# how to perform temperature gradient on a particle (Thermophoretic Force)

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 March 22, 2011, 08:20 how to perform temperature gradient on a particle (Thermophoretic Force) #1 New Member   mu lin Join Date: Oct 2010 Posts: 8 Rep Power: 15 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

 March 22, 2011, 12:36 #2 Senior Member     Amir Join Date: May 2009 Location: Montreal, QC Posts: 735 Blog Entries: 1 Rep Power: 23 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.

 March 22, 2011, 21:21 how to perform temperature gradient on a particle (Thermophoretic Force) #3 New Member   mu lin Join Date: Oct 2010 Posts: 8 Rep Power: 15 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.

 March 23, 2011, 02:10 #4 Senior Member     Amir Join Date: May 2009 Location: Montreal, QC Posts: 735 Blog Entries: 1 Rep Power: 23 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.