Computational study of the effect of winglets on the performance of micro-aerial vehicles

The effect of winglets on the performance of Micro-Aerial Vehicles (MAV) has investigated computationally. The computations have been performed using the been commercially available finite-volume solver Cobalt. Although Cobalt has been used for a wide range of applications previously, the current study provides additional validation of its capabilities.; The MAVs have low-aspect-ratio wings and operate at low-chord-Reynolds numbers, which both contribute to the difficulty of the design of such vehicles. At these low Reynolds numbers, the viscous effects are dominant in the flow-field and thus cannot be neglected been done in classical aerodynamics. Due to this difficulty only a limited number of studies have been done previously, and not much data is published to help the design of low-Reynolds-number aerial vehicles.; For low-aspect-ratio wings, the induced drag or drag-due-to-lift is the dominating source of drag. Earlier studies have shown that the size of the tip vortex that causes the downwash and the induced drag on three-dimensional wings can cover over 50% of the half-span of a low-aspect-ratio wing. It has also been shown that the downwash can be weakened by the use of a properly designed winglet. However, most studies on the effect of winglets have been for higher Reynolds number flows and for larger-aspect-ratio wings and no computations have been performed previously for the current application. The addition of winglets to an MAV is an attractive method of improving their performance, as the goal of the MAV research effort is to minimize the maximum dimension of the vehicle while still achieving the required lift.; The current study emphasizes the importance of validation and verification in computational studies. To gain further confidence in the results, grid convergence studies are presented. This step is of utmost importance for configurations for which computational data is presented without corresponding experimental results. A comparison between laminar and turbulent computations are presented.; The current results show that carefully chosen winglets can improve the performance of an MAV significantly. The results also reveal that the flowfield over a wing without winglets can guide the initial design of winglets.