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A pair of Langmuir cells in two laboratory tanks (II) on generation mechanism

Authors
  • Mizuno, Shinjiro1
  • Noguchi, Hideaki2
  • Kimura, Yasutaka3
  • 1 Hiroshima Institute of Technology, Department of Civil Engineering, Miyake 2-1-1, Saeki-ku, Hiroshima, 731-51, Japan , Hiroshima
  • 2 Chugoku National Industrial Research Institute, Hiro-Suehiro 2-2-2, Kure, Hiroshima, 737-01, Japan , Kure, Hiroshima
  • 3 FUKKEN Co., Ltd., Hikarimachi 2-20-11, Higashi-ku, Hiroshima, 732, Japan , Hiroshima
Type
Published Article
Journal
Journal of Oceanography
Publisher
Springer Netherlands
Publication Date
Jan 01, 1998
Volume
54
Issue
1
Pages
77–100
Identifiers
DOI: 10.1007/BF02744383
Source
Springer Nature
Keywords
License
Yellow

Abstract

Vertical and cross-wind profiles of mean currents were measured systematically in vertical cross-sections of two wind-wave tanks with aspect ratios of order one to study the secondary flow in the tanks. A pair of Langmuir cells turned out to be driven by a close combination of the pressure gradient along the tank and the side-wall effects. That is, part of the adverse pressure gradient produced a parabolic cross-wind profile with the smallest downwind current at the centerline and the largest current along the two sidewalls. As a result, upwelling occurred in the center zone where the return flow was strongest, probably because of the entrainment action of the wind-driven current. In order to compensate for this upwelling, downwelling occurred along the two side-walls from the flow continuity. The resulting vertical circulation formed a pair of Langmuir circulations across the span and served to maintain the parabolic profile formed by the pressure gradient. A positive feedback mechanism is thus found between the primary and secondary circulations through upwelling of the return flow in the center zone. Vertical shears of the span-averaged downwind current measured in two tanks were found to be systematically different from each other. This difference seems to depend on the magnitude of the advective Reynolds stresses in the two tanks.

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