A Flap-Based Gust Generation System for Hair Sensor Investigations

摘要

Active and passive hair sensors (also called micro-pillar sensors) have been developed by several international research groups. Aerodynamic testing of the sensors for low-Reynolds number vehicles has been limited to canonical steady and unsteady flows such as Falkner-Skan boundary layer studies and wave-tube investigations. A dual-flap system was created to produce two-dimensional, low-speed unsteady flows resembling large scale atmospheric gusts in a wind tunnel at Baylor University. The system enables investigations of active and passive hair sensor behavior on small air vehicles, aircraft wings, and aerodynamic bodies. The flaps are mounted on the floor and ceiling of the wind tunnel test section and are actuated using stepper motors and crank-rocker mechanisms. Optics from an inspection microscope and a digital camera with a three-axis positioning system are used to measure passive fiber response in steady and unsteady flows. A rotary stage enables vehicle attitude investigations, and a six degree-of-freedom load cell from JR3 Inc. enables comparisons of fiber response timescales to vehicle dynamic timescales. An x-array, hot-wire probe is used to measure the unsteady flows produced by the gust system. Acquired through a recent NSF Major Research Instrumentation award, a high-speed, stereoscopic PIV system is also available for characterization of the unsteady flows produced using the flap system. The results of several validation studies are presented. The validation studies include: 1) surveys of the unsteady flow across the cross-section of the wind tunnel, 2) measurements of fiber deflection in steady and unsteady flows over a tapered wing based on a NACA 0012 airfoil, and 3) a comparison of synchronized measurements of aerodynamic loading on a swept wing, deflection of passive hair sensor, and hot-wire velocity measurements during an unsteady flow.