mass imbalance in Transient simulation

sina_mech · March 13, 2017, 11:13

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, 13:06

Any suggestions?

sina_mech · March 15, 2017, 14:32

bump!
so nobody ever faced such a problem!?

ggd201 · May 1, 2018, 06:26

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

March 13, 2017, 11:13	mass imbalance in Transient simulation	#1
sina_mech Senior Member SinaJ Join Date: Nov 2009 Posts: 136 Rep Power: 17	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

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
transient mass transfer in multiphase flow	Tensian	Fluent UDF and Scheme Programming	0	November 16, 2015 11:39
Plotting mass flow rate at outlet for transient simulation	Rakib	Fluent Multiphase	4	September 6, 2015 00:46
Exporting data of transient simulation DURING a simulation, at user locations ?	Milan2013	CFX	0	April 18, 2014 04:47
Star-CD transient simulation, problem of loss of mass	kit	STAR-CD	3	April 13, 2010 12:34
transient simulation of a rotating rectangle	icesniffer	CFX	1	August 8, 2009 08:25

March 14, 2017, 13:06		#2
sina_mech Senior Member SinaJ Join Date: Nov 2009 Posts: 136 Rep Power: 17	Any suggestions?

March 15, 2017, 14:32		#3
sina_mech Senior Member SinaJ Join Date: Nov 2009 Posts: 136 Rep Power: 17	bump! so nobody ever faced such a problem!?

May 1, 2018, 06:26		#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?