Lift coefficient in Eulerian multiphase model

hennas · May 17, 2011, 00:23

Hi,
Is anyone able to explain to me how the lift coefficient for a bubble/droplet in multiphase flow is used in Fluent (v12). The theory guide states that the lift force (added to the phase momentum equation) is given by equantion 16.5-8:

Lift Force=-0.5*density_q*volume fraction_p*(v_q-v_p)x(grad x v_q)

which does not include a lift coefficient, but when you activate the lift tab under phase interaction you are invited to input a constant lift coefficient.
Any ideas on this would be very helpful, as I am not a little confused.
Thanks

rajasekaran.raam · July 4, 2011, 17:50

CL=0.5 is the lift coefficient in bubble column(short bubble columns). see the literature.
when you use 0.5 as lift co efficient, solution diverges at once.i do not know why.We have to find the reason out.
using drag co efficient, bubble plume behavior(dynamic) can not be captured correctly.
i suppose fluent does not incorporate bubble induced turbulence in it. it has to be given as UDF.

May 17, 2011, 00:23	Lift coefficient in Eulerian multiphase model	#1
hennas New Member henry clarke Join Date: May 2009 Posts: 7 Rep Power: 17	Hi, Is anyone able to explain to me how the lift coefficient for a bubble/droplet in multiphase flow is used in Fluent (v12). The theory guide states that the lift force (added to the phase momentum equation) is given by equantion 16.5-8: Lift Force=-0.5density_qvolume fraction_p*(v_q-v_p)x(grad x v_q) which does not include a lift coefficient, but when you activate the lift tab under phase interaction you are invited to input a constant lift coefficient. Any ideas on this would be very helpful, as I am not a little confused. Thanks

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July 4, 2011, 17:50		#2
rajasekaran.raam New Member Rajasekaranmanokaran Join Date: Jun 2011 Location: Bangalore Posts: 2 Rep Power: 0	CL=0.5 is the lift coefficient in bubble column(short bubble columns). see the literature. when you use 0.5 as lift co efficient, solution diverges at once.i do not know why.We have to find the reason out. using drag co efficient, bubble plume behavior(dynamic) can not be captured correctly. i suppose fluent does not incorporate bubble induced turbulence in it. it has to be given as UDF.