An experimental study has been carried out to explore the effect of propeller-induced slipstream on the vortex flow field on a fixed-wing Micro Air Vehicle (MAV). Experiments were conducted at a freestream velocity of 10 m/s, corresponding to a Reynolds number based on a root chord of about 1.6 × 105. Surface flow topology on the surface of the MAV wing at propeller-off and propeller-on conditions was captured using surface oil flow visualisation at four angles of incidence. The mean off-body flow over the MAV was documented in the four spanwise planes at different chord position using Stereoscopic Particle Image Velocimetry (SPIV) technique at angle-of-attack of 24° for both conditions. The oil flow visualisation showed minimal differences in flow patterns for propeller-off and propeller-on conditions at 10° and 15° incidence. The small asymmetry between port and starboard side observed at 20° during the propeller-off condition became significantly pronounced at 24°. The fuselage stub which is necessary for housing the motor of the propeller was seen to have a significant effect on the flow symmetry at large incidences that can occur when the MAV encounters sudden vertical gusts. Switching on the propeller restored the symmetry at both incidences. SPIV measurements were carried out at the incidence of 24° which exhibited the highest asymmetry. The off-body data shows the re-establishment of symmetry during propeller-on condition owing to the increase in the magnitude of spanwise and vertical velocities as a result of the propeller slipstream. The findings emphasise the importance of considering the propeller flow and design of the motor housing while evaluating the aerodynamics of low-aspect-ratio MAVs.
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