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Mass Concservation in Two Phase Pipe Flow

Posted Sep 27, 2012, 11:00 a.m. EDT Computational Fluid Dynamics (CFD), Modeling Tools & Definitions, Parameters, Variables, & Functions, Results & Visualization Version 4.3 3 Replies

Rui Silva
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Hi folks,

I was wondering if there is a way to check if the mass conservation principle is uphold in COMSOL for pipe flow.

I am using glass spheres in water in my simulation and due to some instabilities I have employed some Inconsistent Stabilization, and I am fearful that this might mess with the mass conservation.

Any advice?

Best Regards,

Rui
3 Replies Last Post Dec 27, 2012, 2:29 p.m. EST
Rui Silva
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Posted: 1 decade ago Sep 28, 2012, 11:41 a.m. EDT
Anyone?

Could use some help in this issue.

Anyone? Could use some help in this issue.
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago Sep 28, 2012, 3:03 p.m. EDT
Integrate the mass flow rate over the inlet and outlet and check that they are equal. You can do in the Derived Values node under Results.
Integrate the mass flow rate over the inlet and outlet and check that they are equal. You can do in the Derived Values node under Results.
Thomas Brooks
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Posted: 1 decade ago Dec 27, 2012, 2:29 p.m. EST
I did a surface integral across my inlet and outlet. I put fp.rho*v in the integral expression box (where v is the velocity moving perpendicular to the inlet and outlet cross section and fp.rho is the density). The difference between those two results is roughly -0.000802938 kg/s. I then took a volume integral for my air flow domains with fp.rho (density) in the integral expression and got a nearly constant mass of 0.001692 over 600 seconds. Clearly, this is contradictory because the delta in my mass flow rates is large enough to cause a noticeable change in my total mass. Am I using the integration tools wrong here? If not, what could cause this blatant error in COMSOL?
I did a surface integral across my inlet and outlet. I put fp.rho*v in the integral expression box (where v is the velocity moving perpendicular to the inlet and outlet cross section and fp.rho is the density). The difference between those two results is roughly -0.000802938 kg/s. I then took a volume integral for my air flow domains with fp.rho (density) in the integral expression and got a nearly constant mass of 0.001692 over 600 seconds. Clearly, this is contradictory because the delta in my mass flow rates is large enough to cause a noticeable change in my total mass. Am I using the integration tools wrong here? If not, what could cause this blatant error in COMSOL?

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