i have to add UDF to change the equation of following:-
Turbulent Kinetic Energy(k)
Turbulent dissipation(epsilon)
velocity
temperature
so, for velocity and temperature i find out where to incorporate their UDF in fluent but still finding for :-
Turbulent Kinetic Energy(k)
Turbulent dissipation(epsilon)
(i have code in C for above equation )
so please guide me as i am new to CFD Fluent.
I have few modules related to fluent for modelling fluid dynamics, i will mail it to you, give me the email ID. The material will be useful to you for further study as well.
Go to Define--> User defined --> functions. Then you can load your model file based on the file type, either compiled or interpreted.
@xiaolong Zhang the above steps is already done by me.....and also know where to add velocity and temp. function in boundary condition .
But want to know where will I find other 2 parameters to change after get interpreted function in fluent
It depends on what boundary conditions you have given. In case of velocity inlet or pressure inlet or mass-flow inlet, the terms you mentioned (temp, vel, tke or dissipation) can be defined via UDF. To define UDF you may need to write it in the C format but a bit different in the respect that it contains some commands related to Fluent. Then you can define TKE, Eps and velocity. In fluent, go to define --> UDF-->Interpret , then browse to the file (of UDF written in .c) and then click on Interpret. When the interpret is done, you can go to mass flow inlet , velocity inlet or pressure inlet (whatever you have defined in your case) and select the button next to space where you define a constant. the button gives a drop down menu where you have values of the function (select temp in case of temperature, or dissipation ) remember that dissipation is defined in k epsilon model only. An example is given below but you may obviously modify it.
#include "udf.h" // This header is required.
#include "mem.h" // To access density, etc.
#include "math.h"
/* User-defined constants */
#define SIG_TKE 2.0
#define SIG_OMG 2.0
/* User-defined scalars */
enum
{
TKE,
OMG,
N_REQUIRED_UDS
};
DEFINE_ADJUST(eddy_viscosity, domain) /* Consider using DEFINE_TURBULENT_VISCOSITY?*/
{
Thread *t;
cell_t c;
real alpha_star=1.0;
/* Set the turbulent viscosity, looping over all threads and then cells */
thread_loop_c (t, domain)
{
if (FLUID_THREAD_P(t))
{
begin_c_loop(c,t)
{
C_MU_T(c,t) =alpha_star*C_R(c,t)*C_UDSI(c,t,TKE)/C_UDSI(c,t,OMG);
}
end_c_loop(c,t)
}
}
}
DEFINE_DIFFUSIVITY(kw_diff, c, t, eqn)
{
real diff; // define the diffusion coeffcient
real mu = C_MU_L(c,t);
real mu_t = C_MU_T(c,t);
switch (eqn)
{
case TKE:
diff = mu_t/SIG_TKE + mu;
break;
case OMG:
diff = mu_t/SIG_OMG + mu;
break;
default:
diff = mu_t + mu;
}
return diff;
}
But I have both turbulent kinetic energy UDF and dissipation ...so just need the exact place to enter it after getting inteprated.....most of the things get clear from above answer but plz help further
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