The GUI pre-processor used to generate the geometry of the fly wings. (Click on image to enlarge.) All images courtesy Diego Scardaci, INFN

The study of the flight of a fruit fly may one day lead to the development of autonomous ‘Micro-air vehicles’ (MAVs), or independent ‘flying robots,’  if scientists in Argentina have their way.

Working in conjunction with the Italian Institute of Nuclear Physics (INFN) under the EELA-2 initiative, they are conducting the study to understand the flight mechanisms of insects and small birds. Their hope is that someday, 'flying robots' could be developed with maneuvering capabilities similar to insects — the most agile flying creatures on Earth.

MAVs could be used to study and explore places that are too dangerous or inhospitable for humans to tread; examples include search-and-rescue teams exploring buildings to detect fires, or scientists investigating the upper atmosphere, said Bruno Roccia of of the Consejo Nacional de Investigaciones Cientificas y Tecnológicas (CONICET), Argentina.

The research demonstrates the successful execution of a scientific application on the grid running gLite middleware in a Windows environment. This is possibly one of the first times that this has been done; most flight applications have been run using Linux-based environments on the grid, said Diego Scardaci of INFN.

The basic concept behind the study of insect flight is to look to nature to find design concepts for performing highly complex maneuvers. The ultimate goal is to create a biologically inspired, super-maneuverable, flapping-wing micro-air vehicle.

However, there are still major engineering problems, such as creating reliable miniature energy sources, finding ultra-light materials, and completely understanding the unsteady aerodynamics of insect flight. In fluid dynamics, these aerodynamics are expressed as low “Reynolds Numbers” — dimensionless numbers used to measure the ratio of inertial forces compared to viscous forces.

In layman’s terms, these are fixed numbers which describe the relationship between two different systems. Insects and birds generate aerodynamic mechanisms that are effective at low Reynolds Numbers. High numbers indicate more drag as the wing moves through the air. However, low numbers signify more lift per wing stroke and thus a more successful flight.

A) Wings at 25% stroke cycle – Isometric view B) Wings at 75% stroke cycle – Isometric view C) Wings at 75% stroke cycle – Front view.

Unconventional flight

Unlike airplanes and helicopters, which use steady and linear aerodynamics, insects and small birds fly in a very unconventional manner, using unsteady and highly chaotic aerodynamic processes. These include delayed stall (a wind eddy that reduces pressure over the wing), rotational lift (a vortex created that is similar to the airflow from the ‘backspin’ of a basketball) and wake capture — a ‘wobbly’ aerodynamic system in which hovering insects intercept the wake created by their own wing motion. In contrast, the wings of an airplane move through ‘still air.’

Due to the unsteady and three-dimensional nature of the ‘flow’ generated by flapping insect wings, the scientists modified a version of a technique known as the ‘Unsteady Vortex Lattice Method’ (UVLM) to create an aerodynamic model to study insect flight.

UVLM is a numerical tool consisting of two models: aerodynamics and kinematics. Aerodynamics is the study of the motion of air or gas and the forces produce; while kinematics describes the trajectories and velocities of wing motion, and accelerations of arbitrary wing points.

This tool has enabled the scientists to study the flow generated by a fruit fly, Drosophila melanogaster, in ‘hover’ mode. Additionally, the combination of kinematic and aerodynamic models will enable them to predict the field of flow around the flapping wings, therefore aiding in the construction of micro-air vehicles that can perform just as well or better than agile fliers in nature.

Even though the first autonomous MAVs are not projected to be ready until 2030, Roccia says: “Every day, new advances are being made . . . our next step is to develop an elastic model of the wing, and link it to the aerodynamic and kinematic models to study the aero-elasticity of insects and small birds.” This research currently highlights both the usefulness of highly-maneuverable flying robots and gLite middleware to the Latin American academic community.

If successful, the study will potentially also help emergency services with dangerous rescue missions, and provide scientists with a resource for hazardous exploration on Earth and perhaps other planets as well.

—Adrian Giordani, for iSGTW