ I was hoping that there'd be an easier way. However, since groovyBC looks pretty complicated to work with also, I'll probably continue working on trying to write a new BC. I need to learn C++ anyway. Thanks for the reply!

I might return to this thread for questions about the BC code, by the way