UDF 帮助，Cell_t c1= -1 的-1 是什么意思

chenzhaolin

/**********************************************************************/
/*    UDF that implements a simplified advective term in the          */
/*    scalar transport equation                                       */
/**********************************************************************/

#include "udf.h"

DEFINE_UDS_FLUX(my_uds_flux,f,t,i)
{
  cell_t  c0,  c1 = -1;/* 这里的-1是什么意思×/
  Thread *t0, *t1 = NULL;

  real NV_VEC(psi_vec), NV_VEC(A), flux = 0.0;

  c0 = F_C0(f,t);
  t0 = F_C0_THREAD(f,t);
  F_AREA(A, f, t);

  /* If face lies at domain boundary, use face values; */
  /* If face lies IN the domain, use average of adjacent cells. */

if (BOUNDARY_FACE_THREAD_P(t)) /*Most face values will be available*/
    {
      real dens;

      /* Depending on its BC, density may not be set on face thread*/
      if (NNULLP(THREAD_STORAGE(t,SV_DENSITY)))
        dens = F_R(f,t);   /* Set dens to face value if available */
      else
        dens = C_R(c0,t0); /* else, set dens to cell value */

      NV_DS(psi_vec,  =, F_U(f,t), F_V(f,t), F_W(f,t), *, dens);

      flux = NV_DOT(psi_vec, A); /* flux through Face */
    }
  else
    {
      c1 = F_C1(f,t);       /* Get cell on other side of face */
      t1 = F_C1_THREAD(f,t);

      NV_DS(psi_vec,  =, C_U(c0,t0),C_V(c0,t0),C_W(c0,t0),*,C_R(c0,t0));
      NV_DS(psi_vec, +=, C_U(c1,t1),C_V(c1,t1),C_W(c1,t1),*,C_R(c1,t1));

      flux = NV_DOT(psi_vec, A)/2.0; /* Average flux through face */
    }

  /* ANSYS FLUENT will multiply the returned value by phi_f (the scalar's
     value at the face) to get the "complete'' advective term.  */

  return flux;
}