Quadcopter and helicopter wakes measured by large-volume and high-resolution scanning Lagrangian particle tracking

We present large-scale time-resolved and volumetric measurements of the flow surrounding a quadcopter drone and a helicopter model. Five high-speed cameras were used to capture images of hundreds of thousands helium-filled soap bubbles being illuminated by pulsed LED arrays at 3kHz recording frequency. For most cases, an additional scanning approach was applied to further increase the particle concentration. The time-series were evaluated by Lagrangian Particle Tracking using the Shake-The-Box method, yielding dense fields of particle tracks. In a second step, flow structures were identified using the data assimilation method FlowFit. The temporally and spatially highly resolved results document the strong interaction of the wakes induced by several rotors, as well as the interaction of wing tip vortices stemming from a single rotor