Study On Harbour Oscillation Characteristics And The Prevention Measures

A harbor is a partially enclosed basin of water connected through one or more openings to the sea. Wave is the main hydrodynamic force in a harbor . Wave height distribution within a basin and the stationary of the harbor is the primary consideration of port plan and design. Although a variety of external factors can be responsible for significant oscillations with in a harborthe most studied forcing is caused by long period wave which have typical periods from a few minutes to an hour. If the total duration of the wave is sufficiently long, oscillations excited in the harbor may persist for days, resulting in breaking mooring lines, damaging fenders, hazards in berthing and loading or navigation through the entrance, and so on.This paper calculates the wave distribution under different natural conditions of the basin with ideal terrain conditions of different incident wave periods and proposes the control measures of the wave oscillations. The main contents and conclusions of the work are as follows:1,By comparing the wave distribution under different incident wave periods, it is found that the resonance occurs when the basin scale is an integer multiple of half wave length, and the most regular oscillations happen in a/L(the radio of harbor area length and wavelength)from 0.5 to 2, As a / L increases, the port resonance wave height decreases.2,By comparing the wave distribution under different width of the basin entrance, it is found that harbor resonance is related to the entrance width. In a certain scale, the smaller the entrance width is, the more obvious the harbor resonance occurs.3,The entrance position may have impacts to resonant modes by causing a second resonant frequency, As a/L increases, the wave high amplification coefficient of that resonance mode decreases.4,The direction of wave reflection should be carefully selected. Appropriate direction of wave reflection is conducive to the wave energy radiate out from the harbor entrance.5,By comparing the engineering examples, proposed the prevention measures of the wave oscillations:(1)Arrange the breakwater and the harbor entrance to reduce the wave energy spread into the basin(.2)Adopt appropriate measures to eliminate wave(.3)Select the appropriate basin geometric dimension.