Effects of flapping-motion profiles on insect-wing aerodynamics

Bhat, Shantanu; Zhao, Jisheng; Sheridan, John; Hourigan, Kerry; Thompson, Mark C.

doi:10.1017/jfm.2019.929

Cited by 26 publications

(30 citation statements)

References 32 publications

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“…Among other findings, they concluded that the mean drag increases monotonically with increasing angle of attack and a short flip duration advanced of the stroke reversal is beneficial for lift production. The influence of different stroke-and pitch angle waveforms at a fixed flapping frequency and amplitude was investigated recently by Bhat et al [23] for a fruit fly wing planform. The stroke angle evolution was modulated between a sinusoidal and a triangular profile and the pitch angle evolution between a sinusoidal and a trapezoidal profile.…”

Section: Introductionmentioning

confidence: 99%

Phenomenology and scaling of optimal flapping wing kinematics

Gehrke

Mülleners

2021

Bioinspir. Biomim.

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Biological flapping wing fliers operate efficiently and robustly in a wide range of flight conditions and are a great source of inspiration to engineers. The unsteady aerodynamics of flapping wing flight are dominated by large-scale vortical structures that augment the aerodynamic performance but are sensitive to minor changes in the wing actuation. We experimentally optimise the pitch angle kinematics of a flapping wing system in hover to maximise the stroke average lift and hovering efficiency with the help of an evolutionary algorithm and in situ force and torque measurements at the wing root. Additional flow field measurements are conducted to link the vortical flow structures to the aerodynamic performance for the Pareto-optimal kinematics. The optimised pitch angle profiles yielding maximum stroke-average lift coefficients have trapezoidal shapes and high average angles of attack. These kinematics create strong leading-edge vortices early in the cycle which enhance the force production on the wing. The most efficient pitch angle kinematics resemble sinusoidal evolutions and have lower average angles of attack. The leading-edge vortex grows slower and stays close-bound to the wing throughout the majority of the stroke-cycle. This requires less aerodynamic power and increases the hovering efficiency by 93% but sacrifices 43% of the maximum lift in the process. In all cases, a leading-edge vortex is fed by vorticity through the leading edge shear layer which makes the shear layer velocity a good indicator for the growth of the vortex and its impact on the aerodynamic forces. We estimate the shear layer velocity at the leading edge solely from the input kinematics and use it to scale the average and the time-resolved evolution of the circulation and the aerodynamic forces. The experimental data agree well with the shear layer velocity prediction, making it a promising metric to quantify and predict the aerodynamic performance of the flapping wing hovering motion.

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Section: Introductionmentioning

confidence: 99%

Phenomenology and scaling of optimal flapping wing kinematics

Gehrke

Mülleners

2021

Bioinspir. Biomim.

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“…This large offset was justified since the study also considered the LEV formation and lift coefficient comparison between large and small offsets for a range of flapping profiles. Bhat et al [105] found that the overall variation in lift coefficient was mainly influenced by the stroke waveform, as a result of a change in strength of the vortex over the wing. However, the pitch waveform was observed to only influence the instantaneous lift coefficient at stroke reversal.…”

Section: Two Degrees Of Freedom Rigsmentioning

confidence: 99%

Dynamic experimental rigs for investigation of insect wing aerodynamics

Broadley

Nabawy

Quinn

et al. 2022

J. R. Soc. Interface.

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This paper provides a systematic and critical review of dynamic experimental rigs used for insect wing aerodynamics research. The goal is to facilitate meaningful comparison of data from existing rigs and provide insights for designers of new rigs. The scope extends from simple one degree of freedom rotary rigs to multi degrees of freedom rigs allowing various rotation and translation motions. Experimental methods are characterized using a consistent set of parameters that allows objective comparison of different approaches. A comprehensive catalogue is presented for the tested flow conditions (assessed through Reynolds number, Rossby number and advance ratio), wing morphologies (assessed through aspect ratio, planform shape and thickness to mean chord ratio) and kinematics (assessed through motion degrees of freedom). Links are made between the type of aerodynamic characteristics being studied and the type of experimental set-up used. Rig mechanical design considerations are assessed, and the aerodynamic measurements obtained from these rigs are discussed.

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“…Overall, the complexity of the motions increases with the parameter count and different shapes and kinematics can lead to similar Pareto fronts depending on the choice of the parameterisation and the parameter count. This is due to the complex relationship between the flow development and the growth of the leading edge vortex for flapping wings motions [5,8].…”

Section: Pareto Fronts and Optimal Kinematicsmentioning

confidence: 99%

“…Fig.1a. Flapping wing mechanism with stroke angle φ and pitch angle β for the hovering motion, b. wing geometry and axis of rotation, c. pitch angle β kinematics of various natural fliers, adopted from[15] and trapezoidal pitch angle kinematics from a robotic flapper[5].…”

mentioning

confidence: 99%

On the parametrisation of motion kinematics for experimental aerodynamic optimisation

Busch,

Gehrke,

Mulleners

2021

Preprint

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The levels of agility and flight or swimming performance demonstrated by insects, birds, fish, and even some aquatic invertebrates, are often vastly superior to what even the most advanced human-engineered vehicles operating in the same regimes are capable of. Key to this superior locomotion is the animal's manipulation of the generation and shedding of vortices through optimal control of their motion kinematics. Many research efforts related to biological and bio-inspired propulsion focus on understanding the influence of the motion kinematics on the propulsion performance and on optimising the kinematics to improve efficiency or manoeuvrability. One of the first challenges to tackle when conducting a numerical or experimental optimisation of motion kinematics of objects moving through a fluid is the parameterisation of the motion kinematics. In this paper, we present three different approaches to parameterise kinematics, using a set of control points that are connected by a spline interpolation, a finite Fourier series, and a reduced order modal reconstruction based on a proper orthogonal decomposition of a set of random walk trajectories. We compare the results and performance of the different parameterisations for the example of an experimental multi-objective optimisation of the pitching kinematics of a robotic flapping wing device. The optimisation was conducted using a genetic algorithm with the objective to maximise stroke average lift and efficiency. The performance is evaluated with regard to the diversity of the randomly created initial populations, the convergence behaviour of

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Effects of flapping-motion profiles on insect-wing aerodynamics

Cited by 26 publications

References 32 publications

Phenomenology and scaling of optimal flapping wing kinematics

Phenomenology and scaling of optimal flapping wing kinematics

Dynamic experimental rigs for investigation of insect wing aerodynamics

On the parametrisation of motion kinematics for experimental aerodynamic optimisation

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