Wingtip Shape Research Articles

Aerodynamic performance of a flyable flapping wing rotor with dragonfly-like flexible wings

Drawing inspiration from insect flapping wings, a Flapping Wing Rotor (FWR) has been developed for Micro Aerial Vehicle (MAV) applications. The FWR features unique active flapping and passive rotary kinematics of motion to achieve a high lift coefficient and flight efficiency. This study thoroughly investigates the aerodynamic performance and design of a bio-inspired flexible wing for FWR-MAVs, emphasizing its novel backward-curved wingtip and variable spanwise stiffness resembling a dragonfly's wing. The research departs from previous aerodynamic studies of FWR, which focused predominantly on rectangular and rigid wings, and delves into wing flexibility. Employing Computational Fluid Dynamics (CFD), Computational Structural Dynamics (CSD), and experimental measurements, the study demonstrates the aerodynamic benefits of the dragonfly-inspired FWR wingtip shape and its reinforced structure. Fluid-Structure Interaction (FSI) analysis is used to examine the effects of elastic deformation encompassing twist and bending on aerodynamic forces. The results underscore the importance of bending deformation in enhancing lift and power efficiency and propose a method for analysing variable stiffness along the wingspan using a vortex delay mechanism that is induced by delayed flapping motion. By comparing modelled and measured stiffness, the study validates the flexibility of the FWR wing, revealing optimal aerodynamic efficiency is achieved through moderate flexibility and spanwise stiffness variation. The curving leading-edge beam forming the sweep-back wingtip offers a practical approach to obtaining variable stiffness and aerodynamic benefits for FWR-MAVs. Using the same pair of dragonfly-like flexible wings, FWR-MAVs have effectively exhibited VTOL and hovering flight capabilities, spanning from a 25-g single-motor drive model to a 51-g dual-motor drive model. This research provides valuable insights into flexible wing design for FWR-MAVs, leveraging biomimicry to improve flight efficiency.

Sex and State-Dependent Effects on Proactive Behaviors of Bent-Wing Bats Across Contexts

Synopsis Animals within a population may show distinct behavioral types that differ consistently among individuals over time and across contexts, collectively known as animal personality. Individual state variables arising from intrinsic features of organisms and their interactions with the environment may contribute to or aid in maintaining these interindividual behavioral differences. The present study examined the effects of body mass, body condition, flight morphology, and parasite load on the personality traits of bent-wing bats Miniopterus fuliginosus. We assessed the bats in three testing contexts—hole-board box (HB), tunnel-box (TB), and flight-tent (FT)—that mimicked their natural environmental settings and allowed for different locomotion modes. A principal component analysis loaded the three mutually positively correlated personality traits of the bats—boldness, activity, and exploration—in each context onto a single component of proactiveness. In accordance with the AIC criteria, sex, body mass, body condition index, and wingtip shape were selected as predictors for the proactiveness of the bats in the TB and FT tests. In the HB tests, the biomass and abundances of parasitic bat flies were additionally selected, but body condition was excluded. We found a negative effect of the body mass on the proactiveness of the female bats in both the HB and FT tests, and that on the proactiveness of the male bats in the HB tests but not so in the FT tests. The sexual differences and negative correlation between the body mass of the bats and their proactive responsiveness are consistent with the mechanism of state-dependent energy assimilation efficiency. Our results may also concur with the predicted feedback mechanism stemming from the characteristic conditions associated with the environment of the bats. This latter inference offers insights for exploring the patterns of personality traits along gradients or the seasonality of ecological conditions.

Relationships of wingtip shape, song-flight and mating success in male black-headed buntings Emberiza melanocephala

Relationships of wingtip shape, song-flight and mating success in male black-headed buntings Emberiza melanocephala

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.

Experimental investigation on tip-vortex flow characteristics of novel bionic multi-tip winglet configurations

Five bionic multi-tip winglet configurations, inspired by basic feather shapes and wingtip postures of birds, were designed to suppress the tip-vortex structures around their wingtips. Each of the bionic multi-tip winglet configurations consists of multiple novel feather-shaped winglets and looks like a dihedral (or non-planar) wingtip shape. The influence of the distribution density and chord-directional gap for the feather-shaped winglets on the tip-vortex flow characteristics was investigated experimentally at Re = 83 166. The results reveal that the vorticity levels of the tip-vortex structures in the near-wake region can achieve effective suppression by improving the feather-shaped winglets’ distribution density at the wingtip of the bionic wing configuration. The maximum proportions of the induced drag relative to the total drag for the bionic wing configurations I, II, and III are 25.54%, 21.05%, and 19.47%, respectively. The variation of the feather-shaped winglets’ distribution density significantly affects the lift–drag efficiency of the bionic wing configuration. However, the increase in the feather-shaped winglets’ mounting gap weakens the tip-vortex suppression effect for the bionic wing configuration (equipped with the three feather-shaped winglets) to some degree. The maximum proportions of the induced drag relative to the total drag for the bionic wing configurations IV and V are 27.28% and 28.32%, respectively. Compared with the bionic wing configuration I, the slightly worse aerodynamic performance for the bionic wing configurations IV or V (with the larger feather-shaped winglets’ mounting gap) is closely related to its weaker tip-vortex suppression ability.

Speciation Associated with Shifts in Migratory Behavior in an Avian Radiation.

Migratory animals move up to thousands of kilometers every year [1]. Losses of migration (i.e., migratory drop-offs) occur when individuals of a migratory species stop migrating and establish founder sedentary populations, a phenomenon documented in birds [2-5] and butterflies [6]. In theory, losses-and also gains-of migration might promote speciation if sedentary and migratory populations become reproductively isolated [7-9]. Because migratory and sedentary strategies involve alternative physiological, behavioral, and morphological traits [10-13], divergence along multiple axes of organismal function is expected to accompany switches in migratory behavior, potentially accelerating speciation. We present evidence of speciation driven by a migratory drop-off in the fork-tailed flycatcher (Tyrannus savana) resulting in reproductive isolation likely driven by changes in breeding schedules (allochronic speciation [13-15]) and geographic isolation of breeding grounds (allopatric speciation [16]). Phylogenetic analyses across New World flycatchers (Tyrannidae) showed that an association between speciation and drop-offs is also observable at a macroevolutionary scale. Loss of migration was significantly more frequent than its gain, and speciation rates of migratory and partially migratory lineages (i.e., species having both migratory and sedentary populations) exceeded those of sedentary lineages. Models of trait evolution indicated that partial migration is an intermediate step between migratory and sedentary states in this family. Given that partial migration is widespread across migratory animals (e.g., of all migratory birds, ca. 51% are partially migratory [5]), speciation via switches in migratory behavior might be an important yet overlooked mechanism of animal diversification.

Investigation of winglet on the transonic flutter characteristics for a wind tunnel test model CHNT-1

Winglet is of much practical importance in the aerodynamics of a wing with key features to vibrational modes. To study the influences of both geometry and weight of winglets on flutter characteristics, a semi span version of a supercritical wing for a transport airplane was designed. The flutter model was tested cantilever mounted to a rigid fuselage in the China Aerodynamics Research and Development Center with a series of winglets ballasted. The transonic flutter speed boundary for the wing with a basic winglet was measured at Mach number ranging from 0.6 to 0.89, with a minimum flutter speed near M = 0.85. Influences of both winglet geometry and winglet mass properties were acquired at M = 0.7. The winglet weight was observed to reduce the critical dynamic pressure while the wingtip shape has little influence. The winglet effect with a mass effect rather that an aerodynamic effect on flutter has been verified. Furthermore, a linear function was proposed to quantify the effect of weight on the critical dynamic pressure, and the wingtip mass ballast decreased the qF by 0.125 KPa per gram.

Numerical investigation of vortex roll‐up processes using different wingtip shapes

AbstractVortex roll‐up processes of different generic wingtip shapes are investigated using the DLR TAU flow solver in combination with a Reynolds Stress Model. In contrast to a non‐rounded layout an elliptical rounding of the wingtip planform leads to multiple vortices at the wingtip and results in an axial velocity deficit in the vortex core further downstream. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Provenance does matter: links between winter trophic segregation and the migratory origins of European robins.

Amongst migratory species, it is common to find individuals from different populations or geographical origins sharing staging or wintering areas. Given their differing life histories, ecological theory would predict that the different groups of individuals should exhibit some level of niche segregation. This has rarely been investigated because of the difficulty in assigning migrating individuals to breeding areas. Here, we start by documenting a broad geographical gradient of hydrogen isotopes (δ 2H) in robin Erithacus rubecula feathers across Europe. We then use δ 2H, as well as wing-tip shape, as surrogates for broad migratory origin of birds wintering in Iberia, to investigate the ecological segregation of populations. Wintering robins of different sexes, ages and body sizes are known to segregate between habitats in Iberia. This has been attributed to the despotic exclusion of inferior competitors from the best patches by dominant individuals. We find no segregation between habitats in relation to δ 2H in feathers, or to wing-tip shape, which suggests that no major asymmetries in competitive ability exist between migrant robins of different origins. Trophic level (inferred from nitrogen isotopes in blood) correlated both with δ 2H in feathers and with wing-tip shape, showing that individuals from different geographic origins display a degree of ecological segregation in shared winter quarters. Isotopic mixing models indicate that wintering birds originating from more northerly populations consume more invertebrates. Our multi-scale study suggests that trophic-niche segregation may result from specializations (arising in the population-specific breeding areas) that are transported by the migrants into the shared wintering grounds.

Morphological divergence in a continental adaptive radiation: South American ovenbirds of the genusCinclodes

Cinclodes is an ecologically diverse genus of South American passerine birds and represents a case of continental adaptive radiation along multiple axes. We investigated morphological diversification in Cinclodes using a comprehensive set of morphometric measurements of study skins. Principal component analysis identified 2 primary axes of morphological variation: one describing body size and a second capturing differences in wing-tip shape and toe length. Phylogenetic analyses of the first principal component suggest an early divergence of Cinclodes into 2 main clades characterized by large and small body sizes. We suggest that 2 morphological outliers within these main clades (C. antarcticus and C. palliatus) may be cases of island gigantism and that a third (C. patagonicus) may reflect ecological character displacement. Despite its ecological and physiological diversity, the genus Cinclodes does not appear to show morphological diversity beyond what is typical of other avian genera.

The tail plays a major role in the differing manoeuvrability of two sibling species of mouse-eared bats (Myotis myotis and Myotis blythii)

Two sympatrically occurring bat species, the greater mouse-eared bat (Myotis myotis (Borkhausen, 1797)) and the lesser mouse-eared bat (Myotis blythii (Tomes, 1857)) (Chiroptera, Vespertillionidae), share numerous similarities in morphology, roosting behaviour, and echolocation and are often difficult to distinguish. However, despite these similarities, their foraging behaviour is noticeably different. Our aim was to examine the extent to which these different foraging strategies reflect morphological adaptation. We assessed whether the morphology of the wing, body, and tail differed between M. myotis and M. blythii. In addition, in a laboratory experiment involving an obstacle course, we compared differences in manoeuvrability by relating them to our morphological measurements. The two species differed in their overall size, wing-tip shape, and tail-to-body length ratio. The generally smaller sized M. blythii performed better in the obstacle course and was therefore considered to be more manoeuvrable. Although differences in wing-tip shape were observed, we found the most important characteristic affecting manoeuvrability in both species to be the tail-to-body length ratio. Additionally, when we compared two bats with injured wing membranes with unharmed bats of the same species, we found no difference in manoeuvrability, even when the wing shape was asymmetric. We therefore postulate that morphometric differences between the two species in their overall size and, more importantly, in their tail-to-body length ratio are the main physical characteristics providing proof of adaptation to different foraging and feeding strategies.

Numerical simulation of trailed vortex alleviation through chipped wingtip shapes

The shedding of strong vortices generated during take-off and landing poses serious hazards for the following aircraft. To circumvent the vortex wake hazard, a chipped wingtip shape was suggested, and a series of numerical simulations were conducted to verify the conceptual validity of such shape. Numerical simulation was performed by using the incompressible Navier-Stokes solver with the pressure-based semi-implicit method for pressure linked equations algorithm. The Reynolds stressmodel was employed to evaluatethe turbulence effects.The trailed vortices of the chipped wingtip shapes were found to be more dissipative than those of the baseline wingtip shape. The counter-rotating vortices produced by the chipped wingtip shape can weaken the primary wingtip vortex strength in the far field. Regardless of the slightly increasing the drag, the chipped wingtip shape can successfully mitigate the tangential velocity of the vortices. These types of wingtip shapes had various design parameters, such as the aspect ratio, spacing, and area of each chip. Systematic numerical simulations were conducted to evaluate the effect of these parameters. According to the parametric study results, the aspect ratio was sensitive to the increase in the drag coefficient, and the area was susceptible to the moment coefficient. Evidently, a trade-off relationship existed between the tangential velocity reduction and the drag increase.

Competition among European Robins Erithacus rubecula in the winter quarters: sex is the best predictor of priority of access to experimental food resources

Competition for resources by individuals of different sexes, ages, body sizes or geographical origins may have varied implications, from demography to the evolution of migratory systems. European robins Erithacus rubecula display segregation by habitat in relation to sex, age, body size and geographic origin in the winter quarters. Here we report on an experiment to investigate the existence of asymmetries in the priority of access to food resources among unconstrained individuals in their natural environment. Feeders with meal worms were provided in an are a with a high density of wintering robins and, after 15 days of provisioning, were replaced by a spring trap that was operated during a whole day. The first individuals to be caught in each trap were heavier and had higher fat and muscle scores than last-caught individuals. Based on this and on behavioural observations, we conclude that first-caught individuals had priority of access to feeders. First- and last caught individuals did not differ in body size, wingtip shape or age ratios. However, whilst 35% of the first-caught individuals were males, only 6%of the last-caught individuals were males. This suggests that sex is an important predictor of the outcomes of competition in an area where multiple robin populations coexist in winter, while, at least on sites where no strictly sedentary individuals are present, geographic origin may be relatively unimportant.

Effects of treefall gaps created by windthrow on bat assemblages in a temperate forest

Determining the way in which spatial distribution and diversity of forest-dwelling mammals varies with natural disturbance is essential to understanding the spatial dynamics of mammal assemblages in forests. Bats are the only forest-dwelling mammals capable of true flight. At a local scale, bat flight ability, which may be related to ecomorphological traits, is an important factor influencing spatial distribution. We tested two postulates: (1) the spatial distribution of bats is affected by sizes of forest gaps created by natural disturbances and (2) species-specific responses can be predicted from bat ecomorphological traits (aspect ratio (AR) and wingtip shape index (WT)) that influence bat flight ability. We found that sizes of forest gaps affected the occurrence of each bat species and species richness of bats at local scales; species-specific responses were related to the ecomorphological traits of individual species. Bat species with high AR and low WT were not affected by variation in canopy gap size. In contrast, bat species with low AR and high WT responded negatively to gap size, and those with intermediate AR and WT responded positively to canopy gap size at sites with small-sized gaps but responded negatively to large-sized gaps. Overall bat species richness responded negatively to gap size. Thus, ecomorphological traits may be important determinants of bat spatial distributions and species diversity at local scales in disturbed habitats. In this study, forest edges might have been undersampled due to the location of bat detectors. However, this potential undersampling should not have affected the interpretation of occurrence patterns of bat species responding to gap size. Our results imply that bat conservation efforts in forest lands should take into consideration specific responses related to ecomorphological traits of species inhabiting an area. The results also suggest that quantifying the effects of natural disturbances on bat assemblages may provide a knowledge base for forest management to minimize the impacts of unavoidable anthropogenic disturbances on bat species diversity. Rare or infrequent natural disturbances can provide models for forest management aimed at maintaining bat species diversity.

G0501-3-4 翼の地面効果へ及ぼす翼端形状の影響(実験,後流)

G0501-3-4 翼の地面効果へ及ぼす翼端形状の影響(実験,後流)

Sex, Wingtip Shape, and Wing-Loading Predict Arrival Date at a Stopover Site in the Swainson's Thrush (Catharus Ustulatus)

AbstractPointed wingtips and low wing-loading are believed to reduce the amount of energy used during migratory flight. If this is true, individuals with pointed wingtips or consistently low wing-loading should be able to migrate faster than conspecifics and may arrive on the breeding grounds and at stopover sites earlier. To test this hypothesis, I captured 97 Swainson's Thrushes (Catharus ustulatus; hereafter “thrushes”) during May in three consecutive field seasons, 2003-2005, at a stopover site in central Illinois. I used molecular techniques to sex 47 of these thrushes and created a discriminant function analysis using wing, tarsometatarsus, and tail lengths that predicted sex with 80.9% accuracy (P < 0.001). I applied this function to the remaining 50 thrushes so that I could control for any sexual dimorphism in morphology and arrival timing, and then examined seasonal trends in sex and morphology. Male thrushes arrived earlier at my stopover site than females (P < 0.001). After controlling for sex, thrushes with more pointed wingtips (P = 0.002) and lower wing-loading (P = 0.044) arrived earlier than thrushes with more rounded wingtips and higher wing-loading. The general linear model with sex, wingtip pointedness, and wing-loading explained nearly one-third of the variation in arrival date (P < 0.001, r2 = 0.281, n = 90). Pointed wingtips and lower wing-loading may help migratory birds cover distance more quickly and arrive at the breeding grounds sooner; alternatively, thrushes with more pointed wingtips and lower wing-loading may have departed from the wintering grounds earlier. If wing shape and size affect rate of migration, these variables may be important determinants of individual quality in migratory passerines.El Sexo, la Forma de las Puntas de las Alas y la Carga Alar Predicen la Fecha de Arribo de Catharus ustulatus a un Sitio de Escala Migratoria

Bat wing airfoil and planform structures relating to aerodynamic cleanliness

In this paper we examine 12 species of Western Australian bat for anatomical and morphometric attributes related to wing lift and drag characteristics. We present values for bat wing camber (typically 6.5–9%) and its location, measurements of wing planform and tip shape (typically elliptical but with two different tip designs), dimensions of wing leading-edge flaps (typically 8–10.5% of hand wing chord but with some species having much larger flaps up to 18%) and then discuss several features related to airflow separation control. All species assessed had thin, low-camber airfoil sections, an optimisation appropriate to the range of Reynolds Numbers in which bats fly. Wing relative cleanliness was consistent with, and functionally appropriate to, species foraging strategy. The interceptors had the point of maximum camber well forward and no trailing edge wing fences, optimisations for minimum drag generation. The air-superiority bats had leading-edge fences optimised for maximum lift generation while maintaining low drag. Surface bats were characterised by their low-aspect-ratio wingtips and the absence of optimisations for either low section drag or high lift. The frugivore and the carnivore appear to be discrete optimisations while the emballinurid had a long and broad leading edge flap in combination with a high-aspect-ratio tip. We propose a range of lift and drag coefficient values for use in models of metabolic power output.

914 翼先端形状と後流渦の数値的研究(GS-5 揚力,抗力)

914 翼先端形状と後流渦の数値的研究(GS-5 揚力,抗力)

Foraging and roosting ecology of a rare insectivorous bat species, Laephotis wintoni (Thomas, 1901), Vespertilionidae

Laephotis wintoni is a rare bat and little is known about its biology. We studied this species at Algeria Forestry Station in the Western Cape Province, South Africa. A female caught in November 2002 was pregnant and three females caught in November 2004 were all lactating. The three lactating females were radio tagged and roosted in crevices or narrow fissures in a cliff face above the valley where they foraged. Laephotis wintoni is a small insectivorous bat (body mass, x̄ ± SD = 9.6 ± 0.5 g, n = 4) with low wing loading (7.0 ± 0.7 Nm−2, n = 4), low aspect ratio (5.7 ± 0.5, n = 4), low wingtip shape index (1.2 ± 0.2, n = 4) and long ears (20.9 ± 2.3 mm, n = 2). Its morphology suggests that it is a slow manoeuvrable flyer that can fly close to vegetation, or the ground or over water surfaces. Its relatively pointed wings suggest that it probably does not fly in dense clutter. Furthermore, it combines this wing shape with echolocation calls of relatively low intensity, short duration (2.6 ± 0.8 ms, n = 5), narrow band (13.5 ± 2.9 kHz, n = 5) and surprisingly low peak frequency (22.1 ± 0.6 kHz, n = 5). The latter two parameters make it unlikely that the calls are used to overcome masking effects associated with flying in dense clutter. Instead, we propose that its echolocation calls are adapted to be less audible to tympanate insects. This is supported by the fact its diet is dominated by moths in a habitat where tympanate moths comprise 90% of the moth population.

The influence of wing morphology and echolocation on the gleaning ability of the insectivorous bat Myotis tricolor

On the basis of its external morphology, Myotis tricolor (Temminck, 1832) should be able to both aerial-feed and glean. Furthermore, this bat is known to use broadband calls of short duration, reinforcing the prediction that it gleans. However, results from this study indicate that M. tricolor does not commonly glean. This conclusion was reached after studying the foraging behaviour of M. tricolor in a flight room. We presented M. tricolor with mealworms, moths, mole crickets, beetles, and cicadas in a variety of ways that required either gleaning and (or) aerial feeding. Although M. tricolor readily took tethered prey, it did not take any of the variety of insects presented to it in a manner that required gleaning. We therefore compared its wing morphology and echolocation calls with those of several known gleaners, Nycteris thebaica E. Geoffroy, 1818, Myotis lucifugus (Le Conte, 1831), and Myotis septentrionalis (Trouessart, 1897), and an aerial forager, Neoromicia capensis (A. Smith, 1829). In a discriminant analysis wing-tip shape was the only variable to provide some degree of discrimination between species, with M. tricolor having more pointed wing tips than the known gleaners. Discriminant analysis of echolocation-call parameters grouped M. tricolor with the other Myotis species and separated it from N. capensis and N. thebaica. However, M. tricolor did not use harmonics as did the other Myotis species. The apparent failure of M. tricolor to glean might therefore be due to its relatively pointed wings and narrow-bandwidth echolocation calls, owing to the absence of harmonics in its calls.