5.2.3 DEFINE_PB_COALESCENCE_RATE

You can use the DEFINE_PB_COALESCENCE_RATE macro if you want to define your own particle aggregation kernel. The function is executed at the beginning of every time step.

Usage

DEFINE_PB_COALESCENCE_RATE(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, d_2	Diameters of the two colliding particles
Function returns
real

There are five arguments to DEFINE_PB_COALESCENCE_RATE: 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. Your UDF will need to return the real value of the aggregation rate.

Example

Included below is a example UDF for a Brownian aggregation kernel. In this example, the aggregation rate is defined as

where $\beta_0 = 1 \times 10^{-17}$ m $^3$/s.

/************************************************************************
UDF that computes the particle aggregation rate
*************************************************************************/

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

DEFINE_PB_COALESCENCE_RATE(aggregation_kernel,cell,thread,d_1,d_2)
{
  real agg_kernel;
  real beta_0 = 1.0e-17 /* aggregation rate constant */
  agg_kernel = beta_0*pow((d_1+d_2),2.0)/(d_1*d_2);

  return agg_kernel;
}