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Unsteady Fluid Force Acting on In-Line Oscillating Bluff Body in Lock-in Phenomenon

Research Project

Project/Area Number 12650179
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field Fluid engineering
Research InstitutionShibaura Institute of Technology

Principal Investigator

OKAMOTO Shiki  Shibaura Institute of Technology, Dept Mechanical Engineering, Professor, 工学部, 教授 (60052875)

Project Period (FY) 2000 – 2001
Project Status Completed (Fiscal Year 2001)
Budget Amount *help
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2001: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 2000: ¥2,400,000 (Direct Cost: ¥2,400,000)
KeywordsPressure Distribution / Fluctuating Pressure / Vortex / Fluid Forse / Lock-in / Flow Induced Vibration / In-Line / Circular Cylinder / 圧力
Research Abstract

Vortex-excitation oscillation due to a Karman vortex is generally known as oscillation by flow, wherein oscillation in the direction perpendicular to the flow is induced in the vortex flow. Also, when the natural frequency of a bluff body approaches the shedding frequency of the Karman vortex, the value of the shedding frequency of the Karman vortex becomes similar to that of the natural frequency ; this is called the lock-in phenomenon. Under this lock-in condition, the oscillation amplitude of the bluff body increases rapidly, causing, in some cases, a serious accident. Therefore, to examine countermeasures for the oscillation of an obstacle which generates a vortex, it is important to study the fluid force acting on the obstacle in a lock-in state, in particular, to evaluate the hydrodynamic excitation force. However, most of the reports regarding fluid force acting on a circular cylinder concern cases of fixed support, and to date, there is no report on fluid force acting on a circ … More ular cylinder in an oscillating state, except that by Bishop and Hassan. In this report, we describe the fluid force acting on a two-dimensional oscillating circular cylinder in a lock-in region. The experiment was carried out in an N. P. L blow-down wind tunnel with a working section of 500 mm x 500 mm x 2000 mm and Reynolds number of 1.9 x 10^4.The cylinder was then forced to oscillate sinusoidally in the streamwise direction. The power spectrum of the fluctuating velocity in the wake behind the circular cylinder was measured to show the lock-in region in the present experiment. The time-averaged pressure distribution and fluctuating pressure distribution on the circular cylinder were measured for the displacement in the oscillation. Consequently it was found as follows' (1) In this experiment, the lock-in region begins from Sv=0.325, and it leaves from the lock-in state at Sv=0.425 (2) The mean drag and fluctuating drag increase and become maximum in the lock-in region, while the base pressure in the rear surface (θ =180度) of the cylinder becomes low and attains a minimum. Less

Report

(3 results)
  • 2001 Annual Research Report   Final Research Report Summary
  • 2000 Annual Research Report
  • Research Products

    (9 results)

All Other

All Publications (9 results)

  • [Publications] 岡本 史紀, 植松 亮介, 田桑 良彦: "ロックイン状態の二次元円柱に作用する流体力"日本機械学会論文集B編. 67. 430-435 (2001)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2001 Final Research Report Summary
  • [Publications] 岡本 史紀, 田桑 良彦: "渦励振に及ぼす円柱列間隔の影響"日本機械学会論文集B編. 67. 1720-1725 (2001)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2001 Final Research Report Summary
  • [Publications] 岡本 史紀, 近藤 芳宣: "ロックイン状態の二次元角柱に作用する流体力"日本機械学会論文集B編. 68. 726-732 (2002)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2001 Final Research Report Summary
  • [Publications] S.Okamoto, R.Uematsu and Y.Taguwa: "Fluid Force Acting on Two-Dimensional Circular Cylinder in Lock-in Phenomenon"Transaction of JSME. Ser.B, 67-654. 430-435 (2001)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2001 Final Research Report Summary
  • [Publications] S.Okamoto and Y.Taguwa: "Effect of Spacing of Circular Cylinder Row on Vortex Exciting Vibretion"Transaction of JSME. Ser.B, 67-659. 1720-1725 (2001)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2001 Final Research Report Summary
  • [Publications] S.Okamoto and Y.Kondo: "Fluid Force Acting on Two-Dimensional Square Cylinder in Lock-in Phenomenon"Transaction of JSME. Ser.B, 68-667. 726-732 (2002)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2001 Final Research Report Summary
  • [Publications] 岡本史紀, 植松亮介, 田桑良彦: "ロックイン状態の2次元円柱に作用する流体力"日本機械学会論文集B編. 67-654. 430-435 (2001)

    • Related Report
      2001 Annual Research Report
  • [Publications] 岡本史紀, 近藤芳宣: "ロックイン状態の2次元角柱に作用する流体力"日本機械学会論文集B編. 68-667(予定). (2002)

    • Related Report
      2001 Annual Research Report
  • [Publications] 岡本史紀,植松亮介,田桑良彦: "ロックイン状態の2次元円柱に作用する流体力"日本機械学会北陸信越支部第38期総会講演会講演論文集. 017-1. 357-358 (2001)

    • Related Report
      2000 Annual Research Report

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Published: 2000-04-01   Modified: 2016-04-21  

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