|
[Sponsors] |
Does rhoSimpleFoam solver impose a velocity field divergence free? |
![]() |
|
LinkBack | Thread Tools | Search this Thread | Display Modes |
![]() |
![]() |
#1 |
New Member
Ahmhmd
Join Date: Jun 2012
Posts: 4
Rep Power: 14 ![]() |
Hello everyone,
I have been trying to run a 'compressible' simulation using rhoSimpleFoam, and I am still struggling with boundary conditions implementation. In my head 'compressible' means the velocity field has non-zero divergence, it means 'volume' is not constant. But apparently, rhoSimpleFoam is a pressure-based solver, and it uses SIMPLE algorithm for pressure velocity coupling. I think this means it solves an incompressible problem with varying density, am I correct? And therefore, it cannot capture flow discontinuities. From my understanding, compressible implies a density-based solver that obtains the pressure field from the thermodynamic model of the fluid. Moreover, I wanted to use free stream boundary conditions for both velocity and pressure, but I think they wouldn't work as they do in a density-based solver. Thanks! Last edited by MastaMinds; June 18, 2021 at 07:07. |
|
![]() |
![]() |
![]() |
![]() |
#2 |
Senior Member
Join Date: Apr 2020
Location: UK
Posts: 711
Rep Power: 14 ![]() |
rhoSimpleFoam is indeed a compressible solver (see discussion below) - it solves a continuity equation and allows for gas mixtures with differing densities, so the dilatation term (divU) can indeed be non-zero. You are right to note that it is a pressure based solver, though, and so is probably better targeted at lower Mach number, variable density flows, since I guess that density based solvers will be more efficient at high Mach#.
As for the definition of "incompressible" - this seems to be used ambiguously. Many treat it as just a measure of flow compressibility effects or Mach number, i.e. whether flow/pressure perturbations result in significant density perturbations (When choose sensibleInternalEnergy or sensibleEnthalpy in thermophysicalProperties). Others use it to mean that divU = 0, i.e. constant density. OpenFOAM uses the latter, when classifying its solvers. |
|
![]() |
![]() |
![]() |
Tags |
boundary conditions, compressible, incompressible solver, openfoam |
|
|
![]() |
||||
Thread | Thread Starter | Forum | Replies | Last Post |
potential flows, helmholtz decomposition and other stuffs | pigna | Main CFD Forum | 1 | October 26, 2017 08:34 |
divergence free random field | hnemati | Main CFD Forum | 3 | October 18, 2017 11:07 |
velocity field of MRF, GGI and rotatingWallVelocity | tonky | OpenFOAM Programming & Development | 1 | October 14, 2016 11:04 |
Moving mesh | Niklas Wikstrom (Wikstrom) | OpenFOAM Running, Solving & CFD | 122 | June 15, 2014 06:20 |
PISO predictor-corrector scheme for non-divergence free velocity | blais.bruno | OpenFOAM Programming & Development | 0 | April 23, 2014 12:03 |