Non-zero phase-1 backflow through pressure outlet

CeesH · September 13, 2015, 08:07

Hi all,

I have a problem. I run a 2 phase bubble column. The top consists of a freeboard region with only gas. The top boundary is a pressure outlet, backflow is specified to be 100% phase-2 (gas). (I have reasons not to use a degassing outlet).

Still, water accumulates in my freeboard region, until the tank is 100% full. Turns out the massflow of water through the outlet into the domain (backflow) is about 1 kg/s, even though I specified it to be 100% gas.

Is anyone familiar with this problem and how to solve it?

CeesH · September 14, 2015, 04:06

I still have no idea where the problem originated, but switching from pressure outlet to pressure inlet significantly reduces (albeit not completely removes) the creation of phase-1 at the boundary.

It's at least reduced enough for the flowfield to reasonably converge without filling the whole tank...

September 13, 2015, 08:07	Non-zero phase-1 backflow through pressure outlet	#1
CeesH Senior Member Cees Haringa Join Date: May 2013 Location: Delft Posts: 607 Rep Power: 0	Hi all, I have a problem. I run a 2 phase bubble column. The top consists of a freeboard region with only gas. The top boundary is a pressure outlet, backflow is specified to be 100% phase-2 (gas). (I have reasons not to use a degassing outlet). Still, water accumulates in my freeboard region, until the tank is 100% full. Turns out the massflow of water through the outlet into the domain (backflow) is about 1 kg/s, even though I specified it to be 100% gas. Is anyone familiar with this problem and how to solve it?

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September 14, 2015, 04:06		#2
CeesH Senior Member Cees Haringa Join Date: May 2013 Location: Delft Posts: 607 Rep Power: 0	I still have no idea where the problem originated, but switching from pressure outlet to pressure inlet significantly reduces (albeit not completely removes) the creation of phase-1 at the boundary. It's at least reduced enough for the flowfield to reasonably converge without filling the whole tank...