Abstract
Influence of free-stream turbulence on flows past a static three-dimensional SD7003 airfoil is numerically investigated via wall-resolved Large-Eddy Simulation (wall-resolved LES). The Reynolds number and Mach number are 60 000 and 0.2, respectively, with the angle of attack (AoA) varying from 4° to 14°. The purpose of this investigation is to clarify the effects of intensities and integral length scales of turbulence in the approaching flow on the aerodynamic performance of the airfoil. To this end, a synthetic digital filtering technique and a specific source term concept are employed to generate turbulent fluctuations within the incoming flow. It turns out that turbulence with higher intensity in the approaching flow may cause the variations in effective AoAs, which not only postpone flow development but also promote the diversity of flow classifications from an instantaneous point of view. Furthermore, it is shown that the integral length scale has significant and systematic impacts on turbulent fluctuations in the boundary layer. Larger integral length scales tend to result in higher levels of turbulence intensities, which thus induce larger separations at all AoAs.
Highlights
Free-stream turbulence can have a strong impact on the flow fields around solid bodies, especially when laminar-to-turbulent transition plays a crucial role
Simoni et al.7 investigated the aerodynamic properties of a thick flatplate airfoil with the turbulence intensity up to Tu = 2.87%, and Istvan and Yarusevych8 examined the effects of free-stream turbulence scitation.org/journal/adv on the flow patterns around a NACA0018 airfoil at four turbulence intensities from Tu = 0.11% to Tu = 1.92% by using time-resolved Particle Image Velocimetry (PIV) and surface pressure measurement techniques
The present study focuses on the flow past a 3D SD7003 airfoil at a free-stream Mach number of Ma = 0.2 and a Reynolds number of Re = 60 000 within a much wider range of angle of attack (AoA) (4○–14○)
Summary
Free-stream turbulence can have a strong impact on the flow fields around solid bodies, especially when laminar-to-turbulent transition plays a crucial role. The process of laminar separation around a NACA0018 airfoil is investigated in ambient turbulence for a variety of cases with variations in AoAs (4○ and 8○), free-stream turbulence intensities, and integral length scales of the free-stream turbulence using hybrid RANS-LES techniques.. It is suggested that larger scales have an indirect influence through affecting effective AoAs. the impacts of free-stream turbulence properties (especially the integral length scales) on the flow field around an airfoil are rarely discussed at low Reynolds numbers and within a much wider range of AoAs. The purpose of the present investigation is to gain some insight into the effects of inflow turbulence characteristics (turbulence intensities and integral length scales) on the process of static stall of a three-dimensional (3D) airfoil.
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