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udf and uds for transport equation

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Old   September 10, 2013, 02:56
Question udf and uds for transport equation
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Jack Chung
Join Date: Mar 2013
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Hello, every body

My geometry is a 2D suqare enclosure and the fluid fill of inside is Al2O3-Water.

This case is a natural convection and consider the transport equation include the brownian motion and thermophoresis mechanism.
Because i don't have enough experiences to validation the nanoparticle rayleigh number and nusselt number.
should i click the multiphase or discrete phase in models ?

Can any one can help me to solve it. thanks

the transport equation source is u*(Partial phi/Partial x) + v*(Partial phi/Partial y) =[(Partial/Partial x)*(DB*Partial phi/Partial x)+(Partial/Partial y)*(DB*Partial phi/Partial y]+[(Partial/Partial x)*(DT*Partial T/Partial x)+(Partial/Partial y)*(DT*Partial T/Partial y]

DB is brownian motion&DT is thermophoresis coefficient

by the way this is my code(the transport equation source term)困惑:

#include "udf.h"

real x[ND_ND];
real source;
real D_T /* thermophoresis coefficient */
real S_T; /* thermophoresis parameter */
real mu_f; /* water of dynamic viscosity Unit: kg/m-s */
real rho_f; /* water of density Unit: kg/m^3 */
real T; /* Temperatur of cold wall Unit: kelvin scale */
real phi; /* nanoparticle volume fraction */

S_T = 0.13; mu_f = 0.00063544; rho_f = 991.8; T = 313; phi = 0.01;
C_T_G(c,t)[1]; /* returns the x-component of the cell temperature gradient vector */
D_T = S_T*(mu_f/(rho_f*T))*phi;

C_T_G(c,t,i)= c_t_g(c,t,i)/dx +

ds[equ] = D_T*C_UDSI(c,t,0);

return source;
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Old   September 15, 2015, 01:02
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Join Date: Nov 2014
Posts: 34
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I want to use one user defined scalar for transport equation (for volume fraction of nano particle),
I set in fluent but I dont know how I specified that scalar quantity is volume fraction?
I would appreciate if you can help me.
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