Force Measurements on a Flapping and Pitching Wing at Low Reynolds Numbers

Abstract

Force measurements from experiments conducted in water on a flapping-and-pitching thin flat plate wing of semi-elliptic planform at low Reynolds numbers are reported. Time varying force data, measured using a force transducer, provide a means to understand the mechanisms that lead to enhanced performance observed in insect flight compared to fixed wing aerodynamics. Experimental uncertainties associated with low level (~1N) fluid dynamic force measurements on flapping-and-pitching wings are addressed. A previously proposed pitching mode in which the leading edge and trailing edge switch roles to allow using cambered airfoils has been shown to be viable, and may have advantages over the non-switching mode. The present data are part of a larger database planned to experimentally investigate various aspects of insect flight including another previously proposed idea that performance may be improved by flying at optimum reduced flapping frequency. The study has applications in micro air vehicle development.

Experimental investigation of the effect of chordwise flexibility on the aerodynamics of flapping wings in hovering flight

“…There are many reports in which the inertial forces are higher than the aerodynamic forces (Lehmann and Dickinson, 1997;Daniel and Combes, 2002;Singh and Chopra, 2007), while other studies have concluded the opposite (Sun and Tang, 2002). The inertial forces may be simulated or estimated by analytical methods, while experimental methods can be used as well (Ames, 2001;Maybury and Lehmann, 2004;Singh and Ramasamy, 2005;Isaac et al, 2006). Singh and Ramasamy (2005) have also developed theoretical methods to calculate the inertial forces.…”

“…Together with geometric and kinematic similarities, the Reynolds number and the reduced frequency are sufficient to define the aerodynamic similarity for a rigid wing (Maybury and Lehmann, 2004;Isaac et al, 2006;Shyy et al, 2008).…”

Unsteady Flow Features of a Flapping and Pitching Wing at Low Reynolds Number

“…Previous work by many investigators include experiments on live animals as well as model studies. Our flow simulation 5 and experimental 6 studies have led us to propose some interesting aspects of a flapping and pitching wing at low Reynolds numbers. In addition to Reynolds number scaling, reduced frequency scaling was emphasized as a factor that should be considered in analyzing insect flight.…”

“…This paper is part of an ongoing study on the unsteady flow field of a flapping and pitching wing at low Reynolds numbers. The large body of work available in the literature covering various aspects of insect flight has been reviewed in our previous work 5,6 . Previous work by many investigators include experiments on live animals as well as model studies.…”

Computational modeling of unsteady low Reynolds number flapping wing aerodynamics

“…They showed that a spanwise cambered wing generated a larger lift force. Isaac et al [24] provided force measurements on semi-elliptic flapping wings and computed the inertial contribution of the wing to the aerodynamic forces. Parker et al [25] conducted water tunnel experiments on a NACA 0030 cross-section wing and pointed out that three-dimensional effects due to wing tip vortices are negligible compared to the effects of leading-and trailing-edge vortices.…”