• Title/Summary/Keyword: 외부경계층 수직 날

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Investigation of Skin Friction Reduction Mechanism of Outer-Layer Vertical Blades Using POD Analysis (POD 기법을 이용한 경계층 외부 수직날의 마찰저항 저감 기구에 관한 관측)

  • An, Nam Hyun;Park, Seong Hyeon;Chun, Ho Hwan;Lee, Inwon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.37 no.6
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    • pp.567-575
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    • 2013
  • A POD analysis based on time-resolved PIV measurements in a circulating water channel has been conducted to identify the skin friction reduction mechanism of outer-layer vertical blades. A recent PIV measurement indicated 2.73% and 7.95% drag reduction in the blade plane and the blade-in-between plane, respectively. In the present study, the influence of vertical blades array upon the characteristics of the turbulent coherent structures was analyzed by the POD method. It is observed that the vortical structures are cut and deformed by the blades array and that their temporal evolution is strongly associated with the skin-friction drag reduction mechanism in the turbulent boundary layer flow.

Experimental Assessment of the Drag Reduction Efficiency of the Outer-layer Vertical Blades (외부경계층 수직 날의 저항저감효과에 대한 실험적 연구)

  • An, Nam-Hyun;Chun, Ho-Hwan;Lee, In-Won
    • Journal of the Society of Naval Architects of Korea
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    • v.45 no.5
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    • pp.487-494
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    • 2008
  • An experimental assessment has been made of the drag reducing efficiency of the outer-layer vertical blades, which were first devised by Hutchins (2003). The drag reduction efficiency of the blades was reported to reach as much as 30%. The assessment of the drag reducing efficiency is mainly restricted to the downstream region of the blades. Indeed, sufficient care has not been taken to such adverse effects as the increase in the wetted surface area and the flow disturbances due to the presence of the blades. In the present study, a series of drag force measurements in towing tank and circulating water channel has been performed toward the assessments of the total drag reduction efficiency of the outer-layer vertical blades.

Verification of Drag Reduction Effect of Outer-layer Vertical Blades based on Model Test (모형선 시험을 통한 외부경계층 수직 날 배열의 저항저감효과 검증)

  • Lee, Seong Hoon;Lee, Inwon
    • Journal of the Korean Society of Visualization
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    • v.16 no.3
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    • pp.26-34
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    • 2018
  • In the present study, an experimental assessment has been made of the drag reducing efficiency of the outer-layer vertical blades, which were first devised by Hutchins(1). A detailed flow field measurements have been performed using 2-D time resolved PIV with a view to enabling the identification of drag reduction mechanism. In addition, an experimental investigation has been made of the applicability of outer-layer vertical blades to real ship model. The arrays of outer-layer vertical blades have been installed onto the flat side and flat bottom of a 300k KVLCC model. A series of towing tank test has been carried out to investigate resistance (CTM) reduction efficiency with various geometric parameters and installed places of blades. The installation of vertical blades led to the CTM reduction of 1.44~3.17% near the service speed.

PIV Investigation on the Skin Friction Reduction Mechanism of Outer-layer Vertical Blades (경계층 외부 수직날의 마찰저항 저감 기구에 대한 PIV 관측)

  • Park, Hyun;An, Nam-Hyun;Park, Seong-Hyoen;Chun, Ho-Hwan;Lee, In-Won
    • Journal of the Korean Society of Visualization
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    • v.9 no.1
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    • pp.20-28
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    • 2011
  • An experimental assessment has been made of the drag reducing efficiency of the outer-layer vertical blades, which were first devised by Hutchins. The drag reduction efficiency of the blades was reported to reach as much as 30%. However, the drag reduction efficiency was quantified only in terms of the reduction in the local skin-friction coefficient. In the present study, a series of drag force measurements in towing tank has been performed toward the assessments of the total drag reduction efficiency of the outer-layer vertical blades. A maximum 9.6% of reduction of total drag was achieved. The scale of blade geometry is found to be weakly correlated with outer variable of boundary layer. In addition, detailed flow field measurements have been performed using 2-D time resolved PIV with a view to enabling the identification of drag reduction mechanism.

Experimental Investigation on the Drag Reduction Mechanism of Outer-layer Vertical Blades Array using Stereoscopic Time-Resolved PIV (스테레오 시간분해 입자영상유속계를 이용한 외부경계층 수직날 배열에 의한 마찰저항 저감 기구에 관한 실험적 조사)

  • Lee, Inwon;Park, Seong-Hyeon;Chun, Ho-Hwan;Hwang, Arom;An, Nam-Hyun
    • Journal of Power System Engineering
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    • v.17 no.6
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    • pp.95-101
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    • 2013
  • A stereo PIV measurements in a circulating water channel has been performed to investigate the skin friction reduction mechanism of the outer-layer vertical blades first devised by Hutchins. In a recent PIV measurement study, considerable skin friction reduction was achieved as much as 2.73%~7.95% by outer-layer vertical blades array. In the present study, the influence of vertical blades array upon the characteristics of the turbulent coherent structures was analyzed by proper orthogonal decomposition method. It is observed that the vortical structures are cut and deformed by blades array and also the turbulent intensity and the Reynolds stress were weakened by the blades. These phenomena strongly associate the skin-friction drag reduction mechanism in the turbulent boundary layer flow.