Accession Number : ADA296680

Title :   An Experimental Study of Air Entrainment by Breaking Waves.

Descriptive Note : Doctoral thesis,

Corporate Author : WOODS HOLE OCEANOGRAPHIC INSTITUTION MA

Personal Author(s) : Lamarre, Eric

PDF Url : ADA296680

Report Date : JUN 1993

Pagination or Media Count : 330

Abstract : This work reports on a series of laboratory and field experiments on the measurement of air entrainment by breaking waves. The first part of this thesis addresses the measurement of high volumetric concentrations of air (0.3% to 100% void-fraction) found immediately beneath breaking waves. Instrumentation based on the change of electrical impedance of the bubbly mixture is developed. Laboratory and field measurements are conducted. Maps of the evolution of the void-fraction distribution for various size breaking waves yield several bulk characteristics of the air entrainment process. In particular, up to 95% of the initially entrained air volume is lost in the first wave period after breaking and up to 50% of the energy dissipated by breaking is found to be expended in entraining bubbles against their buoyancy. The second part addresses the measurement of very low void-fractions. Instrumentation based on the propagation velocity of low-frequency acoustic pulses is developed. Simultaneous measurements of the sound-speed at several depths are conducted during two field experiments. Time-series of sound-speed and attenuation show dramatic fluctuations over time periods on the order of minutes or less which are attributed to bubble clouds. The time-averaged sound-speed profile is found to have lower velocities and to be shallower than previously reported. (MM)

Descriptors :   *OCEAN WAVES, *VOIDS, *BUBBLES, *AIR WATER INTERACTIONS, *UNDERWATER ACOUSTICS, *ACOUSTIC VELOCITY, *AIR ENTRAINMENT, HEAT TRANSFER, COMPUTER PROGRAMS, SIGNAL PROCESSING, ANOMALIES, WEATHER, OCEAN SURFACE, FIELD TESTS, THESES, DEPTH, GAS DYNAMICS, PULSES, ACOUSTIC SIGNALS, ACOUSTIC ATTENUATION, HYDROPHONES, ELECTRICAL IMPEDANCE, BUOYANCY.

Subject Categories : Physical and Dynamic Oceanography
      Acoustics
      Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE