Non-drag Forces

oliveira1820 · December 17, 2018, 22:33

How can I know if Lift, Turbulent Dispersion Force, Virtual Mass and Wall Lubrification Forces are important or not to my simulation?

Basically it consists in water and steam transient flow, with a continuous heat deposition, with Thermal Phase Change (Nusselt number=6) modelling the interphase mass and heat transfer., cooled by surrounding water cooling with 1.8Kg/s (30 cm size recipient - 1000W)

ghorrocks · December 17, 2018, 23:50

The starting point for any question like this is always the CFX documentation.

Lift force: This is applicable in high-shear flows. CFX has 3 lift force models with difference applicability. The Legendre and Magnaudet model might be applicable to your case.

Turb Dispersion force: This is applicable to model the random dispersion of particle due to turbulence. You should model this if this randomness is important.

Virtual Mass: This is when the continuous phase is dense compared to the particle phase. It is not important for water droplets in air, but it is important for air bubbles in water.

Wall Lube: Usually used with the wall lift force to model bubbles concentrating near, but not on, a wall.

You should research these options, understand them, and make an informed decision about whether they are important in your case or not.

December 17, 2018, 22:33	Non-drag Forces	#1
oliveira1820 Senior Member Pedro Oliveira Join Date: Feb 2018 Location: Portugal Posts: 109 Rep Power: 8	How can I know if Lift, Turbulent Dispersion Force, Virtual Mass and Wall Lubrification Forces are important or not to my simulation? Basically it consists in water and steam transient flow, with a continuous heat deposition, with Thermal Phase Change (Nusselt number=6) modelling the interphase mass and heat transfer., cooled by surrounding water cooling with 1.8Kg/s (30 cm size recipient - 1000W)

December 17, 2018, 23:50		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,705 Rep Power: 143	The starting point for any question like this is always the CFX documentation. Lift force: This is applicable in high-shear flows. CFX has 3 lift force models with difference applicability. The Legendre and Magnaudet model might be applicable to your case. Turb Dispersion force: This is applicable to model the random dispersion of particle due to turbulence. You should model this if this randomness is important. Virtual Mass: This is when the continuous phase is dense compared to the particle phase. It is not important for water droplets in air, but it is important for air bubbles in water. Wall Lube: Usually used with the wall lift force to model bubbles concentrating near, but not on, a wall. You should research these options, understand them, and make an informed decision about whether they are important in your case or not. oliveira1820 likes this. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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