how to implement a boundary conditions on multiphase boundary in fluent?

Anshs · March 31, 2021, 04:59

I'm having a bucket filled with water and oil on top of the water at high temperatures. That makes the problem with 3 phases (water, oil, and air). oil on top of the water and subsequently air on top of the oil. Schematic as shown below ( Phase ID: Blue = air, red = oil, green = water )

I use 'patch' for marking different phases on the cell zone.

I want to apply a boundary condition on the top surface of the oil layer, i.e at the oil-air interface.

e.g = Temperature radiation BC, air above is at 300K and Oil is at 500K.

Thus a mixed temperature boundary condition : (I) Radiation with external emissivity 0.7, so that heat dissipates to the ambient air, (ii) Convection with h= 20 W/m2 on the oil-air interface.

Capture.JPG

Thanks.

InsPyro · April 20, 2021, 04:47

In a true multiphase simulation, the heat transfer on the boundaries is a result of the convection and conduction at the surface and cannot be set with a bc. If everything is stationary, you could trick it by having different fluid zones, the "walls" in between would then accept bcs.

March 31, 2021, 04:59	how to implement a boundary conditions on multiphase boundary in fluent?	#1
Anshs Member Anshuman Sinha Join Date: Oct 2018 Posts: 70 Rep Power: 8	I'm having a bucket filled with water and oil on top of the water at high temperatures. That makes the problem with 3 phases (water, oil, and air). oil on top of the water and subsequently air on top of the oil. Schematic as shown below ( Phase ID: Blue = air, red = oil, green = water ) I use 'patch' for marking different phases on the cell zone. I want to apply a boundary condition on the top surface of the oil layer, i.e at the oil-air interface. e.g = Temperature radiation BC, air above is at 300K and Oil is at 500K. Thus a mixed temperature boundary condition : (I) Radiation with external emissivity 0.7, so that heat dissipates to the ambient air, (ii) Convection with h= 20 W/m2 on the oil-air interface. Capture.JPG Thanks. NicolasCFD likes this.

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April 20, 2021, 04:47		#2
InsPyro New Member België Join Date: Apr 2018 Posts: 3 Rep Power: 8	In a true multiphase simulation, the heat transfer on the boundaries is a result of the convection and conduction at the surface and cannot be set with a bc. If everything is stationary, you could trick it by having different fluid zones, the "walls" in between would then accept bcs.