Tandem Rotor Wake Aerodynamics in Lateral Crossflow Wind Shear

The wake characteristics of multirotor air vehicles present the aerospace industry many challenges with respect to safety that arise when other air vehicles are flying in close proximity. It is important to be able to characterize and estimate the effects of rotor wake and tip vortices on an air vehicle flying in close proximity to another vehicle in question, with the added complexity of crossflow wind shear. The work presented in this paper aims to understand these interactions by way of an experimental aerodynamics approach utilizing a seven-hole 3-D velocity probe (7-HP) on a precise 2-D linear actuator for [Formula: see text] planes, and particle image velocimetry for [Formula: see text] planes. The results of this study indicate that crossflow shear has a favorable 6% increase in the decay rate of turbulence intensity in the wake of rotors in forward flight. With crossflow shear present, lateral tip vortex displacements in the wake were found to be present and varied from 0.1 to 0.6 [Formula: see text] depending on rotor geometry within the studied near-field domain. For purposes of aerodynamic stability, turbulence statistics and frequency analysis of tip vortices in the wake were also analyzed.