Mass flow "outlet" BC reverses flow after 20 iterations

swadejaxsun · January 31, 2018, 10:55

I need to control the mass flow coming out of my outlet. It's essentially a cylindrical tank with a pipe at the end. There is not inlet, just the outlet with some gravity to account for. The tank starts out 3/4 full of water, the rest is air.

When I use the mass flow inlet with a negative mass flow value, the flow out of my outlet ends of up reversing, going into the tank, after about 20 iterations at 0.005s. I tried using a flow-split outlet because it seemed to remedy the problem, the only issue is, is that one the water gets low enough, it starts pulling air through the pipe way too fast and the simulation blows up and the mass flow out of the outlet goes crazy.

I was reading that I need to use the extruder mesh to properly set the outlet so that it can handle the mass flow "outlet" boundary condition.

Reversed Flow in Outlet

If so, how do I do this? I wasn't able to find any directions on how to setup the extruder mesh let alone apply it to the outlet's boundary condition.

swadejaxsun · January 31, 2018, 13:57

Nevermind, please ignore. I figured it out.

Devs please delete if necessary.

January 31, 2018, 10:55	Mass flow "outlet" BC reverses flow after 20 iterations	#1
swadejaxsun New Member Join Date: Dec 2017 Posts: 12 Rep Power: 8	I need to control the mass flow coming out of my outlet. It's essentially a cylindrical tank with a pipe at the end. There is not inlet, just the outlet with some gravity to account for. The tank starts out 3/4 full of water, the rest is air. When I use the mass flow inlet with a negative mass flow value, the flow out of my outlet ends of up reversing, going into the tank, after about 20 iterations at 0.005s. I tried using a flow-split outlet because it seemed to remedy the problem, the only issue is, is that one the water gets low enough, it starts pulling air through the pipe way too fast and the simulation blows up and the mass flow out of the outlet goes crazy. I was reading that I need to use the extruder mesh to properly set the outlet so that it can handle the mass flow "outlet" boundary condition. Reversed Flow in Outlet If so, how do I do this? I wasn't able to find any directions on how to setup the extruder mesh let alone apply it to the outlet's boundary condition.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Foam::error::printStack after large bounding epsilon events	StoneCFD727	OpenFOAM Running, Solving & CFD	1	January 1, 2018 18:04
HeatSource BC to the whole region in chtMultiRegionHeater	xsa	OpenFOAM Running, Solving & CFD	3	November 7, 2016 06:07
settlingFoam unstable?	bendel_boy	OpenFOAM Running, Solving & CFD	38	July 8, 2016 06:07
Compressor Simulation using rhoPimpleDyMFoam	Jetfire	OpenFOAM Running, Solving & CFD	107	December 9, 2014 14:38
Moving mesh	Niklas Wikstrom (Wikstrom)	OpenFOAM Running, Solving & CFD	122	June 15, 2014 07:20

January 31, 2018, 13:57		#2
swadejaxsun New Member Join Date: Dec 2017 Posts: 12 Rep Power: 8	Nevermind, please ignore. I figured it out. Devs please delete if necessary.