Bulletin of the American Physical Society
72nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 64, Number 13
Saturday–Tuesday, November 23–26, 2019; Seattle, Washington
Session B27: Biological Fluid Dynamics: Insect Flight I - Wing Properties |
Hide Abstracts |
Chair: Kai Schneider, Aix-Marseille University Room: 609 |
Saturday, November 23, 2019 4:40PM - 4:53PM |
B27.00001: Vortex bursting corresponds to reduced gradients in wing flexibility Megan Matthews, Bryan McCarty, Simon Sponberg The leading-edge vortex (LEV) is a well-known flight mechanism for flapping insects, but the interplay between the bound LEV and the flexible wing it attaches to is not yet understood. On rigid wings, the LEV often bursts but remains attached at Re $\sim\mathcal{O}$($10^3$). However, this has not been seen on flexible insect wings. Force production increases with decreasing flexural stiffness and further increases when the wing exhibits chord- and spanwise gradients in flexural stiffness. We mounted real hawkmoth wings onto a motor that revolves the wings at a constant frequency and generates a coherent LEV. Using smoke-wire visualization, we observed the qualitative structure of the LEV. On freshly-mounted wings, LEV diameter is consistently 50\% or less than the local chord length with well-defined reattachment streaklines. After desiccating, the wings stiffen in both the chord- and spanwise directions, and the LEV formed on stiffened wings has a diameter of at least 80\% of the local chord length. The reattachment streaklines were also disrupted on stiffened wings, suggesting that the loss of flexibility gradients contributes to LEV bursting. Flexibility gradients on insect wings may compensate for changes in spanwise vorticity that induce vortex bursting. [Preview Abstract] |
Saturday, November 23, 2019 4:53PM - 5:06PM |
B27.00002: ABSTRACT WITHDRAWN |
Saturday, November 23, 2019 5:06PM - 5:19PM |
B27.00003: Unsteady maneuvering of a morphing wing. Kamlesh Joshi, Samik Bhattacharya The unsteady flow over a morphing flat-plate airfoil is investigated in this work. The unsteady flow is generated by accelerating the wing from rest and from one steady speed to a higher speed. The flat plate was towed in a water tank at an angle of attack of 30 degree with different acceleration numbers. The plate can be bent smoothly along the span with a flexion ratio of 0.7 and a flexion angle of 20 degree. In these tests, two different bending rates (BR), namely BR $=$ 1s and 2s were implemented. The wing was towed from rest to Reynolds numbers of 10,000 and 20,000, and it was bent simultaneously along the span with zero phase difference between the forward towing motion and the bending motion. Instantaneous forces were measured with a six-dof force sensor, and the flow field was measured with the help of particle image velocimetry. It was found that spanwise bending has a considerable effect on the unsteady forces during acceleration. The vortex dynamics of the leading-edge-vortex was altered due to the variation of the shear layer velocity along the span which occurred due to the bending motion. In this work, we sought to quantify the effect of bending rate on the stability of the leading-edge vortex. We show that the gradual lifting of the tip vortex closer to the LEV, affects its growth. We also demonstrate that the spanwise bending action alters the added mass peak due to the inertial forces caused by the bending process. . [Preview Abstract] |
Saturday, November 23, 2019 5:19PM - 5:32PM |
B27.00004: Effect of chordwise wing flexibility on the flapping flight of a butterfly-like 3D flapping wing-body model Kosuke Suzuki, Takaaki Aoki, Masato Yoshino In our recent study [K. Suzuki, T. Aoki, and M. Yoshino, Phys. Rev. E 100, 013104 (2019)], we constructed a flexible wing with chordwise flexibility by connecting two rigid plates with a torsion spring, and investigated the effect of chordwise wing flexibility on the flapping flight of a simple butterfly-like flapping wing-body model by using an immersed boundary-lattice Boltzmann method. First, we investigated the effects of the spring stiffness on the aerodynamic performance when the body of the model is fixed. We found that the time-averaged lift and thrust forces and the required power increase with the spring stiffness. In addition, we found an appropriate range of the spring stiffness where the time averaged lift and thrust forces are larger than those of the rigid wings. Second, we simulated free flights when the body of the model can only move translationally. We found that the model with the flexible wings at an appropriate value of the spring stiffness can fly more effectively than the model with the rigid wings, which is consistent with the results when the body of the model is fixed. [Preview Abstract] |
Saturday, November 23, 2019 5:32PM - 5:45PM |
B27.00005: Numerical simulation of insect flight with flexible wings using a mass-spring fluid-interaction solver Kai Schneider, Hung Truong, Thomas Engels, Dmitry Kolomenskiy Fundamental characteristics of insect flight are flexible wings, which play an important role for their aerodynamics. Real wings are delicate structures, composed of veins and membranes, and can undergo significant deformation. Here we present detailed numerical simulations of such deformable wings modeled by a mass-spring network. The mass-spring model uses a functional approach, thus modeling the veins and the membranes of the wing. Results are obtained with a fluid-structure interaction solver, coupling a mass-spring model for the flexible wing with the pseudo-spectral code FLUSI solving the incompressible Navier-Stokes equations. We impose the no-slip boundary condition through the volume penalization method; the time-dependent complex geometry is then completely described by a mask function. We perform a series of numerical simulations of a flexible revolving bumblebee wing at a Reynolds number Re=1800. In order to assess the influence of wing flexibility on the aerodynamics, we vary the elasticity parameters and study rigid, flexible and highly flexible wing models. A better aerodynamic performance of the flexible wing, characterized by the increase of the lift-to-drag ratio, is found while the highly flexible wing appears to be less efficient than the rigid wing. [Preview Abstract] |
Saturday, November 23, 2019 5:45PM - 5:58PM |
B27.00006: Effect of torsional stiffness on passive wing pitch and its aerodynamic performance in hovering flight Menglong Lei, Chengyu Li Insect's wings are able to passively maintain a high angle of attack due to the torsional flexibility of wing basal region without the aid of the active pitching motion. However, there is no clear understanding of how torsional wing flexibility should be designed to achieve optimal aerodynamic performance. In this work, a computational study was conducted to investigate the passive pitching mechanism of a fruit fly wing in hovering flight using a torsional spring model. The torsional wing flexibility was characterized by Cauchy number. Different flapping patterns including zero-deviation, figure-8, oval-shaped stroke kinematics were evaluated. The aerodynamic forces and associated unsteady flow structures were simulated using an in-house immersed-boundary-method based computational fluid dynamic solver. Our simulations revealed that the optimal lift and lift-to-power ratio can be achieved in a particular range of Cauchy number (0.16\textasciitilde 0.30) regardless of its stroke kinematics. This range is consistent with the Cauchy number calculated based on the fruit fly data from literature. The findings of this work could provide important implications for designing more efficient flapping-wing micro air vehicles. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700