Glossary

stage

The absolute water-surface elevation (m), measured from the same vertical datum as elevation. Water depth is stage - elevation, so stage is not the water depth.

elevation

The bed elevation / bathymetry (m).

depth

Water depth — the derived quantity stage - elevation. A cell is dry where the depth is (near) zero; see wetting and drying.

quantity

A physical field stored on the mesh (stage, elevation, friction, xmomentum, ymomentum). Accessed via domain.quantities[...].

operator

An object applied each timestep that modifies domain quantities — for example rainfall, extraction, culverts or inlets. See Operators.

riverwall

An infinitely-thin internal wall (levee, weir or embankment) aligned with triangle edges via breaklines. It blocks or controls flow until overtopped. See Riverwalls.

breakline

A polyline that the mesh generator forces triangle edges to follow — used to align the mesh with riverwalls, channels or roads.

yieldstep

The interval (s) at which evolve() returns control to the Python loop (and, by default, writes output). The internal CFL-limited timestep is usually much smaller.

finaltime

The simulation time (s) at which evolve() stops. Give either finaltime or duration, not both.

duration

The length of time (s) to evolve for, measured from the current simulation time — an alternative to finaltime.

outputstep

An optional coarser interval (s) at which the state is written to the SWW file, while evolve() still yields every yieldstep. Use it to interact frequently while keeping the .sww file small; it should be a whole multiple of the yieldstep.

CFL

The Courant–Friedrichs–Lewy stability condition, which bounds the explicit timestep by the mesh size and wave speed. ANUGA chooses the inner timestep automatically to satisfy it.

wetting and drying

ANUGA’s handling of moving shorelines: a cell is treated as dry once its depth falls below minimum_allowed_height. See Conventions and units.

SWW file

The NetCDF output file (.sww) holding the time series of quantities on the mesh. Viewed with the ANUGA Viewer, SWW_plotter, or GIS.

DE algorithm

The “discontinuous-elevation” family of flow algorithms (DE0, DE1, DE_ader2, DE2). See Choosing a Flow Algorithm.