Visser: Difference between revisions

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| Steering Interval || 0.25 hr || 0.25 hr || none
| Steering Interval || 0.25 hr || 0.25 hr || none
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|-
| Wave-current bottom friction || Fredsoe 1984 || Fredsoe 1984 | Quadratic
| Wave-current bottom friction || Fredsoe 1984 || Fredsoe 1984 || Quadratic
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|-
| Manning's n ||  1.02 m ||  0.018 || 0.025
| Manning's n ||  1.02 m ||  0.018 || 0.025

Revision as of 14:29, 13 October 2010

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.

Computation Grid
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 4
Case 7
Case 7


References

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

Test_Cases