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1998 Fiscal Year Final Research Report Summary

Experiments and Numerical Simulations of Flow Around a Bluff Body in Oscillatory Flow

Research Project

Project/Area Number 08455089
Research Category

Grant-in-Aid for Scientific Research (B)

Allocation TypeSingle-year Grants
Section一般
Research Field Fluid engineering
Research InstitutionKanazawa University

Principal Investigator

OKAJIMA Atsushi  Kanazawa University, Faculty of Engineering, Professor, 工学部, 教授 (80013689)

Co-Investigator(Kenkyū-buntansha) KIWATA Takahiro  Kanazawa University, Faculty of Engineering, Associate Professor, 工学部, 助教授 (40225107)
KIMURA Sigeo  Kanazawa University, Faculty of Engineering, Professor, 工学部, 教授 (70272953)
UENO Hisanori  Kanazawa University, Faculty of Engineering, Professor, 工学部, 教授 (80019752)
Project Period (FY) 1996 – 1998
KeywordsOscillatory flow / U-tube water tank / Numerical Simulation / Fluid dynamic force coefficients / Circular cylinder / Rectangular cylinder / Flat plate / Longitudinal vortices
Research Abstract

The flow around a bluff body submerged in oscillatory flow consists of the envelopment of separating flow, which has flow-characteristics of a starting flow and an unsteady wake with a limited length because of flow of the oscillation in the alternate directions. The studies of forces acting upon and flow patterns around the bluff body are fundamental to such fluid engineering constructions as piers, submarine pipelines and other ocean structures. There are many aspects that remain indistinct yet about fluid forces induced by oscillating flow such as waves. Some experimental studies on fluid forces acting on a circular cylinder under oscillating flow were already reported. In this field of fluid dynamics, a Keulegan-Carpenter number and a viscous parameter beta, where KC=UmT/D (Um : a maximum fluid velocity, T : a period, D : a body diameter), beta=Re/KC-D^2IvT (v= kinematic viscosity) are the most important parameters.
Experiments by using a U-tube water tank :
(1) The fluid dynamic for … More ce coefficients of a circular cylinder were measured and compared with those of other studies in a U-tube water tank to verify the experimental set-up. Then, measurements of both in-line and transverse forces of a square cylinder and flat plates with various angles of attack were made in a wide range of KC numbers from 1 to 90. Flow visualization was also employed to confirm the correspondence between flow patterns and force coefficients. It is found that several classes of flow patterns appear within the measured KC number range and the vortex motions closely corresponds to variations of the in-line and transverse forces.
(2) The forces acting upon and the flow patterns around a rectangular cylinder with a cross-section of width/height ratio of 0.2-3.0 submerged in oscillatory flow were studied by using a U-tube water tank. In particular, we found that a drag coefficient CD of the d/h=0.6 cylinder becomes the biggest only beyond KC=120, compared with other case of the d/h cylinder in oscillatory flow. The good relationships between KC number and the flow patterns, and CD and wake width were shown.
Numerical Simulations by a finite difference method
An ALE (Arbitrary Lagrangian-Eulerian) finite difference method has been employed to simulate the flow around an oscillating bluff body, e.g., a circular cylinder and a square one, submerged in a still water. Simulations have been carried out under the assumption of 3-dimensional, unsteady, incompressible and viscous flow. Predictions are compared with the results of measurements of fluid-dynamic forces and flow-visualization. There is found to be good agreement between the computed and measured in-line forces, i.e., the values of inertia and drag coefficients, CM, CD represented by the well-known Morison equation, across a range of KC values. Several types of flow patterns are successfully reproduced and identified by the numerical simulations also, such as 3-D flow-structure of "longitudinal vortices or Honji's Vortex", "asymmetric pattern", "transverse street" and "double pair" for a circular cylinder. It is confirmed that the computed flow patterns agree well with the flow-visualized ones for both the circular cylinder and the square cylinder. Less

  • Research Products

    (14 results)

All Other

All Publications (14 results)

  • [Publications] 岡島 厚: "振動流中の円柱および正方形柱に作用する流体力の測定と流れの可視化" 日本機械学会論文集. 63巻・615号. 3548-3556 (1997)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Atsushi OKAJIMA: "Force Measurements and Flow Visualization of Bluff Bodies in Oscillatory Flow" Journal of Wind Engineering and Industrial Aerodynamics. Vol.69-71. 213-228 (1997)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Atsushi OKAJIMA: "A Numerical Study of Oscillatory Flow around Circular and Square Cylinders" Proc.4th International Symposium on Fluid-Structure Inter-actions,Aeroelasticity,Flow-Induced Vibration and Noise. AD-Vol.53-1. 127-134 (1997)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Atsushi OKAJIMA: "Aerodynamic Characteristics of Flat Plates with Various Attacked Angles in Oscillatory Flow" JSME International Journal. Vol.41・No.1. 214-220 (1998)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Atsushi OKAJIMA: "Experimental study on flow characteristics of a rectrangular cylinder with cross-section of various width/height ratios submerged in oscillatory flow" Proc.of 1998 ASME FLUIDS ENGINEERING DIVISION (ANNUAL SUMMER MEETING). 20-25 (1998)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Atsushi OKAJIMA: "Force Measurements and Flow Visualization of Circular and Square Cylinders in Oscillatory Flow" JSME International Journal. Vol.41・No.4. 796-805 (1998)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Okajima, A., Matsumoto, T., Kimura, S.: "Force Measurements and Flow Visualization of Bluff Bodies in Oscillatory Flow" Wind Eng.and Industrial Aerodynamics. 69-71. 213-228 (1997)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Okajima, A., Matsumoto, T., Kimura, S.: "Aerodynamic Characteristics of Flat Plates with Various Angles of Attack in Oscillatory Flow" JSME Int., J., B.41,1. 214-220 (1998)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Okajima, A., Matsumoto, T., Kimura, S.: "Force Measurements and Flow Visualization of Circular and Square Cylinders in Oscillatory Flow" JSME Int.J., B.41,4. 796-805 (1998)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] A.Okajima, T.Matsumoto, N.Nakasuji, S.Kimura: "Force Measurements on Bluff Bodies and Flow Visualization in Oscillatory Flow." Proc.of 3rd International Colloquim on Bluff Body Aerodynamics and Applications, Blacksburg, VA,USA. CI9-CI (1996)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] A.Okajima, T.Matsumoto, S.Kumura: "Aerodynamic Characteristics of Flat Plates with Various Angles of Attack in Oscillatory Flow" JSME CENTENNIAL GRAND CONGRESS.Proc.of International Conference on Fluid Engineering. Vol.1. 513-518 (1997)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Okajima, A., Yasuda, T., Matsumoto, T.: "Experimental and Numerical Studies on Flow and Fluiddynamic Forces of a Circular Cylinder Submerged in Oscillatory Flow" Proc.of 3rd Int.Conf.on Fluid Dynamic Measurement and Its Applications, Beijing, China. 277-282 (1997)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Okajima, A., Yasuda, T.: "Numerical Study of Oscillatory Flow around Circular and Square Cylinders" Proc.of the 1997 Int.Mechanical Eng.Congress and Exposition, Dallas, U.S.A.127-134 (1997)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] A.Okajima, T.Matsumoto, S.Kimura: "Experimental study on flow characteristics of a rectangular cylinder with cross-section of various width/height ratios submerged in oscillatory flow." Proc.of 1998 ASME FLUIDS ENGINEERING DIVISION (ANNUAL SUMMER MEETING), Washington, D.C.20 (1998)

    • Description
      「研究成果報告書概要(欧文)」より

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Published: 1999-12-08  

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