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chtMultiRegionFoam wrong value of kappa using constAnIsoSolid |
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Join Date: Nov 2022
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Hello everyone!
Currently, I'm working on simulations of battery cooling using chtMultiRegionFoam with OpenFOAM 10. I performed my first simulation and compared the results to the ANSYS Fluent, which unfortunately had significant differences in cells' temperatures between each other. As one of the steps of searching for the reason for discrepancies, I have prepared a simple simulation consisting only of one solid region with simple boundary conditions that I can calculate analytically. The key here is that I want to use anisotropic thermal conductivity in a cylindrical coordinate system to model conduction in cells, so I created a model as in the picture below: ![]() Using this model I have found that I get a strange behaviour of thermal conductivity in OpenFOAM when using constAnIsoSolid with a cylindrical coordinate system. I have performed 5 simulations:
The results are compared below: ![]() ![]() ![]() As you can see, using ANSYS Fluent the results are very close to analytical. Also, the results for isotropic 1.3 and anisotropic (1.3 28 28) are the same, which in my reasoning makes sense as the top, bottom and side walls are insulated and the only heat transfer direction is radial thus other conductivity vector components do not matter. The results for OpenFOAM with isotropic conductivity 1.3 and anisotropic conductivity (1.3 1.3 1.3) were the same and also close to analytical and Fluent. The problem starts when I use anisotropic thermal conductivity (1.3 28 28) - the maximum temperature is around 4 K lower compared to analytical and Fluent, as well as there is a discrepancy between (1.3 28 28) and (1.3 1.3 1.3) - based on the analytical calculation the kappa in radial direction would need to be 2.38 W/mK to match the temperature achieved at the inner radius wall. I have attached fragments of code with T boundary conditions and conductivity definition in the cylindrical coordinate system as I presume the potential error is somewhere there. There is also no tutorial in $FOAM_TUTORIALS that covers anisotropic conductivity. Based on the results and looking into examples definition of a cylindrical coordinate system seems OK, but maybe I have missed something. I have tried to define additional properties of "externalWallHeatFluxTemperature" boundary conditions (as well as "compressible::turbulentTemperatureCoupledBaffleMi xed", which I have used initially in the more complicated simulation) based on the various threads I have found online (kappaMethod directionalSolidThermo, alphaAni Anialpha, etc.) but none of it seemed to work. Code:
dimensions [ 0 0 0 1 0 0 0 ]; internalField uniform 300; boundaryField { #includeEtc "caseDicts/setConstraintTypes" "sides" { type zeroGradient; } "inner" { type externalWallHeatFluxTemperature; q uniform 1000; value uniform 300; } "outer" { type fixedValue; value uniform 300; } } Code:
thermoType { type heSolidThermo; mixture pureMixture; transport constAnIsoSolid; thermo eConst; equationOfState rhoConst; specie specie; energy sensibleInternalEnergy; } mixture { specie { molWeight 18; } equationOfState { rho 2650; } thermodynamics { Hf 0; Cv 1263; } transport { kappa ( 1.3 28 28 ); } } coordinateSystem { type cartesian; origin ( 0 0 0 ); coordinateRotation { type cylindrical; e3 ( 0 0 1 ); } } Last edited by Bazyl29; November 4, 2022 at 02:45. Reason: Forgot to post version of software used |
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Tags |
anisotropic, chtmultiregionfoam, constanisosolid, cylindrical |
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