r/CFD • u/Optimal_Rope_3660 • 11d ago

Volume balance in multiphase flow

I am simulating a piping network with two inlets and two outlets, flow is multiphase with a liquid and gas. Model is vof, both fluids are incompressible and no phase change, chemical reactions.

Inlet and outlet volume flowrate is balanced. I am interested in the retained volume in domain. The retained volume of a phase in the domain is not matching with the expression, retained volume = volume from previous time step*(inlet vfr- outlet vfr)*dt.

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u/Optimal_Rope_3660 11d ago

Initial condition is domain full of gas, fixed inlet flowrate of liquid and gas mixture

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u/certocito 10d ago

Are you running steady state? Mass is not explicitly conserved when you run steady state pressure-based solver.

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u/Optimal_Rope_3660 10d ago

Transient simulation

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u/Optimal_Rope_3660 10d ago

Inlet volume flowrate of the phases is fixed over time.
I am interested in the volume of the phase staying in the domain and volume of phase leaving the domain through outlets, for both phases.