**NAME**

Diffuse

**SYNOPSIS**

call Diffuse( integer(IN) :: blockCount, integer(IN) :: blockList(blockCount), real(IN) :: dt, integer(IN), OPTIONAL :: pass)

**DESCRIPTION**

This routine advances the heat diffusion equation (i.e., heat conduction). Typically, implicit schemes will be used where available. Currently, only support for advancing the heat diffusion equation (i.e., heat conduction) is available in Diffuse implementations. As of FLASH 3.3, a flux-based implementation in connection with a Hydro solver must be used for other diffusive effects, in particlular viscosity and magnetic resistivity. Supported boundary conditions are ??? and periodic (1). The same boundary conditions are currently applied in all directions.

**ARGUMENTS**

blockCount : The number of blocks in the list blockList(:) : The list of blocks on which the solution must be updated dt : The time step pass : Reverses the direction of solve in between half time steps i.e X-Y-Z, Z-Y-X

**SIDE EFFECTS**

Updates certain variables in permanent UNK storage to contain the updated temperature and some auxiliaries. Invokes a solver (of the Heat diffusion equation). On return, TEMP_VAR: contains updated temperature for the current simulation time. EINT_VAR, ENER_VAR, PRES_VAR, etc.: updated accordingly by EOS call May modify certain variables used for intermediate results by the solvers invoked. The list of variables depends on the Diffuse implementation. The following information is subject to change. WTMP_VAR: contains source term that was passed to Grid solver routines COND_VAR: contains conductivity that was passed to Grid solver routines DTMP_VAR: contains temperature increment for the current simulation time. For the Multigrid implementation: ISLS_VAR (residual) ICOR_VAR (correction)

High-Energy Density Physics

Thermonuclear-Powered Supernovae

Fluid-Structure Interaction

Implicit Solvers

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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.