Numerical study on effect of leading‐edge tubercles

Zhang, Xingwei; Zhou, Chao; Zhang, Tao; Wen-ying, JI

doi:10.1108/aeat-feb-2012-0027

Cited by 33 publications

(12 citation statements)

References 23 publications

(26 reference statements)

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“…1 After this early morphological investigation, many studies attempted to demonstrate the feasibility of leading edge serrations as passive flow control devices for wings to quantify the magnitude of any benefit that they may offer. [2][3][4][5][6][7][8][9][10][11][12][13][14] All the studies concerning the effect of leading edge serrations on airfoil performance draw a consensus that the serrations can delay the stall occurrence, increase post-stall lift, decrease post-stall drag and reduce the laminar separation bubble.…”

Section: Introductionmentioning

confidence: 99%

Rod-Airfoil Interaction Noise Reduction Using Leading Edge Serrations

Chen

Qiao

Wang

et al. 2015

21st AIAA/CEAS Aeroacoustics Conference

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Large eddy simulation and FW-H acoustic analogy method are performed to investigate the effect of serrated leading edge on rod-airfoil interaction (RAI) noise. A NACA 0012 airfoil with straight and serrated leading edge at zero angle of attack is located one chord length behind a cylinder rod. The leading edge serrations are in the form of sinusoidal profiles .The free stream Mach number is 0.2 and the Reynolds number based on the rod diameter is 48,000. Firstly, the numerical results of straight leading edge airfoil are compared with experimental data, both the flow field predictions and the acoustic results are in good agreement with experiment. Secondly, the numerical results are compared between straight and serrated airfoils. The wake of the serrated airfoil is a little bit narrower and weaker and the leading edge serrations efficiently reduce the span-wise correlation coefficient. There is almost no noise reduction effect below the Karman vortex shedding frequency. The reduction of SPL at the Karman vortex shedding frequency is about 2.4 dB. A significant noise reduction is achieved by the serrations over a quite wide frequency range between 2 KHz and 6.5 KHz. It can be noted that the OASPL directivities at different azimuth angles all reduced 2-5.5 dB due to the serrations, which means than the leading serrations are an effective passive flow control method to reduce RAI noise. NomenclatureA = amplitude of the leading edge serration W = wavelength of the leading edge serration c = baseline airfoil chord lenght c(z) = serrated airfoil chord length c = serrated airfoil mean chord length d = cylinder rod diameter L span = span-wise length of the experiment L sim = span-wise length of the simulation R = radius of the observer points around the airfoil a 0 = free stream speed of sound 0  = free stream dendity U 0 = free stream velocity 2 u mean = stream-wise mean velocity RMS = root mean square rms u = root mean square of stream-wise velocity fluctuation rms p = root mean square of pressure fluctuation f 0 = Karman vortex shedding frequency St = Strouhal number C L = lift coefficient of the airfoil C D = drag coefficient of the airfoil C P = pressure coefficient SPL = sound pressure level PWL = sound power level PSD = power spectral density OASPL = overall sound pressure level FFT = fast Fourier transform

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Section: Introductionmentioning

confidence: 99%

Rod-Airfoil Interaction Noise Reduction Using Leading Edge Serrations

Chen

Qiao

Wang

et al. 2015

21st AIAA/CEAS Aeroacoustics Conference

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“…However, under post stall conditions, the lift had recovered, and increased coverage by the undulations ultimately led to increased performance. Recently, Xingwei et al [14] performed a Reynolds-averaged study of wings with a sinusoidal leading edge during forward flapping and gliding flight. Webber et al Favier et al [17] conducted direct numerical simulations of an undulating geometry at low Reynolds number.…”

Section: Introductionmentioning

confidence: 99%

Flow over a Wing with Leading-Edge Undulations

et al. 2015

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International audienceThe stall-delaying properties of the humpback whale flipper have been observed and quantified in recent years, through both experimental and numerical studies. In the present work we report numerical simulations of an infinite span wing with an idealised representation of this geometry, at a Reynolds number of 1.2 × 105 . Us- ing Large Eddy Simulation, we first establish an adequate spatial resolution before also examining the spanwise extent of the domain. We then proceed to analyse these results to provide an explanation of the conditions that drive the lift observed be- yond the conventional stall angle. The undulating leading-edge geometry gives rise to a span-wise pressure gradient that drives a secondary flow towards the regions of minimum chord. In turn, this leads to the entrainment of higher-momentum fluid into the region behind the maximum chord, which energises the boundary layer and delays stall. Aside from demonstrating a significant post-stall lift, the undulations also have the added benefit of substantially reducing lift fluctuations

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“…A pitching study by Wang et al [51] found a negligible change in performance in tubercled designs, although foil geometry was quite different than [12], and Re was an order of magnitude greater. In contrast, a study by Zhang et al [52] revealed potential advantages for tubercled leading edges during flapping flight.…”

Section: Plos Onementioning

confidence: 88%

Performance evaluation of humpback whale-inspired shortboard surfing fins based on ocean wave fieldwork

Shormann

Panhuis

2020

PLoS ONE

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We present field results revealing improved surfing performance when a novel approach ("Real Whale", RW) is used for applying several of the humpback whale's passive flow control mechanisms, including tubercles, to surfboard fins. It is also the first study presenting evidence of dynamic performance of tubercled designs rotating on all three axes. We evaluated low aspect ratio, thruster-style 3-fin configurations used in high-performance surfing. Fieldwork involved surfing almost 2,000 ocean waves from around the world, comparing standard commercial fins with straight leading edges to RW fins. We collected surfing data from instrumentation attached to surfboards, including GPS and 9-axis motion sensors. Eighteen turn performance values were measured and calculated, including novel, surfingspecific rotational power coefficients. ANOVA revealed surfers using RW fins showed significant improvements in power generation compared to when they used standard commercial fins. Turn rates using RW fins also improved, although not significantly. We found using RW fins allowed a skilled surfer to improve their surfing performance relative to a professionally ranked surfer.

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Numerical study on effect of leading‐edge tubercles

Cited by 33 publications

References 23 publications

Rod-Airfoil Interaction Noise Reduction Using Leading Edge Serrations

Rod-Airfoil Interaction Noise Reduction Using Leading Edge Serrations

Flow over a Wing with Leading-Edge Undulations

Performance evaluation of humpback whale-inspired shortboard surfing fins based on ocean wave fieldwork

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