[Manathan]

Hello everyone !

I want to compute the local collection efficiency of constant diameter raindrop on a sphere using this formula :

beta = Concentration_wall/Concentration_injection * NormalVelocity_wall/Velocity_injection

At the origin I wanted to use the ratio of DPM Concentration but the results I got are wrong at the wall (for most of the impacted cells, the concentration is 0), this is my UDF function :




#include "udf.h"
#include "dpm.h"
#include "surf.h"
#include "random.h"
#include "sg_mem.h"
#include "para.h"


real beta[100] ;
real C[100] ;
real C_0[100] ;

real x[100];
real y[100];
real Vn[100];
real V0[100];
real x0[100] ;
real y0[100] ;

int i = 0 ;

DEFINE_DPM_BC(dpm_report,p,t,f,f_normal,dim)
{
Domain *domain; //Domain is declared as a variable
domain = Get_Domain(1); //Returns fluid domain pointer


/*================================================= ================================================== ====================*/
/*BEGINNING OF Wall Concentration Computation for particle p trapped in the wall*/

CX_Cell_Id cwx_cell;
double pwc[2], A[2], center[2];
cell_t cw;
Thread *tw;

pwc[0] = P_POS(p)[0];
pwc[1] = P_POS(p)[1];
x[i] = pwc[0];
y[i] = pwc[1];

DPM_Init_Oct_Tree_Search();

cwx_cell.ct.c = 0;
cwx_cell.ct.t = NULL;
DPM_Locate_Point(pwc,&cwx_cell,0.0,0);

cw = RP_CELL(&cwx_cell);
tw = RP_THREAD(&cwx_cell);

DPM_End_Oct_Tree_Search();

C[i] = C_DPMS_CONCENTRATION(cw,tw) ; /* concentration particle at impact*/

/*END OF COMPUTATION OF Wall CONCENTRATION*/
/*================================================= ================================================== =====================*/

/*================================================= ================================================== ====================*/
/*BEGINNING OF Initial Concentration Computation for particle p trapped in the wall*/

CX_Cell_Id cx_cell;
double pt[2], B[2], centerb[2];
Thread *ft;
face_t f11;
cell_t c1;
Thread *t1;

pt[0] = P_INIT_POS(p)[0] ;
pt[1] = P_INIT_POS(p)[1] ;
x0[i] = pt[0] ;
y0[i] = pt[1] ;

DPM_Init_Oct_Tree_Search();

cx_cell.ct.c = 0;
cx_cell.ct.t = NULL;
DPM_Locate_Point(pt,&cx_cell,0.0,0);

c1 = RP_CELL(&cx_cell);
t1 = RP_THREAD(&cx_cell);

DPM_End_Oct_Tree_Search();

C_0[i] = C_DPMS_CONCENTRATION(c1,t1) ; /* concentration at the injection cell of particle p*/


/*END OF COMPUTATION OF INITIAL CONCENTRATION*/
/*================================================= ================================================== ====================*/

V0[i] = P_INIT_VEL(p)[0] ;
Vn[i] = NV_DOT(P_VEL(p), f_normal)/NV_MAG(f_normal) ;

beta[i] = C[i]/C_0[i] * Vn[i]/V0[i] ;

i=i+1 ;

return x,y,C,C_0,beta,V0,Vn,PATH_ABORT;

}


DEFINE_ON_DEMAND(beta_profile)
{
FILE *f1;
f1 = fopen("1dpm_report_beta_2e_05mm_v_5m_s.txt", "a");
fprintf(f1," Stream Index, X position, Y position, Initial Concentration, Concentration at Wall, Beta, V0, Vn, x0, y0\n");
for (i = 1 ; i <= 100 ; i++)
{
fprintf(f1, "%d %f %f %f %f %f %f %f %f %f\n", i-1 , C_0[i-1] , C[i-1] , beta[i-1] , V0[i-1] , Vn[i-1], x0[i-1], y0[i-1] );


}


fclose(f1);
}