Department of Zoology, University of Cambridge

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Fore and Hindwing Aerodynamic Interaction in Locust Flight

Research Background

Insect flight is finally yielding its secrets. Flapping insect flight is now known to employ a range of lift-enhancing fluid dynamic phenomena. These unsteady aerodynamic mechanisms include the leading edge vortex (LEV), rotational circulation, clap and fling, and wake recapture. The most significant of these lift-generating phenomena appears to be the LEV, in which a low pressure vortex clings to the upper surface of an insect wing during its downstroke. All investigations of the LEV have focused on insects with either one set of wings (i.e. the fruit fly) or one functional set of wings (i.e. the hawkmoth).

Research Objective

The goal of my research is to investigate and quantify the leading edge vortices present in insects with two functional sets of wings and any aerodynamic interaction between the fore and hind wings. The insect of interest in this study is the locust.

Research Methods

An insect wing?s downstroke (when the LEV is present) is continuously simulated by spinning that wing or a model wing like a propeller. The flow around the propeller immersed in a liquid medium can then be visualized by dye in the liquid or a particle image velocimetry (PIV) system. By the principle of dynamic scaling, the fluid dynamics of this model are exactly the same as a real wing in air as long as the Reynolds number, a measure of viscous and inertial forces, is the same for both systems.

Still shots of dye visualization experiments with model wings.

By performing dye flow visualization and particle image velocimetry on a propeller rig spinning both model and real locust wings in water, I hope to determine the effect of different angles of attack and relative wing positions. More specifically, I am collecting wing model data on the permutations resulting from forewing and hindwing angles of attack ranging from 0º to 35º in 5º increments (an 8x8 matrix) in two different relative wing positions. In the first position, the major axes of the wings lie in the same horizontal plane (perpendicular to the axis of rotation). In the second position, designed to simulate the midpoint of a locust downstroke, the hindwing remains in the horizontal plane while the forewing major axis is elevated 30º vertically above the hindwing. Data collection for the real locust wings follows the same general pattern but with fewer angles of attack.

Last updated September 2004
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