[milankjohn]

Please help:

I am trying to simulate the drying of particles in a chamber. For this purpose, I am using a UDF for mass and energy source terms. While interpreting the function, no errors are displayed. However, while initializing the solution I get an error "received a fatal signal (Segmentation fault)".


There is also a warning which points out three lines in the UDF functions. Those lines are as follows:


real Tabs, TC, W, w, pe, re, drebydpe, We, Source_w, psat,drying_constant;

real Tabs,TC,physical_dt,W, We, w, pe, re,Wnew,psat;

real pe, re, We, we, dwsebydt, Source_t;

Note: I am using Fluent 18. in serial mode, double precision

[pakk]

These lines are not enough info to find the problem.
It's better to give the full code.

[milankjohn]

Dear Friend, Please see the full code for moisture transport

#include "udf.h"

/* Chung-Pfost constants */
#define ACP 921.69
#define BCP 18.077
#define CCP 112.35
#define RHOB 639.2
#define PATM 101325
/* Define ambient temperature conditions */
#define TMEAN 288.15
#define TAMP 5
/* Define a global variable that acts as a */
/* comparitor in DEFINE_ADJUST */
int last_ts = -1;
DEFINE_INIT(moisure_init,d)
/* The initial solids moisture content, W, is set */
/* and the corresponding humidity, w, of the */
/* intergranular air is calculated */
{
cell_t c;
Thread *t;
real W,Tabs,TC,r,psat,p,w;
/* Loop over all of the cell threads in the bulk of grain */
thread_loop_c(t,d)
{
begin_c_loop(c,t)
{
C_UDMI(c,t,0) = 0.1364;
W = C_UDMI(c,t,0);
Tabs = C_T(c,t);
TC = Tabs-273.15;
/* Calculate relative humidity of intergranular air, Eqn 11. */
r = exp(-ACP/(TC+CCP)*exp(-BCP*W));
/* Ensure the air does not become supersaturated */
if(r>0.99)
{r = 0.99;}
psat = 6.0e25/pow(Tabs,5) *exp(-6800/Tabs);
p = r*psat;
w = 0.622*p/(PATM-p); /* Eqn 12 */
C_UDSI(c,t,0) = w;
}
end_c_loop(c,t);
}
}
DEFINE_SOURCE(mass_source,c,t,dS,eqn)
{
real Tabs, TC, W, w, pe, re, drebydpe, We, Source_w, psat,drying_constant;
Tabs = C_T(c,t);
TC = Tabs-273.15;
psat = 6.0e25/pow(Tabs,5) *exp(-6800/Tabs);
W = C_UDMI(c,t,0);
w = C_UDSI(c,t,0);
/* The post-fix ‘e’ denotes variables that relate to the equilibrium moisture content,
We.
*/
pe = w*PATM/(0.622+w);
re = pe/psat;
We = -1/BCP*log(-(TC+CCP)/ACP*log(re)); /* Eqn 6 */
drying_constant = 2000*exp(-5094/Tabs); /* Eqn 5 */
C_UDMI(c,t,3) = re;
C_UDMI(c,t,2) = We;
/* Eqn3: */
C_UDMI(c,t,1) = -RHOB*drying_constant*(W-We);
Source_w = -C_UDMI(c,t,1);
dS[eqn] = 0.0;
return Source_w;
}
DEFINE_ADJUST(update_mc,d)
{
real Tabs,TC,physical_dt,W, We, w, pe, re,Wnew,psat;
cell_t c;
Thread *t;
/* The integer time step count (accessed using N_TIME) */
/* is useful in DEFINE_ADJUST functions for detecting */

/* whether the current iteration is the first in the */
/* time step. */
int curr_ts;
curr_ts = N_TIME;
if (last_ts != curr_ts)
{
last_ts = curr_ts;
printf ("ADJUST: iteration = %d , = = = =\n", curr_ts);
physical_dt = RP_Get_Real("physical-time-step");
/* Loop over all of the cell threads in the porous region */
thread_loop_c(t,d)
{
begin_c_loop(c,t)
{
Tabs = C_T(c,t);
TC = Tabs-273.15;
psat = 6.0e25/pow(Tabs,5) *exp(-6800/Tabs);
W = C_UDMI(c,t,0);
w = C_UDSI(c,t,0);
/* The post-fix ‘e’ denotes variables that relate to the equilibrium moisture content,
We
*/
pe = w*PATM/(0.622+w); /* Eqn 7 */
re = pe/psat;
We = -1/BCP*log(-(TC+CCP)/ACP*log(re)); /* Eqn 6 */
Wnew = W+C_UDMI(c,t,1)*physical_dt/RHOB;/* Eqn 10 */
W = Wnew;
C_UDMI(c,t,0) = W;
}
end_c_loop(c,t)
}
}
}
DEFINE_SOURCE(hygro_source,c,t,dS,eqn)
{
real Tabs, TC, w, psat, dpsatdt, drdt, hsbyhv, hs;
real pe, re, We, we, dwsebydt, Source_t;
/* The post-fix ‘e’ denotes variables that relate to the equilibrium moisture content,
We,
*/
Tabs = C_T(c,t);
TC = Tabs-273.15;
we = C_UDSI(c,t,0);
psat = 6.0e25/pow(Tabs,5) *exp(-6800/Tabs);
pe = we*PATM/(0.622+we);
re = pe/psat;
We = -1/BCP*log(-(TC+CCP)/ACP*log(re));/* Eqn 6 */
dpsatdt = psat/Tabs*(-5+6800/Tabs); /* see Eqn 16 */
drdt = ACP*re/pow((TC+CCP),2)*exp(-BCP*We); /*Eqn 17 */
hsbyhv = 1+psat/re*1/dpsatdt*drdt; /* Eqn 15 */
hs = hsbyhv*(2501.33-2.363*TC)*1.0e3;
C_UDMI(c,t,4) = hs;
Source_t = C_UDMI(c,t,1)*hs;/* Eqn 14 */
dS[eqn] = 0.0;
return Source_t;
}

[AlexanderZ]

did you allocate memory for UDMS and UDS?

[pakk]

Initialize without this UDF. Your source tries to read temperature, but during initialization it is not set yet.

[milankjohn]

Thank you, Alexander and pakk for your suggestions.