Droplet Field Sensing in a Low Speed Windtunnel

With the continued operational and technological advancements of small unmanned aerial systems (sUAS), they are capable of contributing to scientific observations. Flights from a sUAS allow more frequent and closer transects than manned aircraft with the small aircraft size and lesser degree of cloud disruption. The tighter grid observations in smaller amount of time will allow better geographic and temporal resolution. Airborne microphysical measurements have shown great sampling zone variability. Optical particle sensor calibration for sUAS flight is performed by applying a droplet field through a wind tunnel at the desired flight speeds.

The preliminary examination is of the sensor's dry air observations under increasing velocity conditions. These are compared with direct imaging observations as an initial test of varied sensor options. Pulsed high-power LED illumination will be used for particle image velocimetry. For sUAS sensor calibration, it is imaging will provide the amount of water in the test volume, and droplet count and size distribution. For a wider physical significance, the droplet field will also be examined for homogeneity, turbulent structures, and sensor impingement characteristics.