Vortex Formation and Force Generation Mechanisms of the DelFly II in Hovering Flight

This paper addresses the unsteady aerodynamic mechanisms in the hovering flight of the DelFly II flapping-wing Micro Aerial Vehicle (MAV). Stereoscopic Particle Image Velocimetry (Stereo-PIV) were carried out around the wings at a high framing rate. Thrust-force was measured to investigate the relation between the vortex dynamics and the aerodynamic force generation. The results reveal that the Leading-Edge-Vortex (LEV), as well as the high flexibility of the wings, have a major effect on thrust generation. Comparison of three wing pairs with different aspect ratio (AR) is also reported, yielding significant differences in both vortical structures and thrust generation.Aerodynamics, Wind Energy & PropulsionAerospace Engineerin

Experimental investigation of turbulent flow through single-hole orifice placed in a pipe by means of time-resolved Particle Image Velocimetry and unsteady pressure measurements

The flow passing through a sharp-edged orifice is studied using two experimental techniques over a pipe Reynolds number range of 4000 to 27000. The flow separates at the orifice inlet and is accelerated through its hole in the form of a confined jet. For a given orifice, the mean reattachment length is found to remain fairly independent of the inflow Reynolds number. Velocity and pressure fluctuations attain peak values in regions lying upstream of the mean reattachment point. Under the conditions tested, the orifice jet shows a low frequency flapping motion which was observed to occur at a Strouhal number 0:02 based on the orifice jet velocity and the difference in internal diameters of the pipe and orifice.Aerodynamic

Experimental Investigation of the Flapping Performance on 'Delfly Micro'

Aerodynamics, Wind Energy & PropulsionAerospace Engineerin