• Title/Summary/Keyword: lift force

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An Experimental Study on Lift Force Generation Resulting from Spanwise Flow in Flapping Wings

  • Hong, Young-Sun
    • International Journal of Aeronautical and Space Sciences
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    • v.7 no.2
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    • pp.86-103
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    • 2006
  • Using a combination of force transducer measurement to quantify net lift force, high frame rate camera to quantify and subtract inertial contributions, and Digital Particle Image Velocimetry (DPIV) to calculate aerodynamic contributions in the spanwise plane, the contribution of spanwise flow to the generation of lift force in wings undergoing a pure flapping motion in hover is shown as a function of flapping angle throughout the flapping cycle. These experiments were repeated at various flapping frequencies and for various wing planform sizes for flat plate and span wise cambered wings. Despite the previous identification of the importance of span wise fluid structures in the generation of lift force in flapping wings throughout the existing body of literature, the direct contribution of spanwise flow to lift force generated has not previously been quantified. Therefore, in the same manner as commonly applied to investigate the chordwise lift distribution across an airfoil in flapping wings, spanwise flow due to bulk flow and rotational fluid dynamic mechanisms will be investigated to validate the existence of a direct component of the lift force originating from the flapping motion in the spanwise plane instead.

Analysis and Optimization of Permanent Magnet Dimensions in Electrodynamic Suspension Systems

  • Hasanzadeh, Saeed;Rezaei, Hossein;Qiyassi, Ehsan
    • Journal of Electrical Engineering and Technology
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    • v.13 no.1
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    • pp.307-314
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    • 2018
  • In this paper, analytical modeling of lift and drag forces in permanent magnet electrodynamic suspension systems (PM EDSs) are presented. After studying the impacts of PM dimensions on the permanent magnetic field and developed lift force, it is indicated that there is an optimum PM length in a specified thickness for a maximum lift force. Therefore, the optimum PM length for achieving maximum lift force is obtained. Afterward, an objective design optimization is proposed to increase the lift force and to decrease the material cost of the system by using Genetic Algorithm. The results confirm that the required values of the lift force can be achieved; while, reducing the system material cost. Finite Element Analysis (FEA) and experimental tests are carried out to evaluate the effectiveness of the PM EDS system model and the proposed optimization method. Finally, a number of design guidelines are extracted.

INVESTIGATION FOR THE AERODYNAMIC CHARACTERISTICS OF HIGH SPEED TRAIN PANTOGRAPH WITH COVER (커버 형상을 고려한 고속전철 팬터그래프 공력특성의 수치해석적 연구)

  • Kang, H.M.;Kim, C.W.;Cho, T.H.;Kim, D.H.;Yoon, S.H.;Kwon, H.B.
    • Journal of computational fluids engineering
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    • v.17 no.3
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    • pp.18-24
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    • 2012
  • The aerodynamic performance of the pantograph on a high speed train was compared for different pantograph covers which are designed to block the aero-acoustic noise from the pantograph. For the study, two types of cover are designed: wedge and cone types. The lift force of pantograph with cover was compared with the force of pantograph only. The comparison clarified that the cone type cover increases the sideslip angle of the flow and decreases the lift force considerably. However, the wedge type cover changes the flow direction upward and increases the lift force of the pan head. This increment of lift force compensates the decrement of lift force caused by the blocking of the flow into the pantograph lower frame due to cover. Therefore, in case of the wedge type cover, the overall lift force changes slightly compared with the cone type cover.

The Experimental Study of Distribution Characteristics of Lift-force Acting under Pier Deck (잔교상판(棧橋床板)에 작용(作用)하는 양압력(揚壓力) 분포특성(分布特性)에 관한 실험적(實驗的) 연구(硏究))

  • Park, Sang Kil;Park, Hyun Soo;Ahn, Ik Seong;Kim, Woo Saeng
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.29 no.1B
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    • pp.83-90
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    • 2009
  • This study describes the characteristics of distribution of lift-force acting under pier deck through physical experiment. The shape of peak wave pressure was sharp when compressed air existed but was not sharp without that. Values of lift-force was different between edge point and center point in the same block. Distribution of lift-force was expressed differently owing to dimensionless of deck length (l/L), wave steepness (H/L), clearance height per wave height (D/H). The dimensionless factor of D/H affected on the lift-force the clearance between still water surface and decks. This decided the maximum of lift-force. In the case of the same values of D/H, the lift-force are changed by the wave steepness (H/L). Because (D/H) become smaller as the wave steepness (H/L) is increased the height of decks must be decided with the condition which don't have the clearance with $D_{max}$ for the stable design of deck of pier. Effect of reducing lift force was greater in the on-shore than the off-shore according to compressed air existence. This researches points out that design of deck should retain compressed air in order to reduce wave lift force.

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Flow Analysis around Tilt-rotor Aircraft at Various Tilt Angles (틸트각 변화에 따른 틸트로터 항공기 주위의 유동해석)

  • Kim, Su-Yean;Choi, Jong-Wook
    • Journal of the Korean Society of Visualization
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    • v.9 no.2
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    • pp.40-47
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    • 2011
  • Tilt-rotor aircraft can be used in various fields because they have the capabilities of the vertical take-off and landing and the high-speed cruise flight. In the present study, the flow analysis of a tilt-rotor aircraft is conducted at various tilt angles. The lift and drag forces of the tilt-rotor aircraft are obtained and the wakes by the rotor-blade are visualized. The result shows that the rotor-blade affects the lift force in a hovering mode and the main wing has an influence on the lift force in a cruise mode. Additional thrust is required at the tilt angle of around 40 degree due to the least lift force. The drag force is dependent on the rotor-blade at overall tilt angles. The minus drag force appears between the tilt angles of 90 degree and 55 degree. Also, the drag force is dramatically increased at the other tilt angles. The wake by rotor-blade affects the flow around the fuselage of the tilt-rotor aircraft at the tilt angles of 75 degree and 60 degree.

Study of aerodynamic characteristic for a device controlling lift force on pantograph for Tilting train eXpress (TTX) (고속 틸팅열차의 판토그라프 양력조절장치 형상 설계 연구)

  • Ko Taehwan;Han Seong-Ho
    • Proceedings of the KSR Conference
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    • pp.467-471
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    • 2004
  • The development of a tilting train with construction of electric line on the conventional railway is required for speed-up on the conventional railway with many curving sections. For development of tilting train, the study and development of the tilting system and tilting bogie having the different mechanism with a general high speed train will play a main role for improving the technology in the field of Korean railway. The study and development of the pantograph tilting mechanism in order to keep a good contact behavior between a pantograph and a contact wire by tilting a pantograph on the opposite direction of the vehicle tilting direction. In this study, we analyzed the aerodynamic characteristic of a developing pantograph on the tilting train and obtained the contact force with catenary by aerodynamic lift force by the aerodynamic analysis. We also performed the numerical analysis for design the device controlling lift force on a pantograph. From the aerodynamic simulation and parameter study for a device to control the lift force, we will suggest the various shape and the optimal shape of it corresponding to a developing tilting pantograph. The Fluent software is used for the calculation of flow profile in this study.

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Study of aerodynamic characteristic for a pantograph for Tilting train eXpress (TTX) (고속 틸팅열차의 틸팅 판토그라프 공력 특성 연구)

  • Ko T. H.;Kim G. N.;Goo D. H.
    • 한국전산유체공학회:학술대회논문집
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    • pp.177-180
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    • 2004
  • The development of a tilting train with construction of electric line on the conventional railway is required for speed-up on the conventional railway with many curving sections. For development of tilting train, the study and development of the tilting system and tilting bogie having the different mechanism with a general high speed train will play a main role for improving the technology in the field of Korean railway The study and development of the pantograph tilting mechanism in order to keep a good contact behavior between a pantograph and a contact wire by tilting a pantograph on the opposite direction of the vehicle tilting direction. In this study, we analyzed the aerodynamic characteristic of a developing pantograph on the tilting train and obtained the contact force with catenary by aerodynamic lift force by the aerodynamic analysis. We also performed the numerical analysis for design the device controlling lift force on a pantograph. From the aerodynamic simulation and parameter study for a device to control the lift force, we will suggest the various shape and the optimal shape of it corresponding to a developing tilting pantograph. The Fluent software is used for the calculation of flow profile in this study.

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The Aerodynamic Analysis of Pantograph of the Next Generation High Speed Train (차세대 고속철도 판토그래프의 공력특성 해석)

  • Kang, H.M.;Kim, C.W.;Cho, T.H.;Yoon, S.H.;Kwon, H.B.;Park, C.S.
    • 한국전산유체공학회:학술대회논문집
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    • pp.362-367
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    • 2011
  • The aerodynamic performance of the pantograph of the next generation high sped train is analyzed. The calculation of the flow around pantograph is carried cut by FLUENT; by the steady state flow calculation with ${\kappa}-{\omega}$ SST turbulence model, the lift force of the pantograph is computed. For the verification of the numerical schemes am grid systems, flow calculations are performed with the pantograph shape which was used at the experiments performed at Railway Technical Research Institute (RTRI) in Japan. Then, the difference of lift force between numerical am experimental results is about 10%. Therefore, selected numerical schemes and the current grid system is adequate for the analysis am prediction of the aerodynamic performance of panthograph system. Based on these numerical schemes am grid system, the flow around pantograph of the next generation high sped train is calculated and the lift force of the pantograph is predicted; the lift force of the pantograph is about 146N.

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Behavior of a Heavy Particle in the Shear Flow Near a Flat Wall (벽 근처 전단 유동 내의 입자의 운동)

  • Jeong Jae-Dal;Cho Seong-Gee;Lee Chang-Hoon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.30 no.8
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    • pp.806-817
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    • 2006
  • The motion of a small rigid particle in the shear flow near a stationary flat wall is investigated in the context of Stokes flow. The lift force proposed by Saffman and later modified by Mclaughlin and Mei is considered in the prediction of the particle motion far away from the wall. Later, the expression of the lift force is modified to take into account the effect of wall. In the analysis, gravity, lift and drag acting on a small rigid particle near the wall are taken into account. Both analytical and numerical results for the terminal velocities, distances from the wall and trajectories of the particle are presented. In addition, we extended the present analysis to turbulent near-wall flow in the vicinity of the wall.

A Design of Optimal Controller with Friction Reduction of Linear Motor-based Transfer System via Lift-force Control

  • Seo, Jung-Hyun;Lee, Jin-Woo;Lee, Kwon-Soon
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • v.1
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    • pp.205-209
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    • 2006
  • A linear motor based transfer vehicle is significantly focused as transportation systems in marine terminals for the future. We propose a control method for the systems to hence mass reduction and propulsion effects at a starting point by using a lift-force mechanism. This method is newly based on a combined levitation-and-propulsion power by a lift and thrust force of a permanent magnet linear synchronous motor (PMLSM), which is carried out by a decoupled control. We exam that our proposed control largely compensates the vehicle weight, reduces friction effect of the system, and increases its velocity. Consequently, this result contributes numerous productivity and economical efficiency for the port systems.

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