Nonlinear-Free Surface Effects: Experiments and Theory
1983
Greenhow, Martin | Lin, Woei-Min
Sponsored in part by the National Science Foundation.
显示更多 [+] 显示较少 [-]The object of this report is to present the results of some simple two-dimensional experiments in which the surface of the water is displaced a good deal from its undisturbed position, and for which linear theory is likely to be in error. Particular attention is paid to the point of intersection of the free surface and a moving body, where the confluence of boundary conditions can cause singularities in the free surface displacements and velocities, as predicted by linear theory. These singularities appear to be avoided in the real fluid by the formation of jets, which at the scale of the experiments, quickly break up into spray under the action of surface tension. Nevertheless it is known that potential theory is adequate to describe the formation of jets and therefore some local model, valid around the intersection point and based on potential theory, is being sought for later matching to appropriate far field conditions. Such far field or outer solutions may be calculated with existing programs, and it is hoped that when complemented by an inner solution, they will provide a reasonably complete description of many extreme wave or extreme motion problems e.g., ship capsize and slamming. For the most part the experiments have been performed at high speed: this means that it is approximately correct to ignore gravity in the local region and this effects a considerable simplification to the theory.
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