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1
Xie, Dan, Min Xu, Honghua Dai i Tao Chen. "New Look at Nonlinear Aerodynamics in Analysis of Hypersonic Panel Flutter". Mathematical Problems in Engineering 2017 (2017): 1–13. http://dx.doi.org/10.1155/2017/6707092.
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A simply supported plate fluttering in hypersonic flow is investigated considering both the airflow and structural nonlinearities. Third-order piston theory is used for nonlinear aerodynamic loading, and von Karman plate theory is used for modeling the nonlinear strain-displacement relation. The Galerkin method is applied to project the partial differential governing equations (PDEs) into a set of ordinary differential equations (ODEs) in time, which is then solved by numerical integration method. In observation of limit cycle oscillations (LCO) and evolution of dynamic behaviors, nonlinear aerodynamic loading produces a smaller positive deflection peak and more complex bifurcation diagrams compared with linear aerodynamics. Moreover, a LCO obtained with the linear aerodynamics is mostly a nonsimple harmonic motion but when the aerodynamic nonlinearity is considered more complex motions are obtained, which is important in the evaluation of fatigue life. The parameters of Mach number, dynamic pressure, and in-plane thermal stresses all affect the aerodynamic nonlinearity. For a specific Mach number, there is a critical dynamic pressure beyond which the aerodynamic nonlinearity has to be considered. For a higher temperature, a lower critical dynamic pressure is required. Each nonlinear aerodynamic term in the full third-order piston theory is evaluated, based on which the nonlinear aerodynamic formulation has been simplified.
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Zhang, Cheng Chun, Wen Qiang Wang, Lei Shi, Jing Wang i Lu Quan Ren. "Experimental and Numerical Study on Aerodynamic Noise Reduction of Cylindrical Rod with Bionic Wavy Surface". Applied Mechanics and Materials 461 (listopad 2013): 690–701. http://dx.doi.org/10.4028/www.scientific.net/amm.461.690.
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Inspired by the non-smooth structure of the leading edge of owls wing,a bionic wavy cylindrical surface is proposed in this paper to reduce the aerodynamic noise of a cylindrical rod. The effects of bionic wavy surface on the aerodynamic and aeroacoustic performance of the cylinder are investigated by wind tunnel and numerical simulation. The fluctuating pressure of the smooth cylinder and the bionic wavy surface cylinder are tested by pulsating pressure sensors in FD-09 low speed wind tunnel of China Aerospace Aerodynamics Research Institute. The fluctuating pressure of the bionic wavy surface cylinder is significantly lower than that of the smooth cylinder. We used the software ANSYS FLUENT to research the effect of the bionic wavy surface on the aerodynamic characteristics and aerodynamic noise of a cylinder by the Large Eddy Simulation (LES) and the Ffowcs Williams and Hawkings (FW-H) equation. Compared with the smooth cylinder, the aerodynamic noise of the bionic wavy cylinder is reduced by 6.7dB. A study of the relationship between the fluctuating lift and the aerodynamic noise size is conducted. We found that the sound pressure level of the wavy surface cylinder is significantly lower when the lift fluctuation amplitude decreased. Bionic wavy surface can effectively restrain the separated shear layer transition to turbulence. The frequency of vortex shedding which causes the lift fluctuations is reduced, so the aerodynamic noise of the circular cylinder is reduced. Keywords: bionics, cylindrical rod, wavy surface, aerodynamic noise, flow control
3
Sun, Xiaoqi, i Han Xiao. "Numerical Modeling and Investigation on Aerodynamic Noise Characteristics of Pantographs in High-Speed Trains". Complexity 2018 (2018): 1–12. http://dx.doi.org/10.1155/2018/6932596.
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Pantographs are important devices on high-speed trains. When a train runs at a high speed, concave and convex parts of the train cause serious airflow disturbances and result in flow separation, eddy shedding, and breakdown. A strong fluctuation pressure field will be caused and transformed into aerodynamic noises. When high-speed trains reach 300 km/h, aerodynamic noises become the main noise source. Aerodynamic noises of pantographs occupy a large proportion in far-field aerodynamic noises of the whole train. Therefore, the problem of aerodynamic noises for pantographs is outstanding among many aerodynamics problems. This paper applies Detached Eddy Simulation (DES) to conducting numerical simulations of flow fields around pantographs of high-speed trains which run in the open air. Time-domain characteristics, frequency-domain characteristics, and unsteady flow fields of aerodynamic noises for pantographs are obtained. The acoustic boundary element method is used to study noise radiation characteristics of pantographs. Results indicate that eddies with different rotation directions and different scales are in regions such as pantograph heads, hinge joints, bottom frames, and insulators, while larger eddies are on pantograph heads and bottom frames. These eddies affect fluctuation pressures of pantographs to form aerodynamic noise sources. Slide plates, pantograph heads, balance rods, insulators, bottom frames, and push rods are the main aerodynamic noise source of pantographs. Radiated energies of pantographs are mainly in mid-frequency and high-frequency bands. In high-frequency bands, the far-field aerodynamic noise of pantographs is mainly contributed by the pantograph head. Single-frequency noises are in the far-field aerodynamic noise of pantographs, where main frequencies are 293 Hz, 586 Hz, 880 Hz, and 1173 Hz. The farther the observed point is from the noise source, the faster the sound pressure attenuation will be. When the distance of two adjacent observed points is increased by double, the attenuation amplitude of sound pressure levels for pantographs is around 6.6 dB.
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Mordasov, M. M., A. P. Savenkov i K. E. Chechetov. "Aerodynamic measurement of surface pressure". Izmeritel`naya Tekhnika, nr 5 (2018): 50–55. http://dx.doi.org/10.32446/0368-1025it.2018-5-50-55.
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Kozmar, Hrvoje, i Boris Laschka. "Pressure tap cavity for unsteady aerodynamic pressure measurements". Measurement 132 (styczeń 2019): 282–91. http://dx.doi.org/10.1016/j.measurement.2018.09.056.
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Zhang, Ying Chao, Zhe Zhang, Shuang Hu Luo i Jian Hua Tian. "Aerodynamic Numerical Simulation in the Process of Car Styling". Applied Mechanics and Materials 16-19 (październik 2009): 862–65. http://dx.doi.org/10.4028/www.scientific.net/amm.16-19.862.
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With the development of automotive industry of China, more and more new cars are brought out. Then more and more stylists and engineers will take part in car styling to design new car. In the process of car styling, Car aerodynamics is important to its performance. Especially for more excellent handling and stability performance, more aerodynamic analysis and optimization should been done. At first it was introduced that the process of car styling in this paper. The functions of aerodynamics in the process were indicated. Secondly some ways of aerodynamic analysis were put forward. The first one is wind tunnel test and the second one called virtual wind tunnel test. The virtual wind tunnel test is one of the best modern ways of aerodynamic design which apply in the fields of aerodynamic research widely. It was based on computational fluid dynamics. The details of the virtual wind tunnel test simulation were narrated in this paper. Applying the virtual wind tunnel test aerodynamic drag coefficient, velocity contour and pressure distribution were got. Some advices to reduce aerodynamic drag of the design car were put forward. In one word, it is one simple, effective, convenient and fast way for aerodynamic design in car styling process using virtual wind tunnel test.
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Ben Mosbah, A., R. M. Botez i T. M. Dao. "New methodology combining neural network and extended great deluge algorithms for the ATR-42 wing aerodynamics analysis". Aeronautical Journal 120, nr 1229 (27.05.2016): 1049–80. http://dx.doi.org/10.1017/aer.2016.46.
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ABSTRACTThe fast determination of aerodynamic parameters such as pressure distributions, lift, drag and moment coefficients from the known airflow conditions (angles of attack, Mach and Reynolds numbers) in real time is still not easily achievable by numerical analysis methods in aerodynamics and aeroelasticity. A flight parameters control system is proposed to solve this problem. This control system is based on new optimisation methodologies using Neural Networks (NNs) and Extended Great Deluge (EGD) algorithms. Validation of these new methodologies is realised by experimental tests using a wing model installed in a wind tunnel and three different transducer systems (a FlowKinetics transducer, an AEROLAB PTA transducer and multitube manometer tubes) to determine the pressure distribution. For lift, drag and moment coefficients, the results of our approach are compared to the XFoil aerodynamics software and the experimental results for different angles of attack and Mach numbers. The main purpose of this new proposed control system is to improve, in this paper, wing aerodynamic performance, and in future to apply it to improve aircraft aerodynamic performance.
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Musa, Mohamad Nor, Samion Syahrullail i Fairuz Zainal Abidin. "Aerodynamic Analysis on Proton Preve by Experimental". Applied Mechanics and Materials 773-774 (lipiec 2015): 575–79. http://dx.doi.org/10.4028/www.scientific.net/amm.773-774.575.
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The purpose of this study is to determine the coefficient drag, CD of the Proton PREVẾ by experimental method using Low Speed Wind Tunnel. All the relevant data are collected through the literature reviews from books and journals. First, the basic thing in aerodynamic is studied. There are two things are concern when studies aerodynamics. They were air flow and vehicle shape which we regard as aerodynamics factor that determine aerodynamic of the vehicle. Fundamental of air flow and vehicle shape is reviewed includes the relationship between air speed with pressure, boundary layer, Reynolds number, drag, lift drag and shape optimization. Wind tunnel is also studied before the experiment. Five selected speed were been tasted during the experiment to determine the CD value.
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Schreck, S., i M. Robinson. "Boundary Layer State and Flow Field Structure Underlying Rotational Augmentation of Blade Aerodynamic Response". Journal of Solar Energy Engineering 125, nr 4 (1.11.2003): 448–56. http://dx.doi.org/10.1115/1.1624087.
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Blade rotation routinely and significantly augments aerodynamic forces during zero yaw horizontal axis wind turbine (HAWT) operation. To better understand the flow physics underlying this phenomenon, time dependent blade surface pressure data were acquired from the National Renewable Energy Laboratory (NREL). Unsteady Aerodynamics Experiment (UAE), a full-scale HAWT tested in the NASA Ames 80-by-120-foot wind tunnel. Time records of surface pressures and normal force were processed to obtain means and standard deviations. Surface pressure means and standard deviations were analyzed to identify boundary layer separation and shear layer impingement locations. Separation and impingement kinematics were then correlated with normal force behavior. Results showed that rotational augmentation was linked to specific separation and impingement behaviors, and to associated three-dimensionality in surface pressure distributions.
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Sun, Xiao-Ying, Tian-E. Li, Guo-Chang Lin i Yue Wu. "A study on the aerodynamic characteristics of a stratospheric airship in its entire flight envelope". Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 232, nr 5 (2.08.2017): 902–21. http://dx.doi.org/10.1177/0954410017723358.
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Aerodynamic characteristics of a stratospheric airship in its entire flight envelope, including take-off, ascending, cruising, descending, and landing, is an important part of its research topic. In this paper, experiments of wind pressure measurement on a 1/30-scale stratospheric airship model were carried out to obtain a better assessment of the aerodynamic characteristics during the cruising process. Based on the wind pressure distribution, the effects of pitch angle, yaw angle, and combined angles (pitch angle and yaw angle acted simultaneously) on the aerodynamics of the airship were analyzed. In addition, the contributions of different portions of the airship hull (namely head, middle, and tail) to the aerodynamic forces and moments were discussed. The experimental results imply that the tail portion is the main contributor to pressure drag force. The combined angles significantly increase aerodynamic forces and rolling moment, and the rolling moment produced by the middle portion accounts for the major proportion. Secondly, the computational fluid dynamics method was verified and employed to study the aerodynamic characteristics of the full-scale model in its entire flight envelope based on the decision of the wind environment parameters and attitude. As a main result, it can be concluded that, more attention should be paid to the airship when it is located in the troposphere and near the ground with an inclined take-off angle.
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Zhao, Liang, Qingfeng Huang, Xinyan Deng i Sanjay P. Sane. "Aerodynamic effects of flexibility in flapping wings". Journal of The Royal Society Interface 7, nr 44 (19.08.2009): 485–97. http://dx.doi.org/10.1098/rsif.2009.0200.
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Recent work on the aerodynamics of flapping flight reveals fundamental differences in the mechanisms of aerodynamic force generation between fixed and flapping wings. When fixed wings translate at high angles of attack, they periodically generate and shed leading and trailing edge vortices as reflected in their fluctuating aerodynamic force traces and associated flow visualization. In contrast, wings flapping at high angles of attack generate stable leading edge vorticity, which persists throughout the duration of the stroke and enhances mean aerodynamic forces. Here, we show that aerodynamic forces can be controlled by altering the trailing edge flexibility of a flapping wing. We used a dynamically scaled mechanical model of flapping flight ( Re ≈ 2000) to measure the aerodynamic forces on flapping wings of variable flexural stiffness (EI). For low to medium angles of attack, as flexibility of the wing increases, its ability to generate aerodynamic forces decreases monotonically but its lift-to-drag ratios remain approximately constant. The instantaneous force traces reveal no major differences in the underlying modes of force generation for flexible and rigid wings, but the magnitude of force, the angle of net force vector and centre of pressure all vary systematically with wing flexibility. Even a rudimentary framework of wing veins is sufficient to restore the ability of flexible wings to generate forces at near-rigid values. Thus, the magnitude of force generation can be controlled by modulating the trailing edge flexibility and thereby controlling the magnitude of the leading edge vorticity. To characterize this, we have generated a detailed database of aerodynamic forces as a function of several variables including material properties, kinematics, aerodynamic forces and centre of pressure, which can also be used to help validate computational models of aeroelastic flapping wings. These experiments will also be useful for wing design for small robotic insects and, to a limited extent, in understanding the aerodynamics of flapping insect wings.
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Shi, Lei, Wen Qiang Wang, Cheng Chun Zhang, Jing Wang i Lu Quan Ren. "The Effect of Bionic V-Ring Surface on the Aerodynamic Noise of a Circular Cylinder". Applied Mechanics and Materials 461 (listopad 2013): 751–62. http://dx.doi.org/10.4028/www.scientific.net/amm.461.751.
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Inspired by stripe shaped structure of owl wing feathers, V-ring surface was proposed in this paper to reduce the aerodynamic noise of a circular cylinder. The effects of V-ring surface on the aerodynamic and aeroacoustic performance of the cylinder were investigated by wind tunnel and numerical simulation. We tested the fluctuating pressure of the smooth cylinder and the V-ring surface cylinder by pulsating pressure sensor in FD-09 wind tunnel of China Academy of Aerospace Aerodynamics（CAAA）. At a wind speed of 42m/s, the Reynolds number is 1.62×105based on the cylinder diameter D of 58mm. The test results showed that the overall fluctuating pressure on the measurement points of the V-ring surface cylinder was significantly decreased compared with the smooth cylinder. The mechanisms of aerodynamic noise control of circular cylinder by V-ring surface were studied by the Large Eddy Simulation（LES）and the Ffowcs Williams and Hawkings （FW-H） equation. The numerical simulation results showed that the aerodynamic noise of the V-ring surface cylinder was reduced by 4.1dB compared to the smooth cylinder. The sound pressure of V-ring surface cylinder model is reduced when the lift fluctuation becomes lower. The V-ring surface is capable of reducing the frequency of the vortex shedding and controlling the fluctuating lift force induced by unstable vortices acting on the cylinder surface.
13
Moreno-Pacheco, Luis A., G. E. Valle-Meléndez, Claudia del Carmen Gutiérrez Torres, J. A. Jiménez-Bernal i M. Toledo-Velázquez. "Influence of the Alignment of Two Airfoils in the Losses Generation". Applied Mechanics and Materials 15 (sierpień 2009): 27–32. http://dx.doi.org/10.4028/www.scientific.net/amm.15.27.
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A numerical simulation of a flow passing throw two NACA 0012 airfoils is presented in this paper. Aerodynamics, drag forces, and pressure drop is quantified when both profiles are axially aligned and then when one of them is vertically displaced. NUMECA code and Spalart-Allmaras turbulence model were used for this purpose. The results showed that aerodynamic losses are present in both profiles, meaning that the presence of the back profile plays an important role in the aerodynamic behavior of the frontal profile.
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Morris, M. J., J. F. Donovan, J. T. Kegelman, S. D. Schwab, R. L. Levy i R. C. Crites. "Aerodynamic applications of pressure sensitive paint". AIAA Journal 31, nr 3 (marzec 1993): 419–25. http://dx.doi.org/10.2514/3.11346.
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Mordasov, M. M., А. P. Savenkov i K. Е. Chechetov. "Aerodynamic Measurements of the Surface Pressure". Measurement Techniques 61, nr 5 (sierpień 2018): 486–93. http://dx.doi.org/10.1007/s11018-018-1456-8.
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McLachlan, B. "Pressure sensitive paints in aerodynamic testing". Experimental Thermal and Fluid Science 7, nr 2 (sierpień 1993): 126. http://dx.doi.org/10.1016/0894-1777(93)90095-z.
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McLachlan, B. G., i J. H. Bell. "Pressure-sensitive paint in aerodynamic testing". Experimental Thermal and Fluid Science 10, nr 4 (maj 1995): 470–85. http://dx.doi.org/10.1016/0894-1777(94)00123-p.
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Xiang, Jinwu, Kai Liu, Daochun Li, Chunxiao Cheng i Enlai Sha. "Unsteady aerodynamic characteristics of a morphing wing". Aircraft Engineering and Aerospace Technology 91, nr 1 (7.01.2018): 1–9. http://dx.doi.org/10.1108/aeat-04-2017-0101.
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Purpose The purpose of this paper is to investigate the unsteady aerodynamic characteristics in the deflection process of a morphing wing with flexible trailing edge, which is based on time-accurate solutions. The dynamic effect of deflection process on the aerodynamics of morphing wing was studied. Design/methodology/approach The computational fluid dynamic method and dynamic mesh combined with user-defined functions were used to simulate the continuous morphing of the flexible trailing edge. The steady aerodynamic characteristics of the morphing deflection and the conventional deflection were studied first. Then, the unsteady aerodynamic characteristics of the morphing wing were investigated as the trailing edge deflects at different rates. Findings The numerical results show that the transient lift coefficient in the deflection process is higher than that of the static case one in large angle of attack. The larger the deflection frequency is, the higher the transient lift coefficient will become. However, the situations are contrary in a small angle of attack. The periodic morphing of the trailing edge with small amplitude and high frequency can increase the lift coefficient after the stall angle. Practical implications The investigation can afford accurate aerodynamic information for the design of aircraft with the morphing wing technology, which has significant advantages in aerodynamic efficiency and control performance. Originality/value The dynamic effects of the deflection process of the morphing trailing edge on aerodynamics were studied. Furthermore, time-accurate solutions can fully explore the unsteady aerodynamics and pressure distribution of the morphing wing.
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Manwaring, S. R., i S. Fleeter. "Inlet Distortion Generated Periodic Aerodynamic Rotor Response". Journal of Turbomachinery 112, nr 2 (1.04.1990): 298–307. http://dx.doi.org/10.1115/1.2927654.
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Fundamental inlet distortion-generated rotor blade row unsteady aerodynamics, including the effects of both the detailed aerodynamic forcing function for the first time and steady loading are experimentally investigated in an extensively instrumented axial-flow research compressor. A two-per-rev forcing function with three gust amplitude ratios is generated. On the rotor blade pressure surface, the unsteady pressure nondimensionalization compresses the magnitude data with mean flow incidence angle. This is not the case on the higher camber suction surface. These pressure surface unsteady data are primarily affected by the steady loading level, whereas the suction surface unsteady data are a function of the steady loading level and distribution as well as the gust amplitude ratio. In addition, a design inlet distortion blade surface unsteady pressure correlation is considered.
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Gu, Shou Chao, Dong Xu Liu i Yu Fu Wang. "Study of Airship Stability Based on a Low Resistance Profile". Advanced Materials Research 791-793 (wrzesień 2013): 1493–96. http://dx.doi.org/10.4028/www.scientific.net/amr.791-793.1493.
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Numerical simulation was conducted to investigate the external flow around airships with different tail layout, with the help of FLUENT 14.5, based on the incompressible Navier-Stokes equation and SST turbulent model. The aerodynamic information of the airships with different tail layout, such as pressure coefficient, torque coefficient and pressure distribution, were analyzed, and the numerical results showed the details of the airship surface flow and changes with different attack angle. According to the results, different tail layout had important influences on the aerodynamics and stability of airship. This will help to understand the aerodynamic characters around the tails of the stratospheric airship, and provide a reference in choosing tail layouts and the stability design of airships.
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Buffum, D. H., i S. Fleeter. "Effect of Wind Tunnel Acoustic Modes on Linear Oscillating Cascade Aerodynamics". Journal of Turbomachinery 116, nr 3 (1.07.1994): 513–24. http://dx.doi.org/10.1115/1.2929440.
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The aerodynamics of a biconvex airfoil cascade oscillating in torsion is investigated using the unsteady aerodynamic influence coefficient technique. For subsonic flow and reduced frequencies as large as 0.9, airfoil surface unsteady pressures resulting from oscillation of one of the airfoils are measured using flush-mounted high-frequency-response pressure transducers. The influence coefficient data are examined in detail and then used to predict the unsteady aerodynamics of a cascade oscillating at various interblade phase angles. These results are correlated with experimental data obtained in the traveling-wave mode of oscillation and linearized analysis predictions. It is found that the unsteady pressure disturbances created by an oscillating airfoil excite wind tunnel acoustic modes, which have detrimental effects on the experimental results. Acoustic treatment is proposed to rectify this problem.
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Gaetani, Paolo, i Giacomo Persico. "Technology Development of Fast-Response Aerodynamic Pressure Probes". International Journal of Turbomachinery, Propulsion and Power 5, nr 2 (12.04.2020): 6. http://dx.doi.org/10.3390/ijtpp5020006.
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This paper presents and discusses the recent developments on the Fast-Response Aerodynamic Pressure Probe (FRAPP) technology at the Laboratorio di Fluidodinamica delle Macchine (LFM) of the Politecnico di Milano. First, the different geometries developed and tested at LFM are presented and critically discussed: the paper refers to single-sensor or two-sensor probes applied as virtual 2D or 3D probes for phase-resolved measurements. The static calibration of the sensors inserted inside the head of the probes is discussed, also taking into account for the temperature field of application: in this context, a novel calibration procedure is discussed and the new manufacturing process is presented. The dynamic calibration is reconsidered in view of the 15-years’ experience, including the extension to probes operating at different temperature and pressure levels with respect to calibration. As for the probe aerodynamics, the calibration coefficients are discussed and the most reliable set here is evidenced. A novel procedure for the quantification of the measurement uncertainty, recently developed and based on the Montecarlo methodology, is introduced and discussed in the paper.
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Hu, He-xuan, Wan-xin Lei i Ye Zhang. "Complexity Analysis on the Aerodynamic Performance of the Mega High-Speed Train Caused by the Wind Barrier on the Embankment". Complexity 2018 (12.07.2018): 1–17. http://dx.doi.org/10.1155/2018/7130532.
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With the world development of high-speed railways and increasing speeds, aerodynamic forces and moments acting on trains have been increased further, making trains stay at a “floated” state. Under a strong crosswind, the aerodynamic performance of a train on the embankment is greatly deteriorated; lift force and horizontal force borne by trains will be increased quickly; trains may suffer derailing or overturning more easily compared with the flat ground; train derailing will take place when the case is serious. All of these phenomena have brought risks to people’s life and properties. Hence, the paper establishes an aerodynamic model about a high-speed train passing an air barrier, computes aerodynamic forces and moments, and analyzes pulsating pressures on the train surface as well as those of unsteady flow fields around the train. Computational results indicate that when the train passed the embankment air barrier, the head wave of air pressure full wave is more than the tail wave; the absolute value of negative wave is more than that of the positive wave, which is more obvious in the head train. When the train is passing the air barrier, pressure pulsation values at head train points are more than those at other points, while pressure changes most violently at the train bottom, and pressure values close to the air barrier are more than those points far from the air barrier. Pressure values at the cross section 1 were larger than those of other points. Pressure values at measurement points of the tail train ranked the second place, with the maximum negative pressure of 1253 Pa. Pressure change amplitudes and maximum negative pressure on the train surface are increased quickly, while pressure peak values on the high-speed train surface are in direct ratio to the running speed. With the increased speed of the high-speed train, when it is running in the embankment air barrier, the aerodynamic force and moment borne by each train body are increased sharply, while the head train suffers the most obvious influences of aerodynamic effects.
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Mailach, Ronald, Lutz Mu¨ller i Konrad Vogeler. "Rotor-Stator Interactions in a Four-Stage Low-Speed Axial Compressor—Part II: Unsteady Aerodynamic Forces of Rotor and Stator Blades". Journal of Turbomachinery 126, nr 4 (1.10.2004): 519–26. http://dx.doi.org/10.1115/1.1791642.
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This two-part paper presents detailed experimental investigations of unsteady aerodynamic blade row interactions in the four-stage low-speed research compressor of Dresden. In Part I of the paper the unsteady profile pressure distributions for the nominal setup of the compressor are discussed. Furthermore the effect of blade row clocking on the unsteady profile pressures is investigated. Part II deals with the unsteady aerodynamic blade forces, which are determined from the measured profile pressure distributions. A method to calculate the aerodynamic blade forces on the basis of the experimental data is presented. The resulting aerodynamic blade forces are discussed for the rotor and stator blade rows of the first stage and the third stage of the compressor. Different operating points between design point and stability limit of the compressor were chosen to investigate the influence of loading on the aerodynamic force excitation. The time traces and the frequency contents of the unsteady aerodynamic blade force are discussed. Strong periodic influences of the incoming wakes and of potential effects of downstream blade rows can be observed. The amplitude and shape of the unsteady aerodynamic blade force depend on the interaction of the superimposed influences of the blade rows.
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Zhong, Liyuan, Qiliang Li, Yigang Wang i Zhigang Yang. "Aerodynamic noise prediction of passenger vehicle with hybrid detached eddy simulation/acoustic perturbation equation method". Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 233, nr 10 (12.07.2018): 2390–404. http://dx.doi.org/10.1177/0954407018782856.
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Aerodynamic noise significantly affects the ride comfort of vehicle. A hybrid method combining detached eddy simulation and acoustic perturbation equations was used together with wind tunnel experiment to perform the aerodynamic noise investigation of a passenger vehicle. A good agreement of exterior overall sound pressure level and turbulent pressure spectra was found between the experiment and simulation with 260 million cells. Both turbulent and acoustic pressures were used as power input in statistical energy analysis, and the predicted interior noise is consistent with the experiment. The turbulent and acoustic pressures show a closely related spatial distribution, while the distribution patterns are different due to the distinction in their ways of propagation. The turbulent pressure travels downstream together with flow, while the acoustic pressure radiates homogeneously. Through statistical energy analysis, the major aerodynamic noise sources are identified as underbody for frequencies under 200 Hz and windows above 200 Hz, respectively. Finally, the studies of mesh resolution show that the finer mesh with 260 million cells can provide better results, while the coarser mesh with 90 million cells performs relatively poorly.
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Gnatowska, Renata, i Marcin Sosnowski. "The influence of distance between vehicles in platoon on aerodynamic parameters". EPJ Web of Conferences 180 (2018): 02030. http://dx.doi.org/10.1051/epjconf/201818002030.
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The paper presents the results of experimental and numerical research focused on the reduction of fuel consumption of vehicles driving one after another in a so-called platoon arrangement. The aerodynamic parameters and safety issues were analyzed in order to determine the optimal distance between the vehicles in traffic conditions. The experimental research delivered the results concerning the drag and was performed for simplified model of two vehicles positioned in wind tunnel equipped with aerodynamic balance. The additional numerical analysis allowed investigating the pressure and velocity fields as well as other aerodynamics parameters of the test case.
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Hu, Xing Jun, Lei Liao, Jing Yu Wang i Li Min Fu. "Research on Aerodynamic Characteristics of a Simplified SUV Model". Applied Mechanics and Materials 275-277 (styczeń 2013): 603–6. http://dx.doi.org/10.4028/www.scientific.net/amm.275-277.603.
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The aerodynamics characteristics of square Mira model were researched by simulation, the drag coefficient and the aerodynamic characteristics around model were achieved with analysis of velocity and pressure distribution. Based on results, the angle of rear wind window, the angle of underbody diffuser and the front transition radius were changed, the drag and lift coefficients were achieved. The conclusions provide reference for how to reduce drag coefficient of SUV
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Yu, Jing Mei, Yan Hong Yu i Pan Pan Liu. "Horizontal Axis Wind Turbine Numerical Simulation of Two Dimensional Angle of Attack". Advanced Materials Research 619 (grudzień 2012): 111–14. http://dx.doi.org/10.4028/www.scientific.net/amr.619.111.
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wind power is the most effective form of wind energy utilization, modern large-scale wind turbine with horizontal axis wind mainly. Horizontal axis wind turbine aerodynamic performance calculation of the wind turbine aerodynamics research hot spot, is a wind turbine aerodynamic optimization design and calculation of critical load. Horizontal axis wind turbine airfoil aerodynamic performance of the wind turbine operation characteristics and life plays a decisive role". Using Fluent software on the horizontal axis wind turbine numerical simulation, analysis of the United States of America S809NREL airfoil aerodynamic characteristics of different angles of attack numerical simulation, analyzes the different angles of attack in the vicinity of the pressure, velocity distribution. By solving the two-dimensional unsteady, compressible N-S equations for the calculation of wind turbine airfoil S809used the characteristics of flow around. N-S equation in body-fitted coordinate system is given, with the Poisson equation method to generate the C grid.
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Gennaretti, M., i G. Bernardini. "Aeroelastic response of helicopter rotors using a 3D unsteady aerodynamic solver". Aeronautical Journal 110, nr 1114 (grudzień 2006): 793–801. http://dx.doi.org/10.1017/s0001924000001664.
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The prediction of blade deflections and vibratory hub loads concerning helicopter main rotors in forward flight is the objective of this work. They are determined by using an aeroelastic model derived through the coupling between a nonlinear blade structural model and a boundary integral equation solver for three-dimensional, unsteady, potential aerodynamics. The Galerkin method is used for the spatial integration, whereas the periodic blade response is determined by a harmonic balance approach. This aeroelastic model yields a unified approach for aeroelastic response and blade pressure prediction that may be used for aeroacoustic purposes, with the possibility of including effects from both blade-vortex interaction and multiple-body aerodynamic interaction. Quasi-steady aerodynamic models with wake-inflow from the three-dimensional aerodynamic solver are also applied, in order to perform a comparative study. Numerical results show the capability of the aeroelastic tool to evaluate blade response and vibratory hub loads for a helicopter main rotor in level flight conditions, and examine the sensitivity of the predictions on the aerodynamics model used.
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Tihonchik, S. S., i N. I. Puchko. "Low-pressure nozzle with aerodynamic fuel atomization". Proceedings of the National Academy of Sciences of Belarus, Physical-Technical Series 65, nr 3 (21.10.2020): 357–64. http://dx.doi.org/10.29235/1561-8358-2020-65-3-357-364.
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A research was carried out with the construction of a model of a low-pressure nozzle with aerodynamic fuel atomization, which shows the advantages of nozzles of this type. In order to reduce the time at the stage of development and calculations, modern computer design systems were used. The research was carried out in the Flow Simulation module of the SolidWorks software package, which allows you to calculate and build a model of the internal flow around the nozzle using already known parameters. These parameters were set through the program conditions panel: fuel consumption per second; air flow rate at the inlet to the nozzle; static pressure in the combustion chamber. The calculations performed by the module made it possible to evaluate the manufacturability of the design, as well as the internal processes of mixing fuel with air. To determine the quality of fine dispersion of the fuel atomization, a model of the velocity field was calculated over the entire section of the nozzle, from which it can be seen that the maximum flow rate of the fuel is achieved in the outlet channels of the fuel atomizer of the nozzle. The results obtained indicate the operation of the low-pressure principle while maintaining high-quality fuel atomization. The use of low-pressure nozzle with aerodynamic fuel atomization is possible in modern gas turbine engines of civil aircraft, as well as in gas turbine.
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Chang, Y. B., i P. M. Moretti. "Aerodynamic Characteristics of Pressure-Pad Air Bars". Journal of Applied Mechanics 67, nr 1 (10.09.1999): 177–82. http://dx.doi.org/10.1115/1.321161.
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Air-flotation ovens are widely used for noncontact support and drying of coated paper and plastic films (generically called webs). The main components in typical air-flotation ovens are air bars which have slot nozzles or holes through which hot air jets are ejected. Problems in air-flotation drying techniques include sideward motion of the web, web flutter, and contact between the web and air bars. The key to analyzing these problems is to determine the aerodynamic forces on the web. This paper discusses the aerodynamic forces generated by pressure-pad-type air bars, each of which has two slot nozzles. Ground-effect theories, which were originally developed for the design of hovercraft, are re-examined. The theories are compared with the measured values of the aerodynamic forces for typical air bars. It is shown that ground effect theories can be applied to pressure-pad-type air bars if we properly define the equivalent values of the ground effect variables, which include thickness of the air jet, flotation height, ejection angle of the air jet, and the effective total pressure of the air jet. [S0021-8936(00)02801-4]
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Li, W. G., D. J. Li, T. B. Cheng i D. N. Fang. "The Effects of Constraint, Size and Aspect Ratio on Thermal Shock Resistance of ZNS Wave-Transparent Ceramic in its Actual Service". Journal of Mechanics 31, nr 4 (sierpień 2015): 449–55. http://dx.doi.org/10.1017/jmech.2015.21.
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AbstractThe thermal shock resistance (TSR) of ZnS wave-transparent ceramic depends on not only the mechanical and thermal properties of materials, but also the aerodynamic heating, pneumatic pressure, external constraint, size, aspect ratio and other factors in its actual service process. The theoretical model was established by introducing the analytical solution of transient heat conduction problem of ZnS plate under aerodynamic heating into its thermal stress field model and the pneumatic pressure was introduced. The present work mainly focused on the influences of constraint, size and aspect ratio on the critical rupture temperature difference of ZnS plate subjected to aerodynamic heating and pneumatic pressure. The numerical simulation was also conducted to verify the theoretical model. The results show that the large heat transfer condition corresponds to the poor TSR unless the constraint is too strong; the square plate provides the better TSR in case of different pneumatic pressures; a reasonable side length according to the range of pneumatic pressure would lead to the better TSR.
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Espinoza, Víctor M., Daryush D. Mehta, Jarrad H. Van Stan, Robert E. Hillman i Matías Zañartu. "Glottal Aerodynamics Estimated From Neck-Surface Vibration in Women With Phonotraumatic and Nonphonotraumatic Vocal Hyperfunction". Journal of Speech, Language, and Hearing Research 63, nr 9 (15.09.2020): 2861–69. http://dx.doi.org/10.1044/2020_jslhr-20-00189.
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Purpose The purpose of this study was to determine whether estimates of glottal aerodynamic measures based on neck-surface vibration are comparable to those previously obtained using oral airflow and air pressure signals (Espinoza et al., 2017) in terms of discriminating patients with phonotraumatic and nonphonotraumatic vocal hyperfunction (PVH and NPVH) from vocally healthy controls. Method Consecutive /pae/ syllables at comfortable and loud level were produced by 16 women with PVH (organic vocal fold lesions), 16 women with NPVH (primary muscle tension dysphonia), and 32 vocally healthy women who were each matched to a patient according to age and occupation. Subglottal impedance-based inverse filtering of the anterior neck-surface accelerometer (ACC) signal yielded estimates of peak-to-peak glottal airflow, open quotient, and maximum flow declination rate. Average subglottal pressure and microphone-based sound pressure level (SPL) were also estimated from the ACC signal using subject-specific linear regression models. The ACC-based measures of glottal aerodynamics were normalized for SPL and statistically compared between each patient and matched-control group. Results Patients with PVH and NPVH exhibited lower SPL-normalized glottal aerodynamics values than their respective control subjects ( p values ranging from < .01 to .07) with very large effect sizes (1.04–2.16), regardless of loudness condition or measurement method (i.e., ACC-based values maintained discriminatory power). Conclusions The results of this study demonstrate that ACC-based estimates of most glottal aerodynamic measures are comparable to those previously obtained from oral airflow and air pressure (Espinoza et al., 2017) in terms of differentiating between hyperfunctional (PVH and NPVH) and normal vocal function. ACC-based estimates of glottal aerodynamic measures may be used to assess vocal function during continuous speech and enables this assessment of daily voice use during ambulatory monitoring to provide better insight into the pathophysiological mechanisms associated with vocal hyperfunction.
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Mateescu, Dan. "Explicit Exact and Third-Order-Accurate Pressure-Deflection Solutions for Oblique Shock and Expansion Waves". Open Aerospace Engineering Journal 3, nr 1 (18.02.2010): 1–8. http://dx.doi.org/10.2174/1874146001003010001.
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This paper presents explicit analytical solutions of the pressure coefficient and the pressure ratio across the oblique shock and expansion waves in function of the flow deflection angle. These new explicit pressure-deflection solutions can be efficiently used in solving applied aerodynamic problems in supersonic flows, such as the aerodynamics of airfoils and wings in supersonic-hypersonic flows and the shock and expansion waves interactions, and can be also used to increase the computational efficiency of the numerical methods based on the Riemann problem solution requiring the pressure-deflection solution of the oblique shock and expansion waves, such as the Godunov method.
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Buzica, Andrei, Lisa Debschütz, Florian Knoth i Christian Breitsamter. "Leading-Edge Roughness Affecting Diamond-Wing Aerodynamic Characteristics". Aerospace 5, nr 3 (19.09.2018): 98. http://dx.doi.org/10.3390/aerospace5030098.
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Diamond wing configurations for low signature vehicles have been studied in recent years. Yet, despite numerous research on highly swept, sharp edged wings, little research on aerodynamics of semi-slender wings with blunt leading-edges exists. This paper reports on the stall characteristics of the AVT-183 diamond wing configuration with variation of leading-edge roughness size and Reynolds number. Wind tunnel testing applying force and surface pressure measurements are conducted and the results presented and analysed. For the investigated Reynolds number range of 2.1 × 10 6 ≤ R e ≤ 2.7 × 10 6 there is no significant influence on the aerodynamic coefficients. However, leading-edge roughness height influences the vortex separation location. Trip dots produced the most downstream located vortex separation onset. Increasing the roughness size shifts the separation onset upstream. Prior to stall, global aerodynamic coefficients are little influenced by leading-edge roughness. In contrast, maximum lift and maximum angle of attack is reduced with increasing disturbance height. Surface pressure fluctuations show dominant broadband frequency peaks, distinctive for moderate sweep vortex breakdown. The experimental work presented here provides insights into the aerodynamic characteristics of diamond wings in a wide parameter space including a relevant angle of attack range up to post-stall.
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Gusev, Vladimir. "Aerodynamic streams at cylindrical internal grinding by the textured wheels". MATEC Web of Conferences 298 (2019): 00018. http://dx.doi.org/10.1051/matecconf/201929800018.
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During internal grinding a large amount of heat is formed. A heat has a negative impact on all processing indicators. The speed of heat removal from the processed workpiece is defined not only by structure of grinding wheel and by giving method of lubricant cooling liquid (LCL), but also by the aerodynamic streams, which are formed by a tool rotation. Aerodynamics of traditional grinding wheels is studied in detail, but for textured wheels to aerodynamic streams did not pay of due attention. The multiple-factor experiment is executed and models of movement speed of the aerodynamic streams are determined. It is established, that the greatest influence on the movement speed of the air flows has an axial distance of a measurement point from an end face of abrasive segments and a radial distance of this point from the cutting surface. Static pressure of air in an internal wheel’s cavity is equal 47 Pas, and outside of the wheel in close proximity to the cutting surface – 212 Pas. Taking into account the received experimental data of the movement speeds of aerodynamic streams and different data of air pressure in the specified areas, possible methods of giving of LCL in a cutting zone are analysed. It is established, that the most effective is the centrifugal method of giving of LCL to an internal cavity of the textured tool.
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Polovyi, Oleh Borysovych, i Dmytro Oleksandrovych Redchyts. "Redchyts Evaluation of aerodynamic and thermal loads on the HYPERLOOP capsule fuselage in a partly evacuated tube". System technologies 4, nr 123 (12.10.2019): 3–12. http://dx.doi.org/10.34185/1562-9945-4-123-2019-01.
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Aerodynamics occupies an important place in the design of high-speed ground transportation systems. When a vehicle is moving at a speed above 500 km/h under atmospheric pressure, the main energy is spent to overcome the aerodynamic drag. Creating a rarefied atmosphere inside a sealed pipe in order to significantly reduce energy loss is one of the key ideas of the HYPERLOOP project [1].The paper assesses the aerodynamic and thermal loads on the HYPERLOOP capsule fuselage in a partly evacuated tube based on the numerical solution of the Navier-Stokes equations of compressible flow closed by a differential turbulence model [2-4]. Numerical modeling was carried out with the help of the computational fluid dynamics software developed by the scientific researchers of the Institute of Transport Systems and Technologies of the National Academy of Sciences of Ukraine [5].It was shown that even under conditions of low air pressure in a partly evacuated tube the high-speed movement of the HYPERLOOP capsule will be accompanied by the formation of local supersonic zones, shock waves and non-stationary vortex systems. The structure of the flow essentially depends on geometry of the streamlined capsule and the speed of its movement.It was found that the flow structure and the values of aerodynamic dimensionless coefficients weakly depend on the pressure in the partly evacuated tube. Thus, the aerodynamic forces acting on the HYPERLOOP capsule at the same speeds are almost directly proportional to the pressure value in the tube.A certain problem in the design of the HYPERLOOP type high-speed vehicles will be the aerodynamic heating of the capsule fuselage. When the capsule moves at transonic speed the temperature of the outer surface of the capsule will be 60÷900 C. This heat load can have a negative impact on the performance of onboard power supply and control systems, as well as on the ensuring of the passengers’ comfort on the way.
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Shan, Yong, Xiaoming Zhou, Xiaoming Tan, Jingzhou Zhang i Yanhua Wu. "Parametric Design Method and Performance Analysis of Double S-Shaped Nozzles". International Journal of Aerospace Engineering 2019 (12.05.2019): 1–24. http://dx.doi.org/10.1155/2019/4694837.
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A parametric design method, which was based on super-elliptical transition and self-adaption infrared radiation shield for the double S-shaped nozzle, was introduced. The complete shielding of high-temperature components in the S-shaped nozzle was realized. Model experiments and numerical simulations were performed to investigate the effects of offset ratio S/D, the ratio of length to diameter L/D, and the aspect ratio W/H on the aerodynamics and infrared radiation. The results showed that the total pressure recovery and thrust coefficients were improved initially, but dropped rapidly with the increase in offset ratios with the range of investigated parameters. There existed an optimal offset ratio for the aerodynamic performances. Considering the weight penalty, the length of nozzles should only be increased properly to achieve better aerodynamic performances. Both friction and viscous losses caused by large streamwise vortices dominated the aerodynamic performances of nozzles. The nozzle with the aspect ratio of W/H=5.0 was recommended for achieving optimal aerodynamics. The increase in aspect and offset ratios could effectively suppress plume radiation, which was, however, not sensitive to overall radiation. Compared to circular nozzles, double S-shaped nozzles reduced overall infrared radiation by over 50%, which proves significant stealth ability. A balance between aerodynamic performances and infrared radiation suppression could be reached for double S-shaped nozzles.
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Liu, Tianshu, B. T. Campbell, S. P. Burns i J. P. Sullivan. "Temperature- and Pressure-Sensitive Luminescent Paints in Aerodynamics". Applied Mechanics Reviews 50, nr 4 (1.04.1997): 227–46. http://dx.doi.org/10.1115/1.3101703.
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This review article presents an overview of the current state of temperature- and pressure-sensitive luminescent paint techniques used in aerodynamic measurements. Topics include photophysical foundations, paint preparation and calibration, measurement systems, accuracy, and time response. Applications of the luminescent paint technique in aerodynamic testing are discussed and typical examples of current research are given. There are 112 references.
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Lombardi, G., i A. Tonelli. "Experimental pressure evaluation near a sail leading edge under real conditions". Aeronautical Journal 98, nr 978 (październik 1994): 319–22. http://dx.doi.org/10.1017/s0001924000026828.
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AbstractThe aerodynamic condition corresponding to the optimum sail trim has been long debated; in the present note this aerodynamic aspect of the sails is studied by means of pressure measurements near the sail leading-edge. By analysing the pressure acting on the leading edge zone it can be evidenced that, when the sail is “optimally” trimmed, it is actually in the aerodynamic condition corresponding to the ideal angle of attack.
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Gierens, K., B. Kärcher, H. Mannstein i B. Mayer. "Aerodynamic Contrails: Phenomenology and Flow Physics". Journal of the Atmospheric Sciences 66, nr 2 (1.02.2009): 217–26. http://dx.doi.org/10.1175/2008jas2767.1.
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Abstract Aerodynamic contrails have been recognized for a long time although they appear sporadically. Usually one observes them under humid conditions near the ground, where they are short-lived phenomena. Aerodynamic contrails appear also at cruise levels where they may persist when the ambient atmosphere is ice-supersaturated. The present paper presents a theoretical investigation of aerodynamic contrails in the upper troposphere. The required flow physics are explained and applied to a case study. Results show that the flow over aircraft wings leads to large variations of pressure and temperature. Average pressure differences between the upper and lower sides of a wing are on the order of 50 hPa, which is a quite substantial fraction of cruise-level atmospheric pressures. Adiabatic cooling exceeds 20 K about 2 m above the wing in a case study shown here. Accordingly, extremely high supersaturations (exceeding 1000%) occur for a fraction of a second. The potential consequences for the ice microphysics are discussed. Because aerodynamic contrails are independent of the formation conditions of jet contrails, they form an additional class of contrails that might be complementary because they form predominantly in layers that are too warm for jet contrail formation.
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Bielek, Boris. "Interaction of Building Thermal Technics with Building Aerodynamics in Problem Solving of Physical Cavities of Double-Skin Transparent Facades". Applied Mechanics and Materials 820 (styczeń 2016): 313–19. http://dx.doi.org/10.4028/www.scientific.net/amm.820.313.
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The new facade technology of ecological, low-energy, cybernetic buildings. The physical theory of cavity. Quantification of the physical regime of corridor-type cavity of double-skin transparent facade with open circuit, employing the highly ecological self-recovery alternative source of solar energy. Aerodynamic quantification of cavity under the convection regime. Total aerodynamic resistance. Aerodynamic quantification of building. Aerodynamic coefficient of external pressure. The air rate of flow through the cavity under the wind pressure regime.
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Gong, Sai, Peng Tang i Cheng Kun Wang. "Study on Surface Pressure Distribution Test of Stayed-Cable Using Aerodynamic Measure". Advanced Materials Research 1065-1069 (grudzień 2014): 851–55. http://dx.doi.org/10.4028/www.scientific.net/amr.1065-1069.851.
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Stayed-cable was being considered as an important component of cable-stayed bridge, with characteristics of its low quality, stiffness and damping, among which rain-wind-induced vibration brings the most serious damage in its high amplitude because of its easy conditions to meet. This paper based on the theory of stayed-cable rain-wind-induced vibration, Through comparing different aerodynamic control measures in wind pressure test of ZhiJiang Bridge cable, this paper analyses the variation rules of two and three dimensional cable surface pressure distribution in different aerodynamic measures and cable aerodynamic coefficient in different surface conditions. The results show that: the wind angle influenced surface wind pressure coefficients and aerodynamic coefficient larger, especially between 25 ° and40 °; when the water was between 40 ° and70 °, the aerodynamic coefficient changed obviously, may happen galloping; It recommend that the cable helix parameter K1 was larger and K2 was between 0.01 and 0.03.
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Oh, Jae-Sung, Taehak Kang, Seokgyun Ham, Kwan-Sup Lee, Yong-Jun Jang, Hong-Sun Ryou i Jaiyoung Ryu. "Numerical Analysis of Aerodynamic Characteristics of Hyperloop System". Energies 12, nr 3 (6.02.2019): 518. http://dx.doi.org/10.3390/en12030518.
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The Hyperloop system is a new concept that allows a train to travel through a near-vacuum tunnel at transonic speeds. Aerodynamic drag is one of the most important factors in analyzing such systems. The blockage ratio (BR), pod speed/length, tube pressure, and temperature affect the aerodynamic drag, but the specific relationships between the drag and these parameters have not yet been comprehensively examined. In this study, we investigated the flow phenomena of a Hyperloop system, focusing on the effects of changes in the above parameters. Two-dimensional axisymmetric simulations were performed in a large parameter space covering various BR values (0.25, 0.36), pod lengths (10.75–86 m), pod speeds (50–350 m/s), tube pressures (~100–1000 Pa), and tube temperatures (275–325 K). As BR increased, the pressure drag was significantly affected. This is because of the smaller critical Mach number for a larger BR. As the pod length increased, the total drag and pressure drag did not change significantly, but there was a considerable influence on the friction drag. As the pod speed increased, strong shock waves occurred near the end of the pod. At this point, the flows around the pod were severely choked at both BR values, and the ratio of the pressure drag to the total drag converged to its saturation level. At tube pressures above 500 Pa, the friction drag increased significantly under the rapidly increased turbulence intensity near the pod surface. High tube temperatures increase the speed of sound, and this reduces the Mach number for the same pod speed, consequently delaying the onset of choking and reducing the aerodynamic drag. The results presented in this study are applicable to the fundamental design of the proposed Hyperloop system.
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Zhang, Yu Xiang, Jin Biao Xu, Fu Hou Xu i Hua Cheng Li. "Research on Influence of Aerodynamic Force on the Aerodynamic Heat for the Hypersonic Vehicle". Applied Mechanics and Materials 198-199 (wrzesień 2012): 207–11. http://dx.doi.org/10.4028/www.scientific.net/amm.198-199.207.
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During the flight of the hypersonic Vehicle, the angle of attack will change with the flight attitude. At the same time, the aerodynamic forces from the surface of aircraft will also be changing. The pressure and friction force are the main causes of the aerodynamic heating, so the surface aerodynamic heating will change. By used the method of numerical calculation, the passage studied the influence the change the pressure and friction force on the distribution of heat flux in different angle of attack and the relationship between the change of the force of lift-drag and aerodynamic heating. The research suggested that the distribution of the heat flux had very good consistency with that of pressure and friction. The lift change was the dominant factors influence of pneumatic thermal change; the change of drag force affected only the speed of heat flux change.
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Laine, Tellervo, Donald W. Warren, Rodger M. Dalston, W. Michael Hairfield i Kathleen E. Morr. "Intraoral Pressure, Nasal Pressure and Airflow Rate in Cleft Palate Speech". Journal of Speech, Language, and Hearing Research 31, nr 3 (wrzesień 1988): 432–37. http://dx.doi.org/10.1044/jshr.3103.432.
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We have suggested that compensatory behaviors associated with cleft palate may be strategies developed for the purpose of satisfying the requirements of a speech regulating system. The purpose of the present study was to test this hypothesis in subjects demonstrating various degrees of velopharyngeal inadequacy. The pressure-flow technique was used to assess aerodynamic responses to a loss of velar resistance in 74 subjects compared to a control group of 137 subjects with adequate velopharyngeal closure. The results of this study demonstrate that as degree of inadequacy increased, airflow rate also increased. Although intraoral pressure fell as inadequacy increased, many subjects were able to maintain pressures above 3.0 cm H 2 0 by increasing airflow rate. Nasal pressure increased in proportion to the decrease in intraoral pressure While combined nasal plus oral pressure remained constant across groups. These findings suggest that a loss of resistance at the velar port is compensated by an increase in resistance at the nasal port. Airflow rate appears to be adjusted to total upper airway resistance. These findings support our contention that the speech system is constrained to meet aerodynamic requirements.
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Li, Hui, i Dian-Gui Huang. "Aerodynamic Optimization Design of a Multistage Centrifugal Steam Turbine and Its Off-Design Performance Analysis". International Journal of Rotating Machinery 2017 (2017): 1–11. http://dx.doi.org/10.1155/2017/4690590.
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Centrifugal turbine which has less land occupation, simple structure, and high aerodynamic efficiency is suitable to be used as small to medium size steam turbines or waste heat recovery plant. In this paper, one-dimensional design of a multistage centrifugal steam turbine was performed by using in-house one-dimensional aerodynamic design program. In addition, three-dimensional numerical simulation was also performed in order to analyze design and off-design aerodynamic performance of the proposed centrifugal steam turbine. The results exhibit reasonable flow field and smooth streamline; the aerodynamic performance of the designed turbine meets our initial expectations. These results indicate that the one-dimensional aerodynamic design program is reliable and effective. The off-design aerodynamic performance of centrifugal steam turbine was analyzed, and the results show that the mass flow increases with the decrease of the pressure ratio at a constant speed, until the critical mass flow is reached. The efficiency curve with the pressure ratio has an optimum efficiency point. And the pressure ratio of the optimum efficiency agrees well with that of the one-dimensional design. The shaft power decreases as the pressure ratio increases at a constant speed. Overall, the centrifugal turbine has a wide range and good off-design aerodynamic performance.
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Li, Ruiping, Weihua Zhang, Zhou Ning, Binbin Liu, Dong Zou i Wei Liu. "Influence of a high-speed train passing through a tunnel on pantograph aerodynamics and pantograph–catenary interaction". Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit 231, nr 2 (4.08.2016): 198–210. http://dx.doi.org/10.1177/0954409715626743.
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Aerodynamics of trains running inside tunnels change more significantly in comparison with open air scenarios. It has been confirmed that the lateral vibration as well as the aerodynamic drag of the trains is increased and the micro-pressure wave is produced at the tunnel exit when the trains are passing through tunnels. The aim of this article is to explore the impact of a high-speed train passing through a tunnel on the pantograph aerodynamics and the dynamic behavior of the pantograph–catenary interaction. The aerodynamic forces acting on the pantograph are investigated thoroughly by extensive numerical simulations as well as systematic field tests. To investigate the effects of the aerodynamic forces of pantograph on the quality of current collection, the numerical simulations of the pantograph–catenary dynamic interaction are conducted with our proposed model, taking into consideration the action of the aerodynamic uplift forces obtained by the numerical simulations on the pantograph. Then, a series of numerical simulations are also carried out to analyze the effects of the train speed and the blockage ratio on the aerodynamic uplift forces of the pantograph, on the contact forces, as well as on the displacement of the contact wire, while the train is passing through a tunnel. The results reveal that compared with the open air scenarios, the aerodynamic drag and uplift forces of the pantograph, the mean value of the contact force and the displacement level of the registration arm can considerably increase as the train runs inside a tunnel. Moreover, the statistical values of the contact forces and the displacement level of the contact wire become larger while the train is passing through the tunnel at different speeds. On the other hand, the quality of current collection decreases with the increasing of the blockage ratio.
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Grolman, Wilko, Eric Grolman, Reindert P. Van Steenwijk i Paul F. Schouwenburg. "Airflow and Pressure Characteristics of Three Different Tracheostoma Valves". Annals of Otology, Rhinology & Laryngology 107, nr 4 (kwiecień 1998): 312–18. http://dx.doi.org/10.1177/000348949810700409.
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Tracheoesophageal speakers can achieve speech without digital occlusion by using a tracheostoma valve. Laryngectomized patients who are successful with this device can regain considerable freedom. However, little is known about which valve suits the patient best. Valve aerodynamics may give a guideline for its use. Three major tracheostoma valves, each divided into four subtypes, were repeatedly measured in this study. Dynamic pressure and airflow rate signals were sampled through an analog-digital interface into a computer. Considerable aerodynamic differences were observed between the tested valves. The maximum airflow rates, closing pressures, and resistances at low velocities were compared. The presented data may help increase the successful use of tracheostoma valves in tracheoesophageal speakers. Patient factors and additional valve factors should always be taken into account. Further clinical study to validate the clinical relevance of the data is needed.
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Zhang, Zhe, Ying Chao Zhang, Jie Li i Jia Wang. "Numerical Simulation on Aerodynamic Characteristics of Heavy-Duty Commercial Vehicle". Advanced Materials Research 346 (wrzesień 2011): 477–82. http://dx.doi.org/10.4028/www.scientific.net/amr.346.477.
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With the development of automotive technology and high-speed highway construction, the speed of the vehicles increase which cause the significant increase in the aerodynamic drag when road vehicles are moving. Thereby the power of the vehicles, fuel economy, operational stability and other properties are affected very seriously. Heavy-duty commercial vehicles as the most efficient way to transport goods on the highway are widely used, and the speed of the vehicles increases faster. Especially the demands for heavy-duty commercial vehicles are increasing in recent years. Reducing the aerodynamic drag by the analysis of external aerodynamic characteristics, improving the fuel economy and reducing energy consumption have become new research topics of heavy-duty commercial vehicles. To make the heavy-duty commercial vehicles meet the national standards of energy saving, a simplified heavy-duty commercial truck model was built in this paper. The numerical simulation of the vehicle was completed based on the theory of the aerodynamics. The aerodynamic characteristics were analyzed, according to the graphs of the pressure distribution, velocity distribution and flow visualization. To improve the aerodynamic characteristics of heavy-duty commercial vehicles, the main drag reduction measures are reducing the vortex of the cab and the container, the end of the container and the bottom of the container.