Laminar flow separation over tapered wings, Part 2: an experimental study*

As the second part of our three-way study, an experimental investigation on tapered and untapered finite span, cantilevered wings was performed using stereo PIV over the suction surface and in the near wake. For all experiments, the wing profile is NACA 0015, the semi-span aspect ratio is 2, and the chord-based Reynolds number is 600. Five planforms were chosen to systematically compare the effects of tapering by sweeping either the leading edge, trailing edge, or both. Two untapered models were tested, one which was unswept and one which was swept back with a sweep angle of 30 degrees, as well as three tapered models, each with a taper ratio of 0.269. The first tapered model has a straight leading edge and a trailing edge swept forward 30 degrees, the second has a straight trailing edge and a leading edge swept aft 30 degrees, and the third has its quarter chord line swept aft 30 degrees. Surface mean topology, mean vortical structures, and RMS of velocity are strongly influenced by sweep angle. As the leading edge is swept back, flow structures and peak unsteadiness shift towards the tip, and as the trailing edge is swept forward flow structures and unsteadiness is shifted towards the root.