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Inflow analysis for multi-rotors and the impact on sensor placement

Brenner, James
As the usage of small multi-rotor unmanned aircraft systems (sUAS) continues to grow there is a need to understand the complex flow-field and its interactions with the propellers and the sUAS airframe. It is particularly important to understand the interactions of the inflow and downwash with sensors mounted on the structure, such as chemical, thermodynamic, or wind sensors where interactions may contaminate the measurements. This effort maps the in-flow around a multi-rotor using experimental techniques of PIV and flow visualization. These experiments determine the effectiveness of sensors onboard multi-UAVs for atmospheric measurements. The study includes a dual and quad rotor systems to analyze the effect of multiple rotors. The rotors are placed in a water tunnel to allow for the flow visualization and PIV data collection. Then the inflow velocities of a single rotor were mapped out using a large rotor in controlled experiment. Finally, an ultra-sonic anemometer was mounted in several different locations on a heavy-lift quad-copter and the performance of each position was evaluated to determine the optimal location for the sensor.