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 Thomas Lescot April 17, 2007 06:06

user defined function

Hello!

I have to modify the heat transfer coefficient function but I don't understand how to do that.

You will find here below what I have to program in C.

My questions are : 1. How can I get the variables used in Fluent ? The variables I need are defined here below in VARIABLES FROM FLUENT.

2. How must I define my new heat transfer coefficient function in my program ?

3. How can I use my program in Fluent?

Thanks for your help, Thomas Lescot

double H; /*Heat transfer coefficient in Fluent*/

/*------------------- VARIABLES FROM FLUENT -------------*/

u_g /* gas velocity - vector [m/s] */ u_m /* solid velocity - vector [m/s] */ double dp ;/* particle diameter [m] */ double epsilon_g ; /* void fraction [-] */ double rho_g ; /* gas density [kg/m³g] */ double rho_m ; /* solid density [kg/m³s] */ double cp_g ; /* specific heat of fluid [kJ/kg*K] */ double mu_g ; /* dynamic viscosity of the gas [kg/m*s] */ double k_g ; /* thermal conductivity [kJ/m*s*K] */

/*-------------------------------------------------------*/

/*-------------------- NEW VARIABLES --------------------*/

double PI = 3.1415926 ;/* pi */ double g = 9.81 ; /* gavity */ double w_g ; /* norme de u_g */ double w_m ; /* norme de u_m */ double a_m ; /* external surface of a particle */ double G ; /* superficial mass flow velocity */ double j_h ; /* Jh factor */ double hf ; /* heat transfer coefficient for film surrounding a particle */ double pr_g ; /* Prandtl number */

/*-------------------------------------------------------*/

/*-------------------------- PROGRAM --------------------*/

/*external surface of a particle*/ a_m = 4*PI*pow(dp/2,2);

/*superficial mass flow velocity*/ w_g = sqrt(pow(u_g[0],2)+pow(u_g[1],2)+pow(u_g[2],2)); w_m = sqrt(pow(u_m[0],2)+pow(u_m[1],2)+pow(u_m[2],2));

G = epsilon_g*rho_g*(w_g-w_m) ;

/*Jh factor*/ j_h = 0.0043*pow((dp*g*(rho_m-rho_g)*pow((1-epsilon_g),2)/(pow((epsilon_g*w_g),2)*rho_g)),0.25);

/* heat transfer coefficent for film surrounding a particle */ pr_g = mu_g*cp_g/k_g;

h = j_h*cp_g*G/pow(pr_g,2/3);

/*heat transfer coefficient*/ H = h*a_m;

 Srisudha busi May 4, 2007 10:13

user defined function

hello, i want to write a UDF for CG motion in dynamic mesh so that my mesh moves with the oscillation of the body that means remeshing.please help me in writing UDF thank you

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