Forces on a flexible pile

The maintenance of pole, stake, and pile structures in streams and waves has been important to man from antiquity. Because of the common occurrence of the flow of a fluid past a cylinder, and the simplicity of the boundaries, one might expect that long ago all related problems could have been solved . However, if one experiments with forcing a pole rapidly through still water, he ,rill find that the pole oscillates laterally and that he can reduce these oscillations, and thus move the pole more easily, by grasping it firmly. These observations suggest a lack of simplicity of the system and an explanation for the present dependence on empirical information in the solution of related engineering problems. The art of building surfaces above water level has been augmented by engineering and scientific investigations so numerous that even citation of all the most important is prohibitive. Current practice produces successful offshore structures, but more design information will be needed to build them competitively in ever deeper water. Marris (1964), Morkovin (1964), and others have summarized much of the pertinent data on the flow details around rigidly supported cylinders and described means of representing phenomena. This paper reviews progress toward solution of problems basic to the design of structures in moving fluids, and toward explanation of differences between force patterns imposed on actual structures under field conditions and on the idealized "infinitely long rigid circular cylinder in a steady stream"