2000 Fiscal Year Final Research Report Summary
Run-up and Reflection of Long-Period Waves Induced by Short-Wave Groups
| Project/Area Number |
11650524
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
水工水理学
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| Research Institution | Nagoya Institute of Technology |
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Principal Investigator |
KIOKA Wataru Nagoya Institute of Technology, Civil Engineering Dept., Professor, 工学部, 教授 (10135402)
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| Co-Investigator(Kenkyū-buntansha) |
DIBAJNIA Mohammad Nagoya Institute of Technology, Civil Engineering Dept., Associate Prof., 工学部, 助教授 (80260503)
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| Project Period (FY) |
1999 – 2000
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| Keywords | Long-Period Wave / Short-Wave Group / Swash Zone / Surf Zone / Wave Run-up / Wave Reflection |
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| Research Abstract |
This study concerns the low-frequency water surface oscillation of swash induced by the short-wave groups on mild to steep beaches of slope 1/10, 1/20 and 1/30. A set of new experiments has been conducted to investigate the hydrodynamics of the inner surf zone and swash zone using regular waves, irregular waves and wave groups, with particular reference to low-frequency motion. Effects of the incident wave spectrum, bottom topography, and long waves on swash oscillations are investigated and various parameters such as swash oscillation period, run-up height and the width of swash zone are formulated.
The functional form of the decay in energy is found to depend on the spectral shape of incident waves. Narrow banded incident waves result in a f^<-1> decay in the swash saturated tail, whereas under highly dissipative conditions over gentle slopes incident waves with broad and continuous spectra would result in f^<-3> decay. Measured run-up heights revealed that run-up height is reduced over barred profiles comparing to that over uniform slopes. Incident free long waves are found to considerably increase the run-up height regardless of the bottom topography. Values of run-up height show strong linear relation with the deepwater wave height.
A method for estimating the net transport rates was applied to sheet flow conditions under nonlinear asymmetric irregular oscillations with and without long wave components. It is found that long waves can significantly enhance the seaward transport of sediments inside the surf zone during a storm. It is also shown that the presence of a standing long wave system may lead to large spatial gradients in the cross-shore transport rates and eventually to formation of a multiple longshore bar.
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