[StefanW]

Dear Foamers,

I want to do a compressible multiphase simulation (air, water) of an horizontal pipe with the solver compressibleInterFoam. Starting the simulation the pipe is full of water. At a certain timestep the air streams in and pushes the water out.

I use the following BC (got them from my predecessor)

U
internalField (0 0 0)

inlet: type timeVaryingUniformFixedValue;
fileName "inletwater.txt"; increases to (4 0 0 )

wall: type fixedValue;
value uniform (0 0 0);

outlet: type zeroGradient;


p_rgh
internalField uniform 0

inlet: type buoyantPressure;
value uniform 0;

wall type buoyantPressure;
value uniform 0;

outlet: type totalPressure;
p0 uniform 20532; //pressure difference due to the
height difference from cut outlet to original outlet
U U;
phi phi;
rho rho;
psi none;
gamma 1;
value uniform 0;


I got worried about these BC....

Would be nice if somebody could give me a hint if they are generaly in a good manner?

and in particular I am wondering according the pressure at the outlet.
Do I have just to define the overpressure (like it is done) or do I have to define the total pressure?? I read al lot to p=rho*g*h+p_rgh but i dont get it completly, cause with this solver I got no chance to specify p.
My goal is to tell OF a pressure at the outlet of 1*atm+ 20532Pa

I read somewhere that compressibleInterFoam allows cavitating of water. Is that true? (But I dont give some information according the temprature??) Therefore I should define the total preassure to get to the right pressure level??? I heard about the function of pmin but then the results will be wrong if the preasure if automaticly "corrected"?

Thanks a lot for your help or some hints you can give

Stefan

[olivierG]

hello,

compressibleInterFoam need absolute pressure, so with 0 Pa you will get in trouble: If you need 1atm + 2e4 Pa, then set 1.2e5 Pa at outlet.

Cavitation is done with interPhaseChangeFoam, not compressibleInterFoam.

regards,
olivier

[StefanW]

Hello Oliver,

thanks a lot for your quick answer! That helps a lot.

So the results wiht "unphysical" areas of air (Alpha-Values)
(there should be water) are probably based on numerical errors...


I try to run it with the real pressure ...lets see whats comming up

THX