Experimental Measurement of Flow Field Around a Rotary Wing Unmanned Aircraft*

Multirotor aircraft are outfitted with sonic anemometers to measures wind speed and direction of winds aloft for atmospheric boundary layer measurements. This effort maps the flow field around a multirotor with a sonic anemometer attached to the top of it to determine accuracy of the mounted anemometer measurements while on the vehicle in flight as air being pulled into the propellers can cause discrepancies in anemometer measurements. The project begins with flow measurements on the anemometer in a wind tunnel and continues with 5 hole probes and hot-wires an vehicle in flight. Flow visualization and particle image velocimetry are being used to map and analyze the flow. Validations are made using towers in the field including the Oklahoma Mesonet and DOE ARM SGP site as well as lidar.