Surrogate Model Based Aerodynamic Shape Optimisation of Fixed Wings at Transitional Low Reynolds Numbers for Micro Air Vehicle Applications

Abstract

Presently, there is a growing need for micro-air vehicles (MAV) for a variety of applications. Owing to their small size O(15 cm) and slow speeds O(5 to 15 m/s), MAVs operate in a very sensitive low Reynolds number (Re) regime O(104-105), where the flow might encounter a laminar-to-turbulent transition phenomenon which, till date, is challenging to understand, predict and model. At such Re, the aerodynamic performance of airfoils and wings is greatly influenced by large viscous effects leading to boundary layer features such as flow separation and formation of laminar separation bubbles (LSB). The presence of LSB modifies the effective shape of the listing surfaces and is thus considered as one of the important phenomena that govern the aerodynamic performance of MAVs. Further complication to this flow field arises from the inherent low aspect ratio O(0.5 to 2) of the wings, which results in significant interaction between the tip vortices and the primary flow over the wing surface.