[mushumbusip@nm-aist.ac.tz]

I am conducting a computational fluid dynamics (CFD) study on a pipe with a leak hole, while varying its orientation angle, to investigate the effect of gravitational forces on pressure drop and leak rate for both uphill and downhill flow. The simulation assumes steady flow of an incompressible fluid (water) using the Reynolds-Averaged Navier-Stokes (RANS) equation and k-epsilon turbulence model in the SimpleFoam solver. However, I am facing a challenge as SimpleFoam does not directly solve for hydrostatic pressure, so I cannot include the P_rgh term. I have tried following some guides from different sources but I have not been successful. I also tried including P_rgh in the fvSolution file and creating g and rho files in the constant directory, but my results remain the same as before. Do you have any ideas on how I can resolve this issue?
fvSolution
solvers
{
p
{
solver PCG;
preconditioner DIC;
tolerance 1e-6;
relTol 0.01;
residualControl yes;

equations ( "p_rgh" );
}

[Tobermory]

I am not clear why you need to "solve for hydrostatic pressure" ... why not just add gravity as a body force and carry on with simpleFoam? You can calculate the hydrostatic pressure as a post-processing exercise.

Or alternatively, use one of the solvers that is designed for buoyant flows (i.e. which contains gravity in the momentum equation and solved for p_rgh) - check the heat transfer tutorials.

As a (pedantic) side note - p_rgh is not the hydrostatic pressure; it only equals the hydrostatic pressure in constant density flows, like the one you are modelling, but it will be much safer for you if you don't call it the hydrostatic pressure... esp when you come to variable density flows.

Hope that helps.

[mushumbusip@nm-aist.ac.tz]

Originally Posted by Tobermory

I am not clear why you need to "solve for hydrostatic pressure" ... why not just add gravity as a body force and carry on with simpleFoam? You can calculate the hydrostatic pressure as a post-processing exercise.

Or alternatively, use one of the solvers that is designed for buoyant flows (i.e. which contains gravity in the momentum equation and solved for p_rgh) - check the heat transfer tutorials.

As a (pedantic) side note - p_rgh is not the hydrostatic pressure; it only equals the hydrostatic pressure in constant density flows, like the one you are modelling, but it will be much safer for you if you don't call it the hydrostatic pressure... esp when you come to variable density flows.

Hope that helps.

Hi Tobermory.
Thank you for your valued comments. It is true P_rgh cannot be called hydrostatic pressure, it is the contribution of hydrostatic pressure to the total pressure in a flow fluid system. I used it here to mean P=rgh. I'll consider your suggestions.
Thank you again for your time.