**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

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The Flash Center for Computational Science is based at the University of Chicago and is supported by U.S. DOE and NSF.