Tracking mass flow in & out

Science2108 · October 20, 2019, 09:52

Hello everybody,

i have a system with a two phases: liquid and gas.
I have set a pressure inlet for the entering gas, so it can flow in and out through this inlet.
My question now: i want to track the mass flow in and out of the pressure inlet of the component gas. I found the report mass flux but i think this report only shows how much gas flows in but not how much gas flows out. Is that right?
I want to determine equilibrium with the report.

Thanks
Science 2108

MKuhn · October 21, 2019, 08:23

The report mass flux function reports the absolut amount of fluid passing this boundary. It can be positive (inlete) or negativ (inlet which acts as an outlet). If you have only one inlet, this mass flux must be zero in a steady state solution. If your inlet is in plane with e.g. XY you can easly create plots, to see where the mass flow goes in and where out.

I'm not sure, if this is a good model set up with only one inlet which acts also as an outlet.

BlnPhoenix · October 29, 2019, 07:53

My guess is you have one inlet set as pressure inlet and one outlet somewhere else.
If you have an inlet that acts also as a potential outlet, you can not determine each amount going in and out at the same time. You only get an total net flow (inlet - outlet), which is calculated by the mass flux function. What you need is an orientation on the patch. You can calculate the mass flows by calculating: velocity in flow direction * density * cell Area, so you end up with a mass flow with negative values (going out your domain) and some mass flow with posistive values (going in your domain)
Things get more complicated in a situation where you have mutiple phases because inflow and outflow for each phase does not necessecarily need to be the same in an unsteady situation.

October 20, 2019, 09:52	Tracking mass flow in & out	#1
Science2108 New Member Join Date: Jul 2019 Posts: 6 Rep Power: 6	Hello everybody, i have a system with a two phases: liquid and gas. I have set a pressure inlet for the entering gas, so it can flow in and out through this inlet. My question now: i want to track the mass flow in and out of the pressure inlet of the component gas. I found the report mass flux but i think this report only shows how much gas flows in but not how much gas flows out. Is that right? I want to determine equilibrium with the report. Thanks Science 2108

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October 21, 2019, 08:23		#2
MKuhn Senior Member Moritz Kuhn Join Date: Apr 2010 Location: Germany, Dresden Posts: 207 Rep Power: 17	The report mass flux function reports the absolut amount of fluid passing this boundary. It can be positive (inlete) or negativ (inlet which acts as an outlet). If you have only one inlet, this mass flux must be zero in a steady state solution. If your inlet is in plane with e.g. XY you can easly create plots, to see where the mass flow goes in and where out. I'm not sure, if this is a good model set up with only one inlet which acts also as an outlet.

October 29, 2019, 07:53		#3
BlnPhoenix Senior Member Join Date: Aug 2014 Location: Germany Posts: 292 Rep Power: 13	My guess is you have one inlet set as pressure inlet and one outlet somewhere else. If you have an inlet that acts also as a potential outlet, you can not determine each amount going in and out at the same time. You only get an total net flow (inlet - outlet), which is calculated by the mass flux function. What you need is an orientation on the patch. You can calculate the mass flows by calculating: velocity in flow direction * density * cell Area, so you end up with a mass flow with negative values (going out your domain) and some mass flow with posistive values (going in your domain) Things get more complicated in a situation where you have mutiple phases because inflow and outflow for each phase does not necessecarily need to be the same in an unsteady situation.