Analysis of propeller-induced ground vortices by particle image velocimetry

Abstract

The interaction between a propeller and its self-induced vortices originating on the ground is investigated in a scaled experiment. The velocity distribution in the flow field in two different planes containing the self-induced vortices is measured by particle image velocimetry (PIV). These planes are a wall–parallel plane in close proximity to the ground and a wall–normal plane just upstream of the propeller. Based on the visualization of the flow field in these two planes, the occurrence of ground vortices and its domain boundary are analysed. The elevation of the propeller from the ground and the thrust of the propeller are two parameters that determine the occurrence of ground vortices. The main features of the propeller inflow in the presence of the ground vortices are highlighted. Moreover, the analysis of the non-uniform inflow in the azimuthal direction shows that with increasing the propeller thrust coefficient and decreasing the elevation of the propeller above the ground, the variation of the inflow angle of the blade increases.Graphical Abstract

Wingtip-Mounted Propellers: Aerodynamic Analysis of Interaction Effects and Comparison with Conventional Layout

“…Although the location of the propeller with respect to the wind-tunnel walls differed between the conventional and wingtip-mounted configurations, it was assumed that the propeller performance was the same for both cases. This is confirmed by previous work focusing on propeller aerodynamics in close ground proximity [14], which showed that propeller performance remains unaffected by wall spacing for spacing values above 1.5 times the propeller radius.…”

Aerodynamic Interaction Between an Over-the-Wing Propeller and the Wing Boundary-Layer in Adverse Pressure Gradients

“…However, these studies do not consider the presence of a rotor close to the wall. The experiments of Murray et al [21] show that, in that case, flow reversal can occur locally beneath the rotor and that additional unsteady vortical structures are formed, comparable to the ground-vortex effect encountered on propeller aircraft at low advance ratios [22]. Similar phenomena were observed in propeller-hull interaction studies [23,24].…”

Experimental Investigation of Over-the-Wing Propeller–Boundary-Layer Interaction

“…These vortex/boundary-layer interaction studies do not consider the presence of a rotor close to the wall, which imposes additional pressure gradients and three-dimensional effects. The experiments of Murray et al [32] show that, in that case, flow reversal can occur locally beneath the rotor and that additional unsteady vortical structures are formed, which are comparable to the ground-vortex effect on propeller aircraft [33] or propeller-hull interaction effects in marine applications [34,35]. Moreover, if the tip clearance between the rotor and the wall is small, the local thrust increases not only due to the local reduction in inflow velocity, but also due to the end-plate effect [36].…”