Research Projects

Flight of small insects has been an area of keen research interest due to scientific curiosity in how such small animals achieve controlled flight and since their flying characteristics provide key inputs for the development of small unmanned aerial vehicles (UAV) such as micro, nano and pico air vehicles for multiple applications. Thus, it is imperative to understand the flight characteristics of organisms such as butterflies, moths, small wasps and thrips. Additionally, the power efficiency of insects is inherently higher than the conventional rotor drones. Thus, insights into how these organisms fly can provide important clues into the future development of flapping wing-based micro or pico drones. Additionally, like these insects, any UAVs based on such flapping wing insect flight should ideally be also able to handle a wide array of atmospheric conditions. Specifically, exposure to atmospheric moisture in the form of fog or dew is a significant challenge that these insects, as well as UAVs inspired from their flight, have to overcome due to their inherently low mass. This aspect has been only briefly investigated so far and only for a few species. Investigating how the small insects deal with such atmospheric conditions can provide valuable insights to this aspect of this important developmental area. In the light of the above-described salient factors, we propose to conduct a systematic study into the response of common butterflies such as Papilio polytes or smaller flying insect such as small wasps or thrips to atmospheric moisture. Evolution has endowed most of such insects with hydrophobic or superhydrophobic wings, legs and thorax. However, as observed for most such surfaces, their superhydrophobicity can be compromised when exposed to micrometric scale droplets of fog and dew. The resulting accumulation of liquid water droplets can severely affect their overall flight dynamics. Since, many of these insects are found in high humidity areas, moisture resistance becomes critical. We aim to investigate the response of such insects during exposure to moisture and how it affects their free flight, using both experimental and numerical methods. We will focus on two main types of insects, namely larger insects such as butterflies with wing chord length of the order of centimetres and smaller insects such as wasps with much shorter chord length. There are a few key differences between these groups. While the wings of the former group are membranous, the latter group can have partially or fully bristled wings. Secondly, while wing deformation plays a key role the overall aerodynamics of the larger insects, the overall flexibility of the wings is significantly smaller. Further, the viscous forces play a much greater role for the smaller insects since the Reynolds number based on the wing chord length is nearly ten times smaller for these insects compared to the larger ones. We will perform experiments on free and, if required, tethered flight of these insects. The observations will be used to record wing motion during a complete upstroke and downstroke of a cycle. These experiments will be performed in dry and moist environment consisting of mist or fog. This data then will be used to set up CFD simulations to investigate the flow field generated by the motion of the wings and estimate the lift and drag forces. Further, this analysis will also enable estimation of contribution by various characteristics of wing morphology such as camber and twist thus providing insights into design of equivalent wings with similar flying characteristics. The research outcomes of this project will contribute towards development of small, flapping-wing based unmanned aerial vehicles for various socio-economic applications such as developing power efficient drones for disaster relief, agriculture management and reconnaissance.