{"id":223245,"date":"2022-08-04T07:53:10","date_gmt":"2022-08-04T07:53:10","guid":{"rendered":"\/forum\/?post_type=topic&p=223245"},"modified":"2022-08-04T07:53:10","modified_gmt":"2022-08-04T07:53:10","slug":"dpm-boundary-udf-for-a-filter","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/dpm-boundary-udf-for-a-filter\/","title":{"rendered":"DPM boundary UDF for a filter"},"content":{"rendered":"

hi all, I’m using DPM to simulate a filter, namely, when a bunch of particles flow to a surface, if the particle size is big then reflect. otherwise, pass through. The problem is the small particles stick on the surface, instead of pass through.<\/p>\n

the figure is my results. I only tested small particles (in the code, it’s < 120 um. big particles are fine, they can reflected) as can be seen, the particles trapped on the surface.<\/p>\n

\"\"<\/p>\n

What I’d like to do is<\/p>\n

if (particle diameter > D_filter_size)<\/p>\n

{<\/p>\n

boundary condition is reflect;<\/p>\n

}<\/p>\n

if (particle diameter < D_filter_size)<\/p>\n

{<\/p>\n

boundary condition interior;<\/p>\n

}<\/p>\n

 <\/p>\n

 <\/p>\n

the following is my code. it only contains the big particle case. However, I also tried to manipulate the small paritcle position and velocity, the results are same. particles < 120 um trapped on the surface.<\/p>\n

#include “udf.h”
#include “dpm.h”
#include “surf.h”
#include “random.h”
#include <stdlib.h>
#include <time.h>
\/* 
define a user-defined dpm boundary condition routine
* bc_reflect: name
* p: the tracked particle
* t: the touched face thread
* f: the touched face
* f_normal: normal vector of touched face
* dim: dimension of the problem (2 in 2d and 2d-axi-swirl, 3 in 3d)
*
* return is the status of the particle, see enumeration of Path_Status
* in dpm.h
*\/<\/p>\n

 <\/p>\n

DEFINE_DPM_BC(bc_filter, p, t, f, f_normal, dim)
{
    real alpha; \/* angle of particle path with face normal *\/
    real vn = 0.;
    real vns = 0.;
    real nor_coeff = 0.5;
    real tan_coeff = 0.7;
    real normal[3];
    int i, idim = dim;
    real NV_VEC(x);<\/p>\n

    for (i = 0; i<idim; i++)
        normal[i] = f_normal[i];<\/p>\n

    if (P_DIAM(p) >= 0.00012)
    {
        if (p->type == DPM_TYPE_INERT)
            alpha = M_PI \/ 2. – acos(MAX(-1., MIN(1., NV_DOT(normal, P_VEL(p)) \/ MAX(NV_MAG(P_VEL(p)), DPM_SMALL))));
        if ((NNULLP(t)) && (THREAD_TYPE(t) == THREAD_F_WALL))
            F_CENTROID(x, f, t);
        \/\/ calculate the normal component, rescale its magnitude by the coefficient of restitution and subtract the change 
        \/\/Compute normal velocity. 
        
        for (i = 0; i<idim; i++)
            vn += P_VEL(p)[i] * normal[i];
        \/\/ Subtract off normal velocity. 
        for (i = 0; i<idim; i++)
            P_VEL(p)[i] -= vn*normal[i];
        \/\/ Apply tangential coefficient of restitution. 
        for (i = 0; i<idim; i++)
            P_VEL(p)[i] *= tan_coeff;
        \/\/ Add reflected normal velocity. 
        for (i = 0; i<idim; i++)
            P_VEL(p)[i] -= nor_coeff*vn*normal[i];
        \/\/ Store new velocity in P_VEL0 of particle 
        
        for (i = 0; i<idim; i++)
            P_VEL0(p)[i] = P_VEL(p)[i];
        return PATH_ACTIVE;
    }<\/p>\n

    return PATH_ACTIVE;
    
}<\/p>\n

 <\/p>\n

Anyone could help me?<\/p>\n","protected":false},"template":"","class_list":["post-223245","topic","type-topic","status-closed","hentry"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t