[Juzzvy]

Good day. I am currently using openFoam in my project in simulation of air pollution in urban canyon. I added a scalar transport equation in my simplefoam solver. I also used toposet in defining my point source. Since it is a trial run, i did it in 100 iterations. After the run, the results weren't the one I am looking for. How can I fix it in such a way that the point source emits pollutants? Thank you

[kcjarvis56]

1. Here is a reference for Vapor CO2 dispersion. Do a google search on openFoam atmosphere dispersion will also give you some more examples and papers, mostly to do with dispersion of hazardous materials.

2. Use rhoReactingBuoyantFoam solver with reactions and chemistry off for dispersion models similar to what you are describing. Use rhoPimpleFoam for an example to get started with BC also reference reactingFoam for BCs.

3. You can use atmBoundaryLayer like the turbineSiting tutorial in the simpleFoam tutorial
directory. Make sure you have a good quality mesh.

4. You can use a patch for emitting the pollutant at the desired rate.

[Juzzvy]

Hi, I am currently reading the paper you have showed me. as for the other suggestions, I notuced that rhoPimpleFoam is for compressible flows. Can it work on my case? and also on the fourth suggestion, I tried to use toposet as a point source. I'm wondering whether there is a toposet setting for 2d and 3d.

[Juzzvy]

Hi again, I've already done my run in an urban canyon setting using scalar transport function, and the results is promising. However, when I tried to run it on a different mesh, I always have an error of floating point, the error says:

TS
#0 Foam::error:rintStack(Foam::Ostream&) at ??:?
#1 Foam::sigFpe::sigHandler(int) at ??:?
#2 ? in "/lib/x86_64-linux-gnu/libc.so.6"
#3 Foam::fv::SemiImplicitSource<double>::addSup(Foam: :fvMatrix<double>&, long) at ??:?
#4 Foam::tmp<Foam::fvMatrix<double> > Foam::fv:ptionList:perator()<double>(Foam::Geo metricField<double, Foam::fvPatchField, Foam::volMesh>&, Foam::word const&) at ??:?
#5 ? at ??:?
#6 __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#7 ? at ??:?
Floating point exception (core dumped)

does this error came from the mesh? since this same code already worked on my initial run on a different mesh.Thank you again

[kcjarvis56]

Did you check you mesh with:

checkMesh -allGeometry -allTopology

That will identify errors to help you troubleshoot the mesh, if the mesh is the problem.

Looking at the error message it looks like it may be something to do with the fvOptions file. Check you BCs also to make sure they are correct. Since it worked with your other mesh, I would guess your solver is ok.

Good luck,

Kirk

[Juzzvy]

Hi, I already run the simulation, and it looks fine. I used the function in fvOptions so that I can set the tracer at z=0. Now I wonder how to simulate the pollution per 5 timesteps? I just saw the functions timeStart and Duration. Is there any use of it? And what is the function of teh injectionRateSuSp, most especially the values to be needed ( the (2,0) in teh script)? Thank you

scalarTracer //name
{
type scalarSemiImplicitSource;
active true;
timeStart 1;
duration 50;
scalarSemiImplicitSourceCoeffs
{
selectionMode points;
points
(
(-129 57 0)
(-132 0 0)
);
volumeMode absolute; // absolute <quantity>; specific <quantity>/m^3
injectionRateSuSp
{
TS (2 0); //kg/s
}
}
}