Future insect-sized nano air vehicles (NAV) will need optimised wing flexibility to maximise thrust, say researchers at the UK's University of Bath.

Degrees of wing flexibility were found to improve propulsive efficiency during water tunnel experiments using larger-than-insect-scale chord-wise flexible aerofoils. The next step is to test a laboratory-scale spanwise flexible aerofoil to model the phenomena fully in three dimensions. The chordwise experiment only enabled a two-dimensional analysis.

"We found flexibility was beneficial for optimal thrust, but too much flexibility gives a [performance] penalty," says aerospace engineering professor Ismet Gursul, whose work is supported by the UK government's Engineering and Physical Sciences Research Council.

The research has not identified possible flexible wing materials for an insect-like entomopter NAV, but is providing bending stiffness optimisation data for material selection and design.

Source: Flight International