TEST HEAD CASE

Sediment Test Headland Case

This test case checks the ability of a model to represent 1) simplified alongshore transport, 2) implementation of open boundary conditions, and 3) resuspension, transport, and deposition of suspended-sediment. This case is based on Signell and Geyer (1991) Journal of Geophysical Research 96(C2): 2561-2575.

Domain

The model domain is open at the east and west ends, has a straight wall at the north end, and a parabolic headland along the south wall.

Model Parameter	Variable	Value
Length (east-west)	$l$	100000 m
Width (north-south)	$w$	50000 m
Depth	$h$	20 m

Bottom Sediment

Single grain size on bottom:

Size	$D_{50}$	0.1 mm
Density	$\rho _{s}$	$2650\,kg/m^{3}$
Settling Velocity	$w_{s}$	0.5 mm/s
Critical Shear Stress	$\tau _{c}$	$0.05\,N/m^{s}$
Bed Thickness	$bed\_thick$	0.005 m
Erosion Rate	$E_{0}$	$5e-5\,kg/m^{2}/s$

Forcing

Coriolis f = 1.0 e-4
No heating/cooling
No wind

Initial Conditions

$u\,=\,0\,m^{3}/s$
Salinity = 0
Temperature = $20_{o}C$

Bathymetry:
Depths increase linearly (slope = 0.0067) from a minimum depth of 2 m at all alongshore points from the southern land boundary offshore to a maximum depth of 20 m at a point 3 km offshore. Offshore of 3 km there is a constant depth of 20 m.

Boundary Conditions

North, south = walls with no fluxes, no friction
South wall = parabolic headland shape
Bottom roughness $Z_{0}\,=\,0.015\,m$

Flow and elevation at western boundary is imposed.
Flow on eastern boundary is open radiation condition, or water level based, or Kelvin wave solution.

Flow and elevation, eastern/western boundaries:

Reference velocity $u_{0}\,=\,0.5\,m/s$
Celerity $C\,={\sqrt {g*20.0}}$
Reference water level $\zeta _{0}\,=\,u_{0}/{\sqrt {g/20}}$
Wave period T = 12 hours (43200 seconds)
Wave length L = C * T
Wave number k = (2 * π)/L

Results

Figure 1. Plan view of final bathymetric change.

Simulations were conducted for 3.0 days. Final bed thickness is shown in Figure 1.