An Experimental Study of Gravity Wave Behavior Near a Straight Caustic

摘要

An experimental study of gravity wave behavior near a straight caustic generated on a uniformly sloping bottom was carried out in a 4.26 meters (14 feet) square and 30.48 centimeters (1 foot) deep wave tank. Gravity waves were generated in shallow water of constant depth and propagated toward a portion of the tank where the depth increased linearly to a value equivalent to deep water. The straight line which the depth started to increase was 50 degrees to the wave crests at the generation source. The waves propagated up to this line, then refracted, totally reflected, and turned back toward the shallow water. The results of the experiment show that the experimental model not only successfully produces a caustic but also verifies the theoretical results near the caustic derived recently by Chao (1970) within a linear theory. When waves approach the caustic their amplitudes increase monotonically and attain maximum values within the caustic boundary that are about two times the amplitude in the source region. Near the caustic in the shadow region, the amplitudes decrease exponentially. (Author)