Section: TerrainDrag

These parameters are active when TerrainDrag is included in incflo.physics.

TerrainDrag has two operation modes:

1. Terrain-file mode (default), where terrain and roughness are read from files.

2. Ocean-wave mode, activated automatically when OceanWaves physics is active and the vof field is not present. In this mode, terrain blanking and drag markers are constructed from wave fields.

TerrainDrag.terrain_file

type: String, optional, default = terrain.amrwind

Input file for terrain height data in terrain-file mode.

TerrainDrag.roughness_file

type: String, optional, default = terrain.roughness

Input file for roughness-length data in terrain-file mode.

If this file is missing or cannot be opened, the roughness is set from TerrainDrag.uniform_roughness.

TerrainDrag.uniform_roughness

type: Real, optional, default = 0.1

Uniform roughness length used when TerrainDrag.roughness_file is not available.

If both uniform_roughness and roughness_file are provided, values from the roughness file are used where available.

TerrainDrag.damp_east_slope

type: Real, optional, default = 0.0

Width of the east (+x) damping ramp region.

TerrainDrag.damp_east_full

type: Real, optional, default = 0.0

Width of the east (+x) full-strength damping region adjacent to the boundary.

TerrainDrag.damp_west_slope

type: Real, optional, default = 0.0

Width of the west (-x) damping ramp region.

TerrainDrag.damp_west_full

type: Real, optional, default = 0.0

Width of the west (-x) full-strength damping region adjacent to the boundary.

TerrainDrag.damp_north_slope

type: Real, optional, default = 0.0

Width of the north (+y) damping ramp region.

TerrainDrag.damp_north_full

type: Real, optional, default = 0.0

Width of the north (+y) full-strength damping region adjacent to the boundary.

TerrainDrag.damp_south_slope

type: Real, optional, default = 0.0

Width of the south (-y) damping ramp region.

TerrainDrag.damp_south_full

type: Real, optional, default = 0.0

Width of the south (-y) full-strength damping region adjacent to the boundary.

TerrainDrag.horizontal_time_scale

type: Real, optional, default = 20.0

Time scale used to convert the assembled damping coefficient into terrain_damping forcing (larger values reduce damping strength).

TerrainDrag.horizontal_abl_height

type: Real, optional, default = 1.0e15

Height at which horizontal damping begins to turn on.

TerrainDrag.horizontal_slope_end

type: Real, optional, default = 1.0e30

Height where the horizontal damping vertical multiplier reaches full value.

TerrainDrag.vertical_slope

type: Real, optional, default = 0.0

Height where additional full-domain vertical damping begins to ramp on.

TerrainDrag.vertical_full

type: Real, optional, default = 1.0e30

Height where additional full-domain vertical damping reaches full strength.

Notes

• The terrain drag marker field (terrain_drag) is derived from transitions in terrain_blank and is used by Section: Momentum Sources when DragForcing is active.

• In ocean-wave mode, TerrainDrag derives terrain_blank and terrain_height from wave fields and sets a uniform low roughness (terrainz0 = 1.0e-4).

• In ocean-wave mode, terrain-file and roughness-file parameters are not used.