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-   -   Instantaneous point release / advection-diffusion (https://www.cfd-online.com/Forums/openfoam-solving/113503-instantaneous-point-release-advection-diffusion.html)

april0100 February 20, 2013 14:11
Instantaneous point release / advection-diffusion
 
1 Attachment(s)
Hi All,

I am simulating what should be a very simple problem: laminar flow in a 2-d channel with scalar transport. I've amended icoFoam to include the scalar transport equation:

Code:
fvScalarMatrix TEqn
    (
        fvm::ddt(T)
      + fvm::div(phi, T)
      - fvm::laplacian(DT, T) == f
    );
where 'f' is a matrix that contains 0 everywhere at all times except at the time and location of the instantaneous release.

My problem is that the scalar 'T' is not properly being advected from the domain. That is, after some time the concentration of my scalar levels off and does not decrease further as shown in the attached plot.


I am thinking I may have a boundary condition problem. Currently I'm using zeroGradient boundaries on all sides of the channel for T. The inlet velocity is parabolic with a maximum centerline value of 2 m/s. If anyone has any ideas where I might be erring I would greatly appreciate it. Thanks,

April

april0100 March 30, 2013 11:59
In case anyone else has this problem, the solution is to set the inlet boundary condition to a fixed value of 0.


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