Acoustics Propagation Through Surface Ship Wakes
Abstract
A ship's wake is a mixture of bubbles and turbulent seawater's 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 ship's 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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2006
- Accession Number
- ADA522132
Entities
People
- R. Goodman
- S. Stanic
- T. Ruppel
Organizations
- United States Naval Research Laboratory