Box Wing: Aerodynamic experimental study for applications in MAVs

Advancements in the field of aerial robotics and micro aerial vehicles (MAVs) have increased the demand for high payload capabilities. Closed wing designs like the annular wing, the joined wing, the box wing and spiroid tip devices improve the aerodynamic performance by suppressing the wingtip vortices along with an enhanced lift coefficient. A box wing may be defined as a wing that effectively has two main planes which merge at their ends so that there are no conventional wingtips. We propose the implementation of box wings as the main lifting surface for such systems. Box wings have a potential of generating lift with considerably less induced drag and delayed stall angles than monoplane wings. We study the aerodynamic aspects of a box wing model using wind tunnel tests and numerical simulations. We conducted Computational Fluid Dynamics (CFD) simulation subjecting the model to a steady flow and later analysed the vortex core using CFD tools. Wind tunnel measurements of the forces were obtained using sting balance. Furthermore, polyester thread tufts and smoke flow visualisation were performed to understand the qualitative behaviour of the scaled model in the open to atmosphere, suction type tunnel. Our results reveal an increase in the lift to drag (L/D) ratio of the wing by 25 % and a delay in the model’s stall angle by +6° compared to a monoplane; implying a lower stalling speed for mini unmanned aerial vehicles (UAVs) and MAVs. These advancements if applied could revolutionize the capabilities of intelligent flying systems by enabling them to carry better sensors, computational units and other payloads as per the mission.