{"id":377842,"date":"2024-08-09T20:29:23","date_gmt":"2024-08-09T20:29:23","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/377842\/"},"modified":"2024-08-12T04:19:58","modified_gmt":"2024-08-12T04:19:58","slug":"377842","status":"publish","type":"reply","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/377842\/","title":{"rendered":"Reply To: Ansys Fluent UDF: DEFINE_DPM_BC"},"content":{"rendered":"<p>&lt;p&gt;Okay I get this, but how do I get the particle to stick on the wall?&lt;br&gt;&lt;br&gt;1. Is there a particular macros I need to look for to access data from P_USER_REAL so I can post process \/ visualise the results?&lt;br&gt;&lt;br&gt;2. What do you think I must do to model particle trajectory after colliding with the boundary?&lt;\/p&gt;&lt;p&gt;3. From the below UDF I do not see a text file being generated to run my simulation, what could be the reason?&lt;br&gt;&lt;br&gt;&lt;\/p&gt;&lt;div&gt;&lt;div&gt;#include &ldquo;udf.h&rdquo;&lt;\/div&gt;&lt;div&gt;#include &ldquo;dpm.h&rdquo;&lt;\/div&gt;&lt;div&gt;#include &ldquo;math.h&rdquo;&lt;\/div&gt;&lt;div&gt;#include &ldquo;mem.h&rdquo;&lt;\/div&gt;&lt;div&gt;#include&lt;\/div&gt;&lt;br&gt;&lt;div&gt;#define Rho_air 1.225 &nbsp;\/* Air density in kg\/m^3 *\/&lt;\/div&gt;&lt;div&gt;#define Cd 0.47 &nbsp; &nbsp; &nbsp; &nbsp;\/* Drag coefficient for a sphere *\/&lt;\/div&gt;&lt;div&gt;#define mu 0.5 &nbsp; &nbsp; &nbsp; &nbsp; \/* Coefficient of friction *\/&lt;\/div&gt;&lt;br&gt;&lt;div&gt;\/* Define your boundary condition function *\/&lt;\/div&gt;&lt;div&gt;DEFINE_DPM_BC(particle_bc, p, t, f, normal, dim)&lt;\/div&gt;&lt;div&gt;{&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; real V = sqrt(P_VEL(p)[0] * P_VEL(p)[0] + P_VEL(p)[1] * P_VEL(p)[1] + P_VEL(p)[2] * P_VEL(p)[2]); &nbsp;\/* Velocity magnitude in m\/s *\/&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; FILE * fp1 ;&lt;\/div&gt;&lt;br&gt;&lt;div&gt;&nbsp; &nbsp; real alpha; &nbsp;\/* angle of particle path with face normal *\/&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; real vn=0.;&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; real nor_coeff = 1.;&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; real tan_coeff = 0.3;&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; \/\/real normal[3];&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; int i, idim;&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; real NV_VEC(x);&lt;\/div&gt;&lt;br&gt;&lt;div&gt;&nbsp; &nbsp; real radius = P_DIAM(p) \/ 2.0;&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; real A = M_PI * radius * radius; &nbsp;\/* M_PI is a constant for &pi; *\/&lt;\/div&gt;&lt;br&gt;&lt;div&gt;&nbsp; &nbsp; \/* Get the face pressure *\/&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; real P_local = F_P(f, t);&lt;\/div&gt;&lt;br&gt;&lt;div&gt;&nbsp; &nbsp; \/* Calculate aerodynamic force Fa *\/&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; real Fa = 0.5 * Rho_air * A * Cd * V * V;&lt;\/div&gt;&lt;br&gt;&lt;div&gt;&nbsp; &nbsp; \/* Calculate normal force Fn *\/&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; real Fn = P_local * A;&lt;\/div&gt;&lt;br&gt;&lt;div&gt;&nbsp; &nbsp; \/* Calculate frictional force Ff *\/&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; real Ff = mu * Fn;&lt;\/div&gt;&lt;br&gt;&lt;div&gt;&nbsp; &nbsp; if (Fa &gt; Ff)&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; {&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; &nbsp; \/* Particle needs to bounce with a coefficient of restitution of 1 *\/&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; \/* Compute normal velocity. *\/&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; for(i=0; i&lt;div&gt;&nbsp; &nbsp; &nbsp; &nbsp;&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; &nbsp; vn += P_VEL(p)[i]*normal[i];&lt;\/div&gt;&lt;br&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; \/* Subtract off normal velocity. *\/&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; for(i=0; i&lt;div&gt;&nbsp; &nbsp; &nbsp; &nbsp; P_VEL(p)[i] -= vn*normal[i];&lt;\/div&gt;&lt;br&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; \/* Apply tangential coefficient of restitution. *\/&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; for(i=0; i&lt;div&gt;&nbsp; &nbsp; &nbsp; &nbsp; P_VEL(p)[i] *= tan_coeff;&lt;\/div&gt;&lt;br&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; \/* Add reflected normal velocity. *\/&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; for(i=0; i&lt;div&gt;&nbsp; &nbsp; &nbsp; &nbsp; P_VEL(p)[i] -= nor_coeff*vn*normal[i]; &nbsp;&lt;\/div&gt;&lt;br&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; \/* Store new velocity in P_VEL0 of particle *\/&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; for(i=0; i&lt;div&gt;&nbsp; &nbsp; &nbsp; &nbsp; P_VEL0(p)[i] = P_VEL(p)[i];&lt;\/div&gt;&lt;br&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; fp1=fopen ( &ldquo;Impact.txt&rdquo; , &ldquo;a&rdquo; ) ;&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; fprintf( fp1 , &ldquo;%f %f %f %f\\n&rdquo;, Fa, Ff, radius, P_local);&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; fclose( fp1 );&lt;\/div&gt;&lt;br&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; return PATH_ACTIVE;&lt;\/div&gt;&lt;br&gt;&lt;div&gt;&nbsp; &nbsp; }&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; else&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; {&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; &nbsp; \/* Particle sticks to the boundary *\/&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; &nbsp; for (int i = 0; i &lt; dim; i++)&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; &nbsp; {&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; P_VEL(p)[i] = 0; \/* Set velocity to zero *\/&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; &nbsp; }&lt;\/div&gt;&lt;br&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; &nbsp; P_USER_REAL(p, 0) = 1.0; \/* Optionally set a user-defined variable to indicate sticking *\/&lt;\/div&gt;&lt;br&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; &nbsp; \/* Save the impingement location *\/&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; &nbsp; P_USER_REAL(p, 1) = P_POS(p)[0]; &nbsp;\/* X-coordinate *\/&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; &nbsp; P_USER_REAL(p, 2) = P_POS(p)[1]; &nbsp;\/* Y-coordinate *\/&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; &nbsp; P_USER_REAL(p, 3) = P_POS(p)[2]; &nbsp;\/* Z-coordinate *\/&lt;\/div&gt;&lt;br&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; &nbsp; P_USER_REAL(p, 4) = 1.0; &nbsp;\/* Mark as stuck *\/&lt;\/div&gt;&lt;br&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; &nbsp; return PATH_ABORT; \/* Stop tracking the particle *\/&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; }&lt;\/div&gt;&lt;div&gt;}&lt;\/div&gt;&lt;\/div&gt;&lt;p&gt;&nbsp;&lt;\/p&gt;&lt;p&gt;&nbsp;&lt;\/p&gt;&lt;\/div&gt;&lt;\/div&gt;&lt;\/div&gt;&lt;\/div&gt;&lt;\/div&gt;&lt;p&gt;&nbsp;&lt;\/p&gt;<\/p>\n","protected":false},"template":"","class_list":["post-377842","reply","type-reply","status-publish","hentry"],"aioseo_notices":[],"aioseo_head":"\n\t\t<!-- All in One SEO 4.9.10 - aioseo.com -->\n\t<meta name=\"description\" content=\"Okay I get this, but how do I get the particle to stick on the wall?1. 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