COMPUTATIONAL METHOD OF WAVE OVERTOPPING RATE USING TIME DEPENDENT MILD-SLOPE EQUATION

摘要

Most of the conventional breakwaters in Korea are impermeable breakwaters which block sea-water exchange between the outside and inside of the harbors. The blocking of seawater exchange may cause pollution of water in harbors. To solve the water pollution problem,various kinds of sea-water exchange breakwaters have been proposed. Their types can be classified into the tidal current type which uses tidal current, and the overtopping type which uses the wave energy. The overtopping type breakwaters require a discharge coefficient to calculate the discharge overflowing into the harbor. The present study is to compute the overtopping rate with introduction of a correct discharge coefficient and to evaluate the effect of the overtopping type breakwater on the water quality of the harbor. The overtopping rate was computed by using Forchheimer formula with time dependent mild slope equation for various wave conditions. The formula has been generally used to calculate the overflow discharge in steady state river flows. The discharge coefficient, which is the key parameter of the calculation, was determined by a series of hydraulic model tests. The present scheme was applied to the sea-water exchange breakwater of Jeju New Harbor's and the efficiency of that was evaluated. The calculated results showed that the overtopping rate into the harbor reached about 27.5 m3/sec in the wave condition (wave height 3.7 m, wave period 8.5 sec, and wave direction NNW).