Aerodynamic characterization of bio inspired corrugated wings

The nature gives effective, robust and straightforward solution for engineering problems and this practice is becoming very popular day by day.1 The deep understanding of nature, how it overcomes the problem of flight in natural flyers like birds and insects have led to tremendous improvements in the aerodynamics of manmade aerial vehicles. Creatures of flight such as birds and insects have inspired human to design aircrafts of various types and sizes. Specifically, the smooth airfoil shapes of familiar aircrafts are inspired by the bird’s wing.2 The smaller aircrafts like unmanned aerial vehicles (UAVs) operate at significantly lower Reynolds number, where the performance of the conventional airfoils is no longer better.3 The aerodynamic effects of low Reynolds numbers on corrugated wings were studied by several researchers4–8 It was found that most insects’ wings specifically dragonflies and locusts have high agility and maneuverability. These insects are capable to hover, climb, dive, land and take-off at different wind speeds and ambient conditions. Another investigation9 reported that the remarkable aerodynamic performance of dragonfly wings was caused by the muscular morphing and wing geometry specially the wing corrugation. Extensive biological and aerodynamic study has been carried out by many researchers to demonstrate the reasons for the superior flight by flapping motion of the wings and the corrugated wing profile (airfoil)10 revealed that the flapping produces significant lift by generating low pressure leading edge vortex (LEV) while corrugated cross section, reduces the overall flow separations in both flapping and static motion. The effects of corrugations were demonstrated, and the results are reported in several experimental studies such as.11,12 These reports confirmed that the corrugation initiates an early transition to turbulent flow thus reducing separation and delay in stall. A better aerodynamic characteristic obtained using pleated airfoil at first sight seems to contradict with the idea of streamlined profiles used in conventional aircrafts. However recent studies by 13–16, suggested otherwise. There also have been several studies related to aerodynamic forces which were conducted on actual dragonflies and dragonfly modeled airfoils to measure the forces associated with both flapping and gliding modes of operation. Some of the more notable and recent studies for gliding flight of a dragonfly wing are the numerical and experimental studies conducted by 17–22 More recently23–25 have performed 3-D computational study on different types of corrugated wings by using commercially available computational software. However, these studies have been primarily conducted at chord Reynolds number 104 or less, which is considerably lower than the range used for MAVs. The aim of the present work is analyze two different types of corrugation in relation to coefficient of lift, drag and glide ratio, which are also relevant for micro aerial vehicles. From author’s knowledge no studies have been conducted before on bio-inspired corrugated wing using panel method. The other aim is to explore whether the 2-D panel method can predict low Reynolds number flows fairly accurately and agree with experiment data conducted on similar profiles.