Analysis and Estimation of the Lift Components of Hovering Insects

Traub, Lance W.

doi:10.2514/1.9323

Cited by 18 publications

(13 citation statements)

References 17 publications

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“…The remaining unknown in Eq 16 is the 2d aerofoil lift curve slope, C lα,2d . For a flat plate at typical insect Reynolds numbers, experimental evidence suggests that C lα,2d is slightly less than the theoretical value of 2 π and takes a value of 0.09 deg -1 = 5.16 rad -1 [ 51 – 53 ]; thus this value will be used in this work.…”

Section: Methodsmentioning

confidence: 99%

A Quasi-Steady Lifting Line Theory for Insect-Like Hovering Flight

Nabawy

Crowthe

2015

PLoS ONE

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A novel lifting line formulation is presented for the quasi-steady aerodynamic evaluation of insect-like wings in hovering flight. The approach allows accurate estimation of aerodynamic forces from geometry and kinematic information alone and provides for the first time quantitative information on the relative contribution of induced and profile drag associated with lift production for insect-like wings in hover. The main adaptation to the existing lifting line theory is the use of an equivalent angle of attack, which enables capture of the steady non-linear aerodynamics at high angles of attack. A simple methodology to include non-ideal induced effects due to wake periodicity and effective actuator disc area within the lifting line theory is included in the model. Low Reynolds number effects as well as the edge velocity correction required to account for different wing planform shapes are incorporated through appropriate modification of the wing section lift curve slope. The model has been successfully validated against measurements from revolving wing experiments and high order computational fluid dynamics simulations. Model predicted mean lift to weight ratio results have an average error of 4% compared to values from computational fluid dynamics for eight different insect cases. Application of an unmodified linear lifting line approach leads on average to a 60% overestimation in the mean lift force required for weight support, with most of the discrepancy due to use of linear aerodynamics. It is shown that on average for the eight insects considered, the induced drag contributes 22% of the total drag based on the mean cycle values and 29% of the total drag based on the mid half-stroke values.

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Section: Methodsmentioning

confidence: 99%

A Quasi-Steady Lifting Line Theory for Insect-Like Hovering Flight

Nabawy

Crowthe

2015

PLoS ONE

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“…This is to be expected as Polhamus did not take into account the effect of rsif.royalsocietypublishing.org J. R. Soc. Interface 11: 20131197 the vortex flow on the attached flow [49], hence would overpredict the lift. Third, the term K Polhamus increases with the increase in aspect ratio.…”

Section: ð3:2þmentioning

confidence: 99%

On the quasi-steady aerodynamics of normal hovering flight part II: model implementation and evaluation

Nabawy

Crowther

2014

J. R. Soc. Interface.

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This paper introduces a generic, transparent and compact model for the evaluation of the aerodynamic performance of insect-like flapping wings in hovering flight. The model is generic in that it can be applied to wings of arbitrary morphology and kinematics without the use of experimental data, is transparent in that the aerodynamic components of the model are linked directly to morphology and kinematics via physical relationships and is compact in the sense that it can be efficiently evaluated for use within a design optimization environment. An important aspect of the model is the method by which translational force coefficients for the aerodynamic model are obtained from first principles; however important insights are also provided for the morphological and kinematic treatments that improve the clarity and efficiency of the overall model. A thorough analysis of the leading-edge suction analogy model is provided and comparison of the aerodynamic model with results from application of the leading-edge suction analogy shows good agreement. The full model is evaluated against experimental data for revolving wings and good agreement is obtained for lift and drag up to 908 incidence. Comparison of the model output with data from computational fluid dynamics studies on a range of different insect species also shows good agreement with predicted weight support ratio and specific power. The validated model is used to evaluate the relative impact of different contributors to the induced power factor for the hoverfly and fruitfly. It is shown that the assumption of an ideal induced power factor (k ¼ 1) for a normal hovering hoverfly leads to a 23% overestimation of the generated force owing to flapping.

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“…The conical LEV created on laminar revolving/ flapping wings is similar in form to the LEV observed over delta wings at subsonic speeds and high angles of attack. This prompted several researchers [1,15,41,43] to use the 'leading edge suction' model for delta wings to analyse the revolving/flapping wing problem. Note that while at first sight revolving/flapping wings and steady delta wings appear quite different, the key similarity is that in each a stable LEV is able to form.…”

Section: Leading Edge Suction Modelmentioning

confidence: 99%

The role of the leading edge vortex in lift augmentation of steadily revolving wings: a change in perspective

Nabawy¹,

Crowther²

2017

J. R. Soc. Interface.

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The presence of a stable leading edge vortex (LEV) on steadily revolving wings increases the maximum lift coefficient that can be generated from the wing and its role is important to understanding natural flyers and flapping wing vehicles. In this paper, the role of LEV in lift augmentation is discussed under two hypotheses referred to as 'additional lift' and 'absence of stall'. The 'additional lift' hypothesis represents the traditional view. It presumes that an additional suction/circulation from the LEV increases the lift above that of a potential flow solution. This behaviour may be represented through either the 'Polhamus leading edge suction' model or the so-called 'trapped vortex' model. The 'absence of stall' hypothesis is a more recent contender that presumes that the LEV prevents stall at high angles of attack where flow separation would normally occur. This behaviour is represented through the so-called 'normal force' model. We show that all three models can be written in the form of the same potential flow kernel with modifiers to account for the presence of a LEV. The modelling is built on previous work on quasi-steady models for hovering wings such that model parameters are determined from first principles, which allows a fair comparison between the models themselves, and the models and experimental data. We show that the two models which directly include the LEV as a lift generating component are built on a physical picture that does not represent the available experimental data. The simpler 'normal force' model, which does not explicitly model the LEV, performs best against data in the literature. We conclude that under steady conditions the LEV as an 'absence of stall' model/mechanism is the most satisfying explanation for observed aerodynamic behaviour.

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Analysis and Estimation of the Lift Components of Hovering Insects

Cited by 18 publications

References 17 publications

A Quasi-Steady Lifting Line Theory for Insect-Like Hovering Flight

A Quasi-Steady Lifting Line Theory for Insect-Like Hovering Flight

On the quasi-steady aerodynamics of normal hovering flight part II: model implementation and evaluation

The role of the leading edge vortex in lift augmentation of steadily revolving wings: a change in perspective

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