Laminar Separation Bubble Development on a Finite Wing

Toppings, Connor E.; Kurelek, John; Yarusevych, Serhiy

doi:10.2514/1.j060258

Cited by 9 publications

(10 citation statements)

References 39 publications

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“…This frequency range is in good agreement with the central shear layer instability frequencies reported for the same wing model and flow conditions in Toppings et al. (2021), and is similar to that expected for natural transition in the separated shear layer (e.g. Hain et al.…”

Section: Resultssupporting

confidence: 91%

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Structure and dynamics of a laminar separation bubble near a wing root: towards reconstructing the complete LSB topology on a finite wing

Toppings

Yarusevych

2022

J. Fluid Mech.

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The influence of the wing root junction on the laminar separation bubble forming on the suction surface of a semispan NACA 0018 wing cantilevered from the wind tunnel test section wall is studied using surface flow visualisations, particle image velocimetry and surface pressure measurements at a chord Reynolds number of 125 000 and an angle of attack of 6 $^\circ$ . The test section wall boundary layer upstream of the wing is turbulent, and the spanwise influence of the junction on the separation bubble extends well beyond the test section wall boundary layer thickness. Substantial three-dimensionality is seen in the separation bubble flowfield near the wing root, where earlier transition and a reduction in separation bubble thickness is observed. In contrast with the wing tip, earlier transition and a reduction in separation bubble length occurs near the wing root. Outside of the junction affected region, the separation bubble is similar to separation bubbles forming on two-dimensional geometries, and displays mild spanwise waviness. The transition process away from the end affected regions is characterised by the formation of spanwise roll-up vortices that are shed in a nearly two-dimensional manner across the span. The analysis of the results shows that, near the wing root, the increased level of perturbations leads to earlier vortex roll-up and spanwise flow contributes to more rapid vortex breakdown. The results in the wing root region are complemented by the analysis of data from Toppings and Yarusevych (J. Fluid Mech., vol. 929, 2021, A39) in the wing tip region to provide a more holistic outlook on the laminar separation bubble topology and dynamics on the entire finite wing.

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Section: Resultssupporting

confidence: 91%

“…Dashed line: ; solid line: zero-net streamwise mass flux line; star: maximum ; and : separation and reattachment locations. Data in ( b ) from Toppings, Kurelek & Yarusevych (2021) and data in ( c ) from Toppings & Yarusevych (2021). …”

Section: Resultsmentioning

confidence: 99%

Structure and dynamics of a laminar separation bubble near a wing root: towards reconstructing the complete LSB topology on a finite wing

Toppings

Yarusevych

2022

J. Fluid Mech.

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“…This trend has been observed for steady airfoils from several authors [8,10]. For finite wing, the similarity with airfoils in LSB topology is restricted to inboard regions with weakly three-dimensional flow [30]. Near the tip, the wingtip vortex reduces the effective angle of attack, and the LSB is delayed and enlarged [11,31].…”

Section: Aerodynamic and Aeroacoustic Characterization A Oil-flow Vis...supporting

confidence: 60%

Aeroacoustic Investigation of a Propeller Operating at Low Reynolds Numbers

et al. 2022

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This paper presents an experimental investigation of a propeller operating at low Reynolds numbers and provides insights into the role of aerodynamic flow features on both propeller performances and noise generation. A propeller operating at a tip Reynolds number regime of 4.3 × 10 4 − 4.38 × 10 4 is tested in an anechoic wind tunnel at an advance ratio ranging from 0 to 0.6. Noise is measured by means of a microphone array, while aerodynamic forces are measured with load and torque cells. Oil-flow visualizations are used to show the flow patterns on the blade surface, whereas phase-locked stereoscopic particle image velocimetry (PIV) measurements are carried out to analyze the flow at 60% of the blade radius. The pressure field around the blade section has been computed from the PIV velocity data. Results reveal a complex flowfield with the appearance of a laminar separation bubble at the suction side of the blade. The separation bubble moves toward the leading edge and reduces in size as the advance ratio decreases. At an advance ratio equal to 0.6, the flowfield is characterized by a laminar separation without reattachment. This causes vortex shedding responsible for a high-frequency hump in the far-field noise spectra.

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“…For each , the value of is chosen so that the boundary face is sufficiently far from the tip of the wing. Toppings & Yarusevych (2021) and Toppings, Kurelek & Yarusevych (2021) used in their experimental investigations for carried out at . Here varies with in the present study to ensure that the computations are unaffected by the location of the lateral boundary.…”

Section: Problem Set-up and Finite Element Meshmentioning

confidence: 99%

Streamwise vortices, cellular shedding and force coefficients on finite wing at low Reynolds number

Pandi

Mittal

2023

J. Fluid Mech.

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Numerical simulations for flow past a finite rectangular wing with a NACA 0012 section at $Re=1000$ for various semi-aspect ratios ( $0.25\le sAR \le 7.5$ ) over a range of angles of attack ( $0^{\circ }\le \alpha \le 14^{\circ }$ ) reveal streamwise vortices, which increase in strength and number to occupy an increasing spanwise extent with increase in $\alpha$ . They result in non-monotonic spanwise variation of local force coefficients and increased strength of wing-tip vortex for $\alpha >8^{\circ }$ . Viscous and pressure drag dominate for low and high sAR, respectively. The time-averaged drag coefficient first decreases and then increases with increase in $sAR$ . Vortex shedding for $\alpha =14^{\circ }$ is single cell and parallel for $sAR<3$ . Shedding is in two cells with an oblique angle that varies with time, leading to large spanwise variation in the root mean square of local force coefficients for higher $sAR$ . Various types of dislocations, reported earlier in wakes of bluff bodies, are seen for different $\alpha$ and $sAR$ . Dislocations for $\alpha =14^{\circ }$ appear at the same spanwise location for $sAR=3$ and at different spanwise locations for $sAR\ge 4$ . Vortex shedding for $\alpha =12^{\circ }$ and $sAR=5$ exhibits one cell structure in the near wake and two cells in the far wake due to splitting and reconnection of vortices near the mid-span in the moderate wake. Linkages form between counter-rotating spanwise vortices for $sAR\ge 1$ . Additional linkages between shed- and wing-tip vortices are observed for lower $sAR$ . At each $\alpha$ , the strength of the wing-tip vortex and radius of its core, estimated using Rankine and Lamb–Oseen models, increases up to a certain $sAR$ beyond which it is approximately constant.

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Laminar Separation Bubble Development on a Finite Wing

Cited by 9 publications

References 39 publications

Structure and dynamics of a laminar separation bubble near a wing root: towards reconstructing the complete LSB topology on a finite wing

Structure and dynamics of a laminar separation bubble near a wing root: towards reconstructing the complete LSB topology on a finite wing

Aeroacoustic Investigation of a Propeller Operating at Low Reynolds Numbers

Streamwise vortices, cellular shedding and force coefficients on finite wing at low Reynolds number

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