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ADCP observation of nearshore current and suspended load profile

ADCP 近岸海流和悬浮负载剖面观测

基本信息

批准号：
09555157
负责人：
YAMASHITA Takao
金额：
$ 2.18万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09555157/
关键词：
nerashore current surf zone ADCP suspended sediment sediment transport

项目摘要

Beach erosion due to offshore-going sediment transport is a serious problem in Japan's coasts facing the Japan Sea. It has hot yet been made clear the mechanism of sediment transport offshore. The main aim of this study is to unveil the nearshore current structure in the surf zone by ADCP observation with the T-shaped Observation Pier(TOP), on the Ogata Coast, Niigata. Prefecture.From the observation, we estimated current characteristics as :(1) Velicity Profile : When the longshore currents become strong due to oblique winds and waves, intensity of the offshore currents becomes weak with undertow-like velocity profile are formed. Velocity profiles of both longshore and offshore currents are almost uniform below the wave trough level.(2) Longshore Currents : Strong and uniform longshore currents are generated in the surf zone by oblique winds and waves. Its direction well responds to changes in wind direction, ex. westerly wind excites east word longshore currents and vice versa.(3) Off-Shore Currents : Almost all current below the wave trough direct offshore in the surf zone. When wind and wave direction changed, W(westward) -> NW(shore-normal) ->N (eastward), the typical wind evolution pattern in this coast, strong offshore currents are observed in the shore-normal wind phase.(4) Wind Drag Coefficient near the surf zone : Wind drag coefficient near extremely shallow and high wave condition including wave breaking is derived by using Turbulent Dissipation Method (TDM), as shown in Fig.3. The fitting curve isCd=0.0223 exp(10/3)**(-U/15) when U(10m)> 10m/s.(5) Turbidity concentration vs Echo intensity of ADCP : under analyzing.

由于近海沉积物输送造成的海滩侵蚀是日本面临日本海的海岸的一个严重问题。近海泥沙输移机理目前尚未明确。本研究的主要目的是通过新泻县大泻海岸 T 形观测码头（TOP）的 ADCP 观测来揭示海浪带的近岸海流结构。根据观测，我们估计水流特征为： (1) 速度剖面：当近岸流因斜风浪而变强时，近岸流强度变弱，形成暗流状速度剖面。波谷平面以下，沿岸流和离岸流的速度剖面几乎是均匀的。(2) 沿岸流：斜风和波浪在冲浪区产生强烈且均匀的沿岸流。它的方向很好地响应风向的变化，例如。西风激发东岸沿岸流，反之亦然。(3) 离岸洋流：几乎所有位于波谷下方的近海洋流均位于冲浪区。当风向和波浪方向发生变化时，W（西向）→NW（岸向）→N（东向）是该海岸典型的风演化模式，在岸向风相中观察到较强的离岸流。（4）海浪区附近的风阻系数：利用湍流耗散法（TDM）推导出包括破浪在内的极浅高浪条件下的风阻系数，如图3所示。当U(10m)>10m/s时，拟合曲线为Cd=0.0223 exp(10/3)**(-U/15)。 (5)ADCP的浊度浓度与回波强度：分析中。