船首状有孔板の流水抵抗に関する基礎的研究 Resistance of Two Perforated Plates Placed Obliquely to a Current

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Abstract

通水性を持った有孔の船首状カバーが水産施設の構成要素になりうるものと考え,同カバーの船首角度と開口部の大きさを変化させたときの流水抵抗を調べた。縦33cm,横20cm,厚さ2mmの鉄板を2枚,ちょうつがいで船首状に接合させて模型を作製した。船首角度すなわち展開角度を, 60度から180度まで30度ずつ5段階に変化させた。ドリル直径を順次変化させて(4.0mm-10.0mm)鉄板に孔を開け,孔の総面積と元の板の面積との比を開口比とした。孔を開けない状態の0%から37.2%まで,開口比を8段階に変化させた。開口比ごとに展開角度を変化させた模型を,大型回流水槽中に設置し,流水抵抗を測定した。船首状有孔板においても一般物体と同様にニュートンの抵抗則が確認できた。測定値より各開口比における展開角度ごとの抵抗係数を得た。開口比の増加に対応して,流水抵抗の増減があることも示した。特に,展開角60度や90度の場合には,開口比15-20%で孔を開けない場合の抵抗の1割余の増加であった。しかし,この抵抗の増減の要因については,今後の検討を要する。

Two perforated plates placed obliquely to a current to form a bow-shape will be effective for use infisheries. We examined the resistance to the two perforated plates as the angle between the hinged plates andthe open area ratio of the two plates were changed. We made a model by joining the two iron plates, each ofwhich was 33cm long, 20cm wide, and 2mm thick, With hinges. The contained angle of the two plates was changedfrom 60 to 180 by 30 steps. we drilled holes of increasing diameter by steps and determined the ratio of thetotal area of the holes to the area of the undrilled plate, 'open area ratio'. The open area ratio was changedfrom 0% to 37.2% in eight different steps. We set up the model, changing the contained angle for each of theopen area ratios in a circulating water tank and measured the resistance. We confirmed that Newton's Law isapplicable to the resistance of the two perforated plates. The drag coefficient of the perforated plates for eachcontained angle at each open area ratio was calculated from the resistance. We showed that there is an increaseand decrease of the resistance corresponding to the increasing of open area ratio.

Journal

  • Journal of Fisheries Engineering

    Journal of Fisheries Engineering 36(2), 137-145, 1999-11-15

    The Japanese Society of Fisheries Engineering

References:  11

Codes

  • NII Article ID (NAID)
    10008275356
  • NII NACSIS-CAT ID (NCID)
    AN10278554
  • Text Lang
    ENG
  • Article Type
    ART
  • ISSN
    09167617
  • NDL Article ID
    4944313
  • 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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