Multibeam echo-sounding measurement of the microbubble field in a ship’s wake

Abstract

Acoustic data collected with the U.S. Navy’s 68 kHz Toroidal Volume Search Sonar (TVSS) system were used to measure the microbubble field generated by the wake of the towing vessel at a constant distance of 18 ship lengths astern. Swath bathymetry beamforming and echo detection techniques were adapted to map the sea surface and the spatial distribution of bubble fields observable in the ocean volume with the TVSS. The sonar was towed at 78 m depth yielding a sea surface measurement swath roughly 550 m wide thus allowing observations of wake bubble fields across three parallel ship tracks spaced 200 m apart and over 22 min after generation. Measurements in microbubble fields about 3 min after generation by the ship’s wake yielded an average vertical attenuation of 2.1 dB/m and a maximum acoustic volume scattering strength of −17.1 dB. [Work supported by the U.S. Naval Research Laboratory.]

Clutter suppression and classification using twin inverted pulse sonar in ship wakes

“…In this way, as time progresses the data refers to the aging process of one element of the wake. Alternatively, a sensor can be towed through or beside the wake 25,26 or mounted on an AUV, 27,28 such that the sensor moves through the water with the wake or relative to it which can in principle allow mapping of the bubble population in different parts of the wake. 29 To provide input for the simulations involving the RIB, a representative wake for a "small" vessel was constructed from the data in Event B of Valge and Burch.…”