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-   -   Lift coefficient in Eulerian multiphase model (http://www.cfd-online.com/Forums/fluent/88398-lift-coefficient-eulerian-multiphase-model.html)

hennas May 16, 2011 23:23

Lift coefficient in Eulerian multiphase model
 
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 16:50

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.


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