Underwater sound radiation from single large raindrops at terminal velocity: the effects of a sloped water surface at impact

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Authors
Miller, Glenn A., Sr.
Subjects
Spectral energy density
Primary bubbles
Type I and Type II mechanisms
Aerosols
Time gap
Advisors
Medwin, Herman
Nystuen, Jeffrey A.
Date of Issue
1992-12
Date
December 1992
Publisher
Monterey, California. Naval Postgraduate School
Language
en_US
Abstract
Previous studies have shown that terminal velocity raindrops striking a smooth water surface create oscillating bubbles that radiate significant underwater sound energy. Those studies identified two diameter ranges that produce bubbles: small drops (.8-1.1 mm diameter) which produce bubbles by one mechanism and large drops (2.2-4.6 mm diameter) which create bubbles by a different mechanism. Effects of oblique incidence have been studied only for small drops. Average energy spectra were calculated for a range of raindrop sizes striking a smooth water surface. This work deals with the real life situation of large raindrops of a size often present in heavy rainfall (4.6 mm diameter) striking a sloped water surface. Terminal velocity is used to simulate natural rainfall, and the sloped surface is used to simulate the surface gravity waves of a natural sea. The effects of a sloped water surface on frequency spectra and energy for 4.6 mm raindrops are estimated. By comparing energy spectra generated by single drops in an anechoic laboratory tank to underwater sound spectra measured at sea, it will be possible to estimate heavy rainfall rate by means of remote underwater listening devices.
Type
Thesis
Description
Series/Report No
Department
Engineering Acoustics Academic Committee
Organization
Naval Postgraduate School
Identifiers
NPS Report Number
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Distribution Statement
Approved for public release; distribution is unlimited.
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.
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