Three-Dimensional Scale-Model Tank Experiment of the Hudson Canyon Region

Abstract

The long-term scientific goal of this project is to advance understanding of three-dimensional (3D) acoustic propagation in range-dependent ocean waveguides by studying propagation in a scale-model laboratory environment. OBJECTIVESThe objective of this work is to generate high quality acoustic data, measured in the laboratory, that will (1) provide a benchmark standard for 3D numerical models currently being developed, (2) allow researchers to carefully investigate 3D acoustic propagation in a controlled waveguide, and (3) assist ONR in planning for future experiments in ocean environments with slopes and canyons. APPROACHThe development of fully 3D numerical acoustic propagation models is an area of ongoing research. [1][2][3][4][5][6][7] These models have the potential to be very accurate, but comparisons between data taken at sea and numerical predictions often suffer because of insufficient environmental inputs to the numerical model. This is already a problem for two-dimensional (2D) data-model comparisons and is likely to be a perpetual problem when trying to employ 3D numerical models to describe experimental data.An alternative way to provide benchmark-quality data for numerical models is to conduct physical scale-model laboratory experiments. Scale-model experiments permit tight control over many of the variables affecting acoustic propagation, such as water temperature, bathymetry, source/receiver geometry, surface and seafloor roughness, and the geoacoustic properties of the modeled seafloor. Control over these variables allow for precise observation of 3D acoustic propagation effects such as horizontal refraction, shadow zones, multiple mode arrivals, and intra-mode interference.Much of the prior work in scale-model experiments has employed flat or sloping bottoms or random rough surfaces. [8][9][10][11][12][13][14][15] While these experiments have been useful for their intended purpose, they represent idealistic bathymetries that are not found in the ocean. The approach employed in this work is to use 1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.