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Old   October 24, 2015, 02:41
Default UDF trouble shoot
  #1
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Join Date: Sep 2015
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Hi Guys,

Could I please have someones help to trouble shoot this UDF code. I keep getting


- Error: received a fatal signal (Segmentation fault).
- Error Object: #f


So I know it has to do with the code. I stole most of the code from other places.


I can compile the code and date file shows up when I 'Execute on Demand'

The error shows up with I try and 'Initialize' my



Thank you Guys





#include "udf.h"

int NPt_mu = 561; /* number of entries in density table */

/* Locate the place in the interpolation vector using bisection algorithm*/
int locate(float xx[], int n, float x)
{
int j = 0;
int jm = 0;
int jl = 0;
int ju = n+1;
int ascnd = 0;

ascnd = (xx[n] >= xx[1]);
while (ju-jl > 1)
{
jm = (ju+jl) >> 1;
if (x >= xx[jm] == ascnd)
jl = jm;
else
ju = jm;
}

if (x == xx[1])
j = 1;
else if (x == xx[n])
j = n-1;
else
j = jl;

return j;
}

float *pres_vec_mu,*dens_vec;
#define FAST_LOOKUP TRUE /* use bisection algorithm for interpolation */
#define TABLE_MESSAGES TRUE
#define DISPLAY_TABLES TRUE

/* Obtaine mu given pressure */
float get_mu_from_T(float xdata)
{
int i = 0;
int j = 0;
float xL,xU,ydata;

#if FAST_LOOKUP
j = locate(pres_vec_mu,NPt_mu,xdata);
xL = pres_vec_mu[j];
xU = pres_vec_mu[j+1];
ydata = dens_vec[j] + (xdata-xL)/(xU-xL)*( dens_vec[j+1] - dens_vec[j] );
#else
for ( i=1; i<NPt_mu ;i++ )
{
xL = pres_vec_mu[i];
xU = pres_vec_mu[i+1];
if ( (xdata>=xL)&&(xdata<=xU) )
{
ydata = dens_vec[i] + (xdata-xL)/(xU-xL)*( dens_vec[i+1] - dens_vec[i] );
break;
}
}
#endif

if ( xdata>pres_vec_mu[NPt_mu] )
{
#if TABLE_MESSAGES
Message("\n pressure is above the bound of dens-array \n");
#endif
ydata = dens_vec[NPt_mu];
}
if ( xdata<pres_vec_mu[1] )
{
#if TABLE_MESSAGES
Message("\n pressure is below the bound of dens-array \n");
#endif
ydata = dens_vec[1];
}

return ydata;
}

/* Read in the data file containing density as a function of pressure */
DEFINE_ON_DEMAND(read_density)
{
int i = 0;
float xdata,ydata;
FILE* fp;

fp = fopen("density.dat","r");
if ( fp!=NULL )
{
#if !RP_NODE
Message(" \n");
Message("Reading file density.dat \n");
Message(" \n");
#endif
}
else
{
#if !RP_NODE
Message(" \n");
Message("Error opening file \n");
Message(" \n");
#endif
}

pres_vec_mu = (float *) malloc(NPt_mu*sizeof(float));
dens_vec = (float *) malloc(NPt_mu*sizeof(float));

if ( (pres_vec_mu==NULL)||(dens_vec==NULL) )
{
#if !RP_NODE
Message("Memory allocation error \n");
#endif
}

for ( i=1;i<=NPt_mu;i++ )
{
fscanf(fp,"%f %e \n",&xdata,&ydata);
pres_vec_mu[i] = xdata;
dens_vec[i] = ydata;
#if DISPLAY_TABLES
#if !RP_NODE
Message("%.1f %e \n",pres_vec_mu[i],dens_vec[i]);
#endif
}
#else
}
#if !RP_NODE
Message(" \n");
#endif
#endif

fclose(fp);
}

/* Interpolate density from look-up table and assign to cell value */
DEFINE_PROPERTY(density,c,t)
{
float mu_lam;
float pres = C_T(c,t);

/* interpolate mu_lam */
mu_lam = get_mu_from_T(pres);

return mu_lam;
}
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Old   October 26, 2015, 05:57
Default
  #2
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Bruno Machado
Join Date: May 2014
Posts: 262
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This kind of error appear when Fluent cant reach some information. It might compile with no error, but when it runs it will try to get information (boundaries, gradient, variable values, etc) and this information is not avilable.

Since you took pieces of code from different places, it is better to have a detailed look at it and check if all the information necessary is provided.
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