[Yingshi]

Hello,

I want to calculate gas mass transfer coefficient kla by using the following UDF:

#include "udf.h"

/* Define constants */
#define D 2.5e-9 /* mass diffusivity (m^2/s) */
#define rho_l 1000.0 /* density of liquid (kg/m^3) */
#define mu_l 0.001 /* viscosity of liquid (Pa.s) */
#define alpha_air_phase 3
#define water_phase 2

/* Define UDF to calculate oxygen mass transfer coefficient kla */
DEFINE_ON_DEMAND(calc_kla)
{
Domain *domain = Get_Domain(1);
Thread *cthread;
cell_t c;

/* Loop over all cells in the domain */
thread_loop_c(cthread, domain)
{
if (FLUID_THREAD_P(cthread)) /* Check if the thread is a fluid thread */
{

Thread **pt = THREAD_SUB_THREADS(cthread);
Thread *primary_phase_thread = pt[water_phase - 1]; /* Water */
Thread *secondary_phase_thread = pt[alpha_air_phase - 1]; /* Air */

/* Loop over all cells in the fluid thread */
begin_c_loop_all(c, cthread)
{
real alpha_air = C_VOF(c, secondary_phase_thread); /* Volume fraction of air */
real epsilon = C_D(c, cthread); /* Turbulence dissipation rate */
real d_b = C_PHASE_DIAMETER(c, secondary_phase_thread); /* Bubble diameter */

/* Calculate k_L using the Lamont and Scott model */
real kl = 0.4 * pow(D, 0.25) * pow(epsilon, 0.25) * pow(rho_l / mu_l, 0.25);

/* Calculate 'a' */
real a = 6.0 * alpha_air / d_b;

/* Calculate kla */
real kla = kl * a;

/* Store kla in a user-defined memory location */
C_UDMI(c, cthread, 0) = kla;
}
end_c_loop_all(c, cthread)
}
}
}


The UDF was successfully compiled and loaded. However, after I finished the calculation and went to contours > contours of user defined memory > user memory 0, the max and min boxes were grayed out.

Also, when I tried to execute on demand, I received: Node 0: Process 19108 has received the signal SIGSEGV. The fluent (f1) process encountered an error: the connection was reset.

How can I resolve this issue? Thanks in advance!

[Yingshi]

This is the log file:

My ansys fluent shut down every time when I want to excecute a UDF on deman. This is the log file: Node 0 Fatal signal raised sig = Segmentation fault
6457e430 CX_Primitive_Error
ae33b9d0 log2f
645f2fe0 logical_right_shift
a83be530 _C_specific_handler
b1054f20 _chkstk
b0fcddd0 RtlFindCharInUnicodeString
b1054010 KiUserExceptionDispatcher
8c690000 Ordinal0
61e8c170 fluent_fprintf
645dcf80 eval
61f44870 PRF_Command_Start
61f46fa0 PRF_Node_repl
61f52db0 Delay_Error
645f2fe0 logical_right_shift
b0872560 BaseThreadInitThunk
b100af00 RtlUserThreadStart

Error [node 0] [time 7/4/24 21:15:2] Abnormal Exit!