Development of a large-array hot-film sensor for detecting flow separation on a large airfoil.

Hot-film sensors have been used for a variety of applications such as measuring wind speed, temperature, and wall shear stress. This study aims to develop a low-cost, constant-current hot-film circuit in an array configuration to detect the boundary layer condition on large, complex lifting surfaces under the influence of unsteady inflow. A specific case of interest is the three-dimensional flow separation which occurs on wind turbine blades caused by atmospheric turbulence. The hot-film array will be tested on both a flat plate and a cambered airfoil actuated by a plunging-pitching rig to evaluate stall detection and frequency response capabilities of the array in both static and unsteady conditions. Dimensional analysis will be used to extrapolate the results to full-scale. The detection capabilities of the array and driving circuitry package will be compared against validation data taken with particle image velocimetry and flow visualization techniques such as tufts.