Negative Drift Forces Acting on a 2-Dimensional Cylinder inSlightly Modulated Waves

유한수심의 불규칙파에 놓인 2차원 주상체에 작용하는 음의 표류력

In this paper negative drift forces are discussed, which act on a two-dimensional cylinder exposed to slightly modulated waves in water of finite depth. By combining matched asymptotic expansion method with multiple scale technique, it is clearly shown that the slowly-varying drift force can be negative under certain circumstances: i) Incident waves are irregular or slightly modulated. ii) The water depth is finite compared to the wave length of carrier waves. iii) The gap between the keel of the cylinder and ocean floor is narrow. Then the negative drift forces are caused by the unbalance of hydrostatic force associated with set down. Real fluid and wave breaking effects are not considered.