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Mass balance in pipe flow module
Posted Dec 4, 2019, 12:35 a.m. EST Computational Fluid Dynamics (CFD), Chemical Reaction Engineering 1 Reply
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I'm using the pipe flow module to solve for advection-diffusion of solute in pipe flow module. I could view the following equations after selecting Transport of dilute species listed in the chemical species transport section in Add physics tab.
Flux is given by
However, it's not clear to me how the above equation holds true while solving for solute transport in pipe sections of variable diameters. Shouldn't the cross-sectional area be included in solute transport equation while solving for transport in pipe sections of varying diameters(For example like the geometry prsented in the tutorial here)?
Could someone elaborate on the flux term that is solved for mass-conservation at the junctions of the pipe flow model presented in the above-mentioned geometry?
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I learnt in a hard way that the mass balance does not necessarily hold in convective diffusion, you must secure it by yourself. Using a dense mesh enough is necessary. As you have noticed, the equations are for flux density. Hence integration over the outflow is needed to check the mass balance.
Lasse