[rachele]

Hello everyone,

I have modified the chtMultiRegionFoam solver in particular the pEq to compute p instead of p_rgh in fluid regions. I have used the pEq of pimpleSolver. The solver compile with no errors but testing with a modified version of shell and tube heat exchange tutorial I get the following error:

--> FOAM FATAL ERROR:
LHS and RHS of - have different dimensions
dimensions : [1 0 -1 0 0 0 0] - [0 3 -1 0 0 0 0]

I think it is a problem of not consistent unit of measure in the pEq file but I dont understated where or how to fix it.

[dlahaye]

Pls. elaborate on what you are trying to accomplish.

p_rgh and p have different physical dimension.

How do you intend to solve for thermodynamics of heat transfer by only solving for p_rgh?

[pferro]

Hello,

Rachele wants to solve p (the pressure) instead of p_rgh (the piezzometric pressure) in the solver.

The problem is that you can't use the pEqn of pimpleFoam because there is no gravity in pimpleFoam. In chtMultiRegionFoam the fluid is compressible and "buoyant".

A very long time ago the solver was implemented with p and not p_rgh (OpenFOAM 1.6).

[dlahaye]

Hello,

I fear that I still do not understand the question.

chtMultiRegionFoam solves for the pressure (in N/m^2 = kg (1/m) (1/s^2) in the fluid domain as checking the dimensions for any of the tutorial examples (e.g. 0/p in the reverseBurner tutorials) shows.

I clearly oversee something here.

[Fauster]

no chtMultiRegionFoam solves the piezzometric pressure p_rgh. p is not solved but explicitly calculated from p_rgh.

p = p_rgh + rho*gh;

[dlahaye]

Sincere thx for pointing out my mistake.

See e.g. line L82 of https://develop.openfoam.com/Develop...m/fluid/pEqn.H

The question raised by Rachele does remain.

If

LHS and RHS of - have different dimensions
dimensions : [1 0 -1 0 0 0 0] - [0 3 -1 0 0 0 0]

then LHS and RHS differ by a density factor? Where exactly does the error occur?

[pferro]

incompressible solvers in OpenFOAM solve p/rho and not p.

[GeekCFD]

Hey there,
Could you let me know if you have successfully compiled the solver? I am working on a similar issue and need to get rid of 'p_rgh' as it is creating quite a bit of nuisance in the simulation...