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1
Hong, Sungchan, John Eric Goff et Takeshi Asai. « Effect of a soccer ball’s surface texture on its aerodynamics and trajectory ». Proceedings of the Institution of Mechanical Engineers, Part P : Journal of Sports Engineering and Technology 233, no 1 (9 octobre 2018) : 67–74. http://dx.doi.org/10.1177/1754337118794561.
Texte intégralRésumé :
The effect of a soccer ball’s surface texture on its aerodynamics and flight trajectory is not definitively known. For this study, five soccer balls were used, each having 32 panels with different surface textures. Their aerodynamics were examined via wind-tunnel experiments and then several non-spin trajectories were calculated for each ball. The results showed that the aerodynamic forces acting on a soccer ball change significantly depending on the surface texture of the ball, which in turn influences flight trajectories. The study contributes to an understanding of how a soccer ball’s surface influences the aerodynamics, which may impact the future design and development of soccer balls.
2
Chen, Zhao Jun. « Application of Aerodynamics in the Automotive Repair ». Applied Mechanics and Materials 556-562 (mai 2014) : 991–95. http://dx.doi.org/10.4028/www.scientific.net/amm.556-562.991.
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In the development process of the car, the aerodynamics has a strong impact on the automotive research and design. The initial research of aerodynamics focused on reducing air resistance and improving the car's fuel efficiency. Aerodynamic lift and side forces generated has a significant effect on the stability of cars, and even a threat to the safe driving. With the rapid development of automotive performance, the comfort and security of cars have put forward new and higher requirements, wind noise and airflow pollution generated by the aerodynamics have also emerged. How to reduce the adverse effects on the aerodynamics of cars, which is thought about by not only the people of the design, but also the users and maintenance workers in the car. In the course of vehicle maintenance, arising issues of aerodynamics have been gradually received wide attention.
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Eskandary, Keivan, Morteza Dardel, Mohammad Hadi Pashaei et Abdol Majid Kani. « Effects of Aeroelastic Nonlinearity on Flutter and Limit Cycle Oscillations of High-Aspect-Ratio Wings ». Applied Mechanics and Materials 110-116 (octobre 2011) : 4297–306. http://dx.doi.org/10.4028/www.scientific.net/amm.110-116.4297.
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In this study aeroelastic characteristics of long high aspect ratio wing models with structural nonlinearities in quasi-steady aerodynamics flows are investigated. The studied wing model is a cantilever wing with double bending and torsional vibrations and with large deflection ability in according to Dowell-Hodges wing model. This wing model is valid for long, straight and thin homogeneous isotropic beams. Aerodynamics model is based on quasi-steady aerodynamic which is valid for aerodynamic flows in low velocity and without wake, viscosity and compressibility effects. The effect of different parameters such as mass ratios and stiffness ratios on flutter and divergence velocities and limit cycle oscillation amplitudes are carefully studied.
4
Liu, Jun, Zhengqi Gu, Taiming Huang, Shuya Li, Ledian Zheng et Kai Sun. « Coupled analysis of the unsteady aerodynamics and multi-body dynamics of a small car overtaking a coach ». Proceedings of the Institution of Mechanical Engineers, Part D : Journal of Automobile Engineering 233, no 14 (22 février 2019) : 3684–99. http://dx.doi.org/10.1177/0954407019831559.
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The severe additional aerodynamic loads that are generated on a small car when overtaking a coach have an adverse effect on the car handling stability and its safety. In this article, a two-way coupling of the unsteady aerodynamics and multi-body dynamics is performed in order to study the mutual interactions of a car in an overtaking maneuver with a coach. The unsteady aerodynamic interactions are obtained by using SST (Menter) K-Omega Detached Eddy Simulation and overset mesh technology. The aerodynamics couple the multi-body dynamics, taking into account the effects of the transverse spacing and the cross winds. To validate the necessity of the two-way coupling method, a one-way coupling of the aerodynamics to the vehicle motion is also conducted. Finally, by comparing the aerodynamic loads and the dynamic response of the overtaking car in different overtaking maneuvers between one- and two-way coupling, the results show that it should be considered with two-way coupling analyses of the car while overtaking a coach, particularly under the severe conditions of a lower transverse spacing or the crosswinds.
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Shinde, Yash. « Dimples Effects on a Spoilers Aerodynamics ». International Journal for Research in Applied Science and Engineering Technology 9, no 8 (31 août 2021) : 1851–68. http://dx.doi.org/10.22214/ijraset.2021.37674.
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Abstract: Over the evolution of automobiles, performance, mileage, and grip have dramatically improved. Nevertheless, there have been some improvements, but now the ideal design has been reached for design of engine, airflow & tires, & ergonomics. This means that even very small design improvements could result in high performance enhancements. As fuel is becoming more expensive, the need for improved aerodynamics is becoming more acute. Thus, the purpose of this paper is to examine the effect of golf-like dimples on the aerodynamic properties of a spoiler. As such, numerical calculations and computational fluid dynamics calculations were performed to investigate the impact on aerodynamics and turbulence spoilers with various surface roughness and angle of attack. Based on the recorded data, this test will provide the best information on the appropriate size for the dimple. The data collected on the test model will be used to calculate the drag coefficient, the downforce, and the wake produced at 56 m/s speed, at four different attack angles. Different sizes & depths of dimples will be used to improve the aerodynamics of spoilers, which will improve their downforce, drag force and wake formation. Keywords: spoiler, aerodynamics, dimples, downforce, aerodynamic forces
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Wenhui, Yan, et Zhang Kun. « Effects of Stage Spacing on Contra-Rotating Propeller Aerodynamic Interactions ». Journal of Physics : Conference Series 2478, no 12 (1 juin 2023) : 122013. http://dx.doi.org/10.1088/1742-6596/2478/12/122013.
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Abstract To identify the law of aerodynamic interactions of contra-rotating propellers (CRPs) and improve their aerodynamics, this study investigates the aerodynamic interactions of 4 CRPs (six blades in front and six in back) with different stage spacings using the Reynolds-averaged Navier-Stokes (RANS) equations-based method. The results showed that the CRP whose stage spacing was 0.25 times the propeller diameter delivered the highest average efficiency and that the aerodynamic interactions between the front and rear propellers decreased as the spacing widened, and compared with the rear propeller, the front one was more sensitive to stage spacing due to the aerodynamic interaction-generated thrust fluctuations. It can be seen that stage spacing exerts a significant effect on CRP aerodynamic interactions. Therefore, choosing an appropriate stage spacing in CRP design is of great significance to enhance its aerodynamics.
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Kornev, Nikolai. « On Unsteady Effects in WIG Craft Aerodynamics ». International Journal of Aerospace Engineering 2019 (6 mai 2019) : 1–14. http://dx.doi.org/10.1155/2019/8351293.
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The paper presents the analysis of unsteady forces and their influence on the aerodynamics and motion of a wing-in-ground (WIG) effect craft. Two-dimensional and three-dimensional aerodynamic models based on the potential flow are coupled with time domain simulations in the longitudinal plane. A special attention is paid to the explanation of the dynamic ground effect on both the sink and pitching motions. The influence of unsteady and quasi-steady forces on the dynamic ground effects and the craft motion is analyzed for different heights of flight.
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Guerrero, Alex, et Robert Castilla. « Aerodynamic Study of the Wake Effects on a Formula 1 Car ». Energies 13, no 19 (5 octobre 2020) : 5183. http://dx.doi.org/10.3390/en13195183.
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The high complexity of current Formula One aerodynamics has raised the question of whether an urgent modification in the existing aerodynamic package is required. The present study is based on the evaluation and quantification of the aerodynamic performance on a 2017 spec. adapted Formula 1 car (the latest major aerodynamic update) by means of Computational Fluid Dynamics (CFD) analysis in order to argue whether the 2022 changes in the regulations are justified in terms of aerodynamic necessities. Both free stream and flow disturbance (wake effects) conditions are evaluated in order to study and quantify the effects that the wake may cause on the latter case. The problem is solved by performing different CFD simulations using the OpenFoam solver. The significance and originality of the research may dictate the guidelines towards an overall improvement of the category and it may set a precedent on how to model racing car aerodynamics. The studied behaviour suggests that modern F1 cars are designed and well optimised to run under free stream flows, but they experience drastic aerodynamic losses (ranging from −23% to 62% in downforce coefficients) when running under wake flows. Although the overall aerodynamic loads are reduced, there is a fuel efficiency improvement as the power that is required to overcome the drag is smaller. The modern performance of Ground Effect by means of vortices management represent a very unique and complex way of modelling modern aerodynamics, but at the same time notably compromises the performance of the cars when an overtaking maneuver is intended.
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Xie, Meng, et Xiaoyan Liu. « The influence and application of nonlinear aerodynamics on static derivatives in transonic regime ». Journal of Physics : Conference Series 2512, no 1 (1 mai 2023) : 012007. http://dx.doi.org/10.1088/1742-6596/2512/1/012007.
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Abstract This paper details two static aeroelastic analysis methods applied to a passenger aircraft model with high aspect ratio wing. The influence of nonlinear aerodynamic force on static aeroelastic derivatives in the transonic regime is analysed. The traditional aerodynamic influence coefficient (AIC) matrix method can produce fast and reliable aerodynamic force and is widely used in aeroelastic analysis. However, the AIC matrix computed by linear aerodynamics will lead to some errors in transonic regime because of the nonlinear effect of aerodynamics. By generating the correction matrices, the AIC matrix is modified, and the accuracy of transonic static aeroelastic correction of aerodynamic data can be improved. The static derivatives are compared to the results of the computational fluid dynamics (CFD) / computational structural (CSD) interaction method.
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Duncan, Bradley, Luca D’Alessio, Joaquin Gargoloff et Ales Alajbegovic. « Vehicle aerodynamics impact of on-road turbulence ». Proceedings of the Institution of Mechanical Engineers, Part D : Journal of Automobile Engineering 231, no 9 (10 avril 2017) : 1148–59. http://dx.doi.org/10.1177/0954407017699710.
Texte intégralRésumé :
The ultimate target for vehicle aerodynamicists is to develop vehicles that perform well on the road in real-world conditions. On the other hand, vehicle development today is performed mostly in controlled settings, using wind tunnels and computational fluid dynamics with artificially uniform freestream conditions and neglecting real-world effects due to road turbulence from the wind and other vehicles. Turbulence on the road creates a non-uniform and fluctuating flow field in which the length scales of the fluctuations fully encompass the length scales of the relevant aerodynamic flow structures around the vehicle. These fluctuations can be comparable in size and strength with the vehicle’s own wake oscillations. As a result, this flow environment can have a significant impact on the aerodynamic forces and on the sensitivity of these forces to various shape changes. Some aerodynamic devices and integral design features can perform quite differently from the way in which they do under uniform freestream conditions. In this paper, unsteady aerodynamics simulations are performed using the lattice Boltzmann method on a detailed representative automobile model with several design variants, in order to explore the effect of on-road turbulence on the aerodynamics and the various mechanisms that contribute to these effects.
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Xiang, Jinwu, Kai Liu, Daochun Li, Chunxiao Cheng et Enlai Sha. « Unsteady aerodynamic characteristics of a morphing wing ». Aircraft Engineering and Aerospace Technology 91, no 1 (7 janvier 2018) : 1–9. http://dx.doi.org/10.1108/aeat-04-2017-0101.
Texte intégralRésumé :
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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Tripathi, Manish, Mahesh M. Sucheendran et Ajay Misra. « Experimental analysis of cell pattern on grid fin aerodynamics in subsonic flow ». Proceedings of the Institution of Mechanical Engineers, Part G : Journal of Aerospace Engineering 234, no 3 (5 septembre 2019) : 537–62. http://dx.doi.org/10.1177/0954410019872349.
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Grid fins consisting of a lattice of high aspect ratio planar members encompassed by an outer frame are unconventional control surfaces used on numerous missiles and bombs due to their enhanced lifting characteristics at high angles of attack and across wider Mach number regimes. The current paper accomplishes and compares the effect of different grid fin patterns on subsonic flow aerodynamics of grid fins by virtue of the determination of their respective aerodynamic forces. Furthermore, this study deliberates the impact of gap variation on aerodynamics of different patterns. Results enunciate enhanced aerodynamic efficiency, and lift slope for web-fin cells and single diamond patterns compared to the baseline model. Moreover, the study indicates improved aerodynamic performance for diamond patterns with higher gaps by providing elevated maximum lift coefficient, delayed stall angle, and comparable drag at lower angles. The study established the presence of an additional effect termed as the inclination effect alongside the cascade effect leading to deviations with respect to lift, stall, and aerodynamic efficiency amongst different gap variants of the individual patterns. Thus, optimization based on the aerodynamic efficiency, stall angle requirements, and construction cost by optimum pattern and gap selection can be carried out through this analysis, which can lead to elevated aerodynamic performance for grid fins.
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Tomasz Lusiak, Andrej Novak, Martin Bugaj et Radovan Madlenak. « Assessment of Impact of Aerodynamic Loads on the Stability and Control of the Gyrocopter Model ». Communications - Scientific letters of the University of Zilina 22, no 4 (1 octobre 2020) : 63–69. http://dx.doi.org/10.26552/com.c.2020.4.63-69.
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Aerodynamic modelling currently relates to development of mathematical models to describe the aerodynamic forces and moments acting on the aircraft. It is a challenging part of aerodynamics that defines a comprehensive approach to using traditional methods and modern techniques to obtain relevant data. The most complicated task for the aerodynamics and flight dynamics is definition, computation and quantification of the aerodynamic description of an object. This paper presents how to determine the aerodynamic load on a gyrocopter and defines the effect on its stability and control. The first step to solution is to develop simpler approximate aerodynamic model - a model that can be used in analysis of aerodynamic load and can represent the aerodynamic properties of the gyrocopter with an acceptable degree of accuracy. Control and stability are very important parts of aircraft characteristics and therefore those characteristics were analyzed in simulation. Finally, the aerodynamic data outputs are assessed in terms of impact of aerodynamic loads on stability and control of the gyrocopter model.
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Capece, V. R., et S. Fleeter. « Experimental Investigation of Multistage Interaction Gust Aerodynamics ». Journal of Turbomachinery 111, no 4 (1 octobre 1989) : 409–17. http://dx.doi.org/10.1115/1.3262288.
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The fundamental flow physics of multistage blade row interactions are experimentally investigated at realistic reduced frequency values. Unique data are obtained that describe the fundamental unsteady aerodynamic interaction phenomena on the stator vanes of a three-stage axial flow research compressor. In these experiments, the effect on vane row unsteady aerodynamics of the following are investigated and quantified: (1) steady vane aerodynamic loading; (2) aerodynamic forcing function waveform, including both the chordwise and transverse gust components; (3) solidity; (4) potential interactions; and (5) isolated airfoil steady flow separation.
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Buffum, D. H., et S. Fleeter. « Effect of Wind Tunnel Acoustic Modes on Linear Oscillating Cascade Aerodynamics ». Journal of Turbomachinery 116, no 3 (1 juillet 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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Jamei, Saeed, Agoes Priyanto, Adi Maimun, Mohammad Mobassher Tofa, Nor Azwadi et Shuhaimi Mansor. « Ground Viscous Effect on Aerodynamics of a Compound Wing with Different Reynolds Number ». Applied Mechanics and Materials 465-466 (décembre 2013) : 379–83. http://dx.doi.org/10.4028/www.scientific.net/amm.465-466.379.
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The fly of wing-in-ground effect (WIG) crafts can be affected by ground boundary layers. In this study, the effect of ground viscous on aerodynamic coefficients of a compound wing of WIG craft was numerically investigated. Computational fluid dynamics (CFD) was used for numerical study. The simulations were done respect to different ground clearance and Reynolds number. A realizable k-ε turbulent model was employed for the modelling flow field around the wing area. The numerical results of the compound wing for fixed ground validated with the experimental data. Aerodynamic coefficients of the compound wing were determined for fixed and moving ground. Accordingly, the numerical result presented that lift and drag coefficients and lift to drag ratio has been affected by ground boundary layers while moment coefficient and centre of pressure of compound wing had no more variation due to remove ground viscous. The effect of ground viscous on aerodynamics of the compound wing had a slight changes respect to Reynolds number. CFD can be employed as a good method to find the influence of ground viscous on aerodynamics of WIG crafts.
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Zhang, Xin, Willem Toet et Jonathan Zerihan. « Ground Effect Aerodynamics of Race Cars ». Applied Mechanics Reviews 59, no 1 (1 janvier 2006) : 33–49. http://dx.doi.org/10.1115/1.2110263.
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We review the progress made during the last 30years on ground effect aerodynamics associated with race cars, in particular open wheel race cars. Ground effect aerodynamics of race cars is concerned with generating downforce, principally via low pressure on the surfaces nearest to the ground. The “ground effect” parts of an open wheeled car’s aerodynamics are the most aerodynamically efficient and contribute less drag than that associated with, for example, an upper rear wing. While drag reduction is an important part of the research, downforce generation plays a greater role in lap time reduction. Aerodynamics plays a vital role in determining speed and acceleration (including longitudinal acceleration but principally cornering acceleration), and thus performance. Attention is paid to wings and diffusers in ground effect and wheel aerodynamics. For the wings and diffusers in ground effect, major physical features are identified and force regimes classified, including the phenomena of downforce enhancement, maximum downforce, and downforce reduction. In particular the role played by force enhancement edge vortices is demonstrated. Apart from model tests, advances and problems in numerical modeling of ground effect aerodynamics are also reviewed and discussed. This review article cites 89 references.
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Baker, C. J. « A review of train aerodynamics Part 2 – Applications ». Aeronautical Journal 118, no 1202 (avril 2014) : 345–82. http://dx.doi.org/10.1017/s0001924000009179.
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Abstract This paper is the second part of a two-part paper that presents a wide-ranging review of train aerodynamics. Part 1 presented a detailed description of the flow field around the train and identified a number of flow regions. The effect of cross winds and flow confinement was also discussed. Based on this basic understanding, this paper then addresses a number of issues that are of concern in the design and operation of modern trains. These include aerodynamic resistance and energy consumption, aerodynamic loads on trackside structures, the safety of passengers and trackside workers in train slipstreams, the flight of ballast beneath trains, the overturning of trains in high winds and the issues associated with trains passing through tunnels. Brief conclusions are drawn regarding the need to establish a consistent risk based framework for aerodynamic effects.
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Close, Philip, et Tracie J. Barber. « Explaining Ground Effect Aerodynamics via a Real-Life Reference Frame ». Applied Mechanics and Materials 553 (mai 2014) : 229–34. http://dx.doi.org/10.4028/www.scientific.net/amm.553.229.
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The principle of relative motion as the cause of forces on a body submersedin a uid is foundational in the study of uid mechanics. In aerodynamics the wind tunnelis used as a convenient and safe method by which to test the aerodynamic performance ofbodies. This body-stationary convention has carried over into the computational world withthe development of CFD, though there is no practical reason why the moving body/stationaryuid set-up that corresponds to reality cannot be used for computational modelling. This pointbecomes particularly important as the concept of ground e ect is introduced. With an extraboundary nearby it becomes harder to appropriatel y match the experimental set-up with reality,and the extra boundary condition also adds complexity to computational simulation. A studywas undertaken to compare the body-stationary and body-moving reference frames in grounde ect. The moving reference frame velocity elds allowed new insight into the aerodynamics ofground e ect.
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Abu Salem, Karim, Giuseppe Palaia, Mario R. Chiarelli et Mario Bianchi. « A Simulation Framework for Aircraft Take-Off Considering Ground Effect Aerodynamics in Conceptual Design ». Aerospace 10, no 5 (15 mai 2023) : 459. http://dx.doi.org/10.3390/aerospace10050459.
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The development of novel aircraft concepts and propulsion technologies requires up-to-date physics-based methods and tools for conceptual aircraft design. In this context, a simulation model for the take-off manoeuvre is proposed in this article, to be employed in the conceptual design phase for aircraft whether of traditional or innovative configuration. The model is capable of evaluating the longitudinal dynamics, both translational and rotational, of the aircraft considered as a rigid body, and influenced by the aerodynamic effects introduced by the presence of the ground. The ground effect, indeed, induces variations in the aerodynamic forces depending on the distance and the attitude of the lifting surfaces from the ground, which may significantly influence the aeromechanical characteristics of the aircraft during the evolution of the take-off manoeuvre. The simulation model is based on the numerical solution of the equations of the dynamics of the rigid aircraft in the longitudinal plane and integrates a vortex lattice aerodynamic solver to evaluate the aerodynamic and aeromechanical characteristics of the aircraft considering the ground effect in each time-step. The proposed approach is configuration independent, as it can model the geometry, evaluate the aerodynamics, and simulate the dynamics of aircraft with any lifting architecture; furthermore, the simulation model is fast and flexible, making it effective for the conceptual phase of aircraft design. The paper proposes the description of the take-off manoeuvre of two aircraft with different airframes: one with a conventional tube-and-wing architecture and one with a box-wing lifting system. The results proposed highlight the potential of the simulation model to detect aeromechanic and dynamic differences during the development of the manoeuvre for different aircraft configurations, and to assess the significance of considering ground effect aerodynamics.
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Valsecchi, Viviana, Giuseppe Gibertini et Andrea Morelli. « Wind Tunnel Test of Drafting at Endurance Run Velocity ». Mathematical Modelling of Engineering Problems 9, no 1 (28 février 2022) : 27–35. http://dx.doi.org/10.18280/mmep.090104.
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The aim of this study is to investigate and quantify the aerodynamics advantage, the physiological and performance advantage produced by pacemaker drafting in the case of long endurance running. The experimental tests have been carried out in a wind tunnel, at submaximal effort two runners done a treadmill run test of five minutes at 4.72 m/s with the same air velocity. By comparison of physiological parameters with and without drafting, the decreasing due to the pacemaker effect was obtained. A CFD simulation is used to analyze aerodynamic effects in terms of drag and drag coefficient with and without drafting at a wind speed of 4.72 m/s. Results indicates that compared to the baseline (running alone), the drafting position show a decrease in drag (-9.73%) and drag coefficient (-9.73%). This reduction in aerodynamic drag also leads to the reduction of the following physiological parameters, as detected by the experimental tests: oxygen consumption (-5.46%), metabolic power (-5.48%), energy cost (-7.31%), produced carbon dioxide (-7.40%), minute ventilation (-5.44%), HR (-0.60%), blood lactate concentration (-16.66%), RPE (-13.89%). Results demonstrate that drafting has a significant effect on aerodynamics parameters, but also on physiological and performance variables in highly and medium trained athletes.
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Singh, J., et S. C. Raisinghani. « Unsteady aerodynamic modelling for aircraft lateral parameter estimation ». Aeronautical Journal 95, no 943 (mars 1991) : 88–94. http://dx.doi.org/10.1017/s0001924000023617.
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SummaryA mathematical model of unsteady aerodynamic effects for use in lateral aircraft dynamics has been proposed based on Weissinger’s arrangement of trailing vortex system. The suggested model is shown to be suitable for use in parameter extraction algorithm. Simulated flight data of an example airplane has been analysed through maximum likelihood parameter estimation algorithm in frequency-domain to show the effect of inclusion and omission of unsteady aerodynamics on estimated parameters.
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Kim, H. W., A. R. Kenyon, R. E. Brown et K. Duraisamy. « Interactional aerodynamics and acoustics of a hingeless coaxial helicopter with an auxiliary propeller in forward flight ». Aeronautical Journal 113, no 1140 (février 2009) : 65–78. http://dx.doi.org/10.1017/s0001924000002797.
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Abstract The aerodynamics and acoustics of a generic coaxial helicopter with a stiff main rotor system and a tail-mounted propulsor are investigated using Brown’s Vorticity Transport Model. In particular, the model is used to capture the aerodynamic interactions that arise between the various components of the configuration. By comparing the aerodynamics of the full configuration of the helicopter to the aerodynamics of various combinations of its sub-components, the influence of these aerodynamic interactions on the behaviour of the system can be isolated. Many of the interactions follow a simple relationship between cause and effect. For instance, ingestion of the main rotor wake produces a direct effect on the unsteadiness in the thrust produced by the propulsor. The causal relationship for other interdependencies within the system is found to be more obscure. For instance, a dependence of the acoustic signature of the aircraft on the tailplane design originates in the changes in loading on the main rotor that arise from the requirement to trim the load on the tailplane that is induced by its interaction with the main rotor wake. The traditional approach to the analysis of interactional effects on the performance of the helicopter relies on characterising the system in terms of a network of possible interactions between the separate components of its configuration. This approach, although conceptually appealing, may obscure the closed-loop nature of some of the aerodynamic interactions within the helicopter system. It is suggested that modern numerical simulation techniques may be ready to supplant any overt reliance on this reductionist type approach and hence may help to forestall future repetition of the long history of unforeseen, interaction-induced dynamic problems that have arisen in various new helicopter designs.
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Ramanujam R, Vellingiri, et Ranjith Mohan. « Effect of Three-Dimensional Aerodynamics and Dynamic Stall on Lead–Lag Damping of an Isolated Rotor ». Journal of the American Helicopter Society 66, no 1 (1 janvier 2021) : 1–13. http://dx.doi.org/10.4050/jahs.66.012007.
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This paper investigates three-dimensional aerodynamic effects due to radial flow on lead–lag damping of a rotor in forward flight conditions. Three-dimensional effects in this study are restricted to yawed flow aerodynamics and radial flow coupling between blade segments. These effects are included in the ONERA dynamic stall model, and lead–lag damping for an isolated torsionally stiff rotor is calculated for different forward flight conditions. This augmented aerodynamic model with three-dimensional effects and Peters–He dynamic wake model improves the correlation of lead–lag damping with experimental data at high advance ratios. The effect of modeling static lift characteristics on damping correlation is also presented. Finally, a modification to the trailing edge separation point–based static lift model for improved yawed flow modeling amenable to aeromechanical stability analysis is proposed.
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Kaewbumrung, Tangsopa et Thongsri. « Investigation of the Trailing Edge Modification Effect on Compressor Blade Aerodynamics Using SST k-ω Turbulence Model ». Aerospace 6, no 4 (25 avril 2019) : 48. http://dx.doi.org/10.3390/aerospace6040048.
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A gas turbine power plant in Thailand had the problem of compressor blade fracture in Stages 6–8, which was caused by housing damage. This gas turbine has a total of 15 stages. The housing damage reduced the lifetime of blades to an unacceptable level. This article shall report the solution and outcomes. Three-dimensional (3D) compressor blade models in the problematic stages were prepared by a 3D scanning machine to find a solution based on computational fluid dynamics (CFD), and then were completed for simulation by adding Stages 5 and 9 to become a multi-stage axial model. The latter models were modified by trimming the trailing edge by 1, 5-, and 10-mm. Using ANSYS CFX R19.2 software, the CFD results of the trailing edge modification effect on flow using the shear stress transport (SST) k-ω turbulence model revealed aerodynamics inside the problematic stages both before and after blade modifications. Modifying the blade by 5 mm was suitable, because it had lesser effects on aerodynamic parameters: pressure ratio, drag, and lift coefficients, when compared to the modification of 10 mm. The larger the modification, the greater the effect on aerodynamics. The effects on aerodynamics were intensified when they were modified by 10 mm. The validation of base line blades was conducted for the overall compressor parameters that were compared with the measurable data. These results were accepted and gave positive feedbacks from engineers who practically applied our reports in a real maintenance period of gas turbine.
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Nakashima, Takuji, Hidemi Mutsuda, Taiga Kanehira et Makoto Tsubokura. « Fluid-Dynamic Force Measurement of Ahmed Model in Steady-State Cornering ». Energies 13, no 24 (14 décembre 2020) : 6592. http://dx.doi.org/10.3390/en13246592.
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The effects of on-road disturbances on the aerodynamic drag are attracting attention in order to accurately evaluate the fuel efficiency of an automobile on a road. The present study investigated the effects of cornering motion on automobile aerodynamics, especially focusing on the aerodynamic drag. Using a towing tank facility, measurements of the fluid-dynamic force acting on Ahmed models during steady-state cornering were conducted in water. The investigation included Ahmed models with slant angles θ = 25° and 35°, reproducing the wake structures of two different types of automobiles. The drag increase due to steady-state cornering motion was experimentally measured, and showed good agreement with previous numerical research, with the measurements conducted at a Reynolds number of 6 × 105, based on the model length. The Ahmed model with θ = 35° showed a greater drag increase due to the steady-state cornering motion than that with θ = 25°, and it reached 15% of the total drag at a corner with a radius that was 10 times the vehicle length. The results indicated that the effect of the cornering motion on the automobile aerodynamics would be more important, depending on the type of automobile and its wake characteristics.
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Barber, Tracie, Christopher Beves, Sam Diasinos, Graham Doig, Eddie Leonardi et Andrew Neely. « Studies of ground effect automotive aerodynamics ». ATZautotechnology 7, no 2 (mars 2007) : 52–55. http://dx.doi.org/10.1007/bf03246992.
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Doig, G. « Transonic and supersonic ground effect aerodynamics ». Progress in Aerospace Sciences 69 (août 2014) : 1–28. http://dx.doi.org/10.1016/j.paerosci.2014.02.002.
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Asai, T., S. Koike, K. Seo, H. Nunome et R. Sakashita. « AERODYNAMICS OF KNUCKLE EFFECT IN SOCCER ». Journal of Biomechanics 40 (janvier 2007) : S194. http://dx.doi.org/10.1016/s0021-9290(07)70190-2.
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Gundy-Burlet, K. L., M. M. Rai, R. C. Stauter et R. P. Dring. « Temporally and Spatially Resolved Flow in a Two-Stage Axial Compressor : Part 2—Computational Assessment ». Journal of Turbomachinery 113, no 2 (1 avril 1991) : 227–32. http://dx.doi.org/10.1115/1.2929090.
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Fluid dynamics of turbomachines are complicated because of aerodynamic interactions between rotors and stators. It is necessary to understand the aerodynamics associated with these interactions in order to design turbomachines that are both light and compact as well as reliable and efficient. The current study uses an unsteady, thin-layer Navier–Stokes zonal approach to investigate the unsteady aerodynamics of a multistage compressor. Relative motion between rotors and stators is made possible by the use of systems of patched and overlaid grids. Results have been computed for a 2 1/2-stage compressor configuration. The numerical data compare well with experimental data for surface pressures and wakes. In addition, the effect of grid refinement on the solution is studied.
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Yuan, Ye, Douglas Thomson et David Anderson. « Aerodynamic Uncertainty Quantification for Tiltrotor Aircraft ». Aerospace 9, no 5 (18 mai 2022) : 271. http://dx.doi.org/10.3390/aerospace9050271.
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The tiltrotor has unique flight dynamics due to the aerodynamic interference characteristics. Multiple aerodynamics calculation approaches, such as the CFD method, are utilised to characterise this feature. The calculation process is usually time-consuming, and the obtained results are generally varied from each other. Thus, the uncertainty quantification (UQ) method will be utilised in this research to identify the aerodynamic inaccuracy effect on the handling qualities of the tiltrotor aircraft. The study aims to quantify the influence of the aerodynamic interference on the tiltrotor flight dynamics in different flight states, such as forward speeds and nacelle tilting angles, which can guide the flight dynamics modelling simplification to improve the simulation efficiency. Therefore, uncertainty identification and full factorial numerical integration (FFNI) methods are introduced to scale these aerodynamic uncertainties. The eigenvalue and bandwidth and phase delay requirements are presented as the failure criteria. The UQ calculation indicates that the uncertainties of the aerodynamic calculation significantly affect the handling quality ratings in two flight ranges: the helicopter mode and the conversion and aeroplane modes with higher forward speed (close to the conversion envelope). Furthermore, a sensitivity analysis is performed to identify the mechanism behind these influences. The results demonstrate that aerodynamics affect the pitching attitude, the pitching damping, and the velocity and incidence stability derivatives. However, the effects of the velocity stability and the incidence stability are the reason causing the handling qualities’ degradation in the helicopter mode and high-speed mode, respectively.
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Bhagya Lakshmi Nageswari, M., et Dr U. S. Jyothi. « Aerodynamic analysis of railway wagon on drag coefficient ». E3S Web of Conferences 184 (2020) : 01058. http://dx.doi.org/10.1051/e3sconf/202018401058.
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Aerodynamics play a major role in transport. When speed increases aerodynamic factors come into existence. By altering the design in an aerodynamic way, it can lead to better efficiency. This paper presents the effect of aerodynamic parameters on the wagon. The analysis was carried out on the existing and modified geometries using ANSYS Fluent 18.1softwareconsidered in the static ground conditions with the wind flowing at zero yaw angles. It was found that the coefficient of drag (Cd) is reduced by 17.7% for the modified wagon with the realistic wagon on an average.
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Zhang, Jingyu, Mingjin Zhang, Yongle Li, Xu Huang et Zhong Zheng. « Aerodynamics of High-Sided Vehicles on Truss Girder Considering Sheltering Effect by Wind Tunnel Tests ». Baltic Journal of Road and Bridge Engineering 15, no 2 (25 juin 2020) : 66–88. http://dx.doi.org/10.7250/bjrbe.2020-15.473.
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Aerodynamic characteristics of vehicles are directly related to their running safety, especially for the high-sided vehicles. In order to study the aerodynamic characteristics under multiple sheltering conditions, a complex large scale (1:20.4) truss model and three high-sided vehicles including articulated lorry, travelling bus and commercial van models with the same scale were built. The aerodynamic coefficients under various sheltering effects of wind barriers with different heights and porosities, bridge tower and the vehicle on the adjacent lane were measured. According to the results, wind barriers can effectively reduce wind speed behind them, thus decreasing the wind load acting on the vehicle, which causes the decrease of the aerodynamic response of all three vehicles. However, the influence at the leeward side is limited due to installation of central stabilizers. When the vehicle passes through the bridge tower, a sudden change occurs, the aerodynamic coefficients decrease and fluctuate in varying degrees, especially for the commercial van. When the vehicle moves in different lanes behind the bridge tower, the sheltering effect of the tower on the aerodynamic coefficient in Lane 1 is much greater than that in Lane 2. With regard to the interference between two vehicles on the adjacent lanes, the relative windward area between the test vehicle and the interference vehicle greatly affects the aerodynamics of the test vehicle.
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Hubbard, Mont, et Christy D. Bergman. « Effect of Vibrations on Javelin Lift and Drag ». International Journal of Sport Biomechanics 5, no 1 (février 1989) : 40–59. http://dx.doi.org/10.1123/ijsb.5.1.40.
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The theory of crossflow aerodynamics is used to estimate the effect of thrower-induced vibrations on javelin mean lift and drag. Vibrations of all modes increase both lift and drag from the vibration-free condition. Percentage in-creases in lift and drag are largest at small mean angles of attack, large vibrational amplitudes, and large relative wind speeds. Thus the consequences of vibration effects on aerodynamics may be most significant for elite throwers.
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Zhu, Tianci, et Wenhui Li. « Numerical study of the trailing vehicle length on train aerodynamics under crosswind ». AIP Advances 13, no 2 (1 février 2023) : 025366. http://dx.doi.org/10.1063/5.0131877.
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Limited by the wind tunnel size, a one-and-a-half train model is generally adopted during the test to represent the realistic long tandem. Thus, the reasonable arrangement of the trailing vehicle length is of significance for experimental accuracy. In this work, the aerodynamic performance of trains with different trailing vehicle lengths subjected to crosswind was studied using the improved detached eddy simulation method combined with the shear–stress–transport k– ω turbulence model. The 1/8th scaled high-speed trains with five trailing lengths were proposed, and the aerodynamic differences were evaluated at yaw angles ranging from β = 0° to β = 60°. The numerical method was validated by the previous wind tunnel test. Results show that the aerodynamics and flow patterns of the L a = 0.50 and the benchmark are highly relevant. The downstream dummy vehicle length has the greatest effect on aerodynamic coefficients at a higher yaw angle ( β > 30°), especially at β = 60°, whereas the effects become insignificant at a lower yaw angle ( β < 30°). For various L a lengths, notable discrepancy appears at the leeward and top side where large vortexes shed off from the roof. The larger contributions to the lateral force and lift force coefficients are mainly due to these areas. A suitable length of L a = 0.50 is therefore recommended to obtain more accurate aerodynamics of a long train set.
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Hong, Sungchan, et Takeshi Asai. « Effect of Surface Groove Structure on the Aerodynamics of Soccer Balls ». Applied Sciences 10, no 17 (25 août 2020) : 5877. http://dx.doi.org/10.3390/app10175877.
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Soccer balls have undergone dramatic changes in their surface structure that can affect their aerodynamics. The properties of the soccer ball surface such as the panel shape, panel orientation, seam characteristics, and surface roughness have a significant impact on its aerodynamics and flight trajectory. In this study, we performed wind-tunnel tests to investigate how the introduction of grooves on the surface of a soccer ball affects the flight stability and aerodynamic forces on the ball. Our results show that for soccer balls without grooves, changing the panel orientation of the ball causes a significant change in the drag coefficient. Soccer balls with grooves exhibited a smaller change in air resistance (Cd) in the supercritical region (20 to 30 m/s; 3.0 × 105 ≤ Re ≤ 4.7 × 105), compared to the ungrooved ball where only the panel orientation was changed. Furthermore, at power-shot speeds (25 m/s), the grooved ball exhibited smaller variations in lift force and side force than the ungrooved ball. These results suggest that a long groove structure on the surface of the soccer ball has a significant impact on the air flow around the ball in the supercritical region, and has the effect of keeping the air flow separation line constant.
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Chen, Zhaolin, et Fan Yang. « Propeller Slipstream Effect on Aerodynamic Characteristics of Micro Air Vehicle at Low Reynolds Number ». Applied Sciences 12, no 8 (18 avril 2022) : 4092. http://dx.doi.org/10.3390/app12084092.
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A numerical investigation on propeller-induced flow effects in tractor configurations on a Zimmerman wing-fuselage using the cambered thin airfoil is presented in this paper. The Reynolds number based on the mean aerodynamic chord was 1.3 × 105. Significant aerodynamic performance benefits could be found for a propeller in the tractor configuration. The numerical results showed that the propeller slipstream effect on the wings was highly dependent on the size of the propeller, and the major slipstream effect was working at 60% inboard wingspan, whereas less effects were observed towards the wingtip. The propeller slipstream increased the local angle of attack on the up-going blade side. This effect simultaneously augmented the section lift. The unsteady Reynolds-averaged Navier–Stokes (URANS) simulations helped to improve understanding of the interaction of the propeller wake and the wing-fuselage, which is an important aspect to guide the design of future efficient and controllable micro air vehicles. The results indicated that, in MAV designs, the slipstream from the propeller had a significant effect on the wing aerodynamics, regarding both performance and stability of the vehicle.
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Yahiaoui, Toufik, Toufik Zebbiche, Abderrazak Allali et Mohamed Boun-jad. « Gas effect for oblique and conical shock waves at high temperature ». Mathematical Modelling of Natural Phenomena 15 (2020) : 73. http://dx.doi.org/10.1051/mmnp/2020036.
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The work focuses to develop a new numerical calculation program for determining the gas effect at high temperature instead air on the calculation of the oblique and conical shock waves parameters and make applications for various external and internal aerodynamics problems like, the calculation of the suitable intake adaptation parameters, dihedron and cone wave drag, aerodynamic coefficients of a pointed supersonic airfoil and oblique shock reflection without forgetting others no less important like the detonation propulsion and the dust explosion applications, where the high temperature gas effect is very important. All this for future aerodynamics (gas dynamics) like the phenomenon of climate change in the near and far future because of the enlargement progressive of the layer ozone hole which will lead to an increase in the temperature of the ambient medium, and by the environment pollution by the shining of the waste which will cause a new decomposition of gases from the ambient environment. Another interesting application for actual aerodynamics (gas dynamics) is the performance of tests in wind tunnels supplied by a combustion chamber making a reaction of gases giving a gas with new thermodynamics parameters which is not necessarily air. To make a calculation, the selected gases are H2, O2, N2, CO, CO2, H2O, NH3, CH4 and air. All shock parameters depend on the stagnation temperature, upstream Mach number, the thermodynamics of the used gas, dihedron and cone deviation and others parameters. The specific heat at constant pressure varies with the temperature and the selected gas. Gas is still considered as perfect. It is calorically imperfect, and thermally perfect, less than the molecules dissociation threshold. A comparison between the parameters of each gas and air is presented to choose the suitable gas witch giving good performances as required by design parameters instead air.
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Mondal, Partha. « Prediction of Moment Using a Modified Discrete Vortex Method in Ground Effect ». Defence Science Journal 71, no 2 (10 mars 2021) : 146–52. http://dx.doi.org/10.14429/dsj.71.16127.
Texte intégralRésumé :
The aerodynamics around a wing is modified when it comes near the ground. This is generally referred to as ground effect. In this work, a discrete vortex method based model which can predict two-dimensional (2D) ground effect from its free flight data is proposed. The required data in free flight could be generated either from high fidelity CFD solver or experiments. In this method, strength of the vortex distribution as obtained from discrete vortex based method is modified using a constrained optimisation procedure to match the free flight aerodynamic data. This vortex distribution is further modified due the presence of the ground. The efficacy of present model is demonstrated for predicting the moment of multi element airfoils in ground effect. The predicted aerodynamic coefficient in ground effect compares well with high fidelity CFD data.
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Pirrung, Georg, Vasilis Riziotis, Helge Madsen, Morten Hansen et Taeseong Kim. « Comparison of a coupled near- and far-wake model with a free-wake vortex code ». Wind Energy Science 2, no 1 (20 janvier 2017) : 15–33. http://dx.doi.org/10.5194/wes-2-15-2017.
Texte intégralRésumé :
Abstract. This paper presents the integration of a near-wake model for trailing vorticity, which is based on a prescribed-wake lifting-line model proposed by Beddoes(1987), with a blade element momentum (BEM)-based far-wake model and a 2-D shed vorticity model. The resulting coupled aerodynamics model is validated against lifting-surface computations performed using a free-wake panel code. The focus of the description of the aerodynamics model is on the numerical stability, the computation speed and the accuracy of unsteady simulations. To stabilize the near-wake model, it has to be iterated to convergence, using a relaxation factor that has to be updated during the computation. Further, the effect of simplifying the exponential function approximation of the near-wake model to increase the computation speed is investigated in this work. A modification of the dynamic inflow weighting factors of the far-wake model is presented that ensures good induction modeling at slow timescales. Finally, the unsteady airfoil aerodynamics model is extended to provide the unsteady bound circulation for the near-wake model and to improve the modeling of the unsteady behavior of cambered airfoils. The model comparison with results from a free-wake panel code and a BEM model is centered around the NREL 5 MW reference turbine. The response to pitch steps at different pitching speeds is compared. By means of prescribed vibration cases, the effect of the aerodynamic model on the predictions of the aerodynamic work is investigated. The validation shows that a BEM model can be improved by adding near-wake trailed vorticity computation. For all prescribed vibration cases with high aerodynamic damping, results similar to those obtained by the free-wake model can be achieved in a small fraction of computation time with the proposed model. In the cases with low aerodynamic damping, the addition of trailed vorticity modeling shifts the results closer to those obtained by using the free-wake code, but differences remain.
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Chiang, H. W. D., et S. Fleeter. « Passive Control of Flow-Induced Vibrations by Splitter Blades ». Journal of Turbomachinery 116, no 3 (1 juillet 1994) : 489–500. http://dx.doi.org/10.1115/1.2929438.
Texte intégralRésumé :
Splitter blades as a passive control technique for flow-induced vibrations are investigated by developing an unsteady aerodynamic model to predict the effect of incorporating splitter blades into the design of an axial flow blade row operating in an incompressible flow field. The splitter blades, positioned circumferentially in the flow passage between two principal blades, introduce aerodynamic and/or combined aerodynamic-structural detuning into the rotor. The unsteady aerodynamic gust response and resulting oscillating cascade unsteady aerodynamics, including steady loading effects, are determined by developing a complete first-order unsteady aerodynamic analysis together with an unsteady aerodynamic influence coefficient technique. The torsion mode flow induced vibrational response of both uniformly spaced tuned rotors and detuned rotors are then predicted by incorporating the unsteady aerodynamic influence coefficients into a single-degree-of-freedom aero-elastic model. This model is then utilized to demonstrate that incorporating splitters into axial flow rotor designs is beneficial with regard to flow induced vibrations.
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Guo, Jinghui, Guiping Lin, Xueqin Bu, Shiming Fu et Yanmeng Chao. « Effect of static shape deformation on aerodynamics and aerothermodynamics of hypersonic inflatable aerodynamic decelerator ». Acta Astronautica 136 (juillet 2017) : 421–33. http://dx.doi.org/10.1016/j.actaastro.2017.03.019.
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Barber, Tracie J. « A Study of Water Surface Deformation Due to Tip Vortices Wing-in-Ground Effect ». Journal of Ship Research 51, no 02 (1 juin 2007) : 182–86. http://dx.doi.org/10.5957/jsr.2007.51.2.182.
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The accurate prediction of ground effect aerodynamics is an important aspect of wing-in-ground (WIG) effect vehicle design. When WIG vehicles operate over water, the deformation of the nonrigid surface beneath the body may affect the aerodynamic performance of the craft. The likely surface deformation has been considered from a theoretical and numerical position. Both two-dimensional and three-dimensional cases have been considered, and results show that any deformation occurring on the water surface is likely to be caused by the wing tip vortices rather than an increased pressure distribution beneath the wing.
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Zhang, Xin, et Willem Toet. « Ground effect aerodynamics research of racing cars ». ATZautotechnology 6, no 6 (novembre 2006) : 40–43. http://dx.doi.org/10.1007/bf03246972.
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Chernousov, V. I., A. A. Krutov, P. V. Savin et E. A. Pigusov. « Ground effect aerodynamics of twin fuselage aircraft ». IOP Conference Series : Materials Science and Engineering 1226, no 1 (1 février 2022) : 012016. http://dx.doi.org/10.1088/1757-899x/1226/1/012016.
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Abstract The paper presents experimental study results of ground effect influence on the aerodynamic characteristics of the twin fuselage transport airplane in a low-speed wind tunnel. The aerodynamic configuration has the two fuselages distributed under high-wing, and a “TT”–shaped tail. The twin fuselage transport airplane model consists of two fuselages, wing, empennage and external tank. The analysis includes studying the ground effect on the longitudinal and lateral aerodynamic characteristics and horizontal tail effectiveness. The effect of installing an external cryogenic fuel tank under the wing between the fuselages of the model was considered too. The obtained data shows the typical behaviour of the aerodynamic characteristics near the ground plate for aircraft model with high-wing and high placed horizontal tail. Ground proximity significantly increases the maximum lift-to-drag ratio and slightly changes the longitudinal moment characteristics. Horizontal tail effectiveness is maintained for all tailplane angles near the ground plate. The longitudinal and lateral stability of the twin fuselage transport airplane model is maintained in all considered modes near the ground plate.
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Zhang, Z., P. G. Lafleur et F. Bertrand. « Effect of Aerodynamics on Film Blowing Process ». International Polymer Processing 21, no 5 (novembre 2006) : 527–35. http://dx.doi.org/10.3139/217.0037.
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Djavareshkian, M. H., A. Esmaeli et A. Parsani. « Aerodynamics of smart flap under ground effect ». Aerospace Science and Technology 15, no 8 (décembre 2011) : 642–52. http://dx.doi.org/10.1016/j.ast.2011.01.005.
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Yang, Qinghua. « The effect of aerodynamics on table tennis ». Theoretical and Natural Science 5, no 1 (25 mai 2023) : 465–73. http://dx.doi.org/10.54254/2753-8818/5/20230284.
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In the table tennis sport category, the different spin formula of table tennis ball will show different motion state, in which the important physical knowledge that is permeated aerodynamics. Besides the effect of aerodynamics, the balls can obtain different trajectories because of Magnus effect and Bernoulli principle. By using these three mainly professional knowledge, this paper analyzed the forces that the top-spin ball and back-spin ball acquired. What is more, the movement of side spin balls also be introduced through these professional knowledge. In addition to these analysis, 40mm and 38mm table tennis balls are compared in the paper. By using the principle of physical mechanics to reveal the secret and mechanism of the spin of table tennis ball, it provides a theoretical basis for improving the spin skill of table tennis ball.
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Zhao, Hong Yan, Peng Fei Zhang et Yun Ma. « The Influence of the Flight Aerodynamic for Interactions of Wings and Body of the Honeybee ». Applied Mechanics and Materials 670-671 (octobre 2014) : 700–704. http://dx.doi.org/10.4028/www.scientific.net/amm.670-671.700.
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The flight mechanism of flapping-wing was studied by using the translation-rotation model. We established the flapping-coordinate of the wing, gave the equation of the motion, and simplified the flapping-wing model. The aerodynamic and vortices were simulated by the CFD software of Fluent. The leading-edge vortex generated in the translation phase, and delayed stall mechanism had an important effect on the high lift. In the rotation phase, lift peaks appear due to the wing rapidly rotating and rotational circulation mechanism. The aerodynamics were obtained in different amplitudes, frequencies, angles of attack, the locations of rotating axis and timings of rotation. The influence of these parameters on average lift coefficient is obvious, while it can be ignored to average drag coefficient. Keywords: wing, aerodynamics, vortices, numerical simulation.
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Vaidhye, Rahul. « Blade Design and Performance Analysis of Wind Turbine ». International Journal for Research in Applied Science and Engineering Technology 10, no 6 (30 juin 2022) : 2220–27. http://dx.doi.org/10.22214/ijraset.2022.44217.
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Abstract: This paper reviews the design optimization of wind turbine blades through investigating the design methods and analyzing the performance of the blades. The current research work in this area include wind turbine blade geometric design and optimization, aerodynamics analysis, wind turbine blade structural design and dynamics analysis. Blade geometric design addresses the design parameters, including airfoils and their aerodynamic coefficients, attack angles, design tip speed ratio, design and/or rated wind speed, rotor diameter, blade aerodynamic shape with chord length and twist distributions, so that the blade achieves an optimum powerperformance. The geometry of the blade is an aerodynamic shape with nonlinear chord and twist distribution, which can be obtained based on the BEM theory with respect to given aerofoil with known aerodynamic coefficients. In terms of blade aerodynamics analysis, there are four types of aerodynamic models which can be used to predict the aerodynamic performance of blades, including blade element momentum (BEM) model, lifting panel and vortex model, actuator line model, and computational fluid dynamics (CFD) model. Among the four, computational fluid dynamics (CFD) model has been used to calculate the aerodynamic effect on the bladeairfoil. Critical Reynolds number and constant wind speed has been considered during analysis under different turbulence models Viz, spallart-almaras, k-epsilon, invicid flow. During investigation it is observed that only k- epsilon showed efficient results than others and 14 degree angle of attack (AOA) is the optimum value at which there is much lift coefficient and minimum drag