5.2.2 DEFINE_PB_BREAKUP_RATE_PDF

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

Usage

DEFINE_PB_BREAKUP_RATE_PDF(name, cell, thread, d_1, d_2)

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
real d_2	Diameter of one of the daughter particles after breakage;
	the second daughter particle diameter is calculated by
	conservation of particle volume
Function returns
real

There are five arguments to DEFINE_PB_BREAKUP_RATE_FREQ: name, cell, thread, d_1, and d_2. You will supply name, the name of the UDF. cell, thread, d_1, and d_2 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 PDF (see Section  2.2.2) that is parabolic, as defined in Equation  2.2-15.

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

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

DEFINE_PB_BREAKUP_RATE_PDF(break_up_pdf_par, cell, thread, d_1, d_2)
{
real pdf;
real kv = M_PI/6.;

real C = 1.0;

real f_2, f_3, f_4;
real V_prime = kv*pow(d_1,3.);
real V = kv*pow(d_2,3.);

f_2 = 24.*pow(V/V_prime,2.);
f_3 = -24.*(V/V_prime);
f_4 = 6.;

pdf = (C/V_prime) + ((1.-C/2.)/V_prime)*(f_2 + f_3 + f_4);
   
return 0.5*pdf;
}