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Articles de revues sur le sujet "Micro air vehicles. Micro air vehicles Insects Wings (Anatomy) Reynolds number"
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Shyy, Wei, Peter Ifju et Dragos Viieru. « Membrane Wing-Based Micro Air Vehicles ». Applied Mechanics Reviews 58, no 4 (1 juillet 2005) : 283–301. http://dx.doi.org/10.1115/1.1946067.
Texte intégralRésumé :
Micro air vehicles (MAVs) with a wingspan of 15cm or shorter, and flight speed around 10m∕s have attracted substantial interest in recent years. There are several prominent features of MAV flight: (i) low Reynolds number (104-105), resulting in degraded aerodynamic performance, (ii) small physical dimensions, resulting in certain favorable scaling characteristics including structural strength, reduced stall speed, and impact tolerance, and (iii) low flight speed, resulting in order one effect of the flight environment and intrinsically unsteady flight characteristics. Flexible wings utilizing membrane materials are employed by natural flyers such as bats and insects. Compared to a rigid wing, a membrane wing can better adapt to the stall and has the potential for morphing to achieve enhanced agility and storage consideration. We will discuss the aerodynamics of both rigid and membrane wings under the MAV flight condition. To understand membrane wing performance, the fluid and structure interaction is of critical importance. Flow structures associated with the low Reynolds number and low aspect ratio wing, such as pressure distribution, separation bubble, and tip vortex, as well as structural dynamics in response to the surrounding flow field are discussed. Based on the computational capabilities for treating moving boundary problems, an automated wing shape optimization technique is also developed. Salient features of the flexible-wing-based MAV, including the vehicle concept, flexible wing design, novel fabrication methods, aerodynamic assessment, and flight data analysis are highlighted.
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Bhat, Shantanu S., Jisheng Zhao, John Sheridan, Kerry Hourigan et Mark C. Thompson. « Evolutionary shape optimisation enhances the lift coefficient of rotating wing geometries ». Journal of Fluid Mechanics 868 (11 avril 2019) : 369–84. http://dx.doi.org/10.1017/jfm.2019.183.
Texte intégralRésumé :
Wing shape is an important factor affecting the aerodynamic performance of wings of monocopters and flapping-wing micro air vehicles. Here, an evolutionary structural optimisation method is adapted to optimise wing shape to enhance the lift force due to aerodynamic pressure on the wing surfaces. The pressure distribution is observed to vary with the span-based Reynolds number over a range covering most insects and samaras. Accordingly, the optimised wing shapes derived using this evolutionary approach are shown to adjust with Reynolds number. Moreover, these optimised shapes exhibit significantly higher lift coefficients (${\sim}50\,\%$) than the initial rectangular wing forebear. Interestingly, the optimised shapes are found to have a large area outboard, broadly in line with the features of high-lift forewings of multi-winged insects. According to specific aerodynamic performance requirements, this novel method could be employed in the optimisation of improved wing shapes for micro air vehicles.
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Zhang, Xiao Quan, et L. Tian. « Three-Dimensional Simulation of Micro Air Vehicles with Low-Aspect-Ratio Wings ». Key Engineering Materials 339 (mai 2007) : 377–81. http://dx.doi.org/10.4028/www.scientific.net/kem.339.377.
Texte intégralRésumé :
Micro Air Vehicles (MAVs) are catching more and more attentions for their broad application in civilian and military fields. Since the theories on the aerodynamics of low Reynolds number are not maturely presented and the wind-tunnel experiments cost long periods and great expenses. The numerical simulation based on computational fluid dynamics (CFD) is a good method to choose. Through three-dimensional simulation of the wings, the aerodynamic characteristics of the flows around MAVs can be easily obtained. The tip vortices produced around low-Reynolds-number and low-aspect-ratio wings can increase the lift and stall angles. The result of numerical simulation can be used as references of theory analysis and wind-tunnel experiments.
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Gourdain, Nicolas, Thierry Jardin, Ronan Serre, Sébastien Prothin et Jean-Marc Moschetta. « Application of a lattice Boltzmann method to some challenges related to micro-air vehicles ». International Journal of Micro Air Vehicles 10, no 3 (septembre 2018) : 285–99. http://dx.doi.org/10.1177/1756829318794174.
Texte intégralRésumé :
The demand for micro-air vehicles is increasing as well as their potential missions. Whether for discretion in military operations or noise pollution in civilian use, the improvement of aerodynamic and acoustic performance of micro-air vehicles propeller is a goal to achieve. Micro- and nano-air vehicles operate at Reynolds numbers ranging from 103 to 105. In these conditions, the aerodynamic performance of conventional fixed and rotary wings concepts drastically decreases due to the increased importance of flow viscous forces that tend to increase drag and promote flow separation, which leads to reduced efficiency and reduced maximum achievable lift. Reduced efficiency and lift result in low endurance and limited payloads. The numerical simulation is a potential solution to better understand such low Reynolds number flows and to increase the micro-air vehicles’ performance. In this paper, it is proposed to review some challenges related to micro-air vehicles by using a Lattice-Boltzmann method. The method is first briefly presented, to point out its strengths and weaknesses. Lattice-Boltzmann method is then applied to three different applications: a DNS of a single blade rotor, a large eddy simulation of a rotor operating in-ground effect and a large eddy simulation of a rotor optimised for acoustic performance. A comparison with reference data (Reynolds Averaged Navier-Stokes, DNS or experimental data) is systematically done to assess the accuracy of lattice-Boltzmann method-based predictions. The analysis of results demonstrates that lattice-Boltzmann method has a good potential to predict the mean aerodynamic performance (torque and thrust) if the grid resolution is chosen adequately (which is not always possible due to limited computational resources). A study of the turbulent flow is conducted for each application in order to highlight some of the physical flow phenomena that take place in such rotors. Different designs are also investigated, showing that potential improvements are still possible in terms of aerodynamic and aero-acoustic performance of low-Reynolds rotors.
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DWIVEDI, Y. D., ABHISHEK MOHAPATRA, T. BLESSINGTON et Md IRFAN. « Experimental Flow Field Investigation of the Bio-Inspired Corrugated Wing for MAV Applications ». INCAS BULLETIN 13, no 2 (4 juin 2021) : 37–50. http://dx.doi.org/10.13111/2066-8201.2021.13.2.5.
Texte intégralRésumé :
This is an experimental flow field study of a bio-inspired corrugated finite wing from the dragonfly intended to assess the flow behavior over the wing and compare it with a wing of the same geometry with filled corrugation, at low Reynolds numbers 46000 and 67000. The work purpose is to explore the potential application of such types of wings for Micro Air Vehicles (MAVs) or micro sized Unmanned Air Vehicles (UAVs). Two types of wings are taken into account: first wing was a bio-inspired corrugated wing which was obtained from the mid span of the dragonfly, and the second wing was the same geometry with filled corrugation. Both wings were fabricated by using 3-D printing machine. The tufts were glued at three different locations i.e. at center, 30%, and 60% of the semi-span towards the right side of the wing at the trailing edge. The boundary layers were measured by using boundary layer rakes inside the open-end low speed wing tunnel with varied angles of attack. The results of the tuft flow visualization showed that the flow pattern at different span locations was different at different angles of attack and different wing velocities (Reynolds number). The fluctuations of the two different wings at the same angle of attack and Reynolds number were found different. Also, the directions of the flow for both wings were found to be different at different span locations. The boundary layer measurement results for both wings were found to be different at the same angles of attack and Reynolds numbers. The flow pattern also showed that the wing’s upper as well as lower surface behaved differently on the same wing under the same measurement conditions. The results showed that the corrugated wing outperformed the conventional wing at low Reynolds number and the stall angle of the corrugated wing was more than the conventional wing.
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Liu, Hao, Sridhar Ravi, Dmitry Kolomenskiy et Hiroto Tanaka. « Biomechanics and biomimetics in insect-inspired flight systems ». Philosophical Transactions of the Royal Society B : Biological Sciences 371, no 1704 (26 septembre 2016) : 20150390. http://dx.doi.org/10.1098/rstb.2015.0390.
Texte intégralRésumé :
Insect- and bird-size drones—micro air vehicles (MAV) that can perform autonomous flight in natural and man-made environments are now an active and well-integrated research area. MAVs normally operate at a low speed in a Reynolds number regime of 10 4 –10 5 or lower, in which most flying animals of insects, birds and bats fly, and encounter unconventional challenges in generating sufficient aerodynamic forces to stay airborne and in controlling flight autonomy to achieve complex manoeuvres. Flying insects that power and control flight by flapping wings are capable of sophisticated aerodynamic force production and precise, agile manoeuvring, through an integrated system consisting of wings to generate aerodynamic force, muscles to move the wings and a control system to modulate power output from the muscles. In this article, we give a selective review on the state of the art of biomechanics in bioinspired flight systems in terms of flapping and flexible wing aerodynamics, flight dynamics and stability, passive and active mechanisms in stabilization and control, as well as flapping flight in unsteady environments. We further highlight recent advances in biomimetics of flapping-wing MAVs with a specific focus on insect-inspired wing design and fabrication, as well as sensing systems. This article is part of the themed issue ‘Moving in a moving medium: new perspectives on flight’.
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Suzuki, Kosuke, Keisuke Minami et Takaji Inamuro. « Lift and thrust generation by a butterfly-like flapping wing–body model : immersed boundary–lattice Boltzmann simulations ». Journal of Fluid Mechanics 767 (20 février 2015) : 659–95. http://dx.doi.org/10.1017/jfm.2015.57.
Texte intégralRésumé :
AbstractThe flapping flight of tiny insects such as flies or larger insects such as butterflies is of fundamental interest not only in biology itself but also in its practical use for the development of micro air vehicles (MAVs). It is known that a butterfly flaps downward for generating the lift force and backward for generating the thrust force. In this study, we consider a simple butterfly-like flapping wing–body model in which the body is a thin rod and the rectangular rigid wings flap in a simple motion. We investigate lift and thrust generation of the model by using the immersed boundary–lattice Boltzmann method. First, we compute the lift and thrust forces when the body of the model is fixed for Reynolds numbers in the range of 50–1000. In addition, we estimate the supportable mass for each Reynolds number from the computed lift force. Second, we simulate free flights when the body can only move translationally. It is found that the expected supportable mass can be supported even in the free flight except when the mass of the body relative to the mass of the fluid is too small, and the wing–body model with the mass of actual insects can go upward against the gravity. Finally, we simulate free flights when the body can move translationally and rotationally. It is found that the body has a large pitch motion and consequently gets off-balance. Then, we discuss a way to control the pitching angle by flexing the body of the wing–body model.
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Lambert, William B., Mathew J. Stanek, Roi Gurka et Erin E. Hackett. « Leading-edge vortices over swept-back wings with varying sweep geometries ». Royal Society Open Science 6, no 7 (juillet 2019) : 190514. http://dx.doi.org/10.1098/rsos.190514.
Texte intégralRésumé :
Micro air vehicles are used in a myriad of applications, such as transportation and surveying. Their performance can be improved through the study of wing designs and lift generation techniques including leading-edge vortices (LEVs). Observation of natural fliers, e.g. birds and bats, has shown that LEVs are a major contributor to lift during flapping flight, and the common swift ( Apus apus ) has been observed to generate LEVs during gliding flight. We hypothesize that nonlinear swept-back wings generate a vortex in the leading-edge region, which can augment the lift in a similar manner to linear swept-back wings (i.e. delta wing) during gliding flight. Particle image velocimetry experiments were performed in a water flume to compare flow over two wing geometries: one with a nonlinear sweep (swift-like wing) and one with a linear sweep (delta wing). Experiments were performed at three spanwise planes and three angles of attack at a chord-based Reynolds number of 26 000. Streamlines, vorticity, swirling strength, and Q -criterion were used to identify LEVs. The results show similar LEV characteristics for delta and swift-like wing geometries. These similarities suggest that sweep geometries other than a linear sweep (i.e. delta wing) are capable of creating LEVs during gliding flight.
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Lin, T., W. Xia et S. Hu. « Effect of chordwise deformation on propulsive performance of flapping wings in forward flight ». Aeronautical Journal 125, no 1284 (17 août 2020) : 430–51. http://dx.doi.org/10.1017/aer.2020.72.
Texte intégralRésumé :
ABSTRACTLack of flexibility limits the performance enhancement of man-made flapping wing Micro Air Vehicles (MAVs). Active chordwise deformation (bending) is introduced into the flapping wing model at low Reynolds number of Re = 200 in the present study. The lattice Boltzmann method with immersed boundary is adopted in the numerical simulation. The effects of the bending amplitude, bending frequency and phase lag between bending and flapping on the propulsive performance are analysed. The numerical results show that all the chordwise deformation parameters including the bending amplitude, bending frequency and phase lag have a great influence on the flow field, Leading-Edge Vortex (LEV), Trailing-Edge Vortex (TEV) and previous Leading-Edge Vortex (pLEV) of the deformable flapping wing, which leads to the variation of the propulsive performance. With decreasing bending amplitude and increasing bending frequency, both the thrust and energy dissipation coefficients increase. The highest thrust coefficient and highest energy dissipation coefficient occur at a phase lag of 180°. On the other hand, strong dependence of the propulsive efficiency on the vortex tangle is found. The highest propulsive efficiency is obtained for the present model at a dimensionless bending amplitude of 0.2, bending frequency of 0.7Hz, and phase lag of 0°.
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Uthra, M. P., et A. Daniel Antony. « Comparative Investigation of Laminar Separation Bubble on a Wing at Low Reynolds Number ». International Journal of Vehicle Structures and Systems 12, no 3 (19 octobre 2020). http://dx.doi.org/10.4273/ijvss.12.3.22.
Texte intégralRésumé :
Most admirable and least known features of low Reynolds number flyers are their aerodynamics. Due to the advancements in low Reynolds number applications such as Micro Air vehicles (MAV), Unmanned Air Vehicles (UAV) and wind turbines, researchers’ concentrates on Low Reynolds number aerodynamics and its effect on aerodynamic performance. The Laminar Separation Bubble (LSB) plays a deteriorating role in affecting the aerodynamic performance of the wings. The parametric study has been performed to analyse the flow around cambered, uncambered wings with different chord and Reynolds number in order to understand the better flow characteristics, LSB and three dimensional flow structures. The computational results are compared with experimental results to show the exact location of LSB. The presence of LSB in all cases is evident and it also affects the aerodynamic characteristics of the wing. There is a strong formation of vortex in the suction side of the wing which impacts the LSB and transition. The vortex structures impact on the LSB is more and it also increases the strength of the LSB throughout the span wise direction.
Thèses sur le sujet "Micro air vehicles. Micro air vehicles Insects Wings (Anatomy) Reynolds number"
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Swanson, Taylor Alexander. « An experimental and numerical investigation of flapping and plunging wings ». Diss., Rolla, Mo. : Missouri University of Science and Technology, 2009. http://scholarsmine.mst.edu/thesis/pdf/Swanson_09007dcc80672efe.pdf.
Texte intégralRésumé :
Thesis (Ph. D.)--Missouri University of Science and Technology, 2009.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed June 2, 2009) Includes bibliographical references (p. 115-126).
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Pitt, Ford Charles William. « Unsteady aerodynamic forces on accelerating wings at low Reynolds numbers ». Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608219.
Texte intégral
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Bradshaw, Christopher John. « An experimental investigation of flapping wing aerodynamics in micro air vehicles ». Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Jun%5FBradshaw.pdf.
Texte intégralRésumé :
Thesis (M.S. in Aeronautical Engineering)--Naval Postgraduate School, June 2003.Thesis advisor(s): Kevin D. Jones, Max F. Platzer. Includes bibliographical references (p. 89). Also available online.
Actes de conférences sur le sujet "Micro air vehicles. Micro air vehicles Insects Wings (Anatomy) Reynolds number"
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Zhang, Xiaoqin, et Ling Tian. « Numerical Simulation of Micro Air Vehicles With Membrane Wings ». Dans 2007 First International Conference on Integration and Commercialization of Micro and Nanosystems. ASMEDC, 2007. http://dx.doi.org/10.1115/mnc2007-21265.
Texte intégralRésumé :
Micro Air Vehicles (MAVs) have advantages of small size, low cost, flexibility and controllability etc., so they will be applied widely in military and civilian fields. They have obviously low Reynolds number aerodynamics, which is different from traditional aircrafts. In this paper, numerical simulation based on fluid-structure interaction for flexible wing MAVs is presented. Flexible wings are composed of carbon frames and covered with membrane skins. Because flexible wing MAVs easily deform in airflow, both structure model and fluid model should be built. The two models are connected by interfaces of membrane wings, which transmit distributed pressure and deformations of membrane wings. When membrane wings are located in airflow, they will deform with actions of surrounding airflow. Deformation of membrane wings also affects airflow and pressure distributed on the wings’ surfaces will also be changed relatively, which will compel the shape of membrane wings to be changed once more. Therefore, numerical simulation of flexible wing MAVs is not only the analysis of fluid field, but also the structure deformation effects. Navier-Stokes Equations are nonlinear and complicated, so direct interaction of fluid and structure equations is rather difficult and costs too much time. Indirect interaction method is more feasible and it is adopted in this paper. Structure deformation and distributed pressure on membrane wings surfaces are calculated separately, and then pressure distribution from fluid solver is transmitted to structure solver. After structure deformation is calculated in structure solver, it will be transmitted to fluid field again. Iteration goes on in this way and finally converges. Simulation results show the deformation, stress and pressure distribution of flexible wings. All these results are good reference for MAVs design, modification and wind tunnel experiments generally.
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Rubio, Jose E., et Uttam K. Chakravarty. « An Investigation of the Aerodynamic Performance of a Biomimetic Insect-Sized Wing for Micro Air Vehicles ». Dans ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-65303.
Texte intégralRésumé :
Biologically-inspired micro air vehicles (MAVs) are miniature-scaled autonomous aircrafts which attempt to biomimic the exceptional maneuver control during low-speed flight mastered by insects. Flexible wing structures are critical elements of a nature-inspired MAV as evidence supports that the wings of aerial insects experience highly-elastic deformations that enable insects to proficiently hover and maneuver in different airflow conditions. For this study, a crane fly (family Tipulidae) forewing is selected as the target specimen to replicate both its structural integrity and aerodynamic performance. The artificial insect-sized wing is manufactured using photolithography with negative photoresist SU-8 to fabricate the vein geometry. A Kapton film is attached to the vein pattern for the assembling of the wing. The natural frequencies and mode shapes of the artificial wing are determined to characterize its vibrations. A numerical simulation of the fluid-structure interaction is conducted by coupling a finite element model of the artificial wing with a computational fluid dynamics model of the surrounding airflow. From these simulations, the deformation response and the coefficients of drag and lift of the artificial wing are predicted for different freestream velocities and angles of attack. The deformation along the span of the wing increases nonlinearly with Reynolds number from the root to the tip of the wing. The coefficient of lift increases with angle of attack and Reynolds number. The coefficient of drag decreases with Reynolds number and angle of attack. The aerodynamic efficiency, defined as the ratio of the coefficient of lift to the coefficient of drag, of the artificial wing increases with angle of attack and Reynolds number.
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Hays, Michael R., Jeffrey Morton, William S. Oates et Benjamin T. Dickinson. « Aerodynamic Control of Micro Air Vehicle Wings Using Electroactive Membranes ». Dans ASME 2011 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. ASMEDC, 2011. http://dx.doi.org/10.1115/smasis2011-5076.
Texte intégralRésumé :
Electrically controlled adaptive materials are ideal candidates for developing high agility micro-air-vehicles (MAV) due to their intrinsic multi-functionality. The dielectric elastomer VHB 4910 is one such material, where deformation occurs with an applied electric field. Here, we study the aerostructural response and control authority of a VHB 4910 membrane wing. An experimental membrane-wing platform was constructed by stretching VHB 4910 over a rigid elliptical wing-frame. The low Reynolds number (chord Reynolds number < 106) aerodynamics of the elliptical wing were characterized with different electrostatic fields applied. We observe an overall increase in lift with maximum gains of 20% at 4.5 kV, and demonstrate the ability to delay stall. Aerodynamic effects are investigated with membrane displacement and strain data obtained through visual image correlation (VIC). The VIC data is compared to a finite deforming finite element shell model to help understand structural shape changes under electrostatic fields and low Reynolds number aerodynamic flows. The model is formulated to directly input three dimensional membrane displacements to quantify aerodynamic loads on the electroactive membrane surface.
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Mojgani, Rambod, et Mehran Tadjfar. « Effects of Kinematics on Low Reynolds Number Wing ». Dans ASME 2013 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/fedsm2013-16531.
Texte intégralRésumé :
Insects’ aerodynamic performance has been an area of interest for years, for both biologists and engineers. Micro-air vehicles developments require more research in this area to determine best flight performance. Their flapping wings’ effectiveness in producing both lift and thrust has been enabled them to hover and fly forward. Recent studies have proved that with capabilities of CFD calculations, parametric investigation of the associated parameters is possible. The purpose of present investigation is to numerically study the effects and phenomena caused by different kinematics of flapping wing, so different flapping kinematics has been simulated and investigated to better understand fluid characteristics in such cases. Effect of wing’s vertical displacement as well as the effects of wing rotation (pitch angle) is studied. Dynamic mesh with laminar finite volume flow solver is used and the method is validated. Results show that how wing-vortex interaction and angle between flapping direction and wing inclination can control hovering (vertical) force.
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Visbal, Miguel R. « Effect of Small-Amplitude Heaving Oscillations on the Flow Structure Above a Low-Aspect Ratio Wing ». Dans ASME-JSME-KSME 2011 Joint Fluids Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajk2011-02011.
Texte intégralRésumé :
Unsteady low-Reynolds-number flows are of importance in understanding the flight performance of natural flyers, as well as in the design of small unmanned air vehicles and micro air vehicles [1,2]. The imposed motion of flapping wings or the large excursions in effective angle of attack during gust encounters may induce the formation of dynamic-stall-like vortices [3–10] whose evolution and interaction with the aerodynamic surfaces impact both flight stability and performance.
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Li, Chengyu, Junshi Wang, Geng Liu, Xiaolong Deng et Haibo Dong. « Passive Pitching Mechanism of Three-Dimensional Flapping Wings in Hovering Flight ». Dans ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/ajkfluids2019-4639.
Texte intégralRésumé :
Abstract Flapping wings of insects can passively maintain a high angle of attack due to the torsional flexibility of wing basal region without the aid of the active pitching motion. However, the lift force generated by such passive pitching motion has not been well explored in the literature. Consequently, there is no clear understanding of how torsional wing flexibility should be designed for optimal performance. In this work, a computational study was conducted to investigate the passive pitching mechanism of flapping wings in hovering flight using a torsional spring model. The torsional wing flexibility was characterized by Cauchy number. The impacts of the inertial effect of wings were evaluated using the mass ratio. The aerodynamic forces and associated unsteady flow structures were simulated by an in-house immersed-boundary-method based computational fluid dynamic solver. A parametric study on the Cauchy number was performed with a Reynolds number of 300 at a mass ratio of 1.0, which covers a wide range of species of insect wings. According to the analysis of the aerodynamic performance, we found that the optimal lift can be achieved at a Cauchy number around 0.16, while the optimal efficiency in terms of lift-to-power ratio was reached at a Cauchy number around 0.3. All the corresponding wing pitching kinematics had a pitching magnitude around 60 degrees with slightly advanced rotation. In addition, 3D wake structures generated by the passive flapping wings were analyzed in detail. The findings of this work could provide important implications for designing more efficient flapping-wing micro air vehicles.
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Kuroki, Taichi, Masaki Fuchiwaki, Kazuhiro Tanaka et Takahide Tabata. « Characteristics of Dynamic Forces Generated by a Flapping Butterfly ». Dans ASME 2013 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/fedsm2013-16363.
Texte intégralRésumé :
Many studies on the mechanism of butterfly flight have been carried out. A number of recent studies have examined the flow field around insect wings. Moreover, Micro-air-vehicles and micro-flight robots that mimic the flight mechanisms of insects have attracted significant attention, and a number of MAVs and micro-flight robots that use various devices have been reported. However, these robots were not practical. One of the reasons for this is that the flying mechanism of insects has not yet been clarified sufficiently. The present authors developed a flapping-wing robot without tail wings and focused on the flow field around the wings created by the flapping motion and its elastic deformation. In the present study, we attempt to clarify the relationship between the vortex ring over the wing and the dynamic lift generated by the flapping wing. The dynamic lift becomes large rapidly in the downward flapping and reaches a maximum at a flapping angle of −30 deg. After the maximum, the dynamic lift decreases gradually and the dynamic lift in upward flapping is approximately constant. The growth of the vortex ring formed by the flapping wing was clarified to contribute significantly to the dynamic lift acting on the butterfly. We should consider the interaction of both vortex ring both in downward flapping and in upward flapping in order to estimate the dynamic lift exactly using the circulation of the vortex ring.
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Gordnier, Raymond E., et Peter J. Attar. « Implicit LES Simulations for an Aspect Ratio Two Flexible Membrane Wing ». Dans ASME-JSME-KSME 2011 Joint Fluids Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajk2011-08008.
Texte intégralRésumé :
Development of an aeroelastic solver with application to flexible membrane wings for micro air vehicle applications is presented. A high-order (up to 6th order) Navier-Stokes solver is coupled with a geometrically nonlinear p-version Reissner-Mindlin finite element plate model to simulate the highly flexible elastic membrane. An implicit LES approach is employed to compute the mixed laminar/transitional/turbulent flowfields present for the low Reynolds number flows associated with micro air vehicles. Intitial computations for a baseline rigid membrane wing are presented to understand the complex vortex dynamics associated with these flows before proceeding with the more challenging flexible cases.
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Fuchiwaki, Masaki, Tomoki Kurinami, Kazuhiro Tanaka et Takahide Tabata. « Detailed Wake Structure Around Moving Elastic Airfoils and Their Characteristics of Dynamic Thrust ». Dans ASME 2012 Fluids Engineering Division Summer Meeting collocated with the ASME 2012 Heat Transfer Summer Conference and the ASME 2012 10th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/fedsm2012-72369.
Texte intégralRésumé :
The unsteady flow field around a moving airfoil has attracted significant attention in bio-hydrodynamics, micro-air-vehicles and micro flight robots. Recently, a number of studies have been performed on the flow field around airfoils with unsteady motion in low Reynolds number regions using both experiment and numerical analysis. On the other hand, it is well known that insects and aquatic animals fly or swim by skillfully controlling their wings or fins, which deform elastically, and vortices are generated around their bodies. The flow around an elastic body is treated as a coupled problem between the fluid and structure. There have been only a few reports on the experimental evaluation of vortex flow structures around an elastic moving airfoil and their fluid dynamical properties. In this study, we investigate the wake structures behind the moving elastic airfoils and the characteristics of the dynamic thrusts acting on them. The thrust producing vortex streets are clearly formed behind the combination airfoils for all phase differences. The dynamic thrust acting on the moving elastic airfoil depends strongly on the Strouhal number based on the maximum trailing edge deformation and is independent of the moving motion and phase difference. The maximum thrust efficiency of the combination airfoil is higher than that for the pure pitching and heaving airfoils and become about 0.5 at φ = 90 deg. around St = 0.3.
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Fuchiwaki, Masaki, Taichi Kuroki, Kazuhiro Tanaka et Takahide Tabata. « Three-Dimensional Vortex Structure Around a Free Flight Butterfly ». Dans ASME 2014 4th Joint US-European Fluids Engineering Division Summer Meeting collocated with the ASME 2014 12th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/fedsm2014-21303.
Texte intégralRésumé :
Micro-air-vehicles (MAVs) and micro-flight robots that mimic the flight mechanisms of insects have attracted significant attention. From this reason, the flight mechanism of the butterflies and their flow fields also has attracted attention. A number of studies on the mechanism of butterfly flight have been carried out. Moreover, a number of recent studies have examined the flow field around insect wings. The present authors conducted a particle image velocimetry (PIV) measurement around the flapping wings of Cynthia cardui and Idea leuconoe and investigated the vortex structure and dynamic behavior produced. However, these results are for a flow field under a fixed condition. The vortex flow structure and the dynamic behavior generated by the wings of a butterfly in free flight are expected to be important for generating the aerodynamic forces required for flight. In the present study, we attempt to clarify the three-dimensional vortex structure around a butterfly in free flight by a scanning PIV measurement. The vortex ring formed by the front wings during the flapping downward grows without attenuation toward the wake. Moreover, during the flapping upward of the wings, a vortex rolls up from the wing, eventually forming a single vortex ring. This vortex ring forms in the vertical direction in contrast to vortex ring formed during the flapping downward, and we may anticipate that the two vortex rings interfere with each other as they advance toward the wake.