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Old   February 10, 2008, 13:09
Default Hi, All! Please, answer my
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Dmitry Kovtunov
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Hi, All!

Please, answer my question. Is it possible to
solve the convection-diffusion equation with OpenFOAM when convection is dominated?
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Old   February 10, 2008, 13:22
Default Yes - in fact, it is quite eas
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Hrvoje Jasak
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Yes - in fact, it is quite easy.
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Old   February 10, 2008, 13:58
Default Thanks for the answer. But cou
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Dmitry Kovtunov
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Thanks for the answer. But could you point to my mistake? I was doing so:

solve(- fvm::laplacian(T) + (u & fvc::grad(T)) == f);

where T - temperature

u - predefined analytical velocity field with multiplier alpha, so u = alpha*b,
where b - some vector field with div b = 0

f - source term calculated from the equation by substitution some analytical function theta satisfying boundary condition for T

so when alpha is small enough (<< 1)
residual = T - theta is tolerable, but
when alpha is >> 1, i obtain something wrong
solution which differs from theta very much.

Be glad to hear any suggestions from you. Thanks.
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Old   February 10, 2008, 16:33
Default Did you every look at scalarTr
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Hrvoje Jasak
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Did you every look at scalarTransportFoam? This is where you should start from:

solve
(
fvm::ddt(T)
+ fvm::div(phi, T)
- fvm::laplacian(DT, T)
);


Hrv
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Old   February 10, 2008, 18:37
Default I've tested your suggestion. I
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Dmitry Kovtunov
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I've tested your suggestion. It has improved my solution but not enough. I've two problems now:
1) it is not clear how small deltaT need to be choosen to obtain stationary solution;
2) while modeling the solution become unstable on some time step i.e. after some time step an absolute residual become growing up.

Any ideas? And what is the best interpolation scheme for my case? I've noticed filteredLiear to be better than limitedLinear.
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