Turbulent structure in water under laboratory wind waves

Ikuo Yoshikawa, Hiroshi Kawamura, Kuniaki Okuda, Yoshiaki Toba

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

The structure of the turbulent boundary layer underneath laboratory wind waves was studied by using a combination of a high-sensitivity thermometer array with a two-component sonic flowmeter. The temperature fluctuations are used to detect movements of water parcels, with temperature as a passive quantity. The turbulence energy was dominant in the frequency range (0.01 ∼ 0.1 Hz), which was much smaller than the wind-wave frequency (2 ∼ 5 Hz), and in which the turbulence was anisotropic. There was a frequency range (0.2 ∼ 2 Hz for velocity, 0.2 ∼ 5 Hz for temperature fluctuation) where the turbulence was isotropic and had a -5/3 slope in the energy spectrum. These points are the same as those in previous works. However, by analyses of the time series by using a variable-interval time-averaging technique (VITA), it has been found that conspicuous events in this main turbulence energy band are the downward bursting from the vicinity of the water surface. Thus the structure of the water layer underneath the wind waves has characters which are similar to the familiar turbulent boundary layer over a rough solid wall, as already conceived. It has been found that, at the same time, the turbulence energy can be related to quantities of the wind waves (the root mean squared water level fluctuation and the wave peak frequency), for different wind and wave conditions. That is, the turbulence underneath the wind waves develops under a close coupling with the wind waves.

Original languageEnglish
Pages (from-to)143-156
Number of pages14
JournalJournal of the Oceanographical Society of Japan
Volume44
Issue number3
DOIs
Publication statusPublished - 1988 Jun 1

ASJC Scopus subject areas

  • Environmental Science(all)
  • Soil Science
  • Engineering(all)
  • Earth-Surface Processes
  • Earth and Planetary Sciences(all)

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