/********************************************************************

Density and speed of sound UDFs for compressible liquid flows.

For use with pressure-based solver, for single phase, multiphase mixture

or cavitation models only.

Note that for density function, dp is the difference between a cell 

absolute pressure and reference pressure.

*********************************************************************/

#include "udf.h" 

#define BMODULUS 2.2e9

#define rho_ref 1000.0

#define p_ref 101325

DEFINE_PROPERTY(superfluid_density, c, t)

{

    real rho;

    real p, dp;

    real p_operating;

    p_operating = RP_Get_Real ("operating-pressure");

    p = C_P(c,t) + p_operating;

    dp = p-p_ref;

    rho = rho_ref/(1.0-dp/BMODULUS);

    return rho;

}

DEFINE_PROPERTY(sound_speed, c,t)

{

    real a; 

    real p, dp,p_operating;

    p_operating = RP_Get_Real ("operating-pressure");

    p = C_P(c,t) + p_operating;

    dp = p-p_ref; 

    a = (1.-dp/BMODULUS)*sqrt(BMODULUS/rho_ref);   

    return a;

}

UDF for density as a function of temperature

/*********************************************************************

   UDF for specifying a temperature-dependent viscosity and density property

 **********************************************************************/

 #include "udf.h"

 DEFINE_PROPERTY(cell_viscosity, cell, thread)

 {

    real mu_lam;

    real temp = C_T(cell, thread);

     mu_lam = 0.6402+18.9612*exp(-.074*temp) ;

    return mu_lam;

 } 

DEFINE_PROPERTY(cell_density,cell,thread)

{ 

real rho;

real temp= C_T(cell,thread);

rho=-0.72222*temp+1087.28;

return rho;

}

Execute Command in FLUENT to store pictures

/display/set/contours surfaces cutplane () \n/display/set/contours/coloring n\n/display/set/picture/color-mode color\n/display/contour/acoustic-source-power-db 47 85\n/display/set/contours n-contour 5\n/display/set/contours/filled-contours yes\n/display/views restore-view cutplane\n/display/save-picture "db_contour-%it.png"