采用粒子成像测速技术(PIV)研究结冰翼型表面气泡分离

The separation bubble on a NACA 0012 airfoil with a two-dimensional, constant span, simulated leading-edge glaze-ice accretion is investigated using Particle Image Velocimetry (PIV). Chordwise PIV measurements, or those along the separation bubble cross-section, are obtained at a Reynolds number of 0.9x106, Mach number of 0.20, and between 0 deg and 5 deg angle-of-attack. Mean reattachment estimated from surface oil-flow visualization indicates increasing bubble length and unsteadiness (based on reattachment zone width) with angle-of-attack, consistent with results extracted from PIV measurements. Timeaveraged streamlines and forward flow intermittency reveal a primary recirculation with clockwise rotation defined by a shear layer and a smaller, secondary recirculation with counter-clockwise rotation directly downstream of the point of separation, both consistent with backward-facing step type flowfields. Mean and RMS velocity component contours highlight these features and wall-normal profiles are extracted and compared to other separation bubble data including those over a backward-facing step and blunt flat plate.