The aim of the new research is to improve the aerodynamic design of wind turbines and specialized aircraft or autonomous drones. To do the researchers, from Lehigh University, turned to owls for inspiration.
Owls are energy efficient in flying and they also fly very quietly. Owls can hunt without being heard by their prey; this is suppressing the noise of their wings at sound frequencies above 1.6 kilohertz (kHz). Curious as to how both of these properties are manifest, the researchers began examining the physical properties of owl feathers.
The answer relates to owl wing porosity. The porosity enables air to pass resistively through the wings and this leads to noise suppression. Taking the resultant aero-acoustic study together with aerodynamic capabilities, the researchers took the physics of owl wings and applied this to the airfoils used on wind turbines.
The process of constructing the mathematical model may have been complex but the outcome is remarkably simple: the results for the pressure distribution on a wing from any given description of the porosity and curvature of a wing section can now be determined explicitly from a single equation.
According to lead researcher, Dr. Justin W. Jaworski: “Our work generalizes the existing theory to yield results for arbitrary porosity distributions along the airfoil and produces a porosity parameter that collapses all of the experimental data onto a single curve.”
The new design has been discussed in the journal Proceedings of the Royal Society A: Mathematical, Physical and Engineering Science. The research paper is titled “The steady aerodynamics of aerofoils with porosity gradients.”
