# [URGENT] Drag Force UDF in Power-Law Fluid

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 October 27, 2012, 11:24 [URGENT] Drag Force UDF in Power-Law Fluid #1 New Member   Ali Join Date: Mar 2011 Posts: 27 Rep Power: 8 Hello, I am going to simulate the behaviour of micron-sized particles in an non-Newtonian fluid medium. In fact, the flow viscosity follows the "power-law". I know that "DEFINE_DPM_DRAG(Drag_force,Re,p)" can pass the force per mass of each particle to Fluent, and that the returned valuee must be in form of "". As you know, in powerlaw fluid, Re is defined as and being the particle diameter and the "consistency index". The problem is, how does Fluent define Re number? Does Fluent think of Newtonian Re or this definition of Re? Should I pass this Re in "18*Cd*Re/24" or the Newtonian Re? Thank you!

June 12, 2017, 13:06
#2
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Marcos
Join Date: Nov 2013
Posts: 11
Rep Power: 6
Quote:
 Originally Posted by ali hemmati Hello, I am going to simulate the behaviour of micron-sized particles in an non-Newtonian fluid medium. In fact, the flow viscosity follows the "power-law". I know that "DEFINE_DPM_DRAG(Drag_force,Re,p)" can pass the force per mass of each particle to Fluent, and that the returned valuee must be in form of "". As you know, in powerlaw fluid, Re is defined as and being the particle diameter and the "consistency index". The problem is, how does Fluent define Re number? Does Fluent think of Newtonian Re or this definition of Re? Should I pass this Re in "18*Cd*Re/24" or the Newtonian Re? Thank you!
Hi!

Where you able to solve your problem?

June 13, 2017, 03:37
#3
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Join Date: May 2015
Posts: 6
Rep Power: 4
Quote:
 Originally Posted by ali hemmati Hello, The problem is, how does Fluent define Re number? Does Fluent think of Newtonian Re or this definition of Re? Should I pass this Re in "18*Cd*Re/24" or the Newtonian Re?
I think that if you use a PL rheology model, Fluent will evaluate the viscosity accordingly based on the magnitude of the rate of strain tensor, i.e. shear rate, for any grid cell. This viscosity is then used to compute the particle Reynolds number.

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