Problem Definition

The following inputs must be preceded by “amr.”

	Description	Type	Default
n_cell	Number of cells at level 0 in each coordinate direction	Int Int Int	None
max_level	Maximum level of refinement allowed (0 when single-level)	Int	None

The following inputs must be preceded by “geometry.”

	Description	Type	Default
coord_sys	0 for Cartesian	Int	0
is_periodic	1 for true, 0 for false (one value for each coordinate direction)	Ints	0 0 0
prob_lo	Low corner of physical domain (physical not index space)	Reals	None
prob_hi	High corner of physical domain (physical not index space)	Reals	None

The following inputs must be preceded by “incflo.”

	Description	Type	Default
geometry	Which type of EB geometry are we using? (EB builds only) Options are box, cylinder, annulus, sphere, jcap, stl, chkptfile, csg (CSG builds), and, in 3D only, twocylinders, spherecube and tuscan. If not set (or set to all_regular), there is no EB.	String	None
gravity	Gravity vector (e.g., incflo.gravity = -9.81 0.0 0.0)	Reals	(0, 0, 0)
delp	Pressure drop across the domain in each coordinate direction, which drives the flow (see Background pressure). At most one value can be non-zero, and not in a direction with gravity or with a pressure inflow/outflow pair	Reals	(0, 0, 0)

Setting basic boundary conditions can be specified by inputs preceded by “xlo”, “xhi”, “ylo”, “yhi”, “zlo”, and “zhi”. No boundary type is given for the faces of a periodic direction (geometry.is_periodic).

	Description	Type	Default
type	Used to define boundary type. Available options include: ‘pi’ or ‘pressure_inflow’ ‘po’ or ‘pressure_outflow’ ‘mi’ or ‘mass_inflow’ ‘dd’ or ‘direction_dependent’ ‘nsw’ or ‘no_slip_wall’ ‘sw’ or ‘slip_wall’ ‘mixed’	String	None
pressure	Sets boundary pressure for pressure inflows, pressure outflows and mixed boundaries (required for these types)	Real	None
velocity	Sets Dirichlet boundary condition for velocity at mass inflow, direction-dependent and mixed boundaries. At a no-slip wall, the tangential components give the velocity of the wall	Reals	(0, 0, 0)
density	Sets Dirichlet boundary condition for density at mass inflow, direction-dependent and mixed boundaries	Real	1.0
tracer	Sets Dirichlet boundary condition for tracer (one value per tracer) at mass inflow, direction-dependent and mixed boundaries. At a wall, the tracer is Dirichlet if this is given, and has zero flux otherwise	Reals	0.0
temperature	Sets Dirichlet boundary condition for temperature, as for tracer	Real	1.0

The ‘mixed’ boundary type allows for inflow and outflow on the same domain face. The implementation requires that there is EB separating the inflow and outflow regions, requires incflo.advection_type = Godunov, and only currently treats constant viscosity (i.e. requires the inputs file contains incflo.use_tensor_solve = false). It does allow for non-constant scalar diffusivity. To create a new problem setup with mixed BCs, one must additionally specify the Dirichlet and Neumann areas in prob/prob_bc.cpp. In this file there are functions to set the needed BC info for the diffusion solver, the MAC projection, and with the same function, the nodal projection and advection. Comments in the code provide a detailed explanation for each instance. For additional details on mixed BCs, also see AMReX-Hydro’s documentation (Boundary conditions).