HYDRODYNAMIC CHARACTERISTICS OF BODIES IN CHANNELS

The effect of channel walls on the hydrodynamic characteristics of fix ed or oscillating bodies is discussed using classical linear water wav e theory. Particular attention is paid to the occurrence of trapped mo des persisting local to the fixed body and which are manifested in a n on-uniqueness of the corresponding forced problem at the trapped mode frequency. The general ideas are illustrated by consideration of two s imple geometries for which semi-analytic solutions are available, name ly a circular cylinder either partly immersed or extending throughout the water depth, and a thin vertical plate parallel to the channel wal ls which extends throughout the water depth. Conclusions are drawn con cerning the conditions under which trapped modes may exist and their e ffect on the hydrodynamic characteristics of more general bodies.