1987 Fiscal Year Final Research Report Summary
Study on macroscopic description based on soliton modes for coastal waves
| Project/Area Number |
61550368
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Hydraulic engineering
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| Research Institution | Gifu University |
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Principal Investigator |
YASUDA Takashi Associate Professor at Gifu University, 工学部, 助教授 (10093329)
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| Co-Investigator(Kenkyū-buntansha) |
SHINODA Seirou Research Associate at Gifu University, 工学部, 助手 (80187369)
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| Project Period (FY) |
1986 – 1987
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| Keywords | Coastal waves / Soliton / Envelope soliton / Amplitude distribution / Perturbed soliton / 浅水変形 |
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| Research Abstract |
In this research project, a method,in which a soliton is treated as elementary excitation of coastal waves, is suggested to describe the microscopic and macroscopic properties of the coastal waves using the asymptotic multi-soliton solution of the KdV class equation, while another approach, that treats natural seasates with remarkable groupiness as random sequences of envelope solitons, is proposed to explain their dynamical and statistical properties. Both the methods are applied to waves observed in field and their applicability are verified.
The primary results are summarized as follows :
1. Description of coastal waves propagating over a two dimensional (2D) domain : A practical method, that uses together the classical linear ray theory and the KdV class equation in a slowly varying ray channel with dissipation, is suggested to describe approximately but simply the ocastal waves propagating over a 2D domain.
2. Microscopic properties of coastal waves : The soliton mode method, that tr
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eats the coastal waves as a random train of asymptotically independent solitons,is applied to the waves observed at Torrey Pines Beach of San Diego in U.S.A and is shown to be sufficiently accurate for describing their free surface elevation, pressure and water particle velocity time series. It is verified that the coastal waves can be regarded to have a microscopic structure making the KdV soliton elementary excitation.
3. Amplitude distribution of coastal waves : An approach is suggested to determine theoretically the amplitude distribution of shallow water waves under the maximum occurrence probability condition, in which the wave energy is assigned to each possible soliton in obedience to the way that is extremely liable to take place. The result derived through this approach is compared with field observations.
4. Coastal waves over a sloping bottom with dissipation : A shoaling soliton solution is derived by solving approximately the KdV equation perturbed by a sloping bottom with dissipation, and its deformation is investigated intensively.It is shown that the microscopic and macroscopic description can be made for the coastal waves over a sloping bottom with dissipation by treating the shoaling soliton as extended elementary excitationof the coastal waves. Less
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