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-   -   Saffman Lift Force: confused (http://www.cfd-online.com/Forums/fluent/30579-saffman-lift-force-confused.html)

CFD_MAN November 26, 2002 19:24

Saffman Lift Force: confused
 
Hallo In the Fluent manual, its writtin as: -- The Saffman's lift force, or lift due to shear, can also be included in the additional force term as an option. The lift force used is from Li and Ahmadi [ 135] and is a generalization of the expression provided by Saffman [ 196]:

(19.2.19) [please see the equation in the manual, V6]

where K=2.594 and d ij is the deformation tensor. This form of the lift force is intended for small particle Reynolds numbers. Also, the particle Reynolds number based on the particle-fluid velocity difference must be smaller than the square root of the particle Reynolds number based on the shear field. Since this restriction is valid for submicron particles, it is recommended to use this option only for submicron particles. ---- My question is, after solving a particulate flow (enabling the saffman lift forc), how can I calculate the saffman lift force at a particular location of the particle trajectory? I know particle size, density, velocity and also fluid velocity, so I know Ur, Cd, Rep, but how do I know deformation tensor along the path of the particles?

Any suggestion would be appreciated.

CFD MAN

CFD_MAN November 27, 2002 13:30

did I ask a difficult question?
 
Hallo, Did I ask a difficult or stupid question ?

Until now no ansers !!:(

CFD MAN

Amid Naz November 27, 2002 17:52

Re: Saffman Lift Force: confused
 
Neiter nor, but actually I have no access to the manual..Anyway, to post a question in this forum dont expect quick answer..CHEEEEEEEERS

CFD_MAN November 27, 2002 21:16

Re: Saffman Lift Force: confused
 
Have you heard of SLF ? :) Just curious. FLUENT calculates this force.

CFD

Amid Naz November 28, 2002 07:22

Re: Saffman Lift Force: confused
 
I know lift due to shear or the viscous lift force..This definetly can be calculated by Fluent.. but you must select viscous slover not inviscid..Good luck..

mmmahdavimanesh September 9, 2010 05:51

saffman lift force estimation
 
Dear freinds

I write this termin my code. how should I calculate dij (rate of deformation)?
Assume that particle is within one cell. Is it neccessary to calculate these term in the both side of particle or just derivate and evaluate it in the base of cell?


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