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reactingFoam, UEqn explained and diffusion calculation |
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#1 |
New Member
Duarte Magalhães
Join Date: Apr 2014
Location: Lisbon, Portugal
Posts: 24
Rep Power: 12 ![]() |
Hello everyone,
I am using reactingFoam solver and am trying to fully understand the Ueqn file, which is a subject I have never found thoroughly explained: " fvm::ddt(rho, U) + fvm::div(phi, U) + turbulence->divDevRhoReff(U) == rho*g + fvOptions(rho, U) " First entry is for time variation, second for convection, and what about third and last entries, turbulence->divDevRhoReff(U), and fvOptions(rho, U), what is it doing exactly? And how does it include diffusion when solving in laminar regime? It would be expected to see a laplacian term, I guess. Any help is much appreciated! Thanks in advance ![]() |
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#2 |
Senior Member
Kevin van As
Join Date: Sep 2014
Location: TU Delft, The Netherlands
Posts: 252
Rep Power: 20 ![]() |
Hi,
If you have a look at laminar solvers, you will indeed see a viscosity diffusion term in this equation. For solvers which allow for turbulence, this diffusion term is in-cooperated in the turbulence->divDevRhoReff(U) term. What exactly that term does, depends on your turbulence model. One of the simplest turbulence models modifies your viscosity using the turbulent viscosity (see: http://www.cfd-online.com/Wiki/Bouss...ity_assumption), and hence you can see why the viscosity-term in in-cooperated with the turbulence model. fvOptions(rho, U) is a rather new function, which allows users to add source terms to the equation without modifying the solver. A decent explanation is found here: http://www.openfoam.org/version2.2.0/fvOptions.php |
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#3 |
New Member
Duarte Magalhães
Join Date: Apr 2014
Location: Lisbon, Portugal
Posts: 24
Rep Power: 12 ![]() |
Thanks Kevin!
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