ELUCIDATION OF THE DEVELOPMENT AND MOVEMENT MECHANISM OF GIANT CUSP AT RIVER MOUTH

为了更好地了解河口附近的泥沙运动，对阿布库马河口经常出现的巨型尖点的发展和运动机理进行了研究。河流水流和沿岸流被认为是运输的外力。用Longuet-Higgins(1970)二维急流模型给出了河流喷流场和沿岸流场。沿两流速度场线性组合的流线，求解泥沙连续性方程。其中输沙率采用Meyer-Peter Muller公式，根据实测水流和波浪资料，对不同波高、不同波向和不同流速进行了7个算例。计算结果表明，在河口沿岸流的天气侧形成了一个窄长的尖点，特别是对河流的高度流速。这一结果与观测结果吻合较好。

In order to get better knowledge of sediment transport near river mouths, the mechanism of development and movement in a giant cusp, which often appears at the Abukuma River mouth, has been studied. River flow and longshore currents are considered as the external forces for the transport. The efflux flow field of the river and longshore current field are given by the two dimensional jet model Longuet-Higgins (1970). Along the stream line of the linearly composed velocity field of two currents continuity equation of sediments is solved. Where Meyer-Peter Muller formula is used for the transport rate.Based on the observed data of river flow and waves, seven computational cases have been performed for various wave height, wave direction and velocity of river flow. The computational results show that a narrow long cusp is formed at the weather side of the longshore current at the river mouth, especially for the height velocity of the river flow. This results agree well with the observation.