Flapping wing structures have drawn increasing attention for harvesting energy from flowing fluids. This work proposes the application of an adaptive Gurney flap to the trailing end of a flapping ...wing foil, which actively adjusts the position of a single Gurney flap to be consistently employed on the foil pressure side. The transient two-dimensional numerical simulations are conducted to compare the energy harvesting efficiency of the proposed adaptive flapping wing structure with that of a conventional flapping wing structure and the one with fixed Gurney flaps. In addition, the effects of wing oscillation frequency, Gurney flap length, and the position of the flap relative to the trailing edge of the foil were also considered. The results demonstrate that the adaptive Gurney flap provides greater energy harvesting efficiency for the oscillating wing primarily by increasing the heave force through the synchronous switching of the flap from one side to the other within the period of motion. Compared with fixed Gurney flaps, the adaptive flap can accommodate greater flap lengths and operation over a wider oscillation frequency range. The results indicate that the optimum position of the Gurney flap is as near as possible to the trailing edge of the foil. The results also reveal two relatively high harvesting efficiency oscillation frequency regions. In the low frequency region, if the leading edge vortex detaches from the trailing edge just when the foil exchanges the heaving direction, the foil can gain much more energy due to the positive power extraction contributed by the pitching moment. In the high frequency region, a small steady attached vortex maintains a high lift force on the foil, and, thus, the enhanced heaving force harvests more power.
•Adaptive Gurney flap oscillating wing greatly improves energy extraction efficiency.•It allows for considerable flexibility in the choice of flap length.•It should be positioned as near as possible to the foil trailing edge.•Two relative high efficiency frequencies were observed with different mechanisms.
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.
Migratory animals are adapted to mediate migration costs using both fixed and flexible traits. Here, the authors demonstrate that migratory and resident male silver‐haired bats (Lasionycteris noctivagans) exhibit few differences in immune function or wing morphology, suggesting that these traits are not under strong selection during spring migration in male bats. Photo credit: Sherri Fenton and M. Brock Fenton.
How does the AfD manage to make its supporters feel comfortable with a party that many people find repulsive? Florian Spissinger ethnographically observed lecture events, regulars' tables and AfD ...election campaign stands and conducted on-site interviews. What became evident was a new-right affective community against which critical objections bounce off without effect and for which the rejection of immigration and climate protection feels good and clever.
Wie gelingt es der AfD, dass sich deren Unterstützer*innen bei einer für viele Menschen abstoßenden Partei wohlfühlen? Florian Spissinger hat Vortragsveranstaltungen, Stammtische und Wahlkampfstände der AfD ethnografisch beobachtet und Gespräche vor Ort geführt. Sichtbar geworden ist eine neurechte Gefühlsgemeinschaft, an der kritische Einwände wirkungslos abprallen und für die sich die Ablehnung von Zuwanderung und Klimaschutz gut und clever anfühlt.
Design and the segment table, while hypothetical in principle, have not as of not long ago been viewed as befuddling. Following quite a while of sad research into voice-over-IP, we approve the change ...of disseminate/assemble I/O, which typifies the instinctive standards of steganography. We affirm not just that robots and SMPs can associate with achieve this goal, yet that the same is valid for repetition
A Methodology for the Emulation of IPv4
International journal of innovative technology and exploring engineering,
8/2019, Letnik:
8, Številka:
9S3
Journal Article
Odprti dostop
Mobile configurations and wide-area net-works have garnered tremendous interest from both cryptographers and electrical en-gineers in the last several years. In this paper, we disconfirm the analysis ...of object-oriented languages, which embodies the un-proven principles of artificial intelligence. BOT, our new system for probabilistic mod-els, is the solution to all of these obstacles.
The present research investigated a multilevel person-context interactionist framework for the relationship between right-wing ideologies and prejudice across two large, representative samples (Study ...1: European Social Survey: N = 56,752; Study 2: World Values Survey: N = 74,042). Across three different operationalizations of right-wing ideology, two contextual levels (regional and national) of right-wing climate, and three types of outgroup attitudes (i.e., age-, ethnicity-, and gender-based), the analyses consistently revealed cross-level interactions, showing a strong association between right-wing attitudes and negative outgroup attitudes at the individual level in contexts with a low right-wing climate, whereas this relationship is weaker and often even absent in contexts with a high right-wing climate. These cross-level interactions remained significant after controlling for statistical artefacts (i.e., restriction of range and outliers). The authors propose norm setting as the mobilizing mechanism through which a right-wing climate develops and curbs the influence of individual right-wing social-ideological attitudes on outgroup attitudes.
Flapping wing devices represent a new type of renewable energy extraction technology that has the advantageous characteristics of simple structure, strong adaptability to surroundings, and little ...impact on the environment. This study numerically investigates the effects of vertical and elliptical airfoil trajectories on the power extraction efficiency of a flapping airfoil device using a transient numerical method based on the overset grid technique. The results are employed to propose a novel reversed-D airfoil trajectory that represents a composite of an elliptical trajectory in the first half of the motion cycle and a standard vertical trajectory in the second half of the motion cycle. The results show that for the elliptical trajectory, when the length of the half-axis in the vertical direction is fixed, the total power harvesting efficiency decreases with the increase of the horizontal half-axis length. In a certain frequency range, the decreased orders of the power extraction ability of the flapping wing are the upstream half-cycle elliptical trajectory, the vertical linear and the downstream half-cycle elliptical trajectory. Based on this understanding, we propose a new type of reversed-D motion trajectory. The power extraction efficiency of flapping wing devices operating in the reversed-D trajectory are investigated using both single and double airfoil designs. The results show that the power extraction efficiency of the single airfoil design moving along the reversed-D trajectory is greater than that obtained for the single airfoil moving along the standard vertical reciprocating trajectory within a specific range of frequency, and the increase is due mainly to an increase in the heave force. The power extraction efficiency of each airfoil in the double airfoil model moving along the reversed-D trajectory is less than that of a single airfoil moving along the vertical trajectory. However, the overall average power extraction efficiency is greater than that of a single airfoil moving along the vertical trajectory, and this increased efficiency is obtained over a larger frequency range than that of a single airfoil moving along the reversed-D trajectory. In addition, the increased efficiency of the double airfoil model is greater in the low frequency region. The proposed reversed-D trajectory facilitates the flexible arrangement of multiple airfoils in a flapping wing design. As such, the proposed reversed-D trajectory provides a promising new methodology for designing flapping wing devices with high power extraction efficiencies.
This paper describes the design and development of the Dove, a flapping-wing micro air
vehicle (FWMAV), which was developed in Northwestern Polytechnical University. FWMAVs have
attracted ...international attentions since the past two decades. Since some achievements
have been obtained, such as the capability of supporting an air vehicle to fly, our
research goal was to design an FWMAV that has the ability to accomplish a task. Main
investigations were presented in this paper, including the flexible wing design, the
flapping mechanism design, and the on-board avionics development. The current Dove has a
mass of 220 g, a wingspan of 50 cm, and the ability of operating fully autonomously,
flying lasts half an hour, and transmitting live stabilized color video to a ground
station over 4 km away.
In the early era of aviation, Frederick Lanchester was both an inventor and a theoretician driven by the need for a theory of flight that would reduce the guesswork in designing new aircraft. His ...book Aerodynamics in 1907 laid down the early foundations of such a theory. The theory with contributions from others, notably Ludwig Prandtl, was refined to become the basis for the sleek designs of WWII aircraft brought about with little guesswork. New technology changed aircraft design radically with the increased speed of jet propulsion reaching into the transonic range with nonlinear aerodynamics. In the late 1940s and early 1950s substantial guesswork returned to aircraft design. The legacy of Lanchester et al., however, lived on with the development of computational fluid dynamics (CFD) that could guide designers through nonlinear transonic effects. This article presents a historical sketch of how CFD developed, illustrated with examples explaining some of the difficulties overcome in the design of the first-generation swept-wing transonic fighters. The historical study is forensic CFD in search for the likely explanation of the designer’s choice for the wing shape that went into production a long time ago. The capability of current CFD applied to the aerodynamics of aircraft with slender wings is surveyed. The cases discussed involve flow patterns with coherent vortices over hybrid wings and wings of moderate sweep. Vortex-flow aerodynamics pertains to understanding the interaction of concentrated vortices with aircraft components. Modern Reynolds-Averaged Navier-Stokes (RANS) technology is useful to predict attached flow. But vortex interaction with other vortices and breakdown lead to unsteady, largely separated flow which has been found out of scope for RANS. Direct simulation of the Navier-Stokes equations is out of computational reach in the foreseeable future, and the need for better physical modeling is evident. Both cruise performance and stalling characteristics are influenced by strong interactions. Two important aspects of wing-flow physics are discussed: separation from a smooth surface that creates a vortex, and vortex bursting, the abrupt breakdown of a vortex with a subsequent loss of lift. Vortex aerodynamics of not-so-slender wings encounter particularly challenging problems, and it is shown how the design of early-generation operational aircraft surmounted these difficulties. Through use of forensic CFD, the article concludes with two case studies of aerodynamic design: how the Saab J29A wing maintains control authority near stall, and how the Saab J32 mitigates pitch-up instability at high incidence.
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