Reynolds number effects on flow characteristics and aerodynamic performances of a swept-back wing

A NACA 0012 wing model with sweep-back angle of 38° was studied. This finite wing has an aspect ratio of 10. Surface-flow fields were visualized using the smoke wire and surface oil-flow schemes. According to the smoke-streak flow patterns for the low Reynolds number ( Re < 1.5 × 10 4 ), five characteristic flow modes are defined — attached surface flow, separation, separation vortex, separation near the leading-edge and bluff-body wake. Based on the surface oil-flow patterns for the high Reynolds numbers ( Re > 3 × 10 4 ), six characteristic flow modes are defined — laminar separation, separation bubble, leading-edge bubble, bubble extension, bubble burst and turbulent boundary layer. The velocity field around the wing was quantified using the particle image velocimetry (PIV). Moreover, the topological scheme was utilized to verified the surface-flow patterns. A six-component balance was used to measure the aerodynamic loadings. The aerodynamic performances are closely related to the characteristic surface-flow patterns.