Visser: Difference between revisions
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== Setup == | == 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. | 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. | ||
| Line 9: | Line 9: | ||
| Period || 1.02 m || 1.02 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. | 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. | ||
| Line 20: | Line 21: | ||
== Results == | == Results == | ||
The figures below show a comparison between measured and computed bed elevations. | The figures below show a comparison between measured and computed bed elevations. | ||
{| border="1" | |||
! 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 | |||
|} | |||
[[Image:Visser4.png|thumb|left|400px|Case 4| alt=Case 4]] | [[Image:Visser4.png|thumb|left|400px|Case 4| alt=Case 4]] | ||
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.
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 | 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 |
References
- Visser, R. J. (1991) “Laboratory measurements of uniform longshore currents”. Coastal Engineering, 15, 563-593.