Accession Number:

ADA522132

Title:

Acoustics Propagation Through Surface Ship Wakes

Descriptive Note:

Journal article

Corporate Author:

NAVAL RESEARCH LAB WASHINGTON DC ACOUSTICS DIV

Personal Author(s):

Report Date:

2006-01-01

Pagination or Media Count:

4.0

Abstract:

A ships wake is a mixture of bubbles and turbulent seawaters hull and its cavitating propellers. These bubble clouds are a common feature of all ship wakes, and the entrapped air bubbles are responsible for the lingering acoustic signatures of a ships wake. It is well known that bubbles, even in small amounts, cause considerable frequency-dependent changes in the speed of sound and absorption. These bubble-cloud characteristics are driven by the type of ship, its speed, and local oceanographic conditions. As the wake ages, it goes from a violent breakup and mixing of bubbles due to turbulence to one where, as the turbulence decays, the bubbles begin to rise toward the surface due to their buoyancy and the changes in the buoyancy of the water mass. It is clear that since bubbles of different sizes rise at different rates, as the wake ages, the horizontal and vertical distributions of bubble densities result in changes to both sound-speed profiles and absorption within the wake. These frequency-dependent sound-speed profiles have dramatic effects on propagating acoustic signals.

Subject Categories:

  • Acoustic Detection and Detectors
  • Acoustics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE