[fard734]

Dear friends
The following udf has been used for calculation of interfacial area density, which is need for prediction of evaporation rate from a single droplet. The udf can not calculate the theta, Anybody know what is the problem?


/**** Compute the interfacial area density ****/
NV_V(G,=,C_VOF_G(c,w_liq)); /* vof gradient vector assignment*/

theta = atan(G[0]/G[1]); /* compute angle of VOF gradient vector, n1/n2 because of how geometry is set up in Fluent */
cotan = cos(theta) / sin(theta); /* compute cotangent of angle*/

A = C_VOLUME(c,mixture_thread)/(2*pi); /* in 2D- axis area computed from volume */

len = sqrt((2*C_VOF(c,w_liq)*A/cotan) + (2*C_VOF(c,w_liq)*A*cotan)); /* compute length of interface in a cell */

ad = len/A; /* calculate interfacial area density*/
/***** Computed the area density ad = length of interface / area of cell ***/

[AlexanderZ]

did you include math.h ?

[fard734]

Originally Posted by AlexanderZ

did you include math.h ?

Dear AlexanderZ
the udf is:
UDF for evaporation
the math.h is not included

[AlexanderZ]

include math.h folder and recompile.
if you need help put here full code, compilation log, description of errors

[fard734]

Dear AlexanderZ
Following udf is working in serial processing option, but under parallel mode, the error "Node 999999: Process 13848: Received signal SIGSEGV. MPI Application rank 0 exited before MPI_Finalize() with status -1 The fl process could not be started"
appear when "excuted on demand" is selected.
please let me know your thought,,,,

#include "udf.h"
DEFINE_ON_DEMAND(on_demand_calc)
{
Domain *d; /* declare domain pointer since it is not passed as an
argument to the DEFINE macro */

real R=8.314;
real D=26.1e-6;
float Y_W,X_W,Y_A;
float T_cell, P_cell, P_sat,Powsat;
Thread *t;
cell_t c;
d = Get_Domain(2); /* Get the domain using ANSYS Fluent utility */

/* Loop over all cell threads in the domain */
thread_loop_c(t,d)
{

/* Compute max, min, volume-averaged temperature */

Y_W = C_YI(c,t,0);
Y_A = C_YI(c,t,1);
X_W = (Y_W*29)/((29*Y_W) + (18*Y_A));
T_cell = C_T(c,t); /*cell mixture temperature*/
P_cell = C_P(c,t);
Powsat=(8.07131-1730.63/(233.426+(T_cell-273.15)));
P_sat = pow(10,Powsat)*133.322;

/* Loop over all cells */
begin_c_loop(c,t)
{
C_UDSI(c,t,0) = C_VOF(c,t);
C_UDSI(c,t,1) = C_YI(c,t,0);

C_UDMI(c,t,1)=NV_MAG(C_UDSI_G(c,t,0));
C_UDMI(c,t,2)=NV_MAG(C_UDSI_G(c,t,1));
C_UDMI(c,t,4)= pow(C_VOLUME(c,t),-0.333)*4.83;

if (C_UDMI(c,t,1)>40)
{
C_UDSI(c,t,1)=P_sat/ P_cell;

C_UDMI(c,t,2)=NV_MAG(C_UDSI_G(c,t,1));

C_UDMI(c,t,0)=D*P_cell/(R*T_cell)* C_UDMI(c,t,2)*C_UDMI(c,t,4);
C_UDMI(c,t,5)=ABS(D*P_cell/(R*T_cell)* C_UDMI(c,t,2));
}
else
{C_UDMI(c,t,0)=0;}
}
end_c_loop(c,t)
}
}

DEFINE_MASS_TRANSFER(mass_transfer1, c, t, from_phase_index, from_species_index, to_phase_index, to_species_index)
{


float m_lg, T_cell, P_cell, P_sat,Powsat;
float NV_VEC(G);
float X_W, Y_W, Y_A;
float cur_ts;
Thread *w_liq, *gas_mix, *w_gas;
face_t f;
Domain *mix_domain, *pdomain;
int i, pdomain_index;
float area[ND_ND], A, ad, theta, cotan, len;

/******** Define variables *********/
mix_domain = Get_Domain(1);
/* pdomain = DOMAIN_SUB_DOMAIN(mixture_domain,2); */ /* For gas domain */
pdomain_index = 0;
pdomain = DOMAIN_SUB_DOMAIN(mix_domain,pdomain_index);

w_liq = THREAD_SUB_THREAD(t, from_phase_index);
gas_mix = THREAD_SUB_THREAD(t, to_phase_index);
w_gas = THREAD_SUB_THREAD(t, to_species_index);
T_cell = C_T(c,t); /*cell mixture temperature*/
P_cell = C_P(c,t); /*cell mixture pressure*/
m_lg = ABS(C_UDMI(c,t,0));
C_UDMI(c,t,3)=m_lg;
return (m_lg); /* return value of mass transfer rate */
}