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#1 |
New Member
Max
Join Date: Jan 2017
Posts: 9
Rep Power: 9 ![]() |
I have a function I can't implement:
![]() a -- is a constant in [m2/s], which I defined via external dictionary (lookup) c -- is a constant in [s], which I defined via external dictionary (lookup) T -- is temperature in [K] Laplacian of T should yield [K/m2] and ![]() I've tried fvm::ddt(c * fvm::laplacian(a,T)), but got an error: no matching function for call to ‘Foam::GeometricField::GeometricField(Foam::tmp >)’ |
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#2 |
Senior Member
Santiago Lopez Castano
Join Date: Nov 2012
Posts: 354
Rep Power: 15 ![]() |
Quote:
fvm::ddt(fvc::laplacian(... Coming to your interpretation problem, you are mixing mathematical notations. The leibniz notation (d/dt) with the vector (nabla, delta) notation for derivatives. Im betting the Delta T in the term above means "temperature difference", not "second order derivative of..."' |
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#3 |
New Member
Max
Join Date: Jan 2017
Posts: 9
Rep Power: 9 ![]() |
Interesting thing:compiles OK:
volScalarField lap(c * fvc::laplacian(a,T)); fvScalarMatrix TEqn (fvm::ddt(T) - fvm::ddt(lap) - fvm::laplacian(a,T) == 0); but solution fails with the following error: incompatible fields for operation [T] - [(c*laplacian(a,T))] compilation error (no matching function for call to ‘ddt(Foam::tmp >)’): fvScalarMatrix TEqn (fvm::ddt(T) - fvm::ddt(c * fvc::laplacian(a,T))) - fvm::laplacian(a,T) == 0); ----------------------------------- As for notation: This is a part of modified Fourier equation: ![]() where a -- thermal diffusivity [m2/s] if one set c=0 s, then will get simple heat equation |
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#4 |
Senior Member
Michael Alletto
Join Date: Jun 2018
Location: Bremen
Posts: 616
Rep Power: 16 ![]() |
did you try:
fvc::ddt(c * fvc::laplacian(a,T))) I think there is no implicit operator implement in openfaom for what you want to do |
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#5 |
New Member
Max
Join Date: Jan 2017
Posts: 9
Rep Power: 9 ![]() |
I did.. same error.
a somewhat solution is that c * fvc::laplacian(a,fvc::ddt(T)) or c * fvc::ddt(volScalarField("lap",fvc::laplacian(a,T)) ) Both compile ok and simulation runs well, but this term doesn't affect solution at all. Seems like ![]() Last edited by nikitin-pro; August 3, 2020 at 17:07. |
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Tags |
laplacian operator, openfoam, time derivative |
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