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Aerodynamics of the Cupped Wings during Peregrine Falcon’s Diving Flight
Abstract
During a dive peregrine falcons can reach velocities of more than 320 km h‐1 and makes them the fastest animals of the world. The aerodynamic mechanisms involved are not fully understood yet. The search for a conclusive answer to this fact motivates the three‐dimensional (3‐D) flow study of peregrine falcon aerodynamics. Especially the cupped wing configuration which is a unique feature of the wing shape in falcon peregrine dive is our focus herein. In particular, the flow in the gap between the main body and the cupped wing is studied to understand how this flow interacts with the body and to what extend it affects the integral forces of lift and drag. Characteristic shapes of the wings while diving are studied with regard to its aerodynamics using computational fluid dynamics (CFD). The results of the numerical simulations via ICEM CFD and OpenFOAM show predominant flow structures around the body surface and in the wake of the falcon model such as a pair of body vortices and tip vortices. The drag for the cupped wing profile is reduced in relation to the configuration of opened wings (without cupped‐like profile) while lift is increased. The purpose of this study is primarily the basic research of the aerodynamic mechanisms during the falcon’s diving flight. The results could be important for maintaining good maneuverability at high speeds in the aviation sector.
... This is confirmed from the live recordings reported in Refs. [7,8], where the bird is seen to open up its wings laterally, sometimes even close to the M shape during the high-speed dive; however, it tucks them back in into the teardrop shape immediately after to reduce the drag. ...
... As a continuation of the previous work by Ponitz et al. [5], Gowree et al. [7], and Ponitz et al. [8], the present paper analyzes the aerodynamics and mechanics of the flight of a falcon in the pullout maneuver and the wing morphing. The study focuses on the early pullout phase where the transition is from teardrop in three stages toward M shape, whereas we use aerodynamic lifting theory to also extend predictions for the open M in the late phase of pullout. ...
... This asymmetrical morphing is also observed during other phases of the stoop when the bird is readjusting its trajectory. Pure yaw control in the cupped shape can be achieved due to the substantial amount of side force generated on the wings, as shown in Fig. 4 (see also Ref. [8]), as well as by the strong vortices that are now aligned to the side of the bird. This side force does not degrade significantly while morphing into the M shape, hence allowing the bird to engage easily into a yaw maneuver if it needs to turn around for another attempt. ...
During the pullout maneuver, peregrine falcons were observed to adopt a succession of specific flight configurations that are thought to offer an aerodynamic advantage over aerial prey. Analysis of the flight trajectory of a falcon in a controlled environment shows it experiencing load factors up to 3g, and further predictions suggest this could be increased up to almost 10g during high-speed pullout. This can be attributed to the high maneuverability promoted by lift-generating vortical structures over the wing. Wind-tunnel experiments on life-sized models in the different configurations together with high-fidelity computational fluid dynamics simulations (large-eddy simulations) show that deploying the hand wing in a pullout creates extra vortex lift, which is similar to that of combat aircraft with delta wings. The aerodynamic forces and the position of the aerodynamic center were calculated from the simulations of the flow around the different configurations. This allowed for an analysis of the longitudinal static stability in the early pullout phase, confirming that the falcon is flying unstably in pitch with a positive slope in the pitching moment and a trim angle of attack of about 5 deg, which is possibly to maximize responsiveness. The hand wings/primaries were seen to contribute to the augmented stability, acting as “elevons” would on a tailless blended-wing/body aircraft.
... As opposed to conventional aircraft the bird does not have a fin and a rudder for lateral control, and therefore uses the wing-tips and the tail to achieve these maneuvers. This is confirmed from the live recordings reported in reference [9][10][11][12] where the bird is seen to open-up its wings laterally, sometimes even close to the M-shape during the high speed dive, however it tucks them back in into the Teardrop-shape immediately after to reduce the drag. ...
... As a continuation of the previous work by Ponitz et al. [5], Gowree et al. [9], Ponitz et al. [10], the present paper analyses the aerodynamics and mechanics of the flight of a falcon in pull-out maneuver with strong wing-morphing, applying classical flight stability criteria in order to draw parallels with current state-of-the-art highly maneuverable flight demonstrators and to explore the possibility of incorporation of the morphing mechanics and control mechanisms in modern Micro-Air-Vehicles (MAVs) and ...
... This asymmetrical morphing is also observed during other phases of the stoop when the bird is re-adjusting it's trajectory. Pure yaw control in the Cupped-shape can be achieved due to the substantial amount of side force generated on the wings as shown in Fig. 7 (compare [10]), also by the strong vortices which are now aligned to the side of the bird. This side force does not degrade significantly while morphing into the M-shape and hence allowing the bird to engage easily into a yaw maneuver, if it needs to turn around for another attempt. ...
During the pull-out maneuver, Peregrine falcons were observed to adopt specific flight configurations which are thought to offer an aerodynamic advantage over aerial prey. Analysis of the flight trajectory of a falcon in a controlled environment shows it experiencing load factors up to 3 and further predictions suggest this could be increased up to almost 10g during high-speed pull-out. This can be attributed to the high maneuverability promoted by lift-generating vortical structures over the wing. Wind-tunnel experiments on life-sized models together with high fidelity simulations on idealized models, which are based on taxidermy falcons in different configurations, show that deploying the hand-wing in a pull-out creates extra vortex-lift, similar to that of combat aircraft with delta wings. The aerodynamic forces and the position of aerodynamic center were calculated from Large Eddy Simulations of the flow around the model. This allowed for an analysis of the longitudinal static stability in a pull-out, confirming that the falcon is flying unstably in pitch with a positive slope in the pitching moment and a trim angle of attack of about 5°, possibly to maximize responsiveness. The hand-wings/primaries were seen to contribute to the augmented stability acting as 'elevons' would on a tailless blended-wing-body aircraft.
... Some lines aim to increase energy production and transition to clean resources [1], other lines investigate how to increase the lifetime of energy production systems [2][3][4]. In wind energy systems, the use of vortex generators or VG devices on turbine blades and how these devices increase service life and power output is studied by research groups [5][6][7]. Previous studies of animals and plants try to mimic their morphological characteristics and add them to wind turbines, this process is known as bio-inspiration, Bio-inspiration can be defined in mechanical engineering as the creation of mechanisms based on living organisms [8][9][10][11]. For this reason, some works analyze species and how their special characteristics allow them to survive in their environment. ...
... The experimental setup developed consists of varying the wind tunnel velocity every 40 s and storing the accelerations and velocity of the wind wake generated by the prototype. The wind tunnel velocities are set at 5,8,10,15, and 20 m/s. This blade is mounted on an aerodynamic housing, in which the acquisition circuit is located. ...
Vortex generators are devices that modify the wind behavior near the surface of wind turbine blades. Their use allows the boundary layer shedding transition zone to be varied. Bio-inspired design has been used to improve the efficiency of aerodynamic and hydrodynamic systems by creating devices that use shapes present in animals and plants. In this work, an experimental methodology is proposed to study the effect of bio-inspired vortex generators and their effect on the structural vibration of a blade. In addition, the wind wake generated by the blade with oscillating vortex generators at different oscillation frequencies is analyzed by means of a hot wire anemometer, obtaining appreciable vibration reduction results in the measured 3D acceleration signals for wind velocities between 10 and 15 m/s. Values of the spectral components of the wake velocity measured at higher tunnel wind velocities increase. Spectral variance is reduced at higher tunnel wind velocities. The system analyzed in this paper can contribute in the future to the construction of actuators for vibration compensation systems in wind turbines.
... The overall body structure orientation induces negative lift forces for better manoeuvrability while diving, as shown in Fig. 1 (The numbers 1 to 4 indicated the interested regions). Different body structure microorientations can generate variant lift forces that provide significant and spontaneous altitude changes [4,5]. ...
... The diving aerodynamics of the peregrine falcon is also made possible by utilising the cupped-wings formation, where the wings of the peregrine falcon are tilted downwards to increase lift and decrease drag. Pop-up feathers near the cupped region also induced local airflow separation to reduce induced drag along the course of flight [5]. As a means of a similar study, the peregrine falcon's manoeuvrability is supported by vortical structures alongside the neck and the wings in controlling the pitch and roll momentum [6]. ...
The aerodynamic aspect is undoubted of high importance in vehicular design as it correlates with improving performance efficiency and reducing fuel consumption for an automotive vehicle. This paper documents the design and optimisation process of the prototype FSAE (Formula of Student Automotive Engineers) vehicle in aerodynamic performance. This project aims to generate design optimisation for the body of FSAE vehicles through a biomimetic approach to simulate the feasibility of biological systems integration in engineering design. Computational fluid dynamics through turbulent models were incorporated in analysing the aerodynamic flow of the optimised model. The geometrical aspect of the model is optimised through shape and parametric optimisation relative to the biological model implemented. The production of a highly reliable and improved prototype was represented as an optimised solution with a 48.65% improvement in drag coefficient and 113.97% in lift coefficient or stability compared to the initial proposed model of the prototype FSAE vehicle body. CAD design of the expected prototype is produced, along with the presentation of a scaled-down fabricated 3D model. The optimised model is fabricated considering the successful improvement in fuel efficiency by 18.19%.
... Fluid dynamics simulation or CFD complements the studies and the analysis of mechanical modifications [5][6][7]. Current work shows the creation of mechanical improvements based on living organisms such as birds [8][9][10]. The special characteristics developed by some living species are applied to improve the turbulence of aerial devices [11][12][13][14]. ...
... It is slightly stiffened by the rachides to prevent unwanted actuation in moderate flight conditions while remaining flexible enough to address flow separation locally. A similar trait exists on the backs of Peregrine falcons, which use covert feathers to prevent flow separation over their backs and tails during rapid descents [28,29]. To prevent pressure accumulation, ridges, and slits are cut into the fabric near the trailing edge, as shown in Figure 4. ...
Featured Application
Unmanned aerial vehicles (UAVs), radio-controlled (RC) drones.
Abstract
Birds have unique flight characteristics unrivaled by even the most advanced drones due in part to their lightweight morphable wings and tail. Advancements in 3D-printing, servomotors, and composite materials are enabling more innovative airplane designs inspired by avian flight that could lead to optimized flight characteristics compared to traditional designs. Morphing technology aims to improve the aerodynamic and power efficiencies of aircraft by eliminating traditional control surfaces and implementing wings with significant shape-changing ability. This work proposes designs of 3D-printed, bio-inspired, non-flapping, morphing wing and tail mechanisms for unmanned aerial vehicles. The proposed wing design features a corrugated flexible 3D-printed structure to facilitate sweep morphing with expansion and contraction of the attached artificial feathers. The proposed tail feather expansion mechanism features a 3D-printed flexible structure with circumferential corrugation. The various available 3D-printing materials and the capability to print geometrically complex components have enabled the realization of the proposed morphing deformations without demanding relatively large actuation forces. Proof-of-concept models were manufactured and tested to demonstrate the effectiveness of the selected materials and actuators in achieving the desired morphing deformations that resemble those of seagulls.
... Fluid dynamics simulation or CFD complements the studies and the analysis of mechanical modifications [5][6][7]. Current work shows the creation of mechanical improvements based on living organisms such as birds [8][9][10]. The special characteristics developed by some living species are applied to improve the turbulence of aerial devices [11][12][13][14]. ...
The peregrine falcon is the fastest bird in the world. Previous studies have made it possible to observe its flight conditions. One characteristic that stands out is its dorsal feathers, which allow it to generate an effect of stability in flight. The form of these feathers can contribute to the design of similar devices in wind turbines, called vortex generators. Vortex generators maintain a turbulence that modifies the zone of detachment of the boundary layer of a blade. This paper shows an experimental wind tunnel study of a falcon prototype with a hotwire sensor, 3D accelerometer and a servomechanism that allows the movement of the feathers. Measured wake wind velocity curves in transient mode showed similarities. The magnitude spectrum of the wind velocity signal measured by oscillating the feathers of the prototype showed reduction peaks in its spectral components. This indicates reduction in the vibration of the prototype at a wind velocity of 10 m/s.
... [22] Many investigations have contributed to 018701-6 the avian anatomy of the muscles and bones. [23][24][25][26] A carcass of Falco peregrinus was donated by the Zhejiang Museum of Natural History as detailed in our previous research. [22] In our previous studies, bird specimens were carried out in a fixed posture using a CT scan approach. ...
This paper presented a novel tinny motion capture system for measuring bird posture based on inertial and magnetic measurement units that are made up of micromachined gyroscopes, accelerometers, and magnetometers. Multiple quaternion-based extended Kalman filters were implemented to estimate the absolute orientations to achieve high accuracy. Under the guidance of ornithology experts, the extending/contracting motions and flapping cycles were recorded using the developed motion capture system, and the orientation of each bone was also analyzed. The captured flapping gesture of the Falco peregrinus is crucial to the motion database of raptors as well as the bionic design.
... Another approach is the creation of mechanical improvements based on living organisms [10,11], previous works study wind turbine blade shapes inspired by living organisms for the purpose of noise reduction and performance analysis [12]. In this work we analyze the behavior of an airfoil blade used in high velocity turbines such as the S822 [13][14][15], with vortex generators devices inspired by the peregrine falcon [16][17][18], previous studies highlight that this bird has flight stabilizer feathers on its back. ...
Vortex generators are used in aircraft wings and wind turbine blades. These devices allow them to maintain a stable turbulent behavior in the wind wake. Vortex generators, or VGs, improve the transition from laminar to turbulent boundary layer regime, avoiding abrupt shedding. HAWT wind turbines have high rotational velocity. Currently, HAWT turbines are being redesigned with fixed vortex generators, achieving higher energy production. This paper presents a wind tunnel analysis of a fixed-wire blade with S822 airfoil and active VGs bio-inspired by the flight-stabilizing feathers of the peregrine falcon. Vibrations measured on the blade show a reduction in intensity at wind velocities close to 15 m/s. The measured wake velocities show fluctuations at higher tunnel wind velocities. An FFT spectral analysis of the wind wake velocities showed differences between the spectral components. When activating the VGs in oscillation at a constant frequency, a reduction of the vibrations on the blade was observed for wind velocities around 20 m/s.
... did not discuss maximum flight speeds but reported average speeds upwards of 88 to 97 kmh -1 for various raptor species. Peregrine falcons can reach horizontal speeds upwards of 150 kmh -1(Ponitz et al. 2014), and the maximum gliding airspeed recorded for a white-backed vulture (Gyps africanus) was 141 kmh -1 (Tucker 1988).Meinertzhagen (1955) listed maximum recorded speeds across taxa, which included several notes of speeds > 100 kmh -1 . We therefore believe moments of extremely fast speeds may be possible for Swainson's hawks in exceptional environmental conditions.Locations of high speeds clustered towards the beginning and end of migration in both seasons. ...
Swainson’s hawks (Buteo swainsoni) are a Neotropical migratory raptor species and a common breeding raptor in the High Plains of Texas. Colleagues and I monitored reproduction across a study area in northern Texas over seven years (2012 – 2018) to determine occupancy of large stick nests by Swainson’s hawks and reproductive output. I found that territories were consistently occupied by Swainson’s hawk pairs, and few other raptors or large stick-nesting species occupied the study area at any given time. Reproductive output (55% nesting success and 1.8 fledglings produced per successful nest) was lower than reports from other regions (70% success and 1.9 fledglings per nest) and was likely impacted by frequent droughts. Colleagues and I equipped adult hawks trapped in nesting territories with satellite transmitters in 2012 and 2013 and tracked hawks for up to five years. I examined data to compare migration characteristics, such as timing, routes, distance travelled, and length of migratory periods, to previous research that tracked Swainson’s hawks from other breeding regions. I found that most of the new data suggested agreement with previous conclusions, and differences were mostly attributable to breeding origin/destination. I described new migratory information, such as speed of travel, new staging and stopover locations, and habitat use and selection across the migratory pathway. One interesting finding was that Swainson’s hawks might be capable of surprisingly fast flight speeds (> 100 kmh-1 and > 800 km per day), though average speeds (25 kmh-1 and 189 km per day) agreed with previous research. Habitat use and selection reflected similar patterns as on breeding and nonbreeding ranges, and the most important conclusion was that avoidance of water and other migratory barriers, such as mountain ranges, heavily influences the migration pathway chosen by this species. In 2016 – 2018 I extended the transmitter study by equipping fledgling hawks with lower-resolution satellite transmitters and tracking them for up to four years. I used these data to describe previously unknown information about survival and behaviors during the juvenile and sub-adult life stages, which lasts 3-5 years in this species. I found a longer post-fledging period than previously described and that siblings gain independence from each other at the same time as they gain independence from adults. Juvenile hawks migrated southward with similar timing as adults, though during the first journey several hawks went off track, which proved fatal for most. Some juvenile hawks stopped short at the end of migration to overwinter in northern Argentina, while others completed the journey to the primary wintering grounds across the Pampas. Spring migration took longer than for adult hawks, with some juveniles arriving to the breeding region significantly later, possibly because they had no intention of attempting to breed. During the breeding season, juvenile hawks were nomadic, with only half making visits to natal territories. Survival was lowest immediately post-fledging and increased with time, though I did not track hawks long enough to observe any recruitment into the breeding population. Last, I used transmitter data from both adult and juvenile hawks to assess risk from the wind energy industry (a known hazard for raptorial and migratory species) throughout their global range. I found that Swainson’s hawks are at highest collision risk on their breeding range, though this species may be at lower overall risk than other raptor species, due to differences in behaviors and their long-distance migratory patterns.
... Most falcon top speeds ranged between 100 and 110 km h −1 in this study. The Peregrine is hailed as the fastest animal in the world, with reported dive speeds in excess of 320 km h −1 (Clark 1995;Ponitz et al. 2014). This is much greater than the maximum speed of 196 km h −1 and 140 km h −1 that we and Alerstam (1986) recorded, respectively. ...
The flight speeds of hunting falconry birds were determined using global positioning system data loggers. Until now, the hunting flight speed of African raptors has not been directly measured. We predicted that hunting flight speeds would differ between species and that flight dynamics, such as altitude, and bird morphology, particularly wing surface area, would influence maximum and mean flight speeds. This study considered five African raptor species, which included two long-wing species, Lanner Falcon Falco biarmicus and Peregrine Falcon F. peregrinus, one short-wing species, Black Sparrowhawk Accipiter melanoleucus, and two broad-wing species, African Hawk-eagle Aquila spilogaster and Jackal Buzzard Buteo rufofuscus. Maximum and mean hunt speeds differed significantly between the long- and short-wing species. There was no difference in acceleration or deceleration rates between these species, but this could be due to small sample sizes. There was a significant positive correlation between maximum hunt speed and maximum flight height for the long-wing species. Maximum and mean flight speeds were significantly negatively correlated with wing area for all five species in this study. However, following phylogenetic correction, no significant relationship between wing area and maximum hunt speeds was found. This study presents baseline data of hunting speeds in African raptors and further highlights the importance of inter-species variation, which can provide accuracy to flight speed models and the understanding of hunting strategies.
... Within the initial phase of the stoop it adopts a 'teardrop' shape (T-shape) where the wings are folded and feathers tucked in a streamlined shape, which is intuitively the lowest drag configuration. The success of the attack largely depends on the manoeuvrability during the second phase of the stoop, when the bird 1 starts to pull out from the dive, while undergoing two important morphological transformations, namely the cupped-wing shape (C-shape, detail presented in ref. 4 ) and the M-shape (the focus of this manuscript). In C-shape the arms are slighly untucked, creating a cavity between the body and the primary feathers, which are oriented vertically. ...
The peregrine falcon (Falco peregrinus) is known for its extremely high speeds during hunting dives or stoop. Here we demonstrate that the superior manoeuvrability of peregrine falcons during stoop is attributed to vortex-dominated flow promoted by their morphology, in the M-shape configuration adopted towards the end of dive. Both experiments and simulations on life-size models, derived from field observations, revealed the presence of vortices emanating from the frontal and dorsal region due to a strong spanwise flow promoted by the forward sweep of the radiale. These vortices enhance mixing for flow reattachment towards the tail. The stronger wing and tail vortices provide extra aerodynamic forces through vortex-induced lift for pitch and roll control. A vortex pair with a sense of rotation opposite to that from conventional planar wings interacts with the main wings vortex to reduce induced drag, which would otherwise decelerate the bird significantly during pull-out. These findings could help in improving aircraft performance and wing suits for human flights
Nature’s evolutionary mastery has perfected design over the years, yielding organisms superbly adapted to their surroundings. This research delves into the promising domain of bio-inspired designs, poised to revolutionize mechanical engineering. Leveraging insights drawn from prior conversations, we categorize innovations influenced by life on land, in water, and through the air, emphasizing their pivotal contributions to mechanical properties. Our comprehensive review reveals a wealth of bio-inspired designs that have already made substantial inroads in mechanical engineering. From avian-inspired lightweight yet robust materials to hydrodynamically optimized forms borrowed from marine creatures, these innovations hold immense potential for enhancing mechanical systems. In conclusion, this study underscores the transformative potential of bio-inspired designs, offering improved mechanical characteristics and the promise of sustainability and efficiency across a broad spectrum of applications. This research envisions a future where bio-inspired designs shape the mechanical landscape, fostering a more harmonious coexistence between human technology and the natural world.
This research study conducts a numerical analysis of torque in modified turbines with vortex generators (VGs) by using computational fluid dynamics (CFD) simulations in 3D. Simulated torques are obtained for angular inclination variations of vortex generators located in the blades’ extra-backs. This is performed at two different air temperatures. The results show that the maximum torque is at 10°C at a 30° vortex generator inclination angle, with a value of 8.5 Nm. The minimum torque is observed at 25°C with a 45° inclination angle, having a value of 4.2 Nm. In conclusion, the CFD simulation shows that at higher air temperature the lower the torque in the turbine, reducing the rotational mechanical power, and that vortex generators reduce turbulence kinetic energy (TKE) in the generated wind wake.
Raptors can change the shape and area of their wings to an exceptional degree in a fast and efficient manner, surpassing other birds, insects, or bats. Some researchers have focused on the functional properties of muscle skeletons, mechanics, and flapping robot design. However, the wing motion of the birds of prey has not been measured quantitatively, and synthetic bionic wings with morphing abilities similar to raptors are far from reality. Therefore, in the current study, a 3D suspension system for holding bird carcasses was designed and fabricated to fasten the wings of Falco peregrinus with a series of morphing postures. Subsequently, the wing skeleton of the falcon was scanned during extending motions using the computed tomography (CT) approach to obtain three consecutive poses. Subsequently, the skeleton was reconstructed to identify the contribution of the forelimb bones to the extending/folding motions. Inspired by these findings, we propose a simple mechanical model with four bones to form a wing-morphing mechanism using the proposed pose optimisation method. Finally, a bionic wing mechanism was implemented to imitate the motion of the falcon wing—divided into inner and outer wings with folding and twisting motions. The results show that the proposed four-bar mechanism can track bone motion paths with high fidelity.
Kısıtlı, pahalı, geri dönüşümü olmayan ve çevreye duyarsız olan yakıtlar çeşitli nedenlerle insanlığa zarar vermektedir. Özellikle ulaşım sektöründe kullanılan yakıtlar çevreyi kirletmede öncü nedenlerdendir. Son zamanlardaki araçların emisyon değerlerini düşürmeye yönelik çalışmaların yanı sıra yakıt tasarrufu sağlamak amacıyla çeşitli çalışmalar mevcuttur. Bu çalışmada özellikle 21. yy’ da önemi artan enerji tasarrufu ar-ge çalışmalarının bir kolu olan aerodinamik araç tasarımında jant tasarımı ele alındı. Bu araştırmada biyomimetik bilimi çalışma metodolojilerinden biri olan ‘biyolojiden tasarıma’ yaklaşımı uygulandı. Bu yaklaşımın çözüm önerisine göre tasarlanan jantın piyasada en çok tercih edilen standart bir jant modeline göre aerodinamik yapısının hava sürtünme direncini azalttığı tespit edilmiştir. Böylelikle enerji tasarrufu sağlanmış ve jantın yüzey kalitesi artırılmıştır.
During a dive, peregrine falcons (Falco peregrinus) can reach a velocity of up to 320 km h- 1. Our computational fluid dynamics simulations show that the forces that pull on the wings of a diving peregrine can reach up to three times the falcon's body mass at a stoop velocity of 80 m s- 1 (288 km h- 1). Since the bones of the wings and the shoulder girdle of a diving peregrine falcon experience large mechanical forces, we investigated these bones. For comparison, we also investigated the corresponding bones in European kestrels (Falco tinnunculus), sparrow hawks (Accipiter nisus) and pigeons (Columba livia domestica). The normalized bone mass of the entire arm skeleton and the shoulder girdle (coracoid, scapula, furcula) was significantly higher in F. peregrinus than in the other three species investigated. The midshaft cross section of the humerus of F. peregrinus had the highest second moment of area. The mineral densities of the humerus, radius, ulna, and sternum were highest in F. peregrinus, indicating again a larger overall stability of these bones. Furthermore, the bones of the arm and shoulder girdle were strongest in peregrine falcons.
An energy efficient Biosafety Cabinet (BSC) has become a big challenge for manufacturers to develop BSC with the highest level of protection. The objective of research is to increase air flow velocity discharge from centrifugal blower. An aerodynamic duct shape inspired by the shape of Peregrine Falcon's wing during diving flight is added to the end of the centrifugal blower. Investigation of air movement is determined by computational fluid dynamics (CFD) simulation. The results showed that air velocity can be increased by double compared to typical manufactured BSC and no air recirculation. As conclusion, a novel design of aerodynamic duct shape successfully developed and proved that air velocity can be increase naturally with same impeller speed. It can contribute in increasing energy efficiency of the centrifugal blower. It is vital to BSC manufacturer and can be apply to Heating, Air Ventilation and Air Conditioning (HVAC) industries.
Considerable confusion surrounds the longstanding question of what constitutes a vortex, especially in a turbulent flow. This question, frequently misunderstood as academic, has recently acquired particular significance since coherent structures (CS) in turbulent flows are now commonly regarded as vortices. An objective definition of a vortex should permit the use of vortex dynamics concepts to educe CS, to explain formation and evolutionary dynamics of CS, to explore the role of CS in turbulence phenomena, and to develop viable turbulence models and control strategies for turbulence phenomena. We propose a definition of a vortex in an incompressible flow in terms of the eigenvalues of the symmetric tensor S 2 + a 2 ; here S and 0 are respectively the symmetric and antisymmetric parts of the velocity gradient tensor Vu. This definition captures the pressure minimum in a plane perpendicular to the vortex axis at high Reynolds numbers, and also accurately defines vortex cores at low Reynolds numbers, unlike a pressure-minimum criterion. We compare our definition with prior schemes/definitions using exact and numerical solutions of the Euler and Navier-Stokes equations for a variety of laminar and turbulent flows. In contrast to definitions based on the positive second invariant of V u or the complex eigenvalues of Vu, our definition accurately identifies the vortex core in flows where the vortex geometry is intuitively clear.
This study investigates the aerodynamics of the falcon Falco peregrinus while diving. During a dive peregrines can reach velocities of more than 320 km h(-1). Unfortunately, in freely roaming falcons, these high velocities prohibit a precise determination of flight parameters such as velocity and acceleration as well as body shape and wing contour. Therefore, individual F. peregrinus were trained to dive in front of a vertical dam with a height of 60 m. The presence of a well-defined background allowed us to reconstruct the flight path and the body shape of the falcon during certain flight phases. Flight trajectories were obtained with a stereo high-speed camera system. In addition, body images of the falcon were taken from two perspectives with a high-resolution digital camera. The dam allowed us to match the high-resolution images obtained from the digital camera with the corresponding images taken with the high-speed cameras. Using these data we built a life-size model of F. peregrinus and used it to measure the drag and lift forces in a wind-tunnel. We compared these forces acting on the model with the data obtained from the 3-D flight path trajectory of the diving F. peregrinus. Visualizations of the flow in the wind-tunnel uncovered details of the flow structure around the falcon's body, which suggests local regions with separation of flow. High-resolution pictures of the diving peregrine indicate that feathers pop-up in the equivalent regions, where flow separation in the model falcon occurred.
Considerable confusion surrounds the longstanding question of what constitutes a vortex, especially in a turbulent flow. This question, frequently misunderstood as academic, has recently acquired particular significance since coherent structures (CS) in turbulent flows are now commonly regarded as vortices. An objective definition of a vortex should permit the use of vortex dynamics concepts to educe CS, to explain formation and evolutionary dynamics of CS, to explore the role of CS in turbulence phenomena, and to develop viable turbulence models and control strategies for turbulence phenomena. We propose a definition of a vortex in an incompressible flow in terms of the eigenvalues of the symmetric tensor ; here and are respectively the symmetric and antisymmetric parts of the velocity gradient tensor . This definition captures the pressure minimum in a plane perpendicular to the vortex axis at high Reynolds numbers, and also accurately defines vortex cores at low Reynolds numbers, unlike a pressure-minimum criterion. We compare our definition with prior schemes/definitions using exact and numerical solutions of the Euler and Navier–Stokes equations for a variety of laminar and turbulent flows. In contrast to definitions based on the positive second invariant of or the complex eigenvalues of , our definition accurately identifies the vortex core in flows where the vortex geometry is intuitively clear.
Two vortex-sheet evolution problems arising in aerodynamics are studied numerically. The approach is based on desingularizing the Cauchy principal value integral which defines the sheet's velocity. Numerical evidence is presented which indicates that the approach converges with respect to refinement in the mesh-size and the smoothing parameter. For elliptic loading, the computed roll-up is in good agreement with Kaden's asymptoic spiral at early times. Some aspects of the solution's instability to short-wavelength perturbations, for a small value of the smoothing parameter, are inferred by comparing calculations performed with different levels of computer round-off error. The tip vortices' deformation, due to their mutual interaction, is shown in a long-time calculation. Computations for a simulated fuselage-flap configuration show a complicated process of roll-up, deformation and interaction involving the tip vortex and the inboard neighboring vortices.
Gliding birds continually change the shape and size of their wings, presumably to exploit the profound effect of wing morphology on aerodynamic performance. That birds should adjust wing sweep to suit glide speed has been predicted qualitatively by analytical glide models, which extrapolated the wing's performance envelope from aerodynamic theory. Here we describe the aerodynamic and structural performance of actual swift wings, as measured in a wind tunnel, and on this basis build a semi-empirical glide model. By measuring inside and outside swifts' behavioural envelope, we show that choosing the most suitable sweep can halve sink speed or triple turning rate. Extended wings are superior for slow glides and turns; swept wings are superior for fast glides and turns. This superiority is due to better aerodynamic performance-with the exception of fast turns. Swept wings are less effective at generating lift while turning at high speeds, but can bear the extreme loads. Finally, our glide model predicts that cost-effective gliding occurs at speeds of 8-10 m s(-1), whereas agility-related figures of merit peak at 15-25 m s(-1). In fact, swifts spend the night ('roost') in flight at 8-10 m s(-1) (ref. 11), thus our model can explain this choice for a resting behaviour. Morphing not only adjusts birds' wing performance to the task at hand, but could also control the flight of future aircraft.
Insekten tun es, Vögel tun es und sogar die Fledermäuse haben es geschafft – das Fliegen. Während der Mensch erst seit gut hundert Jahren erste Schritte in das neue luftige Element macht, bevölkern die Tiere schon seit hunderten von Millionen Jahren den Himmel. Vom majestätisch gleitenden Adler bis zur winzigen Zuckmücke – sie alle haben auf ganz unterschiedliche Weise den Luftraum erobert. Seit Jahrhunderten versuchen Forscher, hinter das Geheimnis der tierischen Flieger zu kommen. Doch noch immer gibt es mehr offene Fragen als Antworten: Woraus haben sich die Insektenflügel entwickelt? Ließen sich die ersten Flieger gleitend von den Bäumen fallen oder liefen und sprangen sie am Boden? Wieso widerspricht der Insektenflug scheinbar allen Gesetzen der Aerodynamik und funktioniert trotzdem? Erst in den letzten Jahren ist es den Forschern gelungen, der Lösung einiger dieser Rätsel zumindest nahe zu kommen.
We investigated the mechanical properties (Young's modulus, bending stiffness, barb separation forces) of the tenth primary of the wings, of the alulae and of the middle tail feathers of Falco peregrinus. For comparison, we also investigated the corresponding feathers in pigeons (Columba livia), kestrels (Falco tinnunculus), and sparrowhawks (Accipiter nisus). In all four species, the Young's moduli of the feathers ranged from 5.9 to 8.4 GPa. The feather shafts of F. peregrinus had the largest cross-sections and the highest specific bending stiffness. When normalized with respect to body mass, the specific bending stiffness of primary number 10 was highest in F. tinnunculus, while that of the alula was highest in A. nisus. In comparison, the specific bending stiffness, measured at the base of the tail feathers and in dorso-ventral bending direction, was much higher in F. peregrinus than in the other three species. This seems to correlate with the flight styles of the birds: F. tinnunculus hovers and its primaries might therefore withstand large mechanical forces. A. nisus has often to change its flight directions during hunting and perhaps needs its alulae for this maneuvers, and in F. peregrinus, the base of the tail feathers might need a high stiffness during breaking after diving. J. Morphol., 2014. © 2014 Wiley Periodicals, Inc.
Quantitative evidence of change over the last 150 years amongst granivorous bird assemblages in the tropical and sub-tropical savannas of northern Australia are provided. Twelve of 49 indigenous and mostly resident species have declined, and three have increased. One species is probably extinct, and two taxa are critically endangered. Four introduced species have become established. The northern Australian savannas are for the most part very sparsely settled and subject only to low intensity pastoralism, and the disarray amongst granivorous bird assemblages is perplexing. Even in areas subject to extensive vegetation clearance, decline is shown to coincide with the pastoral era prior to clearing. Grazing and/or changed fire regimes may be responsible. Determining the cause of change and the implementation of management responses is a key issue for the future management of these savannas.
Summary 1. The mean, minimum drag coefficients (CD,B) of a frozen, wingless peregrine falcon body and a smooth-surfaced model of the body were 0.24 and 0.14, respectively, at air speeds between 10.0 and 14.5 ms" 1. These values were measured with a drag balance in a wind tunnel, and use the maximum cross- sectional area of the body as a reference area. The difference between the values indicates the effect of the feathers on body drag. Both values for CD.B ar e lower than those predicted from most other studies of avian body drag, which yield estimates of CQ.B up to 0.41. 2. Several factors must be controlled to measure minimum drag on a frozen body. These include the condition of the feathers, the angle of the head and tail relative to the direction of air flow, and the interference drag generated by the drag balance and the strut on which the body is mounted. 3. This study describes techniques for measuring the interference drag gener- ated by (a) the drag balance and mounting strut together and (b) the mounting strut alone. Corrections for interference drag may reduce the apparent body drag by more than 20 %. 4. A gliding Harris' hawk (Parabuteo unicinctus), which has a body similar to that of the falcon in size and proportions, has an estimated body drag coefficient of 0.18. This value can be used to compute the profile drag coefficients of Harris' hawk wings when combined with data for this species in the adjoining paper (Tucker and Heine, 1990).
A live laggar falcon (Falco jugger) glided in a wind tunnel at speeds between 6·6 and 15·9 m./sec. The bird had a maximum lift to drag ratio (L/D) of 10 at a speed of 12·5 m./sec. As the falcon increased its air speed at a given glide angle, it reduced its wing span, wing area and lift coefficient. A model aircraft with about the same wingspan as the falcon had a maximum L/D value of 10. Published measurements of the aerodynamic characteristics of gliding birds are summarized by presenting them in a diagram showing air speed, sinking speed and L/D values. Data for a high-performance sailplane are included. The soaring birds had maximum L/D values near 10, or about one quarter that of the sailplane. The birds glided more slowly than the sailplane and had about the same sinking speed. The ‘equivalent parasite area’ method used by aircraft designers to estimate parasite drag was modified for use with gliding birds, and empirical data are presented to provide a means of predicting the gliding performance of a bird in the absence of wind-tunnel tests. The birds in this study had conventional values for parasite drag. Technical errors seem responsible for published claims of unusually low parasite drag values in a vulture. The falcon adjusted its wing span in flight to achieve nearly the maximum possible L/D value over its range of gliding speeds. The maximum terminal speed of the falcon in a vertical dive is estimated to be 100 m./sec.
Der Gleitflug von Vögeln scheint auf den ersten Blick ein verhältnismäßig einfaches physikalisches Problem zu sein, da man von zeitlich invarianten Kräfteverhältnissen ausgehen kann. Bei genauerem Betrachten zeigt sich jedoch ein verwirrend komplexes Zusammenspiel verschiedener aerodynamischer Größen.
Hustler, Kit. 1983. Breeding biology of the Peregrine Falcon in Zimbabwe. Ostrich 54:161-171.A pair of nesting Peregrine Falcons Falco peregrinus was studied in Zimbabwe. Most displays were on ledges and in potholes and consisted of horizontal bows. A courtship ledge was used until 11/2 weeks before egglaying when the nesting ledge became the focus of activity. Most copulations were seen just before egglaying and were preceded by no discernible display. At least two eggs were laid between 2 and 6 August and both sexes incubated. The eggs were covered for 98,8% of the day and incubation shifts averaged 72 min for the male and 101 min for the female. When not incubating the male was absent from the nesting cliff more often than the female. The eggs hatched about 6 September, giving an incubation period of at least 30 days. The male's visits were primarily to bring food after the chicks hatched. The female brooded intensively at first and started to hunt when the chicks were 2 weeks old. Three hunting methods are described and the mean stooping speed for 24 hunts calculated. The main prey was doves (34%); prey types and their vulnerability to predation by Peregrines are discussed.
Measurements in 10-s intervals by a tracking radar showed average speeds of about 25 ms-1 for a Peregrine Falcon Falco peregrinus and a Goshawk Accipiter gentilis during four stoops lasting 40–110 s, with angles of dive between 13o and 64o, and involving height losses between 450 and 1080 m. Maximum speeds during 10-s intervals were between 31 and 39 ms-1 in the Peregrine Falcon, and close to 30 ms-1 in the Goshawk. The observed speeds are well below the maximum possible terminal speeds in steep or vertical dives according to theoretical estimation. By adopting a moderate stooping speed, raptors may gain in hunting precision.
Imaging vector fields has applications in science, art, image pro- cessing and special effects. An effective new approach is to use linear and curvilinear filtering techniques to locally blur textures along a vector field. This approach builds on several previous tex- ture generation and filtering techniques(8, 9, 11, 14, 15, 17, 23). It is, however, unique because it is local, one-dimensional and inde- pendent of any predefined geometry or texture. The technique is general and capable of imaging arbitrary two- and three-dimen- sional vector fields. The local one-dimensional nature of the algo- rithm lends itself to highly parallel and efficient implementations. Furthermore, the curvilinear filter is capable of rendering detail on very intricate vector fields. Combining this technique with other rendering and image processing techniques — like periodic motion filtering — results in richly informative and striking images. The technique can also produce novel special effects.
Some falcons, such as peregrines (Falco peregrinus), attack their prey in the air at the end of high-speed dives and are thought to be the fastest of animals. Estimates of their top speed in a dive range up to 157 m s−1, although speeds this high have never been accurately measured. This study investigates the aerodynamic and gravitational forces on ‘ideal falcons’ and uses a mathematical model to calculate speed and acceleration during diving. Ideal falcons have body masses of 0.5–2.0 kg and morphological and aerodynamic properties based on those measured for real falcons.
The top speeds reached during a dive depend on the mass of the bird and the angle and duration of the dive. Given enough time, ideal falcons can reach top speeds of 89–112 m s−1 in a vertical dive, the higher speed for the heaviest bird, when the parasite drag coefficient has a value of 0.18. This value was measured for low-speed flight, and it could plausibly decline to 0.07 at high speeds. Top speeds then would be 138–174 m s−1.
An ideal falcon diving at angles between 15 and 90 ° with a mass of 1 kg reaches 95 % of top speed after travelling approximately 1200 m. The time and altitude loss to reach 95 % of top speed range from 38 s and 322 m at 15 ° to 16 s and 1140 m at 90 °, respectively.
During pull out at top speed from a vertical dive, the 1 kg ideal falcon can generate a lift force 18 times its own weight by reducing its wing span, compared with a lift force of 1.7 times its weight at full wing span. The falcon loses 60 m of altitude while pulling out of the dive, and lift and loss of altitude both decrease as the angle of the dive decreases.
The 1 kg falcon can slow down in a dive by increasing its parasite drag and the angle of attack of its wings. Both lift and drag increase with angle of attack, but the falcon can cancel the increased lift by holding its wings in a cupped position so that part of the lift is directed laterally. The increased drag of wings producing maximum lift is great enough to decelerate the falcon at −1.5 times the acceleration of gravity at a dive angle of 45 ° and a speed of 41 m s−1 (0.5 times top speed).
Real falcons can control their speeds in a dive by changing their drag and by choosing the length of the dive. They would encounter both advantages and disadvantages by diving at the top speeds of ideal falcons, and whether they achieve those speeds remains to be investigated.
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