[HoCH_10]

Hi guys, I am a university student and are new to UDF. I am trying to model a filter DPM boundary condition using UDF.

Simulation runs well until DPM iteration. Fluent then crashes with errors.
'F1 process could not be started' is the last message I saw in the console before the window closed.

Part of the error log from fluent-0-error.log:

Node 0 Fatal signal raised sig = Segmentation fault
 2bde0330 CX_Primitive_Error
 27600cc0 seh_filter_exe
 2be83730 logical_right_shift
 e38e2f0 _C_specific_handler
 297b1e50 _chkstk
 29761020 RtlRaiseException
 297b0a70 KiUserExceptionDispatcher
 e1650000 Ordinal0
 2b4c6b80 check_dpm_bc_udf
 2b4c0b30 FindNeighbour
 2b4a5510 Deposit_Cache_Sources
 2b4a5510 Deposit_Cache_Sources
 2b4a5510 Deposit_Cache_Sources
 2b4a5510 Deposit_Cache_Sources
 2b4a5510 Deposit_Cache_Sources
 2b4a0760 DPM_Compute_Pathlines
 2b4998b0 DPM_Iteration
 2b563420 sort_to_file_header
 2be6ecf0 eval
 299837d0 PRF_Command_Start
 29985fb0 PRF_Node_repl
 29986870 init_rsubrs
 2be83730 logical_right_shift
 29397020 BaseThreadInitThunk
 29762630 RtlUserThreadStart

Error [node 0] [time 3/3/21 16:6:14] Abnormal Exit!

I believe that the error is associated with the usage of C_W and F_W in my expression to calculate fluid velocity. There is another expression (commented off in the code) using particle velocity instead of fluid velocity, works fine.

I am trying to obtain fluid velocity for my calculation of particle efficiency.
I use C_W and F_W at the moment since these are the only function I found in UDF manual related to fluid velocity, also the filter face I have is normal to z-direction. I have plan to use looping to get the average fluid velocity in front of filter surface.

I welcome and appreciate any suggestion/solution/feedback.

p/s: I also wish to know what calcFaceEquations(tp) does since I am not able to find any documentation on it in UDF manual or online. I found its usage in a sample filter UDF in ANSYS UDF manual.

UDF:

/* UDF for MERV13 */

#include "udf.h"
#include "random.h"
#include "mem.h"

/* Tracked_Particle *tp = Pointer to the particle's data structure being tracked. */
/* Thread *t = Pointer to the face thread the particle is currently hitting. */
/* face_t f = Index of the face that the particle is hitting. */
/* real f_normal[] = Array that contains the unit vector normal to the face. */
/* int dim = Dimension of the flow problem: 2D = 2, 3D = 3/ */

#define AREA 0.1015		//area of filter (m^2) */
#define K_1_2 -0.0750692	//coefficient of v^2, polynomial k1(v)
#define K_1_1 0.34703522	//coefficient of v, polynomial k1(v)
#define K_2_2 0.00432755	//coefficient of v^2, polynomial 1/k2 (v)
#define K_2_1 0.03135811	//coefficient of v, polynomial 1/k2 (v)
#define K_3_2 0.00573440	//coefficient of v^2, polynomial 1/k3 (v)
#define K_3_1 0.01218403	//coefficient of v, polynomial 1/k3 (v)

DEFINE_DPM_BC(dpm_bc_filter, tp, t, f, f_normal, dim)
{
	//filter particles by size and face velocity
	real eff;
	real vel;
	cell_t c0 = F_C0(f,t);
	Thread *t0 = F_C0_THREAD(f,t);

	//velocity normal to face
	/* vel = fabs( f_normal[0] * P_VEL(tp)[0] + f_normal[1] * P_VEL(tp)[1] + f_normal[2] * P_VEL(tp)[2] ); */
	
	if (BOUNDARY_FACE_THREAD_P(t)) //if external face
	{
		vel = F_W(f,t);
	}
	else //if internal face
	{
		vel = C_W(c0,t0);
	}
	
	//efficiency based on particle diameter
	if (P_DIAM(tp) > 3.0e-6)
	{
		eff = 1.0 - exp( -1.0 / ( K_3_2 * vel * vel + K_3_1 * vel ) * AREA * vel );
	} 
	else if (P_DIAM(tp) > 1.0e-6) 
	{
		eff = 1.0 - exp( -1.0 / ( K_2_2 * vel * vel + K_2_1 * vel ) * AREA * vel );
	}
	else if (P_DIAM(tp) > 0.3e-6)
	{
		eff = 1.0 - exp( -1.0 * ( K_1_2 * vel * vel + K_1_1 * vel ) * pow(AREA * vel, -2.0 / 3.0) );
	}
	else
	{
		eff = 0; //let all particle <=0.3 micron pass
	}
	if (eff > cheap_uniform_random())
		return PATH_ABORT;
	
	/* determine switch side of the face the particle is currently in */
	/* and move it to the other side of the face */
	if ( (P_CELL_THREAD(tp)->id == THREAD_T0(t)->id) && (P_CELL(tp) == F_C0(f, t)) )
	{
		STORE_TP_CELL(tp, F_C1(f, t), THREAD_T1(t));
	}
	else
	{
		STORE_TP_CELL(tp, F_C0(f, t), THREAD_T0(t));
	}
	calcFaceEquations(tp);
	
	return PATH_ACTIVE;   
}