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Free & Porous Fluid Flow -- Measure of mass flux

Posted Jan 28, 2013, 1:39 p.m. EST Fluid & Heat, Porous Media Flow, Materials, Parameters, Variables, & Functions, Results & Visualization Version 4.3 2 Replies

John Solder`
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Hi All,

I am attempting to model a stream bottom seepage collection device, but I getting some strange results.

I am starting out fairly simple with no lateral flow in the free fluid, and setting the BC's so that I have a vertical flow field. But my results show the velocity contours have local maxima along the stream bottom under the device. I was expecting the maxima to be near the outlet of the device as it is a considerable constriction.

Also, is there a way to measure the mass flux of fluid through a plane? I am trying to evaluate how much water is being captured by the device and how much fluid is going around.

Thanks,
John
2 Replies Last Post Jan 28, 2013, 5:50 p.m. EST
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jan 28, 2013, 2:04 p.m. EST
Hi

your image looks like a constant value with some numerical noise on it, no ?

The total mass flux should be something as the integration over a given boundary * fluid density*velocity vector normal to the surface, the latter is either one of the vector Cartesian components for an x,y,z normal plane, or a combination of the scalar product of the surface normal and the velocity vector component (nx*u+ny*v*nz*w)

At least that is what I would try first, but be sure you have a good value for the velocity (dense enough mesh values for a good gradient resolution

--
Good luck
Ivar
Hi your image looks like a constant value with some numerical noise on it, no ? The total mass flux should be something as the integration over a given boundary * fluid density*velocity vector normal to the surface, the latter is either one of the vector Cartesian components for an x,y,z normal plane, or a combination of the scalar product of the surface normal and the velocity vector component (nx*u+ny*v*nz*w) At least that is what I would try first, but be sure you have a good value for the velocity (dense enough mesh values for a good gradient resolution -- Good luck Ivar
John Solder`
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Posted: 1 decade ago Jan 28, 2013, 5:50 p.m. EST
Ah, yes. Thank you Ivar.
Ah, yes. Thank you Ivar.

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