Optimum hovering wing planform

Nabawy, Mostafa R. A.; Crowther, William

doi:10.1016/j.jtbi.2016.06.024

Cited by 20 publications

(8 citation statements)

References 22 publications

(34 reference statements)

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“…The majority of large insects have solid wings that consist of thin, impermeable membranes reinforced with veins [13]. The significance of three-dimensional wing shape and outline on lift-generating leading edge vortices (LEVs) has been extensively addressed in the literature [14][15][16][17][18]. In contrast with solid wings, bristled wings feature complex fluid flows that combine flows around each bristle at Re below unity with flows around the entire wing at low-to-medium Re [10,19].…”

Section: Introductionmentioning

confidence: 99%

Flight efficiency is a key to diverse wing morphologies in small insects

Engels

Kolomenskiy

Lehmann

2021

J. R. Soc. Interface.

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Insect wings are hybrid structures that are typically composed of veins and solid membranes. In some of the smallest flying insects, however, the wing membrane is replaced by hair-like bristles attached to a solid root. Bristles and membranous wing surfaces coexist in small but not in large insect species. There is no satisfying explanation for this finding as aerodynamic force production is always smaller in bristled than solid wings. This computational study suggests that the diversity of wing structure in small insects results from aerodynamic efficiency rather than from the requirements to produce elevated forces for flight. The tested wings vary from fully membranous to sparsely bristled and were flapped around a wing root with lift- and drag-based wing kinematic patterns and at different Reynolds numbers ( Re ). The results show that the decrease in aerodynamic efficiency with decreasing surface solidity is significantly smaller at Re = 4 than Re = 57. A replacement of wing membrane by bristles thus causes less change in energetic costs for flight in small compared to large insects. As a consequence, small insects may fly with bristled and solid wing surfaces at similar efficacy, while larger insects must use membranous wings for an efficient production of flight forces. The above findings are significant for the biological fitness and dispersal of insects that fly at elevated energy expenditures.

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“…Wing chord distribution can be considered at a later stage of the design process to tune the aerodynamics to desired performances (e.g. as proposed in [ 20 ]) depending on vehicle requirements. Following wing geometric considerations, wing kinematics should be decided.…”

Section: Discussionmentioning

confidence: 99%

“…Aspect ratio is important for aerodynamic considerations, whereas wing length is essential for defining inertia and scalability characteristics. Higher values of the wing aspect ratio are known to improve the aerodynamic induced effects [ 19 , 20 ]. However, as the aspect ratio increases there can be insufficient chord length to allow smooth flow reattachment on the wing upper surface.…”

Section: Methodsmentioning

confidence: 99%

Scalability of resonant motor-driven flapping wing propulsion systems

Nabawy

Marcinkeviciute

2021

R. Soc. open sci.

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This work aims to develop an integrated conceptual design process to assess the scalability and performance of propulsion systems of resonant motor-driven flapping wing vehicles. The developed process allows designers to explore the interaction between electrical, mechanical and aerodynamic domains in a single transparent design environment. Wings are modelled based on a quasi-steady treatment that evaluates aerodynamics from geometry and kinematic information. System mechanics is modelled as a damped second-order dynamic system operating at resonance with nonlinear aerodynamic damping. Motors are modelled using standard equations that relate operational parameters and AC voltage input. Design scaling laws are developed using available data based on current levels of technology. The design method provides insights into the effects of changing core design variables such as the actuator size, actuator mass fraction and pitching kinematics on the overall design solution. It is shown that system efficiency achieves peak values of 30–36% at motor masses of 0.5–1 g when a constant angle of attack kinematics is employed. While sinusoidal angle of attack kinematics demands more aerodynamic and electric powers compared with the constant angle of attack case, sinusoidal angle of attack kinematics can lead to a maximum difference of around 15% in peak system efficiency.

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“…Based on their results, we estimated the optimal wing shape in Figure 2 e and for the calculations in Figure 3 (see Supplementary Materials ). In contrast to Betz and Prandtl, Nabawy and Crowther [ 113 , 114 , 115 ] derived the optimal wing shape of two revolving wings assuming the elliptical circulation distribution of a pair of translating wings, with maximum circulation at the revolving axis. In this theoretical case, wing chord must continuously increase from wing tip to root in order to compensate for the drop in inflow velocity, leading to an “optimum” wing shape [ 114 , 115 ].…”

Section: Aerodynamic Properties Of Root-flapping Rectangular Wingsmentioning

confidence: 99%

Wing Design in Flies: Properties and Aerodynamic Function

Krishna

Cho

Wehmann

et al. 2020

Insects

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The shape and function of insect wings tremendously vary between insect species. This review is engaged in how wing design determines the aerodynamic mechanisms with which wings produce an air momentum for body weight support and flight control. We work out the tradeoffs associated with aerodynamic key parameters such as vortex development and lift production, and link the various components of wing structure to flight power requirements and propulsion efficiency. A comparison between rectangular, ideal-shaped and natural-shaped wings shows the benefits and detriments of various wing shapes for gliding and flapping flight. The review expands on the function of three-dimensional wing structure, on the specific role of wing corrugation for vortex trapping and lift enhancement, and on the aerodynamic significance of wing flexibility for flight and body posture control. The presented comparison is mainly concerned with wings of flies because these animals serve as model systems for both sensorimotor integration and aerial propulsion in several areas of biology and engineering.

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“…As can be seen in figure 1, the Beta function results in a wing planform with a straight leading edge and a sharp wing tip, unlike the original fruitfly wing planform of the same c, b,r 1 andr 2 . The Beta function has been widely used to generate wing planforms by researchers [10,16,14], which have resulted in straight leading edges similar to that shown in figure 1. However, the high lift acting on an insect wing is generated by the leading-edge vortex (LEV) formed during the rotational translation phase of flapping and stabilised by the spanwise outward flow driven by the Coriolis acceleration [9].…”

Section: Introductionmentioning

confidence: 99%

Curved leading edges and wing tips help enhance the lift on insect wings

Bhat¹,

Thompson²

2020

Australasian Fluid Mechanics Conference (AFMC)

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Shape of an insect wing is important in determining the aerodynamics during its flapping motion. Most studies on the insectwing aerodynamics simplify the wing shapes with a straight leading edge. Previous studies show that a stable leading-edge vortex (LEV) is responsible for the higher lift observed in insect wings. However, a straight leading edge and a sharp wing tip might disturb the spanwise transport of the excess vorticity required to keep the LEV size intact. In the present work, rotating wings of various leading edge curvatures are numerically simulated at insect Reynolds numbers to observe the effect on the leading edge vortex and the lift. The study reveals that the curved leading edges and wing tips enhance the lift acting on the wing as a result of the increased vorticity flux from the leadingedge vortex to the tip vortex.

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Optimum hovering wing planform

Cited by 20 publications

References 22 publications

Flight efficiency is a key to diverse wing morphologies in small insects

Scalability of resonant motor-driven flapping wing propulsion systems

Wing Design in Flies: Properties and Aerodynamic Function

Curved leading edges and wing tips help enhance the lift on insect wings

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