FLASH4.6.1 API

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[Functions] source/Grid/Grid_advanceDiffusion

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NAME

  Grid_advanceDiffusion

SYNOPSIS

  call Grid_advanceDiffusion (integer(IN)  :: iVar,
                              integer(IN)         :: iSrc,
                              integer(IN)  :: iFactorB,
                              integer(IN)  :: iFactorA,
                              integer(IN)  :: bcTypes(6),
                              real(IN)     :: bcValues(2,6),
                              real(IN)     :: dt,
                              real(IN)     :: chi,
                              real(IN)     :: scaleFact,
                              real(IN)     :: theta,
                              logical(IN)  :: solnIsDelta,
                     OPTIONAL,integer(IN)  :: iFactorC,
                     OPTIONAL,integer(IN)  :: iFactorD,
                     OPTIONAL,integer(IN)  :: pass)

DESCRIPTION

      This routine advances a generalized diffusion operator of the form

         A*(df/dt) + C*f = div(B*grad(f)) + D ,

      where
         f = f(x,t) is the  Variable to be diffused (x=1D..3D position);

         A,B,C,D are optional given scalar factors/terms that may depend
         on position; they are either physcially constant in time, or at
         least considered time-independent for the purpose of the operation
         implemented here (typically by computing their values from the
         solution state reached by the previous time step).

      Presently it is used to do heat conduction and multigroup diffusion.

ARGUMENTS

   iVar           : Variable on which the diffusion operation is performed (e.g., TEMP_VAR)
   iFactorA       :| Are factors in the equation with spatial variation.
   iFactorB       :| Factor C,D are optional and are generally used
   iFactorC       :| to represent emission/absorption in MGD.
   iFactorD       :| iFactorA is not needed (and thus set to constant 1.0) for
                   | radiation diffusion.
                   | The factor B (whose role is that of diffusion coefficient) is passed to
                   | the solver implementation in cell-centered form in UNK; the solver will
                   | use averaging of adjacent cells (or perhaps some other mechanism) to
                   | derive the required face-cented diffusion coefficent values.
   bcTypes        : Presently OUTFLOW, VACUUM, DIRICHLET are supported, with additional
                    limited support for OUTSTREAM, in the HYPRE implementation.
   bcValues       : Values of iVar,iFactorB on boundary (DIRICHLET).                        
   dt             : The time step.
   scaleFact      : Factor by which the end solution is scaled (not used).
   chi            : useful for constant diffusion problems (not used).
   theta          : varies scheme (0-> Explicit, 1-> backward euler, 0.5 -> Crank Nicholson
   pass           : Ignored in unsplit solver.
                    pass=1 order of directional sweep X-Y-Z, 
                    pass=2 order of directional sweep Z-Y-X.
   iSrc           : Ignored.
   solnIsDelta    : Is the solution only a delta that the caller has to apply to the
                    temperature, rather than temperature itself (ignored).

SEE ALSO

  Diffuse_solveScalar
  diff_advanceTherm
  Diffuse_advance1D