If it's right to use this UDF in DPM calculation?

welch

Hi,all when i calculate the gas-liquid two phase flow, i use the following UDF to impose the body forces on particles

#include "udf.h"

#define r 0.01 /* particle diameter*/ #define pi 3.14 /* pi */ #define dens 2.1*1000 /* bath density*/ #define g 9.8 /*gravity acceleration*/

DEFINE_DPM_BODY_FORCE(particle_body_force, p, i) {

real bforce;

if(i==0) bforce=0;

else if(i==1) bforce=4*3.14*(P_DIAM(p)/2)*(P_DIAM(p)/2)*(P_DIAM(p)/2)*dens*g/3;

else

bforce=0.0;

/* an acceleration should be returned */

return (bforce/P_MASS(p)); }

obtain the bubble volume (4*3.14*(P_DIAM(p)/2)*(P_DIAM(p)/2)*(P_DIAM(p)/2)/3) at first,then multiply the gas density(dens) and gravity acceleration(g) to get the buoyant force.

but the result was not good, the velocity of the fluid flow is larger than the water modelling, and the turbulent energy and dissipation rate were in the order of 10e+0 and 10e+2 respectively; the residual of the mass, velocity and k,e were in the order of 10e-4.

I don't know if I have used the UDF correctly and how to reduce the reidual.would you please help me out the trouble?

Any help from you would be appreciated.