• Title/Summary/Keyword: Oscillating foil

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Propulsion by Oscillating Foil Attached to Ship in Waves (동요하는 날개를 이용한 파랑 중 선박의 추력발생)

  • Choi, Yoon-Rak
    • Journal of Ocean Engineering and Technology
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    • v.27 no.1
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    • pp.31-36
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    • 2013
  • In this paper, the effects of a foil attached to a ship on the ship motion, added resistance, and thrust generation in waves are analyzed. The unsteady theory for a two-dimensional foil is introduced to determine the coupled motion responses of the ship and foil. The thrust caused by the oscillating foil is evaluated and compared to the added resistance of the ship, so that a positive net thrust can be possible in waves. A comparison of the results of unsteady, quasi-steady, and experimental analyses is performed.

Powering Analysis of Oscillating Foil Moving in Propagating Wave Flow Field (전파하는 파동유장 중 전진하며 동요하는 2차원 날개의 동력해석)

  • Choi, Yoon-Rak
    • Journal of Ocean Engineering and Technology
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    • v.33 no.3
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    • pp.229-235
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    • 2019
  • In this study, a two-dimensional oscillating foil with forward speed in a propagating wave flow field was considered. The time-mean power to maintain the heaving and pitching motions of the foil was analyzed using the perturbation theory in an ideal fluid. The power, which was a non-linear quantity of the second-order, was expressed in terms of the quadratic transfer functions related to the mutual product of the heaving and pitching motions and incoming vertical flow. The effects of the pivot point and phase difference among the disturbances were studied. The negative power, which indicates energy extraction from the fluid, is shown as an example calculation.

Characteristics of Vortical Jet Structures of a Hydrofoil

  • Yang, Chang-Jo;Kim, You-Taek;Choi, Min-Seon
    • Journal of Advanced Marine Engineering and Technology
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    • v.31 no.7
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    • pp.842-851
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    • 2007
  • Oscillating foil propulsion, the engineering application of fish-like movement of a hydrofoil, has received in recent decades as a possible competitor for propellers. The oscillating foil produces an effective angle of attack, resulting in a normal force vector with thrust and lift components, and it can be expected to be a new highly effective propulsion system. We have explored propulsion hydrodynamics as a concept in wake flow pattern. The present study has been examined various conditions such as oscillating frequencies and amplitudes in NACA0010 profile. Flow visualizations showed that high thrust was associated with the generation of moderately strong vortices, which subsequently combine with trailing-edge vorticity leading to the formation of a reverse $K\acute{a}rm\acute{a}n$ vortex street. Vortex generation was inherent to jet production and playeda fundamental role in the wake dynamics. And it was shown that the strong thrust coefficient obtained as the Strouhal number was larger.

Unsteady Fluid Forces Acting on a Pitching Foil (피칭 운동익에 작용하는 비정상 유체력)

  • Yang, C.J.
    • The KSFM Journal of Fluid Machinery
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    • v.8 no.6 s.33
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    • pp.47-54
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    • 2005
  • An oscillating foil can produce a driving force through the generation of a reversed $K\'{a}rm\'{a}n$ vortex street, and it can be expected to be a new highly effective propulsion system. A simple pitching foil model was made and it was operated within a water channel. The wake formation behind a pitching foil was visualized and unsteady fluid forces were measured using a 6-axis force sensor based on force and moment detectors. We have been examined various conditions such as reduced frequency, amplitude and pivot point in NACA 0010. The results showed that thrust coefficients increased with a reduced frequency. We also presented the experimental results on the characteristics of a pitching foil at various parameters.

Computation of Viscous Flows around a Two-dimensional Oscillating Airfoil ( Part 1. without Dynamic Stall ) (진동하는 2차원 날개 단면 주위에 대한 점성 유동장 계산( Part 1. 동적실속이 없는 경우 ))

  • Lee, Pyoung-Kuk;Kim, Hyoung-Tae
    • Journal of the Society of Naval Architects of Korea
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    • v.44 no.1 s.151
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    • pp.8-15
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    • 2007
  • In this paper, numerical calculations are performed to analyze the unsteady flow of NACA airfoil sections. In order to ease the flow computation for the fluid region changing in time, improve the quality of solution and simplify the grid generation for the oscillating foil flow, the computational method adopts a moving and deforming mesh with the multi-block grid topology. The multi-block, structured-unstructured hybrid grid is generated using the commercial meshing software Gridgen V15. The MDM (Moving & Deforming Mesh) and the UDF (User Define function) function of FLUENT 6 are adopted for computing turbulent flows of the foil in pitching motion. Computed unsteady lift and drag forces are compared with experimental data. in general, the characteristics of unsteady lift and drag of the experiments are reproduced well in the numerical analysis.

A Study on the Vortical patterns of a Heaving Foil (히빙익 후류의 유동패턴에 관한 연구)

  • Yang Chang-Jo
    • Journal of Advanced Marine Engineering and Technology
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    • v.29 no.8
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    • pp.899-906
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    • 2005
  • It is known that an oscillating airfoil can Produce a driving force through the generation of a reversed $K\'{a}rm\'{a}n$ vortex street, and this can be expected to be a new highly effective propulsion system. The wake formation behind the heaving airfoil was visualized and was measured using PIV systems We have been examined various conditions such as frequency number, amplitude in NACA 0010. As Strouhal number is greater than 0.08. wake profile with velocity deficit can be transformed into the wake with velocity excess After evaluating vortex center flow patterns in the wake investigated using tracking trajectories in temporal evaluation of the shedding vortices. We also Presented the experimental results on the unsteady vortices structure of the heaving airfoil at various parameters.

A Study on Vortical Flow Patterns of a Heaving Foil (히빙익 후류의 유통패턴에 관한 연구)

  • Yang, Chang-Jo;Kim, You-Taek;Choi, Min-Seon;Lee, Young-Ho
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • 2005.11a
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    • pp.31-32
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    • 2005
  • It is known that an oscillating airfoil can produce a driving force through the generation of a reversed $K\acute{a}rm\acute{a}n$ vortex street, and this can be expected to be a new highly effective propulsion system. We have been examined various conditions such as frequency number, amplitude in NACA 0010. As Strouhal number is greater than 0.08, wake profile with velocity deficit can be transformed into the wake with velocity excess. We also presented the experimental results on the unsteady vortices structure of the heaving airfoil at various parameters.

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Wireless Telemetry of an Oscillating Flow using Mesoscale Flexible Cantilever Sensor (메소스케일 유연 외팔보 센서를 이용한 진동유동의 무선 계측)

  • Park, Byung Kyu;Lee, Joon Sik
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.37 no.5
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    • pp.495-501
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    • 2013
  • This paper describes a flexible wireless telemetering system using a mesoscale cantilever sensor, which is microfabricated with a patterned thin Ni-Cu foil on a resin substrate. The dynamic validation of the sensor has been conducted in a flow. The wireless telemetry is used to obtain data regarding the oscillating flows. It is shown that the sensor is nearly independent of the environmental temperature and is suitable for application to primary healthcare and diagnostic devices. It can be easily integrated with other modules for measuring physiological parameters, e.g., blood pressure, oxygen saturation, and heart rate, to increase the convenience and reliability of diagnosis. The precision and reliability of the sensor are also dependent on the design of the analog front-end and noise reduction techniques. It is shown that the present system's minimum interval between packet transmissions is ~16 ms.