Measurements of air/water interfaces in plunging breaking waves

C Blenkinsopp, J.R. Chaplin

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Of the energy dissipation that takes place in violent breaking waves, some is accounted for by work done against the buoyancy of bubbles, and some by work done in generating splashes that may rise to elevations far above the crest. In deep water the probability of encountering air in such conditions
varies from almost zero at large submergences to almost unity at high elevations. Between these extremes in regular long-crested waves, there is a two-dimensional continuum of time-dependent ensemble-averaged void fractions. A detailed knowledge of this distribution would represent a major
contribution to a better understanding of the process of wave breaking, but largely for practical reasons, little of this information exists.
Previous studies of air entrainment beneath breaking waves have made use of a variety of techniques including local conductivity probes (Cox & Shin, 2003; Hoque 2002), global conductivity probes (Lamarre & Melville, 1994), acoustic techniques and laser methods (Hwung & Jih, 1993). Many of these have shortcomings such as large measurement volumes, limited sensitivity at at least one end of the range of void fractions, or probes that are significantly intrusive. This paper describes detailed measurements made with an instrument that detects individual air/water interfaces over extremely small areas at high frequency. The results allowed us to compute time-dependent void fractions, not
only in that part predominantly occupied by water, but in the region above, including (probably for the first time) the splash-up created by the plunging jet.
Original languageEnglish
Title of host publication20th International Workshop on Water Waves and Floating Bodies
EditorsJ Grue
PublisherIWWWFB
Number of pages4
Publication statusPublished - 2005
Event20th International Workshop on Water Waves and Floating Bodies - Longyearbyen, Norway
Duration: 19 May 20051 Jun 2005

Conference

Conference20th International Workshop on Water Waves and Floating Bodies
CountryNorway
CityLongyearbyen
Period19/05/051/06/05

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