Modélisation expérimentale et numérique de milieux marins réels

Abstract
In order to realize a complete geoacoustical model of the sea we have created a vertical variation in the sound velocity in a liquid layer presenting a minimum like in real sea by a diffusion technique in a tank. This technique involves the superimposing of several layers of miscible liquids with different densities without mixing. To simulate the sea bottom (with or without a 5 % slope) we have used two types of material - Polyurethane resin to represent a sedimentary ground and marble to represent an elastic rock. To account for the scale, the measures were made at a frequency of 1 MHz corresponding to 50 Hz in a real situation. The measured values are compared with the results of a numerical integration of the Helmholtz equation. We use a variant of the parabolic approximation.