岬先端より発生する剥離渦の特性 Characteristics of Separated Vortices Generated from the Tip of a Cape

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Abstract

潮流が岬や半島にあたる場合,岬先端部で剥離渦が生じる。この剥離渦は岬に沿って発達する境界層内で渦度を発達させたもので,剥離後スピンダウンし湧昇流を発生させる。本研究はこの剥離渦の発生周期と強さについて水理実験によって検討した。発生周期のストローハル数は一定値となりレイノルズ数によらないことを実験と現地データから明らかとなった。剥離状態の可視化から渦を形づくる過程が明らかとなり,剥離渦の強さは剥離点における渦度で求められ,岬長,外縁流速およびストローハル数で表される。さらに,岬に沿って発達する境界層厚さは岬長に比例することが導かれ,実験結果とよく一致した。

Separation vortices are generated at the tip of a cape exposed to a tidal current perpendicular to the majoraxis of the cape. The boundary layer thickness increases with increasing distance along the cape. Vortices aregenerated when the flow separates at the tip of the cape. An upwelling is generated due to the spin down of thisseparated vortex. This study examines the generation period and the strength (circulation) of the separated vortexby means of hydraulic experiments. The experimental results show that the Strouhal number is constant and doesnot depend on the Reynolds number when the flow condition is higher than a Reynolds of 300. The formationprocess of separated vortices is visible by these experiments. The strength of the separated vortex is related tothe vorticity at the separation point. This vorticity is govemed by the headland length, the current velocity andthe Strouhal number. A theorem is proposed to describe the boundary layer development along a cape in whichthe boundary layer thickness increase along the cape is proportional to the headland length. This theorem showsgood agreement with the experimental data.

Journal

  • Journal of Fisheries Engineering

    Journal of Fisheries Engineering 35(2), 131-137, 1998-12-01

    The Japanese Society of Fisheries Engineering

References:  8

Codes

  • NII Article ID (NAID)
    10008274874
  • NII NACSIS-CAT ID (NCID)
    AN10278554
  • Text Lang
    ENG
  • Article Type
    ART
  • ISSN
    09167617
  • NDL Article ID
    971382
  • NDL Source Classification
    ZR26(科学技術--農林水産--水産)
  • NDL Call No.
    Z18-1327
  • Data Source
    CJP  NDL  J-STAGE  JASI 
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