• Title/Summary/Keyword: Lift plate

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Unsteady Force Characteristics on Foils Undergoing Pitching Motion (피칭 운동익에 작용하는 비정상 유체력)

  • Yang Chang-Jo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.30 no.2 s.245
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    • pp.117-125
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    • 2006
  • In the present study the unsteady forces acting on the pitching foils such as a flat plate, NACA0010, NACA0020, NACA65-0910 and BTE have been measured by using a six-axis sensor in a circulating water tunnel at a low Reynolds number region. The unsteady characteristics of the dynamic drag and lift have been compared to the quasi-steady ones which are measured under the stationary condition. The pitching motion is available for keeping the lift higher after the separation occurs. Especially, the characteristics of the dynamic lift are quite different from the quasi-steady one at high pitching frequency regions. As the pitching frequency deceases, the amplitude of the dynamic lift becomes closer to the quasi-steady one. However, the phase remains different between the steady and unsteady conditions even at low pitching frequencies. On the other hand, the dynamic drag is governed strongly by the angle of attack.

Numerical Study on the Flow Field about Multi-element Airfoils and the Effect of the Lift-enhancing Tabs (다중-익형 주위 유동장 및 양력-향상 탭의 영향에 대한 수치적 연구)

  • Park, Yin-Chul;Chang, Suk;Lee, Deuk-Young;Kim, Byoung-Soo
    • 한국전산유체공학회:학술대회논문집
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    • 2011.05a
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    • pp.331-336
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    • 2011
  • The flow fields over multi-element airfoils with lift-enhancing flat-plate tabs were numerically investigated. Common choice of the height of the lift-enhancing tabs usually ranges from 0.25% to 1.25% of the reference airfoil chord, and in this study the effect of the position of the tab with l%-chord height was studied by varying the distance of the tab from the trailing edge ranging from 0.5% to 2% of the reference chord. In this paper, the effects of lift-enhancing tabs with various position were studied at a constant Reynolds number on a two-element airfoil with a slotted flap. Computed streamlines show that the additional turning caused by the tab reduces the amount of separated flow on the flap.

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A Study on the Structural Stability of the Swash Plate Piston Pump for Marine Hydraulic Power Supply (선박 유압공급 장치용 사판식 유압 피스톤 펌프의 구조적 안정성에 관한 연구)

  • Gwak, Beom-Seop;Lim, Jong-Hak;Lee, In-Wook;Yi, Chung-Seob;Lee, Ho Seong;Song, Chul Ki
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.20 no.4
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    • pp.24-30
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    • 2021
  • In this paper, a structural stability analysis of the swash plate hydraulic piston pump installed on hydraulic supply systems in marine vessels is presented. In order to verify the integrity of the pump design, a standard structural analysis technique based on the finite element method has been applied for various operating and boundary conditions. For the maximum operational torque (223 N·m) at 5°, 10°, and 15° of the swash plate angle, the maximum deformation, equivalent stress and safety factor are evaluated. The analytical results show that under current operating conditions, the structural reliability of the design has been confirmed.

Inspection of Welded Zone and Flat Plate Using Flexible ECA Probe (Flexible ECA Probe를 이용한 평판 및 용접부 검사)

  • Lee, Chang-Jun;Lee, Kyu Sung;Shin, Chung-Ho;Lee, Kyoung-Jun;Jang, Yoon Young
    • Journal of the Korean Society for Nondestructive Testing
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    • v.36 no.4
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    • pp.288-294
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    • 2016
  • This paper aims to compare the ability to detect notch defects existing in the plate and welded area using a flexible ECA (eddy current array) probe with OmniScan MX and MS-5800E. The characteristics of signals with various frequencies and lift-offs were also compared. As a result, when signals of frequencies 500, 1000, and 1500 kHz were used, the amplitude of the signal increased, as the depth of the notch increased, but reduced linearly in accordance with the lift-off variation. In addition, the detection sensitivity of the weld defect was found to be closely related to the contact surface of the probe and specimen. In this paper, it was demonstrated that the detection sensitivity was excellent when the contact surface of the probe and the specimen was sufficient, but it was poor when the contact surface was insufficient.

The Characteristics on Water Surface Effects of Air Supported TP 620 Hydrofoil over Water (박용 TP 620익형의 공기 부양 특성)

  • 김시영
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.22 no.2
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    • pp.36-39
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    • 1986
  • The steady potential flow about a TP 620 hydrofoil, flying in air above a dynamic water surface. is calculated by the one dimensional theory as the clearance-to-length ratio tends to very small. The characteristics on water surfare effects of air supported TP 620 hydrofoil over water are compared NACA 4412, NACA 66 and plate. respectively. It is found that using the TP 620 hydrofoil is superior lift coefficients. Moreover for trailing edge shape of the hydrofoil, high lift coefficients at 1 Fmn can be obtained.

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An Experimental Study on the Lift and Drag Characteristics of a Wing with a Helical Ring Wing Tip (나선 고리형 날개끝을 가진 날개의 양항특성에 관한 실험적 연구)

  • Lim, J.H.;Lee, B.J.
    • Journal of the Korean Society for Aviation and Aeronautics
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    • v.6 no.1
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    • pp.7-20
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    • 1998
  • A reduction of induced drag is an important problem in order to save fuels. In this study, the aerodynamic characteristics of wing tip devices to reduce induced drag, such as end plate, plain ring, helical ring wing tip device, was experimentally investigated in a low speed wind tunnel. The experimental results showed that the wing model with a helical ring wing tip device reduced a induced drag and increased lift-drag ratio.

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Drag Reduction on a Square Prism Using a Detached Splitter Plate (분리된 분할판에 의한 정방형주의 항력감소)

  • Ro, Ki-Deok;Yoon, Seong-Min;Choi, Dong-Hyeon;Kim, Jae-Hyeon;Sim, Eun-Chong
    • Journal of Advanced Marine Engineering and Technology
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    • v.36 no.6
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    • pp.808-813
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    • 2012
  • The Characteristics of the drag reduction of a square prism having a detached splitter plate at the wake side were investigated by measuring of lift and drag on the square prism. The experimental parameters were the width ratios(H/B=0.5~1.5) of splitters to the prism width and the gap ratios (G/B=0~2) between the prism and the splitter plate. As the results the amplitude of the lift on the square prism having a detached splitter plate was remarkably decreased by comparison with the prototypical square prism. The drag reduction rate of the square prism was increased with H/B in case of the same G/B, and was increased and decreased with G/B in case of the same H/B. The maximum drag reduction rate was represented by 24.2% at H/B=1.5 and G/B=0.5.

A Study on the Structure Strength of Wing In Ground effect Ship (표면 효과익선(WIG)의 구조 강도에 관한 연구)

  • 고재용;박석주;정성호;박성현
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 2002.11a
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    • pp.95-100
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    • 2002
  • The wing in ground effect (WIG) ship is an energy saying vessel that uses the lift from its air-wing along with the lift increase from the ground effect by flying low above the sea surface. The WIG Ship should consist of thin plate in order to float on the sea and to fly in the air. Therefore, the structure of WIG, Ship has very thin and light shell plate and stiffener like stringer and frame has comparatively large cross section area. This structure makes shell plate nearly pure shear field when shell plate is pressed by in-plane load. This complex thin plate structure of WIG Ship can he considered as a closed section beam which makes it possible to analyze structure response of WIG Ship affected by shear load and bending load. In this respect, the present study will show basic theory for analysing shear stress and focus on the analysis of structure strength of model WIC Ship's wing.

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A new rotational force model for quasi-steady theory of plate-like windborne debris in uniform flow

  • Lin, Huatan;Huang, Peng;Gu, Ming
    • Wind and Structures
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    • v.35 no.2
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    • pp.109-120
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    • 2022
  • The force coefficients of rotating plates in the acceleration stage will vary with rotation rate from 0 to stable rotation rate w0, which are important for quasi-steady theory of plate-like windborne debris to simulate the trajectory. In this paper, a wind tunnel experiment is carried out to study the effects of geometry and the Reynolds number on the variations of mean force coefficients of rotating plates. The rotational lift coefficients are sensitive to both geometry effect and Reynolds number effect, while the rotational drag and moment coefficients are only sensitive to geometry effect. In addition, new empirical formulas for the rotational lift coefficient and moment coefficients are proposed. Its accuracy is verified by comparing the predicted results with existing test data. Based on the experimental data of rotating plates, a new rotational force model for quasi-steady theory, which can be applied to a wider scope, is proposed to calculate the trajectory of plate-like windborne debris. The results show that the new model provides a better match with the tested trajectories than previous quasi-steady theories.

Maintenance and Dynamic Behavior of Advanced Spherical Bearings under Railway Open-Steel-Plate-Girder Bridges (판형교에서 개량된 스페리칼받침의 유지보수 및 동적 거동)

  • Choi, Eun-Soo;Lee, Hee-Up;Lee, Seung-Yong
    • Journal of the Korean Society for Railway
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    • v.11 no.2
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    • pp.165-175
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    • 2008
  • Line type rigid bearings for Open-Steel-Plate-Girder railway bridges have several problems in service, and they are unstable structurally. A series of lateral resistance tests were performed for a retrieved line type bearing. A spherical bearing with advanced maintenance-capability and a device to resist the up-lift was developed and replaced the existing ones. An experiment of maintenance for a new spherical bearing under real Open-Steel-Plate-Girder bridge was conducted and their good maintenance performance was proved. Also, a test against up-lift was performed for the bearing. The dynamic behavior of the bridge was measured and analyzed for the two cases of the existing and replaced bearings. Therefore, the suitability of the new spherical bearings on the railway bridge was improved.