# udf and uds for transport equation

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 September 10, 2013, 02:56 udf and uds for transport equation #1 New Member   Jack Chung Join Date: Mar 2013 Posts: 3 Rep Power: 13 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" DEFINE_SOURCE(temperature_source,c,t,dS,eqn) { 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_CENTROID(x,c,t); C_UDSI(c,t,1); 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; }

 September 15, 2015, 01:02 question #2 Member   Join Date: Nov 2014 Posts: 42 Rep Power: 11 Hi 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.