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-   -   how to perform temperature gradient on a particle (Thermophoretic Force) (http://www.cfd-online.com/Forums/fluent/86412-how-perform-temperature-gradient-particle-thermophoretic-force.html)

wwt650420 March 22, 2011 09:20

how to perform temperature gradient on a particle (Thermophoretic Force)
 
hi, everyone.
Now i model dpm in a turbulent flow with a significant thermophoretic force.
And just like what user's guide of fluent has introduced in 22.2.1 Equations of Motion for Particles. thermophoretic force is proportional to temperature gradient.
F_thermal force=f(dT/dx)
While in a 2D model, there are 2 directions for temperature gradient acted on a particles (as UDF manual , C_T_G(c,t)[0] and C_T_G(c,t)[1])
My Questions:
(1) How could i write a correction formulation for thermophretic force on a particle with these two temperature gradient vector?
(2) Why there is only Fx for a particle in user's guide of fluent when thermophoretic force is formed? What about Fy and Fz(if 3D case)?
(3) if any body had a UDF about thermophoretic force, please send me a copy.Thank you very much.
My email:mulin0803@sina.com or wwtmwtd@hotmail.com

Amir March 22, 2011 13:36

Hi,
I don't think that you're right. in user manual F_x is just a notation and the force acts in resultant gradient vector direction. you can also check that in a simple case which has temperature gradient only in y-direction.

wwt650420 March 22, 2011 22:21

how to perform temperature gradient on a particle (Thermophoretic Force)
 
Maybe i know what you mean. What i have modeled is a cross flow. so for a tueb surface it is a circle, even in the flow field it is hardly to show what is the exact direction of thermophoresis. Well, if U have a better code ,please send me a copy, and i will still study and search some literatures on it.
Thank you Amir.

Amir March 23, 2011 03:10

I meant that you can generate a simple mesh(e.g. a cube) and perform a temperature gradient in y-direction with boundary conditions and see whether it influences the particles or not.


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