Discretization

The following inputs must be preceded by “mfix.”

Key	Description	Type	Default
advection_type	Predictor-Corrector Method of Lines (“mol”) or Godunov (“godunov”)	String	Godunov
redistribution_type	Use flux (“FluxRedist”), state (“StateRedist”) or no (“NoRedist”) redistribution	String	StateRedist
redistribute_before_nodal_proj	Redistribute the velocity field before the nodal projection	Bool	True
redistribute_nodal_proj	Redistribute the velocity field after the nodal projection	Bool	False
redistribute_after_initial_nodal_proj	Call initial redistribution of all fields after the initial nodal projection	Bool	True
use_drag_coeff_in_proj_gp	Algebraically consistent p coeff in proj or (default) simplified form	Bool	False
use_drag_in_godunov	Include a drag term in the Godunov flux or (default) not	Bool	False
correction_small_volfrac	Threshold volume fraction for correcting small cell velocity at the end of the predictor and corrector	Real	1.e-4

Notes: The code was originally developed with MOL and FluxRedist. Preliminary tests show that the new single-step Godunov method is roughly twice as fast as the predictor-corrector MOL at the same time step (e.g., CFL limited to 0.5). Further, the Godunov method allows for roughly twice the time step, CFL should be limited to 0.9 for stability. Finally, it is recommended that the Godunov method be used in conjunction with StateRedist. While not fully vetted, early tests also show increased stability in complex geometries for a StateRedist- Godunov scheme compared to the previous FluxRedist-MOL scheme.