Abstract
Flow visualizations have been performed on a free flying, flapping-wing micro air vehicle (MAV), using a large-scale particle image velocimetry (PIV) approach. The PIV method involves the use of helium-filled soap bubbles (HFSB) as tracer particles. HFSB scatter light with much higher intensity than regular seeding particles, comparable to that reflected off the flexible flapping wings. This enables flow field visualization to be achieved close to the flapping wings, in contrast to previous PIV experiments with regular seeding. Unlike previous tethered wind tunnel measurements, in which the vehicle is fixed relative to the measurement setup, the MAV is now flown through the measurement area. In this way, the experiment captures the flow field of the MAV in free flight, allowing the true nature of the flow representative of actual flight to be appreciated. Measurements were performed for two different orientations of the light sheet with respect to the flight direction. In the first configuration, the light sheet is parallel to the flight direction, and visualizes a streamwise plane that intersects the MAV wings at a specific spanwise position. In the second configuration, the illumination plane is normal to the flight direction, and visualizes the flow as the MAV passes through the light sheet.
Highlights
The development of flapping-wing micro air vehicles (MAVs) has received interest in view of their small size, relatively high aerodynamic performance, and advanced maneuvering capabilities.The design of Micro Air Vehicle (MAV) often draws inspiration from nature, like birds, bats, or insects [1,2,3,4], but copying nature cannot be expected to lead to optimized MAV designs
Flow visualizations have been performed on a flapping-wing Micro Air Vehicle (MAV) in free directly obvious, in view of the fact that similar structures do not always occur in the same form in flight, using an innovative large-scale particle image velocimetry (PIV) approach
Other recordings, which leads to the assumption that they are in some way connected to the asymmetric methodology involves the use of helium filled soap bubbles (HFSB)
Summary
The development of flapping-wing micro air vehicles (MAVs) has received interest in view of their small size, relatively high aerodynamic performance, and advanced maneuvering capabilities. The physical restriction imposed on the flapping MAV inhibits the dynamic body modes that occur in real flight, which may affect the aerodynamic behavior [10] In line with these considerations, the particular interest of the current investigation is to visualize the unsteady flow structures around a flapping-wing MAV in actual free and unconstrained forward flight. The MAV used in the current tests is the DelFly II ( called DelFly for simplicity) [3], for which tethered experiments have been previously performed in hovering [14,15] and symmetric for which tethered experiments have been previously performed in hovering [14,15] and symmetric forward flight (at zero pitch angle) [9] configurations.
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