Accession Number:

ADA180450

Title:

Magnetohydrodynamic Underwater Acoustic Transducer

Descriptive Note:

Technical rept.

Corporate Author:

TEXAS UNIV AT AUSTIN APPLIED RESEARCH LABS

Personal Author(s):

Report Date:

1986-12-01

Pagination or Media Count:

173.0

Abstract:

The magnetohydrodynamic MHD and thermoacoustic sound generation mechanisms were investigated analytically and experimentally for a source volume region generated by a time harmonic electric current distribution interacting in a static magnetic field using sodium chloride and water as an electrolyte. The MHD sound source is the result of the Lorentz force on a conducting medium generated by the interaction of electrical current and a magnetic field. The thermoacoustic source is the result of fluid density changes produced by Joule heating when electrical power is dissipated in a resistive medium. MHD and thermoacoustic source mechanisms were found to produce two distinct acoustic radiation moments a dipole field, respectively. The source volume region is contained in a rigid walled waveguide where sound from the source volume region radiates into the free medium through apertures at either end of the waveguide. Transmitting sensitivities for both mechanisms were derived analytically for the waveguide geometry and compared to experimental data where good agreement was found in a frequency band of 500 to 4000 Hz. The source directivity for the dipole moment radiation was measured and found to be in good agreement with the classic cosine radiation pattern at low frequencies. Expressions for the transduction process efficiency and input electrical impedance were also derived and compared to measurements.

Subject Categories:

  • Acoustic Detection and Detectors
  • Non-Radio Communications

Distribution Statement:

APPROVED FOR PUBLIC RELEASE