Visser

Experimental Setup

In 1991, Visser conducted eight laboratory experiments of monochromatic wave on a planar beach and collected measurements on waves, currents and water levels. The bathymetry consisted of a 1:10 slope for the first 1-m seaward distance, a 1:20 slope for the next 5-m distance, followed by a 5.9 m distance of flat bottom to the wave generator. Both experiments had incident wave heights of 0.078 m, peak periods of 1.02 sec and an incident wave angle of 15.4°. Experiment 4 was run over a concrete bed and experiment 7 was run of a thin 0.005-0.01 m layer of gravel grouted on the concrete floor.

Wave Parameter	Case 4	Case 7
Height	0.08 m	0.08 m
Period	1.02 m	1.02 m
Incident Angle	15.4°	15.4°

Model Setup

The computational grid (shown in Figure 1) consists of 84 rows and 147 columns with a constant grid resolution in the longshore direction of 0.15 and a variable grid resolution between 0.04 and 0.15 m in the cross-shore direction. A zero water level was forced at the offshore boundary.

Computational Grid

Results

The figures below show a comparison between measured and computed bed elevations.

Settings	Case 4	Case 7	Default
Time Step	60 sec	60 sec	none
Steering Interval	0.25 hr	0.25 hr	none
Wave-current bottom friction	Fredsoe 1984	Fredsoe 1984	Quadratic
Manning's n	1.02 m	0.018	0.025
Roller	On	Off	Off
Roller dissipation coefficient	0.1	-	0.1
Roller efficiency coefficient	0.8	-	1.0
Turbulence Model	Subgrid	Subgrid	Subgrid
Eddy viscosity base value	1.e-6	1.e-6	1.e-6
Eddy viscosity bottom coefficient	0.06	0.06	0.06
Eddy viscosity horizontal coefficient	0.2	0.2	0.2
Eddy viscosity horizontal coefficient	0.2	0.2	0.2
Eddy viscosity wave coefficient	0.1	0.1	0.1
Eddy viscosity wave breaking coefficient	0.05	0.05	0.05

Case 4

Case 7

References

• Visser, R. J. (1991) “Laboratory measurements of uniform longshore currents”. Coastal Engineering, 15, 563-593.

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Test_Cases