1999 Fiscal Year Final Research Report Summary
Hydrodynamic analysis of nonlinear waves for assessment of coastal ecosystems
| Project/Area Number |
10450385
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
海洋工学
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| Research Institution | Hiroshima University |
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Principal Investigator |
MORI Kazu-hiro Hiroshima University, Engineering, Professor, 工学部, 教授 (90011171)
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| Co-Investigator(Kenkyū-buntansha) |
HIGO Yasushi Hiroshima University, Engineering, Associate Professor, 工学部, 助教授 (20156582)
DOI Yasuaki Hiroshima University, Engineering, Associate Professor, 工学部, 助教授 (10134454)
BABA Eiichi Hiroshima University, Engineering, Professor, 工学部, 教授 (30274129)
NIMOMIYA Sinji Hiroshima International University, Clinical engineering, Associate Professor, 保険医療学部, 助教授 (60237774)
IWASHITA Hidetsugu Hiroshima University, Engineering, Associate Professor, 工学部, 助教授 (60223393)
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| Project Period (FY) |
1998 – 1999
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| Keywords | Costal ecosystems / environmental conservation / nonlinear waves / seawater percolation |
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| Research Abstract |
In the present research, it was found that nonlinear breaking waves on a sloping beach caused sea water percolation into sea bed. The flow visualization showed that the water moved into the sea bed with radial direction neat the run-up point, and then returned to the surface near the breaking point.
Measurement of the pressure on the surface of sea bed revealed the relation between the percolating water flow and the time averaged pressure on the surface of sea bed. The time averaged pressure was found to be estimated through the Wave Set-up and Set-down based on the nonlinear water wave theory.
The pressure distribution in the sea bed was calculated assuming Darcy's law. The pressure on the boundary was derived from Wave Set-up and Set-down. Laplace equation for the time-averaged pressure was solved by finite difference method. The calculated velocity distribution was in accordance with the observed flow pattern.
Finally, the relation between the slope of beach and percolation in the surf zone was made clear through the numerical simulation.
Internal flow inside the surf zone closely relates to the purging of silt and the biological activities. Because the sea water is cleaned up by percolation into sea bed and water flow into sea bed is transporting a kind of nutrients and oxygen to benthos in the surf zone. The present research threw light on the relation between waves and costal ecosystems.
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