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-   -   [URGENT] Drag Force UDF in Power-Law Fluid (https://www.cfd-online.com/Forums/fluent-udf/108592-urgent-drag-force-udf-power-law-fluid.html)

ali hemmati October 27, 2012 11:24

[URGENT] Drag Force UDF in Power-Law Fluid
 
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 "18*Cd*Re/24".

As you know, in powerlaw fluid, Re is defined as Re = \rho V^{2-n} d^{n} / m , and d being the particle diameter and m 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!

marcoscp2 June 12, 2017 13:06

Quote:

Originally Posted by ali hemmati (Post 388834)
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 "18*Cd*Re/24".

As you know, in powerlaw fluid, Re is defined as Re = \rho V^{2-n} d^{n} / m , and d being the particle diameter and m 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?

trbprnz June 13, 2017 03:37

Quote:

Originally Posted by ali hemmati (Post 388834)
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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