Boundary conditions outlet

SarahLee · November 27, 2015, 07:34

Dear,

I am trying to solve a simple test case (2 inlets, 2 outlets, buoyant flow, steady state, incompressible) and have problems with defining my outlets so they behave as I want.

Details
- inlet 1
velocity: fixed velocity
pressure: fixedfluxpressure
pressure_rgh: fixedfluxpressure
temperature: fixedvalue

- inlet 2
velocity: fixed velocity
pressure: fixedfluxpressure
pressure_rgh: fixedfluxpressure
temperature: fixedvalue

- outlet 1
velocity: flowrateinletvelocity (positive, patch outlet)
pressure: fixedfluxpressure
pressure_rgh: fixedfluxpressure
temperature: fixedvalue

- outlet 2
velocity: pressureInletOutletVelocity(patch outlet)
pressure: fixedfluxpressure
pressure_rgh: totalpressure
temperature: fixedvalue

The idea is that I define the total inflow through the inlets, I define the outflow via one of the outlets and the continuity results in the correct outflow via the second outlet.

However, I get too high outflow over outlet 1 and additional outflow over outlet 2. The mass balance just doesn't make sense..

What am I doing wrong?

Thank you!

Sarah

jherb · November 28, 2015, 10:34

Have you tried calculated for the pressure boundaries? Also for the outflow regions fixedValue for temperatures does not sound correctly. Better should be zeroGradient or inletOutlet.

November 27, 2015, 07:34	Boundary conditions outlet	#1
SarahLee New Member Sarah Leenknegt Join Date: Aug 2015 Posts: 14 Rep Power: 11	Dear, I am trying to solve a simple test case (2 inlets, 2 outlets, buoyant flow, steady state, incompressible) and have problems with defining my outlets so they behave as I want. Details - inlet 1 velocity: fixed velocity pressure: fixedfluxpressure pressure_rgh: fixedfluxpressure temperature: fixedvalue - inlet 2 velocity: fixed velocity pressure: fixedfluxpressure pressure_rgh: fixedfluxpressure temperature: fixedvalue - outlet 1 velocity: flowrateinletvelocity (positive, patch outlet) pressure: fixedfluxpressure pressure_rgh: fixedfluxpressure temperature: fixedvalue - outlet 2 velocity: pressureInletOutletVelocity(patch outlet) pressure: fixedfluxpressure pressure_rgh: totalpressure temperature: fixedvalue The idea is that I define the total inflow through the inlets, I define the outflow via one of the outlets and the continuity results in the correct outflow via the second outlet. However, I get too high outflow over outlet 1 and additional outflow over outlet 2. The mass balance just doesn't make sense.. What am I doing wrong? Thank you! Sarah

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November 28, 2015, 10:34		#2
jherb Senior Member Joachim Herb Join Date: Sep 2010 Posts: 650 Rep Power: 22	Have you tried calculated for the pressure boundaries? Also for the outflow regions fixedValue for temperatures does not sound correctly. Better should be zeroGradient or inletOutlet.