Low Aspect Ratio Wing Under Large-Scale Turbulent Inflow Conditions at Low Reynolds Numbers

Herbst, Sebastian; Hain, Rainer; Kähler, Christian J.

doi:10.1007/978-3-030-25253-3_62

Cited by 2 publications

(1 citation statement)

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“…The extent of the mean reverse flow region (depicted by the darkest blue contour level) on the wing (figure 8a) and on the two-dimensional airfoil at the same effective angle of attack (figure 8b) show no substantial differences, confirming the close similarity between the mean LSB sufficiently far away from the wingtip and that on the airfoil at the matching effective angle. Compared with the airfoil at the same geometric angle of attack (figure 8c), the LSB location on the wing (figure 8a) is shifted downstream due to the reduction in effective angle of attack, which reduces the adverse pressure gradient and delays separation (Bastedo & Mueller 1986;Boutilier & Yarusevych 2012a;Herbst, Hain & Kähler 2020).…”

Section: Mean Flow Topologymentioning

confidence: 99%

Structure and dynamics of a laminar separation bubble near a wingtip

Toppings

Yarusevych

2021

J. Fluid Mech.

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The three-dimensional flow topology of a laminar separation bubble forming on the suction surface of a semispan wing with an aspect ratio of $2.5$ and NACA 0018 airfoil section is characterised experimentally using surface pressure measurements and particle image velocimetry at a chord Reynolds number of $125\ 000$ . In the inboard region of the wing, the separation bubble is essentially two-dimensional, and the transition process in the separated shear layer leads to periodic vortex shedding, which dominates the bubble dynamics, similar to two-dimensional separation bubbles. However, progressive spanwise changes in the mean structure and vortex dynamics occur near the wingtip, leading to an open separation and eventual suppression of the bubble. In the immediate proximity of the wingtip, the boundary layer remains attached, no vortex shedding occurs and the flow remains laminar, terminating separation bubble formation. Despite variations in the mean separation bubble topology and vortex dynamics along the span, the fundamental shedding characteristics remain nearly invariant across the portion of the wing where vortex shedding occurs, and the flow appears to lock onto a common instability mode across the span, leading to minimal changes in the mean bubble characteristics despite notable changes in the effective angle of attack along the span. A comparison with available surface flow visualisations from previous studies indicates that the observed changes to the mean bubble footprint along the span of the wing are similar across different geometries and flow characteristics, suggesting similarities in the three-dimensional bubble topology and dynamics on finite wings.

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Section: Mean Flow Topologymentioning

confidence: 99%