Free stream turbulence effect on the flow structure over the finite span straight wing

Abstract

Flow visualization tests have been performed to examine the structure of the near-wall flow over a low-aspect ratio straight wing installed at various angles of attack IX and chord Reynolds number Re,» Ucct» = 1.76 X 10 5 The experiments were carried out at two free-stream turbulence levels, E = 0.1% and E = 1%, the latter one having been achieved using a baffling grid. To visualize the flow, termochromic cholesteric liquid crystals and digital processing of video images were used. At the low turbulence level and IX = 27", a flow stall on the lee side of the wing was observed, with a pair oflargescale vortices rotating in the wing plane. Simultaneously, no vortex structures were observed on the windward wing surface. It was found the flow patterns on either side of the wing significantly changed with increasing free-stream turbulence level. A separation bubble appeared near the leading edge on the lee side of the airfoil at E = 1%, and large-scale stationary longitudinal vortices originated over the wing windward surface. The number and sizes ofthe longitudinal structures were found to be dependent on the angle of attack.

Visualization of sinusoidal and varicose instabilities of streaks in a boundary layer

“…Görtler vortices, crossflow vortices on swept wings) and unsteady (streaky structures in the case of high free-stream turbulence, Λ-, Ω-, and hairpin vortices) streamwise flow perturbations. The origination and evolution of the mentioned disturbances has been studied in numerous experimental and numerical researches (see Haidary and Smith, 1994;Panton, 2001;Winoto et al, 2005;Zharkova et al, 2002). The streamwise structures have been also found in the turbulent boundary layers about 50 years ago (Panton, 2001), and their role in the regeneration of turbulent oscillations has been extensively examined since that time.…”

Investigation of the Flow behind the Roughness Element on the UAV Surface at a Favorable Pressure Gradient

“…6, а). Необходимо отметить, что в работе [14] при больших значениях отрицательного угла атаки наблюдались аналогичные продольные структуры. На рис.…”

Actual Problems of Aerodynamics (Prospect of Shear Flows Control)

“…9. Дымовая визуализация течения в пограничном слое плоской пластины при ε < 0, 04% (а) и ε = 1, 5% (б); поток направлен слева направо [15] Закономерности образования полосчатых структур в пограничном слое под действием внешних турбулентных пульсаций изучались в экспериментах [14], [16], [17], где исследовались характеристики течений, возмущенных установленными на входе в рабочую часть аэродинамической трубы турбулизирующими сетками. Данные были получены на моделях крыла и клина, помещенных в потоке несжимаемого газа.…”