Aerodynamics of two-dimensional flapping wings in tandem configuration

Abstract

This paper reports a fundamental investigation on the aerodynamics of two-dimensional flapping wings in tandem configuration in forward flight. Of particular interest are the effects of phase angle (φ) and center-to-center distance (L) between the front wing and the rear wing on the aerodynamic force generation at a Reynolds number of 5000. Both experimental and numerical methods were employed. A force sensor was used to measure the time-history aerodynamic forces experienced by the two wings and digital particle image velocimetry was utilized to obtain the corresponding flow structures. Both the front wing and the rear wing executed the same simple harmonic motions with φ ranging from −180° to 180° and four values of L, i.e., 1.5c, 2c, 3c, and 4c (c is the wing chord length). Results show that at fixed L = 2c, tandem wings perform better than the sum of two single wings that flap independently in terms of thrust for phase angle approximately from −90° to 90°. The maximum thrust on the rear wing occurs during in-phase flapping (φ = 0°). Correlation of transient thrust and flow structure indicates that there are generally two types of wing-wake interactions, depending on whether the rear wing crosses the shear layer shed from the front wing. Finally, increasing wing spacing has similar effect as reducing the phase angle, and an approximate mathematical model is derived to describe the relationship between these two parameters.

Flow-mediated organization of two freely flapping swimmers

“…Meanwhile, the performance of downstream foil can be improved when it weaves between vortices that shed from the upstream foil (Muscutt, Weymouth & Ganapathisubramani 2017). Moreover, the hydrodynamic benefit depends strongly on the streamwise distance and the phase difference between two foils (Lua et al 2016). In the side-by-side arrangement, the lateral interference can improve the thrust generation and propulsive efficiency of two foils (Dewey et al 2014).…”

Unsteady aerodynamics investigation of deploying tandem-wing with different methods

“…19 Broering and colleagues analyzed the effects of the wing spacing and the phase angle on the tandem flapping wing aerodynamics in both two and three dimensions by solving the incompressible Navier-Stokes equation on overlapping grids. [20][21][22][23] Moreover, Lim and Tay investigated the effect of the airfoil arrangement to improve the performance of the efficiency, thrust, and lift of flapping wings in tandem arrangement with the Immersed Boundary staggered Cartesian grid Navier-Stokes-Solver. 24 Besides, Chou et al studied the aerodynamic properties and flow structures of flow field between two wings in the tandem arrangement by experiments.…”

Bypass transition in flow over a vibrating flat plate

“…For steady inflow perturbations, the plate vibration tends to break the streamwise velocity into segments and thus weakens the lift-up mechanism. A similar staggering mechanism of a moving streamlined body can also be found in the study of flapping wings in the tandem configuration (Lua et al 2016). The flapping of the wings also introduces a periodically varying angle of attack, which shifts the wake of the front wing to upside or downside of the rear wing.…”