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Accessing heat flux in velocity BC

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Old   June 21, 2020, 21:28
Default Accessing heat flux in velocity BC
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Daniel Grebe
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TL;DR: I'm creating a custom boundary condition where the inlet velocity depends on the heat flux to the patch (radiation and conduction/convection). I'm trying to figure out how to access/calculate the heat flux in this boundary condition.

Long Version of the question:
I'm trying to implement the following boundary condition in openfoam: (Leccese 2017, page 35)
Quote:
\dot{q}_{w,cond} + \dot{q}_{w,rad} - \dot{m}_w[\delta h_{f} + c_s(T_f - T_{s,d})] = 0
I'm basing my new boundary condition off of flowRateInletVelocity boundary condition. The only part I'm having trouble with is the wall heat fluxes.

Thus far I've tried copying the procedure used in turbulentTemperatureRadCoupledMixed to calculate the heat flux, but it seems to access properties that it has inherited from temperatureCoupledBase. I'm not sure how I would be able to access those properties from my BC which is for velocity and not temperature. The following are the lines that I,m not sure how to implement in my code:
Quote:
const turbulentTemperatureRadCoupledMixedFvPatchScalarFi eld&
nbrField = refCast
<const turbulentTemperatureRadCoupledMixedFvPatchScalarFi eld>
(
nbrPatch.lookupPatchField<volScalarField, scalar>(TnbrName_)
);
On the other hand, if there is already an existing function or something like that to calculate the heat flux at a boundary, I'd be very glad to use that instead of calculation it my self.

For background, I'm developing this BC for use with reactingFoam to simulate the regression of a paraffin grain in a hybrid rocket motor.
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Old   July 20, 2020, 19:27
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Joachim Herb
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For a code example of calculating the wall heat flux have a look at the corresponding function object:
https://github.com/OpenFOAM/OpenFOAM...HeatFlux.C#L61
This might help you.
Also to access e.g. the pressure field on the patch, you could use code like :
Code:
const fvPatchScalarField& pPatch = patch().lookupPatchField<volScalarField, scalar>("p");
Gerry Kan likes this.
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