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In the present work, we have focused on the understanding of the effect of gap between micro propellers in coplanar and in coaxial arrangements on the thrust generation experimentally. In a way it’s a preliminary optimization of the spacing and placement of the micro propellers in a multirotor UAV system. APC 12-inch diameter (D) (12X8 E) and Master air screw (MAS) 11-inch diameter (11X6) propellers each 2 in numbers were considered in the study. A static testing rig was built with a provision to mount the propellers in coplanar and in coaxial arrangements. A thrust was measured using a single component load cell. Parameters like current consumption by BLDC motors and propeller RPM were also monitored. For coplanar arrangement, there is no influence of gap (G) between the propellers on the coefficient of thrust (CT). However, for G/D<0.2 random variation in CT is observed. Similarly, for propellers in coaxial arrangement, for smaller gap between the propellers along the axis is found to generate higher thrust. This optimization of the gap between the propellers may be lead to a compact multi-rotor UAV system having higher payload carrying capacity or higher endurance.

An experimental study has been carried out to explore the effect of propeller induced slipstream on the flow field of a fixed wing micro air vehicle (MAV). Tests were conducted at freestream velocity of 10m/s, corresponding to Reynolds number based on root chord of about 160000. Flow pattern on the surface of MAV planform with propeller-on and off condition was captured using oil flow visualization at four angles of incidence. Mean flow field on the MAV planform at four chordwise planes with propeller-on and off condition were measured using stereo PIV technique at angle of incidence of 24°. Little difference has been seen on the oil flow pattern at 10° and 15° angle of incidence towards leading edge in the inboard region. Significant difference in flow field was observed at 24° between propeller-on and off condition. The induced slipstream from the propeller makes the flow more symmetric and well attached over the wing planform. Nomenclature x = streamwise coordinate y = vertical coordinate z = transverse coordinate U ∞ = freestream velocity U = streamwise velocity V = vertical velocity W = tangential velocity c = chord AR = aspecratio