FLASH4.5 API

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TABLE OF CONTENTS


[Functions] source/physics/Diffuse/Diffuse_species

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NAME

  Diffuse_species

SYNOPSIS

 Diffuse_species(integer(IN) :sweepDir, 
                 integer(IN) : igeom, 
                 integer(IN) : blockID,
                 integer(IN) : numCells,
                 integer(:,:)(IN):blkLimits, 
                 integer(:,:)(IN):blkLimitsGC
                 real(:)(IN):leftCoords,
                 real(:)(IN):rightCoords,
                 real(:,:)(INOUT) :temp_flx, 
                 real(:,:)(INOUT) :temp_fly, 
                 real(:,:)(INOUT) :temp_flz)

DESCRIPTION

  Diffuse_species alters the mass-fraction flux to account for 
  material diffusion.  This is an explicit method, so a timestep limiter
  will be required.  Stability is guaranteed for

                           dx**2
                 dt < .5* -------
                             D

  where D is the diffusion coefficient.

  Fluxes in PPM are stored at the zone boundaries; mass fractions are 
  at the zone centers.  So the flux {F = -sigma * grad(T)} is

                      D_i + D_{i-1}     T_i - T_{i-1}
             F_i = - -------------- * ---------------
                           2                  dx

NOTES

    This routine computes the species fluxes and adds them to the flux
    returned from hydro.  It is to be called after calling hydro_1d on a
    block.  The updated energy fluxes are then used in update_soln to
    produce the updated energy.

    Boundary conditions are handled through tot_bnd,
    not in this routine.  Ex: setting a reflecting boundary will reflect the
    species into the guard cells, which are used in computing the flux
    at the block boundaries.

ARGUMENTS

  sweepDir        the current sweep direction

  igeom           the geometry flag for the current sweep direction

  blockID        the block number to operate on
  numCells        the number of Cells along the sweep direction
  leftCoords      Coordinates of the left edge of the zones
  rightCoords     Coordinates of the right edge of the zones

  tempflx         Temporary storage for flux along first direction
  tempfly         Temporary storage for flux along second direction
  tempflz         Temporary storage for flux along third direction