• Title/Summary/Keyword: Lift Generation

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The Design Optimization of a Flow Control Fin Using CFD (CFD를 이용한 유동제어 핀의 최적설계)

  • Wie, Da-Eol;Kim, Dong-Joon
    • Journal of the Society of Naval Architects of Korea
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    • v.49 no.2
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    • pp.174-181
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    • 2012
  • In this paper, the Flow Control Fin(FCF) optimization has been carried out using computational fluid dynamics(CFD) techniques. This study focused on evaluation for the performance of the FCF attached in the stern part of the ship. The main advantage of FCF is to enhance the resistance performance through the lift generation with a forward force component on the foil section, and the propulsive performance by the uniformity of velocity distribution on the propeller plane. This study intended to evaluate these functions and to find optimized FCF form for minimizing viscous resistance and equalizing wake distribution. Four parameters of FCF are used in the study, which were angle and position of FCF, longitudinal location, transverse location, and span length in the optimization process. KRISO 300K VLCC2(KVLCC2) was chosen for an example ship to demonstrate FCF for optimization. The optimization procedure utilized genetic algorithms (GAs), a gradient-based optimizer for the refinement of the solution, and Non-dominated Sorting GA-II(NSGA-II) for Multiobjective Optimization. The results showed that the optimized FCF could enhance the uniformity of wake distribution at the expense of viscous resistance.

Cavitating Flow Characteristics around a 2-Dimensional Hydrofoil Section (2차원 날개 단면 주위의 캐비테이팅 유동 특성 연구)

  • Choi, Jung-Eun;Chung, Seok-Ho;Lee, Dong-Hyun
    • Journal of the Society of Naval Architects of Korea
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    • v.44 no.2 s.152
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    • pp.74-82
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    • 2007
  • Recently, the erosion due to cavitation frequently occurs on a horn-type rudder of a high-speed large container carrier. It is necessary to understand the flow characteristics around a rudder in fully wetted and cavitating flow condition, and the process of generation and collapse of cavitation for a rudder design to minimize the cavity-induced erosion. The flow characteristics around a two-dimensional hydrofoil(NACA66) are investigated through the computational method utilizing a viscous flow theory applied to a cavitation model. The computational results from the viscous flow theory are verified by the comparison with the experimental results, and are compared with those from the potential flow theory. The effects of angle of attack, Reynolds number, cavitation number, and thickness ratio on the cavitating flow are also investigated.

Design Optimization of Wake Equalizing Duct Using CFD (CFD를 이용한 Wake Equalizing Duct의 최적설계)

  • Lee, Ho-Sung;Kim, Dong-Joon
    • Journal of Ocean Engineering and Technology
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    • v.25 no.4
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    • pp.42-47
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    • 2011
  • In this paper, wake equalizing duct (WED) form optimization was carried out using computational fluid dynamics (CFD) techniques. A WED is a ring-shaped flow vane with a foil-type cross-section fitted to a hull in front of the upper propeller area. The main advantage of a WED is the power savings resulting from the uniformity of the velocity distribution on the propeller plane, a reduction in the flow separation at the aft-body, and lift generation with a forward force component on the foil section. This paper intends to evaluate these functions and find an optimized WED form for minimizing the viscous resistance and equalizing the wake distribution. In the optimization process, the study uses four WED parameters: the angle of the section, longitudinal location, and angles of the axes for the half rings against the longitudinal and transverse planes of the ship. KRISO 300K VLCC2 (KVLCC2) is chosen as an example ship to demonstrate the WED optimization. The optimization procedure uses genetic algorithms (GAs), a gradient-based optimizer for the refinement of the solution, and Non-dominated Sorting GA-II(NSGA-II) for Multiobjective Optimization. The results show that the optimized WED can reduce the viscous resistance at the expense of the uniformity of the wake distribution.

Design of 2-Dimensional WIG Section by a Nonlinear Optimization Method (비선형 최적화 기법을 이용한 2차원 지면효과익의 형상설계)

  • Hee-Jung Kim;Ho-Hwan Chun
    • Journal of the Society of Naval Architects of Korea
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    • v.36 no.3
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    • pp.50-59
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    • 1999
  • This paper is concerned on the generation of an optimal section of wing in ground effect by a SQP method which is one of nonlinear optimization techniques. A potential panel method is used for the flow analysis and the ground effect is taken into account by an image method. The numerical method is first verified by an inverse problem where a shape of wing section is sought for the prescribed pressure distribution. The purpose of the present paper is to generate a wing section which can give a maximum lift subjected to the design constraints including the height stability which is important in the WIG design. The effect of the tail wing is also included.

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Experimental Studies on Aerodynamic Characteristics of Pantograph system for HEMU-400X (차세대 고속열차(HEMU-400X)의 팬터그래프 시스템에 대한 공력특성 연구)

  • Lee, Yeong-Bin;Rho, Joo-Hyun;Kwak, Min-Ho;Lee, Jae-Ho;Kim, Kyu-Hong;Lee, Dong-Ho
    • Proceedings of the KSR Conference
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    • 2010.06a
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    • pp.133-138
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    • 2010
  • This paper describes on aerodynamic characteristics of pantograph system for Next generation high speed train(HEMU-400). The pantograph which supports electric power is located on the roof. Because of this, it generate high drag, severe acoustic noise and vibration which induced unstable flow due to complex configuration. Therefore, the design of high efficient pantograph needs to increase operational speed. In this research, wind tunnel tests were performed to design a high efficient pantograph system using 1/4 scaled model which were KTX-II pantograph, single arm pantograph and periscope type pantograph with square cylinder shape panhead and optimized shape panhead. For real operational condition, flow directions were adapted by rotation of pantograph. From this results of wind tunnel, it is checked that the pantograph with optimized panhead and single arm type or periscope type has better aerodynamic performance. In addition, lift control device and spoiler in pantograph were tested to investigate the validity of application.

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Unsteady Aerodynamic characteristics at High Angle of Attack around Two Dimensional NACA0012 Airfoil (고 받음각 2차원 NACA0012 에어포일 주위의 비정상 공기역학적 특성)

  • Yoo, Jae-Kyeong;Kim, Jae-Soo
    • 한국전산유체공학회:학술대회논문집
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    • 2011.05a
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    • pp.414-419
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    • 2011
  • Missile am fighter aircraft have been challenged by low restoring nose-down pitching moment at high angle of attach. The consequence of weak nose-down pitching moment can be resulting in a deep stall condition. Especially, the pressure oscillation has a huge effect on noise generation, structure damage, aerodynamic performance and safety, because the flow has strong unsteadiness at high angle of attack. In this paper, the unsteady aerodynamics coefficients were analyzed at high angle of attack up to 60 degrees around two dimensional NACA0012 airfoil. The two dimensional unsteady compressible Navier-Stokes equation with a LES turbulent model was calculated by OHOC (Optimized High-Order Compact) scheme. The flow conditions are Mach number of 0.3 and Reynolds number of $10^5$. The lift, drag, pressure distribution, etc. are analyzed according to the angle of attack. The results at a low angle of attack are compared with other results before a stall condition. From a certain high angle of attack, the strong vortex formed by the leading edge are flowing downstream as like Karman vortex around a circular cylinder. Unsteady velocity field, periodic vortex shedding, the unsteady pressure distribution on the airfoil surface, and the acoustic fields are analyzed. The effects of these unsteady characteristics in the aerodynamic coefficients are analyzed.

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A Physical-based Particle Method for Small Scale Feature in Multi-phase Fluid Simulation (다상 유체 시뮬레이션에서 격자 크기 이하의 미세한 특징 표현을 위한 물리기반 입자 기법)

  • Lee, Ho-Young;Hong, Jeong-Mo;Kim, Chang-Hun
    • Journal of Korea Multimedia Society
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    • v.12 no.3
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    • pp.445-450
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    • 2009
  • This paper presents a multi-phase fluid simulation that realistically represents small scale details. We achieve this by creating escaped particles based on physical methods. Escaped particles are the remained particles after correcting levelset. Generation of escaped particles in this paper differs from previous works; this fluid simulation is extended by adding lift force and drag force to positive escaped particles. And negative escaped particles represent droplet or splash effect; when they are merged into the negative levelset value, they affect the nodes' velocity (two-way coupling). This simulation that uses positive and negative escaped particles deals with detailed fluid motions dynamically in small scale.

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An Effect of Roof-Fairing and Deflector System on the Reduction of Aerodynamic Drag of a Heavy-Duty Truck (대형트럭용 루프 훼어링과 디프렉트의 공기저항력 저감 특성에 관한 연구)

  • Kim, Chul-Ho
    • Transactions of the Korean Society of Automotive Engineers
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    • v.14 no.2
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    • pp.194-201
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    • 2006
  • Roof-fairing and deflector system have been used on heavy-duty trucks to minimize aerodynamic drag force not only for driving stability of the truck but also for energy saving by reducing the required driving power of the vehicle. In this study, a numerical simulation was carried out to see aerodynamic effect of the drag reducing device on the model vehicle. Drag and lift force generated on the five different models of the drag reducing system were calculated and compared them each other to see which type of device is efficient on the reduction of driving power of the vehicles quantitatively. An experiment has been done to see airflow characteristics on the model vehicles. Airflow patterns around the model vehicles were visualized by smoke generation method to compare the complexity of airflow around drag reducing device. From the results, the deflector systems(Model 5,6) were revealed as a better device for reduction of aerodynamic drag than the roof-fairing systems(Model 2,3,4) on the heavy-duty truck and it can be expected that over 10% of brake power of an engine can be saved on a tractor-trailer by the aerodynamic drag reducing device at normal speed range($80km/h{\sim}$).

Numerical Analysis of the Unsteady Subsonic Flow around a Plunging Airfoil

  • Lee, Kyungwhan;Kim, Jaesoo
    • International Journal of Aeronautical and Space Sciences
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    • v.14 no.3
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    • pp.201-209
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    • 2013
  • Much numerical and experimental research has been done for the flow around an oscillating airfoil. The main research topics are vortex shedding, dynamic stall phenomenon, MAV's lift and thrust generation. Until now, researches mainly have been concentrated on analyzing the wake flow for the variation of frequency and amplitude at a low angle of attack. In this study, wake structures and acoustic wave propagation characteristics were studied for a plunging airfoil at high angle of attack. The governing equations are the Navier-Stokes equation with LES turbulence model. OHOC (Optimized High-Order Compact) scheme and 4th order Runge-Kutta method were used. The Mach number is 0.3, the Reynolds number is, and the angle of attack is from $20^{\circ}$ to $50^{\circ}$. The plunging frequency and the amplitude are from 0.05 to 0.15, and from 0.1 to 0.2, respectively. Due to the high resolution numerical method, wake vortex shedding and pressure wave propagation process, as well as the propagation characteristics of acoustic waves can be simulated. The results of frequency analysis show that the flow has the mixed characteristics of the forced plunging frequency and the vortex shedding frequency at high angle of attack.

Sanguinarine Increases Sensitivity of Human Gastric Adenocarcinoma Cells to TRAIL-mediated Apoptosis by Inducing DR5 Expression and ROS Generation (AGS 인체 위암세포에서 DR5의 발현 및 ROS 생성의 증가를 통한 sanguinarine과 TRAIL 혼합처리의 apoptosis 유도 활성 촉진)

  • Lee, Taek Ju;Im, Yong Gyun;Choi, Woo Young;Choi, Sung Hyun;Hwang, Won Deok;Choi, Yung Hyun
    • Journal of Life Science
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    • v.24 no.9
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    • pp.927-934
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    • 2014
  • Sanguinarine, a benzophenanthridine alkaloid originally derived from the root of Sanguinaria canadensis, has been shown to possess antimicrobial, antioxidant, and anti-cancer properties. Although tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is known to induce apoptosis in cancer cells, but not most normal cells and has shown efficacy in a phase 2 clinical trial, development of resistance to TRAIL by tumor cells is a major roadblock. Our previous study indicated that treatment with TRAIL in combination with subtoxic concentrations of sanguinarine sensitized TRAIL-mediated apoptosis in TRAIL-resistant human gastric carcinoma AGS cells; however, the detailed mechanisms are not fully understood. In this study, we show that sanguinarine sensitizes AGS cells to TRAIL-mediated apoptosis as detected by MTT assay, agarose gel electrophoresis, chromatin condensation and flow cytometry analysis. Combined treatment with sanguinarine and TRAIL effectively induced expression of death receptor (DR) 5 but did not affect expression of DR4 and mitogen activated protein kinases signaling molecules. Moreover, the combined treatment with sanguinarine and TRAIL increased the generation of reactive oxygen species (ROS); however, N-acetylcysteine, ROS scavenger, significantly recovered growth inhibition induced by the combined treatment. Taken together, our results indicate that sanguinarine can potentiate TRAIL-mediated apoptosis through upregulation of DR5 expression and ROS generation.