The effect of Reynolds number on the separated flow over a low-aspect-ratio wing

Abstract

At high incidence, low-aspect-ratio wings present a unique set of aerodynamic characteristics, including flow separation, vortex shedding, and unsteady force production. Furthermore, low-aspect ratio wings exhibit a highly impactful tip vortex, which introduces strong spanwise gradients into an already complex flow. In this work, we explore the interaction between leading edge flow separation and a strong, persistent tip vortex over a Reynolds number range of $600\le Re\le 10,000$. In performing this study, we aim to bridge the insight gained from existing low Reynolds number studies of separated flow on finite wings ($Re\approx 10^2$) and turbulent flows at higher Reynolds numbers ($Re\approx 10^4$). Our study suggests two primary effects of Reynolds number. First, we observe a break from periodicity, along with a dramatic increase in the intensity and concentration of small-scale eddies, as we shift from $Re=600$ to $Re=2,500$. Second, we observe that many of our flow diagnostics, including the time-averaged aerodynamic force, exhibit reduced sensitivity to Reynolds number beyond $Re=2,500$, an observation attributed to the stabilizing impact of the wing tip vortex. This latter point illustrates the manner by which the tip vortex drives flow over low-aspect-ratio wings, and provides insight into how our existing understanding of this flowfield may be adjusted for higher Reynolds number applications.

References in corpus (4)

• On the formation of three-dimensional flows over finite-aspect-ratio wings under tip effects
• Linear modal instabilities around post-stall swept finite-aspect ratio wings at low Reynolds numbers
• Unsteady lifting-line theory and the influence of wake vorticity on aerodynamic loads
• The impact of finite span and wing-tip vortices on a turbulent NACA0012 wing

Cited by in corpus (2)

• Extreme vortex gust encounters by a square wing
• Wake dynamics of finite-aspect-ratio rotating circular cylinders at low Reynolds number