A study on the leeway drift characteristic of a typical fishing vessel common in the Northern South China Sea

Abstract

Leeway drift characteristics of drifting objects are essential to accurately forecast the drifting trajectory of lost persons, boats and other objects. Traditionally, leeway coefficients of the drifting objects are calculated using the observed wind, current and drift speed data from field experiments. Based on the combined samples of four drift experiments for a new type of 20 m length fishing vessel common in the northern South China Sea, this study determine the wind-induced drift characteristic through leeway speed, downwind component of leeway (DWL), crosswind component of leeway (CWL) coefficients, and explore how the fishing vessels drift in the surface water with the wind effect. Both the combined samples’ mean value and standard deviation (std) of the three rates (containing leeway rate, absolute DWL rate, and absolute CWL rate) show a decreasing trend as wind speed at 10 m increasing. Changes of the coefficients along with wind speed should be considered in the future calculation of drift simulation. Sign changes of CWL is observed in low wind speed, and the sharp variations of wind speed or wind direction. The forecast search area and the probability distribution of drift particles are sensitive to the wind condition and the frequencies of sign change respectively.