| Wind turbine aerodynamics are largely governed by unsteady flows. While experimental investigations of unsteady airfoils have been conducted for decades, the complexity and cost of the experiments generally limit the resulting information obtained. An experimental apparatus was developed to investigate the unsteady flows associated with two-dimensional pitch oscillating airfoils. By taking advantage of rapid prototyping technology, airfoils were manufactured quickly at low cost, and high spatial resolution pressure data were obtained due to embedded tubing channels in the airfoils. A method to obtain robust and cost effective high temporal resolution pressure measurements from conventional tap-tubing systems utilizing electronically scanning pressure (ESP) modules was implemented. The flow fields were examined through the use of a dual-laser, dual-camera particle image velocimetry (PIV) system that allowed the full near-field flow structures to be imaged simultaneously. The combination of high resolution pressure measurements and PIV flow field information allowed both the airfoil forces and moments and the causal physics to be examined. The development of the hardware, instrumentation and experimental methods necessary to conduct unsteady wind tunnel testing on wind turbine airfoils is described and a demonstration case of the capabilities developed is presented. |
