mass imbalance in Transient simulation

sina_mech · March 13, 2017, 10:13

Hi,

I'm doing a simulation of multiphase flow (2-phases) into a large tank. There is 1 inlet and 1 outlet. I exported the following values at every time steps:

phase-2 mass flow rate at outlet
phase-2 mass inside the tank

Having the phase-2 mass flow rate at inlet, I could calculate the accumulative mass flowing into the tank. and having the phase-2 mass flow rate at outlet, I could calculate the accumulative mass flowing out of the tank! Technically, the difference of the two calculated values should give me the mass inside the tank! But I expect a reasonable error because of errors occurring at each time step! but the error for my case keeps increasing on the transient solution and it even reaches 20%-30%! It means the mass inside the tank is 20% less than the difference of accumulative inflow and outflow masses.

Do you have any suggestion, idea to fix or at least mitigate the error?

Thanks

sina_mech · March 14, 2017, 12:06

Any suggestions?

sina_mech · March 15, 2017, 13:32

bump!
so nobody ever faced such a problem!?

ggd201 · May 1, 2018, 05:26

I am quite late to this thread, but were you able to fix this problem?

March 13, 2017, 10:13	mass imbalance in Transient simulation	#1
sina_mech Senior Member SinaJ Join Date: Nov 2009 Posts: 136 Rep Power: 16	Hi, I'm doing a simulation of multiphase flow (2-phases) into a large tank. There is 1 inlet and 1 outlet. I exported the following values at every time steps: phase-2 mass flow rate at outlet phase-2 mass inside the tank Having the phase-2 mass flow rate at inlet, I could calculate the accumulative mass flowing into the tank. and having the phase-2 mass flow rate at outlet, I could calculate the accumulative mass flowing out of the tank! Technically, the difference of the two calculated values should give me the mass inside the tank! But I expect a reasonable error because of errors occurring at each time step! but the error for my case keeps increasing on the transient solution and it even reaches 20%-30%! It means the mass inside the tank is 20% less than the difference of accumulative inflow and outflow masses. Do you have any suggestion, idea to fix or at least mitigate the error? Thanks

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March 14, 2017, 12:06		#2
sina_mech Senior Member SinaJ Join Date: Nov 2009 Posts: 136 Rep Power: 16	Any suggestions?

March 15, 2017, 13:32		#3
sina_mech Senior Member SinaJ Join Date: Nov 2009 Posts: 136 Rep Power: 16	bump! so nobody ever faced such a problem!?

May 1, 2018, 05:26		#4
ggd201 New Member Gaurav Join Date: Dec 2011 Posts: 2 Rep Power: 0	I am quite late to this thread, but were you able to fix this problem?