Two- and Three-Dimensional Iced Airfoil Separation Bubble Measurements by Particle Image Velocimetry

Numerical and experimental study of flow field characteristics of an iced airfoil

“…The main separated bubble length increases with the angle-of-attack but the smaller bubble trapped between the glaze-ice and a little accreted ice behind the main ice and do not change significantly with increasing the angle-of-attack. These phenomenon has been predicted in previous works for NACA0012 [9,10] and for backward-facing step flow investigated by Kostas et al [13], and Hudy et al [8]. On the lower surface of the airfoil the same pattern is detected.…”

“…15. Such characteristics are reported for NACA 0012 airfoil by Jacobs and Bragg using PIV [10] and Khodadoust [11] using LDV. Similar behavior was also reported by Kostas et al [13] and Hudy et al [8] for backward-facing step flow.…”

“…As mentioned before the flow field unsteadiness on NACA 0012 airfoil with simulated glaze-ice accretion was reported in [6,7,10]. These unsteadiness on the iced airfoil is due to vortices that form in the shear layer and vortex shedding downstream of the reattachment location in regular frequencies and shear layer vertical flapping in low frequencies.…”

“…Both investigations identified a vertical flapping motion of the separated shear layer near the separation line that accompanied fluctuating bubble reattachment. Jacobs and Bragg [10] performed an investigation on NACA0012 airfoil with two and three dimensional simulated leading edge, glaze-ice accretion using surface oil-flow visualization and Particle Image Velocimetry (PIV). Time-averaged PIV results showed a primary recirculation with clockwise rotation defined by a shear layer and a smaller, counter-clockwise secondary recirculation aft of the ice accretion; both recirculation regions were similar to backwardfacing step flow field.…”

Experimental investigation of flowfield over an iced aerofoil

“…The behaviour of large-scale vortex shedding and the differences in the iced-aerofoil flowfields between a three-dimensional ice shape casting and a two-dimensional extrusion of the ice shape casting were identified by Jacobs and Bragg (5,6) . From this investigation, it was discovered that the three-dimensional horn-ice shape produced stream-wise vortex structures, which led to a faster pressure recovery of the separated boundary layer, and thus a shorter mean reattachment length than the two-dimensional extrusion of the ice shape.…”