5.2.1 DEFINE_PB_BREAKUP_RATE_FREQ

You can use the DEFINE_PB_BREAKUP_RATE_FREQ macro if you want to define the breakage frequency using a UDF. The function is executed at the beginning of every time step.

Usage

DEFINE_PB_BREAKUP_RATE_FREQ(name, cell, thread, d_1)

Argument Type	Description
char name	UDF name
cell_t cell	Cell index
Thread *thread	Pointer to the secondary phase thread
real d_1	Parent particle diameter or length
Function returns
real

There are four arguments to DEFINE_PB_BREAKUP_RATE_FREQ: name, cell, thread, and d_1. You will supply name, the name of the UDF. cell, thread, and d_1 are variables that are passed by the ANSYS FLUENT solver to your UDF.

Example

Included below is an example of a UDF that defines a breakage frequency (see Section  2.2.2) that is based on the work of Tavlarides [ 4], such that

where $C_1$ and $C_2$ are constants, $\varepsilon$ is the dissipation rate, $d$ is the parent diameter, $\sigma$ is the surface tension, $\alpha$ is the volume fraction of the dispersed phase, and $\rho_l$ is the density of the primary phase.

/************************************************************************
UDF that computes the particle breakage frequency
*************************************************************************/

#include "udf.h"
#include "sg_pb.h"
#include "sg_mphase.h"

DEFINE_PB_BREAKUP_RATE_FREQ(break_up_freq_tav, cell, thread, d_1)
{
real epsi, alpha, f1, f2, rho_d;
real C1 = 0.00481, C2 = 0.08, sigma = 0.07;
Thread *tm = THREAD_SUPER_THREAD(thread);/*passed thread is phase*/
epsi = C_D(cell, tm);
alpha = C_VOF(cell, thread);
rho_d = C_R(cell, thread);
f1 = pow(epsi, 1./3.)/((1.+epsi)*pow(d_1, 2./3.));
f2 = -(C2*sigma*(1.+epsi)*(1.+epsi))/(rho_d*pow(epsi,2./3.)*pow(d_1, 5./3.));
return C1*f1*exp(f2);
}