[ghost82]

Hi!
the code below is an example of an old define cavitation rate for fluent v.6.
Can somebody please explain me why in the code below there is vofM and not vofM[c]?

Is this because vofM is declared as real and not as array and its value is automatically updated at every cell iteration, whilst rhoV, rhoL, vofV are arrays?

#include "udf.h"
#define MIN_VOF 1.e-5
#define MAX_VOF 0.99999

DEFINE_CAVITATION_RATE(Rayleigh, c, t, p, rhoV, rhoL, vofV, p_v, n_b, m_dot)
{
      real p_vapor = *p_v; /* vapor pressure */
      real n_bubbles = *n_b; /* bubbles per liquid volume */
      real dp, vofM, radV, Rdot;
      dp = p_vapor-ABS_P(p[c],op_pres); /* p_vap - p_abs */
      /* vapor volume fraction restricted to [1.e-5,1.0-1.e-5] */
      vofM=MIN(MAX(MIN_VOF,vofV[c]),MAX_VOF);
      /* bubble radius */
      radV = pow(3.0*vofM/((1.-vofM)*4.0*M_PI*n_bubbles), 1./3.);
      /* radius time derivative */

      if (dp > 0.0)
      {/* bubble grow */
            Rdot = sqrt(2.*dp/(3.*rhoL[c]));
      }
      else
      {/* bubble collapse */
            Rdot = -sqrt(-2.*dp/(3.*rhoL[c]));
            if (vofV[c]<=MIN_VOF)
            {
                        Rdot=0.0;
            }
      }
      /* compute interphase mass flow rate per unit volume */
      *m_dot = rhoV[c]*rhoL[c]*vofM*(1.0-vofM)/(vofM*rhoV[c]+(1.0-vofM)*rhoL[c]) *3.0/radV*Rdot;
}

[pakk]

Originally Posted by ghost82

Is this because vofM is declared as real and not as array and its value is automatically updated at every cell iteration, whilst rhoV, rhoL, vofV are arrays?

Yes, it is because it is not an array. It is not automatically updated, but that is programmed in the line:

vofM=MIN(MAX(MIN_VOF,vofV[c]),MAX_VOF);