Size effects on insect hovering aerodynamics: an integrated computational study

Liu, H.; Aono, Hikaru

doi:10.1088/1748-3182/4/1/015002

Cited by 141 publications

(131 citation statements)

References 33 publications

(61 reference statements)

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“…As illustrated in figure 2c, both flexible and rigid wings show a similar high peak of vertical force immediately after the wing turns to decelerate. This is because the LEV keeps growing and attaching coherently onto the wing surface even after the LEV breaks down with the TV shedding off the wing surface [6,35]. However, there does exist pronounced discrepancy at early down-stroke, where the flexible wing obviously creates more vertical forces than the rigid wing (figure 2c).…”

Section: Discussionmentioning

confidence: 99%

“…Since the LEV and the TV play a key role in the force production of hovering flight, influence of the vortex structures near the body can be negligible [34]. An intense hovering downwash is formed flowing through the centre of the DVR [6,35]. However, there does exist pronounced discrepancy between the flexible and rigid wings: the direction of air-flow generated by the flexible wing approaches the vertical direction more than that of the rigid wing.…”

Section: (D) Wake Structures Induced By Flexible Wingsmentioning

confidence: 99%

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Aerodynamic performance of a hovering hawkmoth with flexible wings: a computational approach

2011

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Insect wings are deformable structures that change shape passively and dynamically owing to inertial and aerodynamic forces during flight. It is still unclear how the three-dimensional and passive change of wing kinematics owing to inherent wing flexibility contributes to unsteady aerodynamics and energetics in insect flapping flight. Here, we perform a systematic fluid-structure interaction based analysis on the aerodynamic performance of a hovering hawkmoth, Manduca, with an integrated computational model of a hovering insect with rigid and flexible wings. Aerodynamic performance of flapping wings with passive deformation or prescribed deformation is evaluated in terms of aerodynamic force, power and efficiency. Our results reveal that wing flexibility can increase downwash in wake and hence aerodynamic force: first, a dynamic wing bending is observed, which delays the breakdown of leading edge vortex near the wing tip, responsible for augmenting the aerodynamic force-production; second, a combination of the dynamic change of wing bending and twist favourably modifies the wing kinematics in the distal area, which leads to the aerodynamic force enhancement immediately before stroke reversal. Moreover, an increase in hovering efficiency of the flexible wing is achieved as a result of the wing twist. An extensive study of wing stiffness effect on aerodynamic performance is further conducted through a tuning of Young's modulus and thickness, indicating that insect wing structures may be optimized not only in terms of aerodynamic performance but also dependent on many factors, such as the wing strength, the circulation capability of wing veins and the control of wing movements.

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Section: Discussionmentioning

confidence: 99%

Section: (D) Wake Structures Induced By Flexible Wingsmentioning

confidence: 99%

Aerodynamic performance of a hovering hawkmoth with flexible wings: a computational approach

2011

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“…At the scale of flow between each individual bristle, the continuum assumption for the fluid may introduce errors (Liu and Aono, 2009). The Knudsen number, Kn, gives a measure of the mean free path of a molecule over the characteristic length scale and is given by the equation:…”

Section: Possible Rarefied Effectsmentioning

confidence: 99%

Clap and fling mechanism with interacting porous wings in tiny insect flight

Santhanakrishnan

Robinson

Jones

et al. 2014

Journal of Experimental Biology

118

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The aerodynamics of flapping flight for the smallest insects such as thrips is often characterized by a 'clap and fling' of the wings at the end of the upstroke and the beginning of the downstroke. These insects fly at Reynolds numbers (Re) of the order of 10 or less where viscous effects are significant. Although this wing motion is known to augment the lift generated during flight, the drag required to fling the wings apart at this scale is an order of magnitude larger than the corresponding force acting on a single wing. As the opposing forces acting normal to each wing nearly cancel during the fling, these large forces do not have a clear aerodynamic benefit. If flight efficiency is defined as the ratio of lift to drag, the clap and fling motion dramatically reduces efficiency relative to the case of wings that do not aerodynamically interact. In this paper, the effect of a bristled wing characteristic of many of these insects was investigated using computational fluid dynamics. We performed 2D numerical simulations using a porous version of the immersed boundary method. Given the computational complexity involved in modeling flow through exact descriptions of bristled wings, the wing was modeled as a homogeneous porous layer as a first approximation. High-speed video recordings of free-flying thrips in take-off flight were captured in the laboratory, and an analysis of the wing kinematics was performed. This information was used for the estimation of input parameters for the simulations. Compared with a solid wing (without bristles), the results of the study show that the porous nature of the wings contributes largely to drag reduction across the Re range explored. The aerodynamic efficiency, calculated as the ratio of lift to drag coefficients, was larger for some porosities when compared with solid wings.

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“…With a diameter of 200 mm, the small sphere functioned as the wing block. The distance from its surface to the wing tip was 34.5 mm (or 2.8 times as much as C m ), which was larger than the 2C m value adopted in previous researches [19,25]. With a diameter of 650 mm, the large sphere functioned as the body block.…”

Section: Grid Generationmentioning

confidence: 76%

Numerical analysis of the three-dimensional aerodynamics of a hovering rufous hummingbird (Selasphorus rufus)

Yang

Zhang

2015

Acta Mech. Sin.

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Hummingbirds have a unique way of hovering. However, only a few published papers have gone into details of the corresponding three-dimensional vortex structures and transient aerodynamic forces. In order to deepen the understanding in these two realms, this article presents an integrated computational fluid dynamics study on the hovering aerodynamics of a rufous hummingbird. The original morphological and kinematic data came from a former researcher's experiments. We found that conical and stable leading-edge vortices (LEVs) with spanwise flow inside their cores existed on the hovering hummingbird's wing surfaces. When the LEVs and other near-field vortices were all shed into the wake after stroke reversals, periodically shed bilateral vortex rings were formed. In addition, a strong downwash was present throughout the flapping cycle. Time histories of lift and drag were also obtained. Combining the three-dimensional flow field and time history of lift, we believe that high lift mechanisms (i.e., rotational circulation and wake capture) which take place at stroke reversals in Electronic supplementary material The online version of this article (insect flight was not evident here. For mean lift throughout a whole cycle, it is calculated to be 3.60 g (104.0 % of the weight support). The downstroke and upstroke provide 64.2 % and 35.8 % of the weight support, respectively.

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Size effects on insect hovering aerodynamics: an integrated computational study

Cited by 141 publications

References 33 publications

Aerodynamic performance of a hovering hawkmoth with flexible wings: a computational approach

Aerodynamic performance of a hovering hawkmoth with flexible wings: a computational approach

Clap and fling mechanism with interacting porous wings in tiny insect flight

Numerical analysis of the three-dimensional aerodynamics of a hovering rufous hummingbird (Selasphorus rufus)

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