Numerical simulation of unsteady flows over a slow-flying bat

Wang, Shizhao; Zhang, Xing; He, Guowei; Liu, Tianshu

doi:10.1016/j.taml.2015.01.006

Cited by 14 publications

(5 citation statements)

References 16 publications

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“…The lift coefficient remains positive during the transition stage from the downstroke to the upstroke, which is attributed to the positive vortex lift in the upstroke (see §5). The time history of the lift coefficient for the Pallas' longtongued bat is similar to that reported by Wang et al [43] for a model of the grey-headed flying fox (Pteropus poliocephalus) with different wing morphology at a higher Reynolds number (1000). However, there are some differences in the detailed histories of the lift coefficient between the two kinds of bats, which might be associated with the different wing geometry.…”

Section: Flow Structures and Lift Coefficientsupporting

confidence: 84%

Lift enhancement by bats' dynamically changing wingspan

Wang

Zhang

et al. 2015

J. R. Soc. Interface.

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This paper elucidates the aerodynamic role of the dynamically changing wingspan in bat flight. Based on direct numerical simulations of the flow over a slow-flying bat, it is found that the dynamically changing wingspan can significantly enhance the lift. Further, an analysis of flow structures and lift decomposition reveal that the elevated vortex lift associated with the leading-edge vortices intensified by the dynamically changing wingspan considerably contributed to enhancement of the time-averaged lift. The nonlinear interaction between the dynamically changing wing and the vortical structures plays an important role in the lift enhancement of a flying bat in addition to the geometrical effect of changing the lifting-surface area in a flapping cycle. In addition, the dynamically changing wingspan leads to the higher efficiency in terms of generating lift for a given amount of the mechanical energy consumed in flight.

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Section: Flow Structures and Lift Coefficientsupporting

confidence: 84%

Lift enhancement by bats' dynamically changing wingspan

Wang

Zhang

et al. 2015

J. R. Soc. Interface.

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“…Therefore, these studies cannot segregate the respective role of particular structural elements of the membrane/wing composition or that of flight kinematics in the bat’s performance. Similarly, previous numerical simulations rely either on marker measurements, fixed and discrete by definition, and one-way fluid–structure interaction coupling [12,21], or on overly simplistic kinematics and constitutive laws for membrane skin [22,23]. In the first case, these numerical studies inherit the experimental study’s fixed set of parameters by design, thus preventing any further wider parametric studies, and in the second case, the respective influence of the microstructural constitutive parameters and motions of the wing membrane, and their interplay, are not captured because of the low fidelity of the kinematics and material law used.…”

Section: Introductionmentioning

confidence: 99%

Rapid flapping and fibre-reinforced membrane wings are key to high-performance bat flight

Lauber,

Weymouth,

Limbert

2023

J. R. Soc. Interface.

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Bats fly using significantly different wing motions from other fliers, stemming from the complex interplay of their membrane wings’ motion and structural properties. Biological studies show that many bats fly at Strouhal numbers, the ratio of flapping to flight speed, 50–150% above the range typically associated with optimal locomotion. We use high-resolution fluid–structure interaction simulations of a bat wing to independently study the role of kinematics and material/structural properties in aerodynamic performance and show that peak propulsive and lift efficiencies for a bat-like wing motion require flapping 66% faster than for a symmetric motion, agreeing with the increased flapping frequency observed in zoological studies. In addition, we find that reduced membrane stiffness is associated with improved propulsive efficiency until the membrane flutters, but that incorporating microstructural anisotropy arising from biological fibre reinforcement enables a tenfold reduction of the flutter energy while maintaining high aerodynamic efficiency. Our results indicate that animals with specialized flapping motions may have correspondingly specialized flapping speeds, in contrast to arguments for a universally efficient Strouhal range. Additionally, our study demonstrates the significant role that the microstructural constitutive properties of the membrane wing of a bat can have in its propulsive performance.

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“…Though their decomposition of wing kinematics was based on a single wing, the overall strategy showed excellent potential to identify important kinematics in designing flapping wing MAVs based on bat flight data. In 2015, Wang et al [48,49] used the immersed boundary method to simulate a slow flying bat at an intermediate Reynolds number (Re = 1000). The wing kinematic data for their simulations—borrowed from Wolf et al [50]—consisted of only five markers points per wing.…”

Section: Introductionmentioning

confidence: 99%

Canonical description of wing kinematics and dynamics for a straight flying insectivorous bat (Hipposideros pratti)

et al. 2019

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Bats, with highly articulated wings, are some of the most agile flyers in nature. A novel three-dimensional geometric decomposition framework is developed to reduce the complex kinematics of a bat wing into physical movements used to describe flapping flight: namely flapping, stroke plane deviation and pitching, together with cambering and flexion. The decomposition is combined with aerodynamic simulations to investigate the cumulative effect of each motion on force production, and their primary contribution to the unsteady vortex dynamics. For the nearly straight and level flight of Hipposideros pratti , results show that the flapping motion by itself induced a moderate drag and lift. Stroke plane deviation increased lift, and nullified the drag. With the inclusion of the pitching motion into the kinematics, lift production further increased by a factor of more than 2.5, and exhibited a positive net thrust by virtue of the favorable wing orientation during the upstroke. The primary contribution of cambering, which included a maximum chord line displacement of ≈40% standard mean chord, was the stabilization of the leading edge vortex during the downstroke. This increased mean lift by about 35% at the expense of net thrust. Flexion was perhaps the most complex motion with maximum displacements of 75% standard mean chord. This was instrumental in reducing the negative lift during the upstroke by preventing the formation of strong leading edge vortices. The aerodynamic effective angle of attack emerged as a heuristic parameter to describe lift and net thrust production across movements.

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Numerical simulation of unsteady flows over a slow-flying bat

Cited by 14 publications

References 16 publications

Lift enhancement by bats' dynamically changing wingspan

Lift enhancement by bats' dynamically changing wingspan

Rapid flapping and fibre-reinforced membrane wings are key to high-performance bat flight

Canonical description of wing kinematics and dynamics for a straight flying insectivorous bat (Hipposideros pratti)

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