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buoyantPimpleFoam General Assumptions (thermophysical model, energy equation, etc) 

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October 7, 2017, 03:37 
buoyantPimpleFoam General Assumptions (thermophysical model, energy equation, etc)

#1 
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Join Date: Oct 2017
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I am trying to use buoyantPimpleFoam to simulate RayleighTaylor instability of a gas (eventually a reacting simulation). I was looking through the source files and I had some general questions on the assumptions that the solver takes, and hope that someone can shed some light on it for me.
1. The energy equation is states as Code:
fvScalarMatrix EEqn ( fvm::ddt(rho, he) + fvm::div(phi, he) + fvc::ddt(rho, K) + fvc::div(phi, K) + ( he.name() == "e" ? fvc::div ( fvc::absolute(phi/fvc::interpolate(rho), U), p, "div(phiv,p)" ) : dpdt )  fvm::laplacian(turbulence>alphaEff(), he) == rho*(U&g) + radiation>Sh(thermo, he) + fvOptions(rho, he) ); But in the solver energy equation, this is simply states as . Obviously this does not matter for a thermally perfect gas as the specific heat is constant, but for gases with varying specific heats, there should be a gradient there. I have never seen the form used in buoyantPimpleFoam. Is this additional gradient term simply just ignored because it is negligible? 2. The divergence of gradients in OpenFoam (e.g. or ) are simply written as laplacians, i.e. laplacian(mu,D(U)). Again, this is only true if the transport properties do not vary. This is definitely not the case for reacting flows. Is this simply ignored in OpenFoam calculations or is this handled behind the scenes? 3. The thermophysical properties for gases seem to me to be overdefined. For example, a sample thermophysical model could be: Code:
thermoType { type heRhoThermo; //Thermophysical Model Based on h/e and rho mixture pureMixture; // Passive Gas Mixtures transport const; // Constant transport properties (mu, Pr, etc.) thermo hConst; // Constant Cp and heat of fusion equationOfState perfectGas; // Ideal Gas Law specie specie; energy sensibleEnthalpy; // Solve Energy Eqn. In Terms of Enthalpy } 4. Why is read from the initial conditions and then redefined, i.e. in createFields.H Code:
#include "readGravitationalAcceleration.H" #include "readhRef.H" #include "gh.H" Info<< "Reading field p_rgh\n" << endl; volScalarField p_rgh ( IOobject ( "p_rgh", runTime.timeName(), mesh, IOobject::MUST_READ, IOobject::AUTO_WRITE ), mesh ); // Force p_rgh to be consistent with p p_rgh = p  rho*gh; Thank you in advance. 

October 23, 2018, 05:30 

#2 
Senior Member
Jianrui Zeng
Join Date: May 2018
Location: China
Posts: 157
Rep Power: 7 
Hello,I am also confused about these questions above.
Have you found the answer of it? Any idea will be appreciated. 

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assumptions, buoyantpimplefoam, consistency, laplacian operator 
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