Low Wing Research Articles

Measurement of aircraft ground roll distance during takeoff and landing on a grass runway

The aim of this study was to develop a method for airplane ground roll distance measurement. This method is based on measurements of aircraft accelerations, magnetic field vector, as well as Global Positioning System (GPS) position. A convolution neural network was developed in this study and it recognizes characteristic moments of flight during takeoff: longitudinal acceleration, nose wheel up (rotation), and liftoff, as well as during landing: approach, touchdown, rollout, and stop. The developed neural network includes two filters that enable collection of input data from both the total dataset as well as from data portions for information about the occurrence of a peak at the time of touchdown and the change of acceleration at the time of takeoff.The distance traveled by the plane on the ground during takeoff or landing is then calculated using the GPS coordinates, measured simultaneously. The method uses a sensor system consisting of accelerometers, magnetometers, and a GPS receiver; a prototype hardware was based on a single-board miniature computer. The hardware is small in size and fits anywhere in the aircraft cockpit. The method has been practically examined by means of flight tests and it was concluded that it performs well: the mean difference in the measured take-off and landing distances from the results obtained with the reference method was 2,92 % and 6,31 % respectively. The method was not sensitive to airplane design type: low wing vs. high wing. Also, the method has been tested for two different pilots and no significant difference in the results of measurement was observed.

EFFECT OF ANHEDRAL AND DIHEDRAL ON THE LATERAL DIRECTIONAL STATIC STABILITY OF THE AIRCRAFT.

Developments and advancements in Aircraft industry have led to an increasing the stability and maneuverability of an aircraft. When the aircraft subjected to unbalanced force it needs the suitable wing to overcome the side slip and maneuverability of an aircraft. This work proposed a Dihedral and Anhedral wing simulation in XFLR5 software to increase the stability and maneuverability of an aircraft. XFLR5 analysis was then carried out for Dihedral and anhedral angles of 5deg, 10deg ,with side slip angles 2deg and 5deg. The aerofoil used in wing is NACA 4412 and in tail is 0009..Lateral-Directional Static Stability of 5,10 deg of both anhedral and dihedral wings are analyzed. The graphs are plotted between co-efficient of rolling moment and side slip angle ; co-efficient of yawing moment and side slip angle. The simulation is done in a free stream velocity of 60 m/s and inviscid flow. Anhedral is a negative dihedral angle .The anhedral reduces the dihedral effect bringing the wing's roll characteristics into a more desirable performance envelope while keeping it stable yet maneuverable.Dihedral is the upward angle of an aircraft's wings, which increases lateral stability in a bank by causing the lower wing to fly at a higher angle of attack than the higher wing.

Relating wing morphology and immune function to patterns of partial and differential bat migration using stable isotopes.

Migration is energetically expensive and is predicted to drive similar morphological adaptations and physiological trade-offs in migratory bats and birds. Previous studies suggest that fixed traits like wing morphology vary among species and individuals according to selective pressures on flight, while immune defences can vary flexibly within individuals as energy is variably reallocated throughout the year. We assessed intraspecific variation in wing morphology and immune function in silver-haired bats Lasionycteris noctivagans, a species that follows both partial and differential migration patterns. We hypothesized that if bats experience energy constraints associated with migration, then wing morphology and immune function should vary based on migratory tendency (sedentary or migratory) and migration distance. We predicted that long-distance migrants would have reduced immune function and more migration-adapted wing shapes compared to resident or short-distance migrating bats. We estimated breeding latitude of spring migrants using stable hydrogen isotope techniques. Our sample consisted primarily of male bats, which we categorized as residents, long-distance northern migrants, short-distance northern migrants and southern migrants (apparent breeding location south of capture site). Controlling for individual condition and capture date, we related wing characteristics and immune indices among groups. Some, but not all, aspects of wing form and immune function varied between migrants and residents. Long-distance northern migrants had larger wings than short-distance northern migrants and lower wing loading than southern migrants. Compared with resident bats, short-distance northern migrants had reduced IgG while southern migrants had heightened neutrophils and neutrophil-to-lymphocyte ratios. Body fat, aspect ratio, wing tip shape and bacteria killing ability did not vary with migration status or distance. In general, male silver-haired bats do not appear to mediate migration costs by substantially downregulating immune defences or to be under stronger selection for wing forms adapted for fast, energy-efficient flight. Such phenotypic changes may be more adaptive for female silver-haired bats, which migrate farther and are more constrained by time in spring than males. Adaptations for aerial hawking and the use of heterothermy by migrating bats may also reduce the energetic cost of migration and the need for more substantial morphological and physiological trade-offs.

Improvement of European thin haul mobility: the role of small Green commuter aircraft

In the last years, transportation demand has grown up as consequence of the increase in leisure, and business for both heavily travelled routes (between major cities) and thin routes (between remote areas, and remote areas with major cities).In parallel, aviation sustainability issues have become more and more important, being aviation pollution an important source of global environmental pollution. Moreover, several States, as well as private Companies travelling for business, have introduced bans and/or special taxes on short flights covering distances that could be travelled by train in less than 3 hours. These regulations have a major impact on short haul thin routes, which could be covered by small air transport (up to 19 seats). Thus, dedicated research and technology innovation effort has been put in place over the last years to develop eco-friendly, and economically viable, aircraft able to answer sustainability needs, market demand, and cost-effectiveness.In particular, Clean Sky 2 Joint Undertaking, a public-private partnership between the European Commission and the European aeronautics industry, has co-financed the SAT (Small Air Transport) TA (Transverse Activity) initiative. SAT TA main goal is to address technology innovations to reduce environmental impact as well as operational cost of small commuters, ensuring improved levels of operational safety. SAT TA is a Project with an overall EU (European Union) funding of about 68 mln€, including small aircraft OEMs (Original Equipment Manufacturers), major aircraft suppliers, SMEs (Small and Medium Enterprises), research centres and academia (more than 80 Partners involved).The research activity has focused on the following main technology streams:•New generation turboprop engine with reduced fuel consumption, emissions, noise and maintenance costs for 19 seats aircraft.• More electric digital systems including:• Affordable fly-by-wire architecture for small aircraft (CS23 certification rules).• More electric systems replacing pneumatic and hydraulic aircraft systems (hybrid de-ice system, landing gear and brakes, high voltage EPGDS –Electrical Power Generation and Distribution System –).• Advanced avionics for small aircraft, to reduce pilot workload, paving single pilot operations for 19 seats.• Affordable airframe structures including:• Low cost composite wing box and nacelle using OoA (Out of Autoclave) technology, LRI (Liquid Resin Infusion) and automated deposition process.• Affordable small aircraft manufacturing of metallic fuselage by means of FSW (Friction Stir Welding) and LMD (Laser Metal Deposition).• Advanced cabin comfort with new materials and more comfortable seats.To address the abovementioned technologies, two different platforms have been designed: a Reference and a Green aircraft. Reference aircraft is a virtual aircraft designed considering 2014 technologies with an existing engine assuring requested take-off power. Green aircraft is designed integrating the technologies developed within Clean Sky 2.The present work describes designed aircraft, and preliminary mission analyses, showing the achievement of Project goals (20% CO2, 20% NOx reduction for the design mission).

Design and CFD Analysis of a Rear Wing of a Motorsport Car

The rear wing of a motorsport car is one of the 3 main components to produce the downforce required by the car to take a corner with the maximum speed possible. This paper aims to design and analyse the rear wing of a motorsport car. The design consists of a lower wing element (main plane), an upper wing element (flap) and the endplates. In this study, the rear wing is designed as per the FIA 2020 F1 technical regulations and is analyzed using Computational Fluid Dynamics (CFD). The rear wing model is designed using Autodesk Fusion 360 and the analysis is made using Autodesk CFD. Benzing airfoils were used in this project as the wing elements. The results of the stock and modified model are compared and discussed. The results show how the modified version of the endplate has better aerodynamic properties than the stock model. The whole rear wing assembly has also been analysed and the results were discussed.

Energy harvesting properties of a flapping foil with blow aspirators: A numerical investigation

In recent years, researchers have worked hard to improve the efficiency of energy collection devices because a better use of renewable energy is required for energy protection and emission reduction. To improve the energy harvesting efficiency of a flapping wing, this study proposes a blower model for the first time. By installing blower aspirators at the rear of the upper and lower wing surfaces of an airfoil, this airfoil can achieve higher lift and torque than the original airfoil. This study was performed under a Reynolds number Re=1100 and focused on the impact of the attenuation frequency, the effective angle of attack, and a fixed selection of optimal blower speeds. The unsteady laminar two-dimensional numerical simulation results show that there is an optimal working area on the upper and lower airfoil blowers under the given working conditions, and the energy collection efficiency increases when the upper and lower airfoil blowers have similar speeds. For different attenuation frequencies and effective angles of attack, the optimal blower speed improved by 10%, with the highest being 26.7%. Through a flow field analysis, the vortex of the flapping wing equipped with a blower was found to be closer to the airfoil than the vortex of original airfoil at different times and it had a higher vortex intensity than the original. Choosing a reasonable blower velocity can help to capitalize on the blower’s ability to increase lift and torque, and thus improve the efficiency of a flapping wing.

Plant canopy may promote seed dispersal by wind

Seed dispersal has received much research attention. The plant canopy can intercept diaspores, but the effect of the plant canopy (the aboveground portion of a plant consisting of branches and leaves) on dispersal distance has not been explored empirically. To determine the effect of plant canopy on seed dispersal distance, a comparison of diaspores falling through open air and through plant canopy was made in a wind tunnel using three wind speeds and diaspores with various traits. Compared with diaspores falling through open air, the dispersal distance of diaspores falling through plant canopy was decreased or increased, depending on wind speed and diaspore traits. When falling through a plant canopy, dispersal distance of diaspores with thorns or those without appendages was promoted at low wind speed (2 m s−1), while that of diaspores with low wing loading (0.5 mg mm−2) and terminal velocity (2.5 m s−1) was promoted by relatively high (6 m s−1) wind speed. A plant canopy could increase seed dispersal distance, which may be due to the complicated updraft generated by canopy. The effect of maternal plants on seed dispersal regulates the distribution pattern and the species composition of the community.

Damage tolerance of a hybrid lower wing bonded stiffened panel with a Fiber Metal Laminate skin

Fiber Metal Laminates (FML) represent a highly damage tolerant option for lower wing skins that can be included in an advanced high performance metallic wing box. The purpose of the present study is to assess the damage tolerance behavior of a panel made of FML with 0.8 mm 2024 T3 sheet and bonded stringers.A 5-stringer test panel, 800 mm wide, is tested at R=0.1 at a maximum stress of 135 MPa. This stress conservatively represents a spectrum with a sustained flight stress (1 g stress) of 90 MPa corresponding to a 20% increase versus a conventional 2024 T351 lower wing allowable stress.Crack growth from an initial defect is monitored using Thermal Surface Analysis and visual inspection. The propagation life between the chosen detection event and the residual strength test is 137580 cycles. This detection event is a broken stringer; it occurs after the crack in the FML skin has reached a 39 mm length. The residual strength exceeds the required limit load. The total life from crack initiation at the notch to the crack length reached before the residual strength test is 220000 cycles.Combining the stress allowable increment and density reduction, the test justifies a 25% weight saving potential versus a lower wing in 2024 T351, with 45000 flight cycles inspection intervals and 90000 flight cycles Design Service Goal.

Mathematical Formulation of Bubble Formation after Compressible Boundary Layer Separation: Preliminary Numerical Results

Laminar boundary layer (BL), under adverse pressure gradient, can separate. The separated shear layer reattaches to form a laminar separation bubble. Such bubbles are usually observed on gas turbine blades, on low Reynolds number wings and close to the leading edges of airfoils. Presence of bubbles has a weakening effect on the performance of a fluid device. The understanding of the prevailing mechanism of the separation bubble and ways to control it are essential for the efficient design of these devices. This is due to the significance of drag reduction in these various aerodynamic devices, such as gas turbines, re-entry space vehicles and airfoils. This study introduces a two-dimensional mathematical formulation of bubble formation after flow separation. The laminar BL equations with appropriate boundary conditions are dimensionalized using the Falkner-Skan transformation. Additionally, using the Keller-box method, the nonlinear system of partial differential equations (PDEs) is numerically solved. This study presents preliminary numerical results of bubble formation in low Mach numbers. These results reveal that after separation, a laminar bubble is formed in all studied cases, for Mach numbers, M = 0.2, 0.33 and 1.0. The flow after separation reverses close to the wall and finally reattaches downstream, in a new location. As the Mach number increases, this effect is more intense. After reattachment, the BL is again established in a lower energy level and the velocity field is substantially reduced, for all cases.

Aerodynamic effects of a folding wingtip to increase take-off, landing and cruise performance.

The main purpose of a folding wing tip is to allow aerodynamically efficient high aspect ratio wing. To allow a wing tip to move in flight is to alleviate the loads and achieve lower wing weight or enable wing span to maximize. Thus reduces the induced drag and improve fuel efficiency. The folding wing tip may include spring devices in order to provide an additional gust loads alleviation ability in flight. A wing without a winglet produces wingtip vortices which increases drag as the air from the bottom surface of the wing (high pressure) tries to move to the upper surface (low pressure). To avoid this and have less vortices a winglet is used, around which the flow is same on both surfaces. A folding wingtip can be set at an angle of 0° to have maximum cruise performance and aspect ratio. If the wingtip is set in the range of 15°-50° it can increase lift during take-off. This folding wingtip can access any airport in the world because if it is folded at an angle of 90°, it can meet the gate requirements and restrictions of any airport. To study the performance of this mechanism, the wing tip was designed by using CATIA V5 software. The analysis of the wingtip at different angle of attacks was done using ANSYS and XFLR 5 softwares.

Peen forming and stress peen forming of rectangular 2024–T3 aluminium sheets: Curvatures, natural curvatures and residual stresses

AbstractAluminium skins on the lower wings of most commercial aircraft are shaped using shot peen forming. This process, which involves bombarding the skins with hard shot, uses nonuniform plastic flow to induce curvatures—in the same way that differential expansion makes metal bilayers bend when heated. Here, we investigate experimentally how constraining conditions affect the final shape of peen formed parts. We report peen forming experiments for 4.9‐mm‐thick rectangular 2024–T3 aluminium sheets of different aspect ratios uniformly shot peened on one face with a low intensity saturation treatment. Some specimens were free to deform during peening while others were elastically prestressed in a four‐point bending jig. For each aspect ratio and prestress condition, residual stresses were measured near the peened surface with the hole drilling method. Additional residual stress profiles were also obtained with the slitting method. The residual stress measurements show that the progressive deformation of unconstrained specimens had the same effect as an externally applied prestress. For the peening conditions investigated, this progressive deformation caused unconstrained strips to exhibit curvatures 33% larger than identical strips held flat during peening. Furthermore, we found that the relative importance of material anisotropy and geometric effects did determine the bending direction of unconstrained specimens.

Functional and taxonomic responses of tropical moth communities to deforestation

Abstract Global insect decline has recently become a cause for major concern, particularly in the tropics where the vast majority of species occurs. Deforestation is suggested as being a major driver of this decline, but how anthropogenic changes in landscape structure affect tropical insect communities has rarely been addressed. We sampled Saturniidae and Sphingidae moths on 27 farms located in Brazilian Amazonia (Pará state) and characterised by different deforestation histories. We used functional traits (forewing length, body mass, wing load, trophic niche breadth and resource use strategy), analysed by combining RLQ and null model analyses, to investigate the responses of their taxonomic and functional diversity to landscape change dynamics and current structure. We found that communities had a higher proportion of large and polyphagous species with low wing load in landscapes with low forest quality and relative cover and high land use turnover. This was mainly due to a significant response to deforestation by saturniids, whereas the more mobile sphingids showed no significant landscape‐related pattern. We also observed an overall increase of species richness and functional dispersion in landscapes that have been deforested for a long time when compared with more recent agricultural settlements. Our results highlight the complex way in which landscape structure and historical dynamics interact to shape Neotropical moth communities and that saturniid moths respond clearly to the structure of the surrounding landscape, confirming their potential use as an indicator group for environmental monitoring programmes.

On the design and manufacturing of topologically optimized wings

PurposeThe purpose of this paper is to evaluate the impact of different Additive Manufacturing (AM) orientations on the structural behavior of topologically optimized wings for Unmanned Aerial Systems (UAS), which might enable lightweight and low cost, yet complex, wing structural designs.Design/methodology/approachBased on an aerodynamic load, a two dimensional NACA0012 airfoil is topologically optimized considering PolyLatic Acid (PLA), several volume fractions and different manufacturing orientations. Then, the resulting topologies are post-processed to allow for manufacturing and extrude to three dimensional wing geometries with constant cross-sections. These wings are then manufactured using Fusion Deposition Modeling (FDM) technology and their dynamic structural behavior analyzed by means of Experimental Modal Analysis (EMA) in the linear elastic region.FindingsVolume fraction increase is observed to improve the structural performance without increasing the manufacturing time. Despite manufacturing the wing from the leading edge to the trailing edge can reduce manufacturing time using FDM technology, it is found to be more difficult to build.Originality/valueThis research is a contribution toward the design and built of lightweight and low cost wings for UAS.

Application of cell models to the melting and sublimation lines of the Lennard-Jones and related potential systems.

Harmonic cell models (HCMs) are shown to predict the melting line of the Lennard-Jones (LJ) but not the sublimation line. In addition, even for the melting line, the HCMs are found to be physically unrealistic for inverse power potential systems near the hard-sphere limit, and for the Weeks-Chandler-Andersen system at extremely low temperatures. Despite this, the HCM accurately predicts the LJ mean-square displacement (MSD) from molecular-dynamics (MD) simulations along both lines after simple scaling corrections, to include the effects of anharmonicity and correlated dynamics of the atoms, are applied. Single caged atom molecular dynamics and Monte Carlo simulations provide further quantitative characterization of these additional effects, which go beyond harmonicity. The melting indicator and a modification of the cell model in a similar form are shown to be approximately constant along the melting line, which indicates an isomorph. The less well studied LJ sublimation line is shown not to be an isomorph, yet it still can be represented analytically very accurately by the relationship k_{B}T=aρ^{4}+bρ^{2}, where a and b are constants (k_{B} is Boltzmann's constant, T is the temperature, and ρ is the number density). This relationship has been found previously for the melting line, but the two constants have opposite signs for the sublimation and melting lines. This simple formula is also predicted using a nonharmonic static lattice expression for the pressure. The probability distribution function of the melting factor indicates departures from harmonic or Gaussian behavior in the lower wing. Nevertheless, the mean melting factor is shown to follow a simple MSD Debye-Waller factor dependence along both the melting and sublimation lines. This work combining HCM and MD simulations provides a comparison of the melting and sublimation lines of the LJ system, which could provide the foundations for a more unified statistical mechanical description of these two solid boundary lines.

Gust mitigation with an oscillating airfoil at low Reynolds number

The encounter between micro-aerial vehicles (MAVs) and gusts is often detrimental and mitigating the effects of the gust is important for operating MAVs under severe environmental conditions. This study investigates the impact of vertical gusts on stationary and oscillating NACA0012 (National Advisory Committee for Aeronautics) airfoils at low Reynolds numbers using high-order computational fluid dynamics methods, and identifies key dynamics that dominate gust mitigation. The interaction of the gusts with the stationary airfoil generates large unsteady forces, which exceed the peak static lift coefficient. A simple pitch-down maneuver and oscillating airfoil motion were tested as methods for mitigating the effects of the gusts. A rapid and significant pitch-down maneuver is observed to inadvertently cause a stall event by exceeding the negative stall angle. A stepwise change in the angle of attack (AoA), as the gust develops, is shown to be more effective at mitigating the gust effect. However, this gust mitigation strategy is still not effective if the gust continues to grow in magnitude. Low amplitude wing oscillations were then tested as a novel method for gust mitigation. Increasing the reduced frequency of the oscillating airfoil is shown to dominate the gust and results in a predictable oscillatory lift and drag/thrust behavior. Results also show that this effect is relatively insensitive to variations in the Strouhal number. These results suggest there may be gust mitigation strategies leveraging oscillating wing behaviors on MAVs.

Maternal Environmental Light Conditions Affect the Morphological Allometry and Dispersal Potential of Acer palmatum Samaras

Seed dispersal plays critical roles in determining species survival and community structures. Since the dispersal is biologically under maternal control, it is hypothesized that intraspecific variation of dispersal potential and associated traits of seeds (diaspores) should be influenced by maternal habitat quality. We tested this hypothesis by examining the effects of maternal environmental light condition on morphological traits and descending performance of nearly 1800 wind-dispersed samaras collected from maple species Acer palmatum. Results showed that samaras produced by trees from shaded microhabitats had greater dispersal potential, in terms of slower terminal velocity of descent, than those produced in open microhabitats. This advantage was largely attributed to morphological plasticity. On average, samaras produced in shaded microhabitats, as compared to those produced in open habitats, had lower wing loading by only reducing weight but not area. In allometric details, in the large size range, samaras from shaded microhabitats had larger areas than those from open microhabitats; in the small size range, samaras from shaded microhabitats had wider wings. These findings suggest that greater dispersal potential of samaras in response to stressful maternal light environment reflected an active maternal control through the morphological allometry of samaras.

Wing movements underlying sound production in calling, rivalry, and courtship songs of the cricket Gryllus bimaculatus (DeGeer)

We recorded the wing movements and sound signals during the production of calling, rivalry, and courtship song in the bispotted field cricket Gryllus bimaculatus. Recordings confirm that salient sound pulses during calling and rivalry song are generated during the closing movements of the wings. Wing movements for calling and rivalry song start from an elevated wing position and are performed with a very similar opening-closing movement, indicating that both types of songs may be generated by the same neuronal network. Wing movements for courtship song start from a low wing position; rapid closing movements generate high-frequency ticks and low-amplitude wing oscillations lead to low–amplitude pulses, generated during the opening and closing movements with a carrier frequency corresponding to the calling song. The two types of wing movements underlying courtship song indicate a different motor control as compared to calling song and may represent an early evolutionary phenotype.

Very low Reynolds number causes a monotonic force enhancement trend for a three-dimensional hovering wing in ground effect

This research reports the numerical results of the ground effect trend for a three-dimensional flapping insect wing at a very low Reynolds number (Re = 10). It demonstrates that the ground effect trend at this Re has a ‘single force regime,’ i.e. the forces only enhance as the ground distance decreases. This phenomenon is unlike the widely expected non-monotonic trend publicized in previous studies for higher Reynolds numbers, that shows ‘three force regimes,’ i.e. the forces reduce, recover, and also enhance as the ground distance decreases. The force trend in the ground effect correlates to a similar trend in wing–wake interaction or the downwash strength on the wing’s head. At very low Re (10), the very large viscosity causes diffused vortices and less advected vortex wake, while at relatively high Re, the vortices are easily separated from the wing and then advected downwards. This different development of the vortex wake caused different force trends for the flapping wing in the ground effect. Furthermore, by examining only the first stroke when there is no vortex wake, we found that the ‘ramming effect’ enhances the forces on the wing. This effect increases the pressure of the lower wing surface due to the squeezed air between the wing and the ground. The ‘ramming effect’, combined with the reduced downwash (or wing–wake interaction) effect, causes the force enhancement of the wing near the ground’s vicinity. It is further comprehended that the trend is dependent on Re. As the Re is increased, the trend becomes non-monotonic. The effect of varying angles of attack, flapping amplitude and wing planform at very low Re does not change this trend. This ground effect might help insects by enhancing their lift while they hover above the surface. This finding might prove beneficial for developing micro air vehicles.

Seasonal Patterns of Fat Deposits in Relation to Migratory Strategy in Facultative Migrants

Physiological preparations for migration generally reflect migratory strategy. Migrant birds fuel long-distance flight primarily with lipids, but carrying excess fuel is costly; thus, the amount of fat deposited prior to departure often reflects the anticipated flight duration or distance between refueling bouts. Seasonal pre-migratory deposition of fat is well documented in regular seasonal migrants, but is less described for more facultative species. We analyze fat deposits of free-living birds across several taxa of facultative migrants in the songbird subfamily Carduelinae, including house finches (Haemorhous mexicanus), American goldfinches (Spinus tristis), pine siskins (Spinus pinus) and four different North American ecotypes of red crossbills (Loxia curvirostra), to evaluate seasonal fat deposition during facultative migratory periods. Our data suggest that the extent of seasonal fat deposits corresponds with migratory tendency in these facultative taxa. Specifically, nomadic red crossbills with a seasonally predictable annual movement demonstrated relatively large seasonal fat deposits coincident with the migratory periods. In contrast, pine siskins, thought to be more variable in timing and initiation of nomadic movements, had smaller peaks in fat deposits during the migratory season, and the partial migrant American goldfinch and the resident house finch showed no peaks coincident with migratory periods. Within the red crossbills, those ecotypes that are closely associated with pine habitats showed larger peaks in fat deposits coincident with autumn migratory periods and had higher wing loading, whereas those ecotypes associated with spruces, Douglas-fir and hemlocks showed larger peaks coincident with spring migratory periods and lower wing loading. We conclude that population averages of fat deposits do reflect facultative migration strategies in these species, as well as the winter thermogenic challenges at the study locations. A difference in seasonal fattening and wing loading among red crossbill ecotypes is consistent with the possibility that they differ in their migratory biology, and we discuss these differences in light of crossbill reproductive schedules and phenologies of different conifer species.

Experimental Flow Field Investigation of the Bio-Inspired Corrugated Wing for MAV Applications

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.