[louis123]

We are currently using Ansys student version 19. We can compile and hook the UDF to Ansys but when we try to Initialize or run the calculation the Ansys set up crashes the error states that:

999999 mpt_accept ; error: accept failed: no error
999999 mpt_accept ; error: accept failed: no error
999999 mpt_accept ; error: accept failed: no error
999999 mpt_accept ; error: accept failed: no error
999999 mpt_accept ; error: accept failed: no error

The f1 process could not be started


We got this UDF code from a research paper: "The application of computational fluid dynamics codes to simulate heat and moisture transfer in stored grains"

#include "udf.h"
#define ACP 921.69
#define BCP 18.077
#define CCP 112.35
#define RHOB 639.2
#define PATM 101325
#define TMEAN 288.15
#define TAMP 5
int last_ts = -1;
DEFINE_INIT(initial_humidity, d)
{
real W, Tabs, TC, r, psat, p, w;
Thread *t;
cell_t c;
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;
r = exp(-ACP/(TC+CCP)*exp(-BCP*W));
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);
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);
pe = w*PATM/(0.622+w);
re = pe/psat;
We = -1/BCP*log(-(TC+CCP)/ACP*log(re));
drying_constant = 2000*exp(-5094/Tabs);
C_UDMI(c,t,3) = re;
C_UDMI(c,t,2) = We;
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;
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");

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);
pe = w*PATM/(0.622+w);
re = pe/psat;
We = -1/BCP*log(-(TC+CCP)/ACP*log(re));
Wnew = W+C_UDMI(c,t,1)*physical_dt/RHOB;
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;

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));
dpsatdt = psat/Tabs*(-5+6800/Tabs);
drdt = ACP*re/pow((TC+CCP),2)*exp(-BCP*We);
hsbyhv = 1+psat/re*1/dpsatdt*drdt;
hs = hsbyhv*(2501.33-2.363*TC)*1.0e3;
C_UDMI(c,t,4) = hs;
Source_t = C_UDMI(c,t,1)*hs;
dS[eqn] = 0.0;
return Source_t;
}

[AlexanderZ]

changes which are not related to your problem:
change physical_dt = RP_Get_Real("physical-time-step");
to
physical_dt = CURRENT_TIMESTEP;
printf to Message0

code must be compiled

did you allocate 5 user defined memory locations and 1 user defined scalar in Fluent GUI?

as the code is complicated I recommend to test your case with very simple UDF to check if everything is correct in your case settings:

#include "udf.h"
DEFINE_SOURCE(mass_source,c,t,dS,eqn)
{
return 0.01;
}
DEFINE_SOURCE(hygro_source,c,t,dS,eqn)
{
return 0.01;
}

0.01 is just a random value, you do better put something reasonable here.
if this simple code works well, add some parts of code and check if they work