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Influences of aerodynamic loads on hunting stability of high-speed railway vehicles and parameter studies

Acta Mechanica Sinica 2014年第6期30卷 889-900页

作者： Xiao-Hui Zeng Han Wu Jiang Lai Hong-Zhi Sheng Key Laboratory for Mechanics in Fluid Solid Coupling Systems Institute of Mechanics Chinese Academy of Sciences

The influences of steady aerodynamic loads on hunting stability of high-speed railway vehicles were investigated in this study.A mechanism is suggested to explain the change of hunting behavior due to actions of aerodynamic loads：the aerodynamic loads can change the position of vehicle system（consequently the contact relations）,the wheel/rail normal contact forces,the gravitational restoring forces/moments and the creep forces/moments.A mathematical model for hunting stability incorporating such influences was developed.A computer program capable of incorporating the effects of aerodynamic loads based on the model was written,and the critical speeds were calculated using this *** dependences of linear and nonlinear critical speeds on suspension parameters considering aerodynamic loads were analyzed by using the orthogonal test method,the results were also compared with the situations without aerodynamic *** is shown that the most dominant factors a ff ecting linear and nonlinear critical speeds are different whether the aerodynamic loads considered or *** damping of yaw damper is the most dominant influencing factor for linear critical speeds,while the damping of lateral damper is most dominant for nonlinear *** the influences of aerodynamic loads are considered,the linear critical speeds decrease with the rise of cross wind velocity,whereas it is not the case for the nonlinear critical *** variation trends of critical speeds with suspension parameters can be significantly changed by aerodynamic *** actions of aerodynamic loads and suspension parameters also a ff ect the critical *** effects of such joint action are more obvious for nonlinear critical speeds.

关键词： Hunting stability Linear critical speed Nonlinear critical speed aerodynamic loads Suspension parameters Orthogonal experimental design

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Characteristic aerodynamic loads and Load Effects on the Dynamics of a Floating Vertical Axis Wind Turbine

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Transactions of Tianjin University 2017年第6期23卷 555-561页

作者： Zhengshun Cheng Puyang Zhang Department of Marine Technology CeSOS and AMOSNorwegian University of Science and Technology7491 TrondheimNorway State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300072China School of Civil Engineering Tianjin UniversityTianjin 300072China

The development of offshore wind farms in deep water favors floating wind turbine designs, but floating horizontal axis wind turbines are facing the challenge of high cost of energy (CoE). The development of innovative designs to reduce the CoE is thus desirable, such as floating vertical axis wind turbines (VAWTs). This study demonstrates the characteristics of aerodynamic loads and load effects of a two-bladed floating VAWT supported by a semi-submersible platform. Fully coupled simulations are performed using the time-domain aero-hydro-servo-elastic code SIMO-RIFLEX-AC. It is found that thrust, lateral force, and aerodynamic torque vary considerably and periodically with the rotor azimuth angle. However, the variation in the generator torque can be alleviated to some extent by the control strategy applied. Moreover, the variations of platform motions and tensions in the mooring lines are strongly influenced by turbulent winds, whereas those of tower-base bending moments are not. The tower-base bending moments exhibit notable two-per-revolution (2P) response characteristics. © 2017 Tianjin University and Springer-Verlag GmbH Germany

关键词： aerodynamic loads aerodynamics Bending moments loads (forces) Mooring cables Offshore wind farms Wind power

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Effects of aspect ratio and inclination angle on aerodynamic loads of a flat plate

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Advances in aerodynamics 2020年第1期2卷 278-300页

作者： Mehrdad Shademan Arash Naghib-Lahouti Institute for Aerospace Studies University of TorontoM3H5T6TorontoOntarioCanada

Large Eddy Simulations are carried out to analyze flow past flat plate in different configurations and inclinations.A thin flat plate is considered at three inclination angles(α=30°,60°and 90°)and three aspect ratios(AR=0.5,2 and 5).The Reynolds number based on the free stream velocity and chord length of the plate at different inclination angles varies between 75,000 to 150,*** increase in the inclination angle while the aspect ratio(span to chord)is constant results in higher drag and lower lift on the *** the aspect ratio at a constant inclination angle increases the mean aerodynamic loading except for theα=30°and AR=0.5 case where the mean forces are larger than the other aspect ratios for this specific inclination *** small aspect ratio suppresses and blocks the separation of the flow from the top and bottom edges causing larger aerodynamic forces relative to AR=2,*** of the flow structures shows the tip vortices have a significant role in controlling the shedding vortices from the top and bottom ***α=30°and AR=0.5,the two tip vortcies control and suppress the flow separation from the top and bottom edges.A stable wake was found for this case with no *** the aspect ratio increases,the influence of the tip vortices on flow separation from the top and bottom edges *** a result,larger fluctuations were found for cases with higher aspect ratios.

关键词： Flat plate Aspect ratio Inclination angle CFD OpenFOAM aerodynamic loads

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Numerical simulation of the aerodynamic characteristics of heavy-duty trucks through viaduct in crosswind

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Journal of Hydrodynamics 2014年第3期26卷 394-399页

作者：胡兴军秦鹏廖磊郭鹏王靖宇杨博 State Key Laboratory of Automobile Simulation and Control Jilin University

In our numerical simulation the hybrid mesh and the SST k-ω turbulence model are adopted to investigate the variations of the aerodynamic loads and the flow field of heavy-duty trucks while crossing a viaduct with 1.1 m high fences in a crosswind at a velocity of 20 m/s. The results show that, with the protection of a fence, the side force is weakened, and the rolling and yaw moments are strengthened while the truck is crossing the viaduct, which relatively reduces the roll-over safety and the driving stability of the truck. Meanwhile, the direction of the side force changes when the truck enters the viaduct, which makes the roll-over safety and the driving stability the lowest during the process.

关键词： computational fluid dynamics heavy-duty truck crosswind cross viaduct aerodynamic loads flow field

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Effects of Avian Wings Color Patterns on Their Flight Performance:Experimental and Computational Studies

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Journal of Bionic Engineering 2023年第2期20卷 683-710页

作者： Ahmed Aboelezz Brenden Herkenhoff Mostafa Hassanalian Department of Mechanical Engineering New Mexico Institute of Mining and TechnologySocorroNM87801USA

There are many theories behind the colors of a bird’s *** of these theories point to the color’s purpose to attract mates and hide from *** recent investigations concluded that the dark colors of birds help in reducing the drag force during flight.A new theory is presented in the current research,which states that a bird's dark color not only reduces the drag,but the color pattern also improves the overall flight performance,and each color pattern has a different type of flight performance *** difference in improvement is a result of variation in hot and cold surfaces on the bird skin as a result of the variation between light and dark feather *** prove this new theory,thermal images were captured of real bird wings under the effect of infrared ***,a novel wind tunnel wing with the ability to adjust the temperature in desired locations and patterns on the wing’s surface was manufactured and tested to evaluate the effect of aerodynamics forces as a function in the surface temperature and the hot–cold *** collected data from this wing showed potential flight efficiency improvements of 20%,comparing the lift-to-drag ratio for specific heating cases,which could increase the flight *** considering lift and drag,there were specific heating cases with corresponding angles of attack in which these parameters improved by up to 20%and 7%,*** heating cases could increase the lift at a low angle of attack,which is helpful in cruise flight performance,while some cases could increase the maximum lift coefficient by 6%.This is very helpful in lowering stall and the minimum flight ***,some cases could increase the lift-to-drag ratio,which led to an increase in the flight *** better understand the effect of the various patterns,computational fluid dynamics(CFD)simulations were conducted on the *** new theory was proved based on the CFD results and verified through the success

关键词： aerodynamic loads CFD Drag Heated boundary layer Surface temperature

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Design concepts of an aircraft wing： composite and morphing airfoil with auxetic structures

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Frontiers of Structural and Civil Engineering 2016年第4期10卷 394-408页

作者： P R BUDARAPU Sudhir Sastry Y B R NATARAJAN Department of Aerospace Engineering Indian Institute of Science Bangalore 560 012 India Department of Aeronautical Engineering College of Engineering Defence University Ethiopia Department of Aeronautical Engineering Institute of Aeronautical Engineering Hyderabad India

This paper is categorized into two parts. （1） A frame work to design the aircraft wing structure and （2） analysis ofa morphing airfoil with auxetic structure. The developed design frame work in the first part is used to arrive at the sizes of the various components of an aircraft wing structure. The strength based design is adopted, where the design loads are extracted from the aerodynamic loads. The aerodynamic loads acting on a wing structure are converted to equivalent distributed loads, which are further converted point loads to arrive at the shear forces, bending and twisting moments along the wing span. Based on the estimated shear forces, bending and twisting moments, the strength based design is employed to estimate the sizes of various sections of a composite wing structure. A three dimensional numerical model of the composite wing structure has been developed and analyzed for the extreme load conditions. Glass fiber reinforced plastic material is used in the numerical analysis. The estimated natural frequencies are observed to be in the acceptable limits. Furthermore, the discussed design principles in the first part are extended to the design of a morphing airfoil with auxetic structure. The advantages of the morphing airfoil with auxetic structure are （i） larger displacement with limited straining of the components and （ii） unique deformation characteristics, which produce a theoretical in-plane Poisson＇s ratio of -1. Aluminum Alloy AL6061-T651 is considered in the design of all the structural elements. The compliance characteristics of the airfoil are investigated through a numerical model. The numerical results are observed to be in close agreement with the experimental results in the literature.

关键词： wing design aerodynamic loads morphing airfoil auxetic structures negative Poisson's ratio

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EXPERIMENTAL INVESTIGATION OF aerodynamicINTERACTION EFFECT OF ROTOR WAKE ONFUSELAGE OF HELICOPTER

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Chinese Journal of Aeronautics 2000年第1期13卷 1-7页

作者：徐锦法高正梅卫胜 National Key Laboratory of Rotorcraft Aeromechanics Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

The interaction effect of rotor wake on fuselage of helicopter was investigated with experimental method. The results from experiment have proved that for the drag of fuselage the effect of rotor airflow is closely in connection with both the flight speed and the collective pitch of blades, while for the thrust and pitch moment of fuselage the collective pitch angle of blades plays more important role. A simple and effective computing method about aerodynamic interaction can be derived from the measured data. In order to implement the experiment, a fuselage model, a special sensor, the measurement and data acquisition and processing system were designed and manufactured according to the special requirements of this research project, thereby a good base was built up for carrying out experiments successfully with high quality.

关键词： aerodynamic loads Computational methods Data acquisition Drag Fuselages Helicopter rotors Mathematical models Sensors Wakes

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FINITE ELEMENT ANALYSIS OF THE FLOW INDUCED BY ROTATING BLADES IN AN INCOMPRESSIBLE VISCOUS FLUID

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Journal of Hydrodynamics 2002年第2期14卷 36-40页

作者： Wang, Yan-Xing Yang, Guo-Wei Lu, Xi-Yun Zhuang, Li-Xian Dept. of Mech. and Mech. Eng. Univ. of Sci. and Technol. of China Hefei 230026 China

aerodynamic loads on a multi-bladed helicopter rotor in hovering flight were calculated by solving the three-dimensional incompressible Navier-Stokes equations. The rotor wake effects were accounted by the correction of local geometric angle of attack according to a free-wake modeling in addition to an empirical modification for the tip flow effect. The validity and efficiency of the present method were verified by the comparisons between numerical results and experimental data.

关键词： aerodynamic loads Finite element method Helicopter rotors Navier Stokes equations Three dimensional Turbomachine blades Wakes

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Operational Safety Assessment of a High-Speed Train Exposed to the Strong Gust Wind

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Fluid Dynamics & Materials Processing 2020年第1期16卷 55-66页

作者： Mengge Yu Zhenkuan Pan Jiali Liu Haiqing Li Postdoctoral Research Station of System Science College of Automation and Electrical EngineeringQingdao UniversityQingdao266071China College of Mechanical and Electronic Engineering Qingdao UniversityQingdao266071China College of Computer Science&Technology Qingdao UniversityQingdao266071China CRRC Qingdao Sifang Co. Ltd.Qingdao266111China

The operational safety characteristics of trains exposed to a strong wind have caused great concern in recent *** the present paper,the effect of the strong gust wind on a high-speed train is investigated.A typical gust wind model for any wind angle,named“Chinese hat gust wind model”,was first constructed,and an algorithm for computing the aerodynamic loads was elaborated accordingly.A vehicle system dynamic model was then set up in order to investigate the vehicle system dynamic *** assessment of the operational safety has been conducted by means of characteristic wind curves(CWC).As some of the parameters of the wind-train system were difficult to measure,we also investigated the impact of the uncertain system parameters on the *** indicate that,the descending order of the operational safety index of the vehicle for each wind angle is 90°-60°-120°-30°-150°,and the worst condition for the operational safety occurs when the wind angle reaches around 90°.According to our findings,the gust factor and aerodynamic side force coefficient have great impact on the critical wind ***,these two parameters require special attention when considering the operational safety of a railway vehicle subjected to strong gust wind.

关键词： Operational safety high-speed train gust wind aerodynamic loads characteristic wind curves

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UNSTEADY TRANSONIC aerodynamic LOADINGS ON THE AIRFOIL CAUSED BY HEAVING, PITCHING OSCILLATIONS AND CONTROL SURFACE

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Applied Mathematics and Mechanics(English Edition) 1992年第9期13卷 805-813页

作者：高正红 Northwestern Polytechnical University Xi'an

An implicit upwind finite volume solver for the Euler equations using the improved flux - splitting method is established and used to calculate the transonic flow past the airfoils with heaving, pitching oscillations and the control surface. Results are given for the NACA64A - 10 airfoil which is in harmonic heaving and pitching oscillation and with the control surface in the transonic flow field. Some computational results are compared with the experiment data and the good agreements are shown in the paper.

关键词： aerodynamic loads Eigenvalues and eigenfunctions Finite element method Mathematical models Mathematical transformations Matrix algebra Oscillations Transonic aerodynamics Unsteady flow

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