Multiple leading edge vortices of unexpected strength in freely flying hawkmoth

Johansson, Lars; Engel, Sophia; Kelber, Almut; KleinHeerenbrink, Marco; Hedenström, Anders

doi:10.1038/srep03264

Cited by 30 publications

(35 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In both studies, a single LEV occurs at the inner wing and multiple LEVs were observed in the mid-wing region. Our results of LEV structure along the cicada wingspan are qualitatively consistent with these studies [24,32]. The cicada thorax-generated vortex was also found on the slice cut at the 15% spanwise location, indicating the importance of wing-body interactions in insects with a wide body.…”

Section: Leading Edge Vorticessupporting

confidence: 90%

“…In some more recent studies, it was found that multiple LEVs were generated on the wings of real hawkmoths [24], and in a wing model of fruit fly [32]. In both studies, a single LEV occurs at the inner wing and multiple LEVs were observed in the mid-wing region.…”

Section: Leading Edge Vorticesmentioning

confidence: 95%

“…Although flow visualizations on free and tethered dragonflies have shown some similar properties [12], the tethered flights can nevertheless convincingly reproduce the scenarios of free flight [13], in both kinematics [14] and force generation [15]. Hence, studies on the aerodynamics of insects in free flight are consistently pursued [16][17][18][19][20][21][22][23][24]. It has been pointed out that insects generate forces through a quite complex combination of aerodynamic mechanisms, including wake capture, active and inactive upstrokes, clap and fling, and LEV.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Computational investigation of cicada aerodynamics in forward flight

Wan

Dong

Gai

2015

J. R. Soc. Interface.

View full text Add to dashboard Cite

Free forward flight of cicadas is investigated through high-speed photogrammetry, three-dimensional surface reconstruction and computational fluid dynamics simulations. We report two new vortices generated by the cicada's wide body. One is the thorax-generated vortex, which helps the downwash flow, indicating a new phenomenon of lift enhancement. Another is the cicada posterior body vortex, which entangles with the vortex ring composed of wing tip, trailing edge and wing root vortices. Some other vortex features include: independently developed left-and right-hand side leading edge vortex (LEV), dual-core LEV structure at the mid-wing region and nearwake two-vortex-ring structure. In the cicada forward flight, approximately 79% of the total lift is generated during the downstroke. Cicada wings experience drag in the downstroke, and generate thrust during the upstroke. Energetics study shows that the cicada in free forward flight consumes much more power in the downstroke than in the upstroke, to provide enough lift to support the weight and to overcome drag to move forward.

show abstract

Section: Leading Edge Vorticessupporting

confidence: 90%

Section: Leading Edge Vorticesmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Computational investigation of cicada aerodynamics in forward flight

Wan

Dong

Gai

2015

J. R. Soc. Interface.

View full text Add to dashboard Cite

show abstract

“…The dominating unsteady mechanism used in nature is the dynamic stall and associated LEV, which have been shown for many insects (Ellington et al, 1996;Birch and Dickinson, 2001;Sane, 2003;Johansson et al, 2013), and a few bird species (Muijres et al, 2012a, Warrick et al, 2009, Wolf et al, 2013. In this context, wind tunnel experiments of on-wing flow measurements of slow flying bats have demonstrated the presence of LEVs in the relatively small Palla's long-tongued bats ( ) the LEV contributes up to 40% of the total aerodynamic force (Table 1).…”

Section: U=4 M Smentioning

confidence: 96%

Bat flight: aerodynamics, kinematics and flight morphology

Hedenström

Johansson

2015

Journal of Experimental Biology

Self Cite

101

View full text Add to dashboard Cite

Bats evolved the ability of powered flight more than 50 million years ago. The modern bat is an efficient flyer and recent research on bat flight has revealed many intriguing facts. By using particle image velocimetry to visualize wake vortices, both the magnitude and timehistory of aerodynamic forces can be estimated. At most speeds the downstroke generates both lift and thrust, whereas the function of the upstroke changes with forward flight speed. At hovering and slow speed bats use a leading edge vortex to enhance the lift beyond that allowed by steady aerodynamics and an inverted wing during the upstroke to further aid weight support. The bat wing and its skeleton exhibit many features and control mechanisms that are presumed to improve flight performance. Whereas bats appear aerodynamically less efficient than birds when it comes to cruising flight, they have the edge over birds when it comes to manoeuvring. There is a direct relationship between kinematics and the aerodynamic performance, but there is still a lack of knowledge about how (and if ) the bat controls the movements and shape ( planform and camber) of the wing. Considering the relatively few bat species whose aerodynamic tracks have been characterized, there is scope for new discoveries and a need to study species representing more extreme positions in the bat morphospace.

show abstract

“…The flapping motion results in large geometrical AOA which would stall conventional translating wings. For flapping wings, generally, the flow starts to separate at the LE after wing reversals, and forms a LEV or LEVs [Johansson et al, 2013]. Instead of growing quickly and then shedding into the wake, the LEV on flapping wings generally remains attached over the entire half-strokes for two possible reasons: (1) the spanwise flow from the wing root to tip removes energy from the LEV which limits the growth and the shedding, as shown on Hawkmoth wings [Ellington et al, 1996]; and (2) due to the downwash flow induced by the tip and wake vortices, the effective AOA decreases and the growth of the LEV is restricted, as indicated by the wings of Drosophila [Birch & Dickinson, 2001].…”

Section: Formulationmentioning

confidence: 99%

A predictive quasi-steady model of aerodynamic loads on flapping wings

Goosen

Keulen

2016

J. Fluid Mech.

View full text Add to dashboard Cite

Quasi-steady aerodynamic models play an important role in evaluating aerodynamic performance and conducting design and optimization of flapping wings. The kinematics of flapping wings is generally a resultant motion of wing translation (yaw) and rotation (pitch and roll). Most quasisteady models are aimed at predicting the lift and thrust generation of flapping wings with prescribed kinematics. Nevertheless, it is insufficient to limit flapping wings to prescribed kinematics only since passive pitching motion is widely observed in natural flapping flights and preferred for the wing design of flapping wing micro air vehicles (FWMAVs). In addition to the aerodynamic forces, an accurate estimation of the aerodynamic torque about the pitching axis is required to study the passive pitching motion of flapping flights. The unsteadiness arising from the wing's rotation complicates the estimation of the centre of pressure (CP) and the aerodynamic torque within the context of quasisteady analysis. Although there are a few attempts in literature to model the torque analytically, the involved problems are still not completely solved. In this work, we present an analytical quasi-steady model by including four aerodynamic loading terms. The loads result from the wing's translation, rotation, their coupling as well as the added-mass effect. The necessity of including all the four terms in a quasi-steady model in order to predict both the aerodynamic force and torque is demonstrated. Validations indicate a good accuracy of predicting the CP, the aerodynamic loads and the passive pitching motion for various Reynolds numbers. Moreover, compared to the existing quasi-steady models, the presented model does not rely on any empirical parameters and, thus, is more predictive, which enables application to the shape and kinematics optimization of flapping wings.

show abstract

Multiple leading edge vortices of unexpected strength in freely flying hawkmoth

Cited by 30 publications

References 39 publications

Computational investigation of cicada aerodynamics in forward flight

Computational investigation of cicada aerodynamics in forward flight

Bat flight: aerodynamics, kinematics and flight morphology

A predictive quasi-steady model of aerodynamic loads on flapping wings

Contact Info

Product

Resources

About