Similarities in Massive Separation Across Reynolds Numbers for Swept and Tapered Finite Span Wings

TL;DR

This study investigates flow features over swept and tapered finite-span wings at different Reynolds numbers, revealing that large-scale vortical structures share similar topological features despite Reynolds number differences.

Contribution

It provides a detailed comparison of flow structures over wings with varying sweep angles and tapers at high and low Reynolds numbers, highlighting their topological similarities.

Findings

Flow separation shifts with sweep angles and taper ratios.

Large-scale vortical structures are topologically similar across Reynolds numbers.

Reynolds number has limited effect on vortex topology in these configurations.

Abstract

Experimental investigations were performed to elucidate the features of flow fields occurring over cantilevered finite-aspect ratio NACA 0015 wings at high angles of attack with various sweep angles and taper ratios. Volumetric Stereoscopic Particle Image Velocimetry experiments were performed at mean chord based Reynolds number of 247,500 in a wind tunnel and 600 in a water tunnel. Direct Numerical Simulations (DNS) of the water tunnel test section, including the cantilevered model, were also performed at the lower Reynolds number. The low Reynolds number experiments, low Reynolds number simulations, and high Reynolds number experiments all showed that sweeping the leading edge back shifted the largest portion of the reversed flow towards the wingtip while sweeping the trailing edge forward shifted the reversed flow towards the wing root. A detailed parametric sweep of planform geometry systematically varied the leading and trailing edge sweep angles and taper ratios of the finite wings. It was found that the large scale vortical structures resulting from varying these parameters at the two Reynolds numbers share surprisingly many three-dimensional topological features, despite the orders of magnitude different Reynolds numbers.