Experimental study of flow separation control on a low-Re airfoil using leading-edge protuberance method

Zhang, M. M.; Wang, G. F.; Xu, Jianzhong

doi:10.1007/s00348-014-1710-z

Cited by 69 publications

(36 citation statements)

References 31 publications

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“…By contrast, Reynolds number played only a minor role in establishing the lift and drag characteristics of the leading-edge modified foil. Zhang et al 10,11 measured the lift and drag forces of Johari et al's 7 8L airfoil within a wider range of angles of attack at Re = 5.0 3 10 4 and 2.0 3 10 5 , finding significant improvement of aerodynamics performance when the angle of attack 16°\ a \ 70°. Particle image velocimetry (PIV) results revealed that the trough sections of protuberances played a primary role in the flow control.…”

Section: Introductionmentioning

confidence: 99%

“…Particle image velocimetry (PIV) results revealed that the trough sections of protuberances played a primary role in the flow control. However, the biperiodic flow patterns were not discovered or mentioned in Zhang et al 10,11 Full-span NACA 0021 and NACA 65-021 with leading-edge protuberances were tested by Hansen et al 12 at Re = 1.2 3 10…”

Section: Introductionmentioning

confidence: 99%

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Numerical investigations of hydrodynamic performance of hydrofoils with leading-edge protuberances

Cai

Zuo

Liu

et al. 2015

Advances in Mechanical Engineering

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Leading-edge protuberances on airfoils or hydrofoils have been considered as a viable passive method for flow separation control recently. In this article, the hydrodynamic performance of a NACA 63 4 -021 (baseline) foil and two modified foils with leading-edge protuberances was numerically investigated using the Spalart-Allmaras turbulence model. It was found that modified foils performed worse than the baseline foil at pre-stall angles, while the lift coefficients at high angles of attack of the modified foils were increased. Both the deterioration of pre-stall and the improvement of post-stall performance were enhanced with larger amplitude of protuberance. Near-wall flow visualizations showed that the leading-edge protuberances worked in pairs at high angles of attack, producing different forms of streamwise vortices. An attached flow along some valley sections was observed, leading to a higher local lift coefficient at post-stall angles. The leadingedge protuberances were considered as sharing a similar mechanism as delta wings, increasing nonlinear lift at large angles of attack. The specific stall characteristics of this leading-edge modification could provide some guidelines for the design of some special hydrofoils or airfoils.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Numerical investigations of hydrodynamic performance of hydrofoils with leading-edge protuberances

Cai

Zuo

Liu

et al. 2015

Advances in Mechanical Engineering

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“…The results indicated that the airfoil with leading-edge tubercles displayed a reduction of performance in the pre-stall region and a gradual decrease in lift coefficient for the post-stall behavior, avoiding the abrupt stall exhibited by the baseline airfoil. Zhang et al 8 further experimentally investigated the controlling mechanism of leading-edge tubercles on the same airfoil 7 but for Reynolds number of 50,000. The PIV technique captured that the flow in troughs separate prior to the flow in peaks.…”

Section: Introductionmentioning

confidence: 99%

“…20 Many researchers have suggested that leading-edge tubercles have prominent effects on improving stall behavior since the control mechanism of leadingedge tubercles is similar to vortex generators that generate streamwise vortices. 3,6,7 The advantages of leading-edge tubercles can be summarized as milder stall behavior, better post-stall performance, and a more stable dynamic stall characteristic. Therefore, airfoils with leading-edge tubercles are a better choice at high angles of attack.…”

Section: Introductionmentioning

confidence: 99%

“…Hansen et al 6 conducted an experimental investigation to determine the influence of sinusoidal leading-edge protrusions on the performance of two NACA airfoils (NACA 0021 and NACA 65-021) and suggested that tubercles act in a manner similar to conventional vortex generators. Zhang et al 7 carried out experimental analysis of the effect of leading-edge protuberances on the aerodynamic performance of a NACA 63 4 -021 airfoil for a wide range of angles of attack at Reynolds number 200,000. The results indicated that the airfoil with leading-edge tubercles displayed a reduction of performance in the pre-stall region and a gradual decrease in lift coefficient for the post-stall behavior, avoiding the abrupt stall exhibited by the baseline airfoil.…”

Section: Introductionmentioning

confidence: 99%

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An empirically-based model for the lift coefficients of twisted airfoils with leading-edge tubercles

Dhanak

2018

AIP Advances

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Experimental data for untwisted airfoils are utilized to propose a model for predicting the lift coefficients of twisted airfoils with leading-edge tubercles. The effectiveness of the empirical model is verified through comparison with results of a corresponding computational fluid-dynamic (CFD) study. The CFD study is carried out for both twisted and untwisted airfoils with tubercles, the latter shown to compare well with available experimental data. Lift coefficients of twisted airfoils predicted from the proposed empirically-based model match well with the corresponding coefficients determined using the verified CFD study. Flow details obtained from the latter provide better insight into the underlying mechanism and behavior at stall of twisted airfoils with leading edge tubercles.

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Numerical investigation of drag reduction effects on a track bicycle fork using wings with a wavy leading edge

Klein,

Kessler,

Schmidt

2024

Proc Appl Math and Mech

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Reynolds‐averaged Navier–Stokes (RANS) and large‐eddy simulations (LES) of the flow around wings with a wavy leading edge (WLE) are conducted in order to assess the capabilities of a passive flow control strategy for drag reduction. The intended application is indoor track cycling with controlled flow conditions. A section of a single fork rod is investigated in order to make the numerical simulations feasible. The present study reveals that net drag reduction is possible by a nonsinusoidal modification of the leading edge of the wing. However, the drag reduction effect remains limited to a few percent. While RANS and LES yield the same drag coefficient for a reference case, RANS underestimates the drag reduction effect for a longer wing and the WLE cases, but exhibits otherwise a qualitatively similar trend as the LES. With the aid of RANS, an optimal geometry is obtained defined by the wavelength‐to‐chord length ratio of and the amplitude‐to‐chord length ratio of . Corresponding LES results give an indication of the origin of drag reduction by a hampered vortex shedding. The generation of smaller and more streamwise oriented vortical flow structures at the trailing edge and behind the WLE wing is correlated with significantly reduced lift fluctuations and drag reduction.

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Experimental study of flow separation control on a low-Re airfoil using leading-edge protuberance method

Cited by 69 publications

References 31 publications

Numerical investigations of hydrodynamic performance of hydrofoils with leading-edge protuberances

Numerical investigations of hydrodynamic performance of hydrofoils with leading-edge protuberances

An empirically-based model for the lift coefficients of twisted airfoils with leading-edge tubercles

Numerical investigation of drag reduction effects on a track bicycle fork using wings with a wavy leading edge

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