WAVE FORCES ON CYLINDERS NEAR PLANE BOUNDARY

Potential flow theory predicts: (1) the added mass of a cylinder near a plane boundary is independent of the direction of the flow and more than twice as large as that of the same cylinder far away from the boundary; (2) a possible failure mechanism of alternating positive and negative lift force, which is proportional to horizontal velocity squared, for pipelines resting on the bottom boundary and subjected to waves and currents; and (3) the force from convective acceleration of the ambient flow can be as large as 30% of total acceleration force for waves. Laminar boundary-layer theory suggests that a phase shift exists between maximum velocity and maximum drag force for cylinders subjected to waves. Laboratory wave force experimentation confirms the aforementioned theoretical findings 1 and 2.