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，对阿武熊河口附近经常出现的一个巨大尖点的形成和运动机制进行了研究。河流和沿岸流被认为是运输的外力。采用Longuet-Higgins（1970）的二维射流模型，给出了河流的外流场和沿岸流场。沿着流线求解两股水流线性合成流速场的泥沙连续性方程。其中输沙率采用Meyer-PeterMuller公式，根据实测的河道水流和波浪资料，对不同波高、波向和流速的河道进行了7个算例的计算。计算结果表明，在河口沿岸流顺风侧形成一个狭长的尖点，特别是对水流的高流速影响更大。这一结果与观测结果吻合得很好。

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.