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Journal articles on the topic 'Leading edge tubercles'

Author: Grafiati

Published: 4 June 2021

Last updated: 6 February 2022

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1

Weber, Paul W., Laurens E. Howle, and Mark M. Murray. "Lift, Drag, and Cavitation Onset On Rudders With Leading-edge Tubercles." Marine Technology and SNAME News 47, no. 01 (January 1, 2010): 27–36. http://dx.doi.org/10.5957/mtsn.2010.47.1.27.

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This paper presents the experimental measurement of lift and drag as well as the determination of the onset of cavitation on rudders with leading-edge protuberances (tubercles) that are operating at low to moderate Reynolds Numbers in water. The leading-edge shape used for the rudders in this study is derived from our earlier work concerning the analysis of the leading-edge morphology found on the pectoral flippers of humpback whales. While humpback whales do not swim at speeds that induce cavitation, engineered control surfaces based on this bio-inspired control surface modification might operate in cavitation conditions. This point motivates our present work to investigate the onset of cavitation on small aspect ratio rudders with tubercles. Our findings are that (i) the presence of leading-edge tubercles accelerates the onset of cavitation, (ii) the tubercles can modify the location of the onset of cavitation, (iii) the tubercle geometry has an influence on the rudder's hydrodynamic performance, (iv) for the lower Reynolds Numbers considered in this paper, the tubercles decrease lift and increase drag for angles of attack between 15 and 22 deg, (v) for angles above 22 deg, rudders with tubercles generate more lift than smooth rudders, and (vi) for the higher Reynolds Numbers investigated, the difference in performance between the smooth and tubercled rudders diminishes, suggesting the existence of a critical Reynolds Number for a given tubercle geometry beyond which tubercles have no significant effect on hydrodynamic performance.

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2

Chang, Xin, Xin Ning Wang, and Xiang Ru Cheng. "Research on Hydrodynamic Performance of Three-Dimensional Airfoil with Tubercles on Leading-Edge." Applied Mechanics and Materials 575 (June 2014): 405–13. http://dx.doi.org/10.4028/www.scientific.net/amm.575.405.

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This paper aims to improve and control hydrodynamic performance of three-dimensional airfoils and investigate hydrodynamic performance of three-dimensional airfoil with tubercles on leading-edge by imitating the sinusoidal leading-edge systematically. Based on the DES method, a series of parameters, such as amplitudes and numbers of tubercles, had been studied via the FLUENT software with model constructed by ICEM software and divided by structural grid. According to the results, the amplitudes significantly affect the hydrodynamic performance of three-dimensional airfoil. With maintaining other conditions,tubercle airfoils can make stall angle delay, raise the lift and the drag ratio coefficient. Especially, if there is a bigger attack angle, it is better to reduce resistance and save energy, which will be a cornerstone for further study. It is of vital importance to find out appropriate amplitudes and numbers of tubercles to achieve further progress in hydrodynamic performance of three-dimensional airfoil.

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3

Baofeng, Tu, Zhang Kai, and Hu Jun. "Investigation on Performance of Compressor Cascade with Tubercle Leading Edge Blade." International Journal of Turbo & Jet-Engines 37, no. 3 (August 27, 2020): 295–303. http://dx.doi.org/10.1515/tjj-2019-0023.

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AbstractIn order to improve compressor performance using a new design method, which originates from the fins on a humpback whale, experimental tests and numerical simulations were undertaken to investigate the influence of the tubercle leading edge on the aerodynamic performance of a linear compressor cascade with a NACA 65–010 airfoil. The results demonstrate that the tubercle leading edge can improve the aerodynamic performance of the cascade in the post-stall region by reducing total pressure loss, with a slight increase in total pressure loss in the pre-stall region. The tubercles on the leading edge of the blades cause the flow to migrate from the peak to the valley on the blade surface around the tubercle leading edge by the butterfly flow. The tubercle leading edge generates the vortices similar to those created by vortex generators, splitting the large-scale separation region into multiple smaller regions.

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4

Gopinathan, Veerapathiran Thangaraj, John Bruce Ralphin Rose, and Mohanram Surya. "Investigation on the effect of leading edge tubercles of sweptback wing at low reynolds number." Mechanics & Industry 21, no. 6 (2020): 621. http://dx.doi.org/10.1051/meca/2020095.

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Aerodynamic efficiency of an airplane wing can be improved either by increasing its lift generation tendency or by reducing the drag. Recently, Bio-inspired designs have been received greater attention for the geometric modifications of airplane wings. One of the bio-inspired designs contains sinusoidal Humpback Whale (HW) tubercles, i.e., protuberances exist at the wing leading edge (LE). The tubercles have excellent flow control characteristics at low Reynolds numbers. The present work describes about the effect of tubercles on swept back wing performance at various Angle of Attack (AoA). NACA 0015 and NACA 4415 airfoils are used for swept back wing design with sweep angle about 30°. The modified wings (HUMP 0015 A, HUMP 0015 B, HUMP 4415 A, HUMP 4415 B) are designed with two amplitude to wavelength ratios (η) of 0.1 & 0.24 for the performance analysis. It is a novel effort to analyze the tubercle vortices along the span that induce additional flow energy especially, behind the tubercles peak and trough region. Subsequently, Co-efficient of Lift (CL), Co-efficient of Drag (CD) and boundary layer pressure gradients also predicted for modified and baseline (smooth LE) models in the pre & post-stall regimes. It was observed that the tubercles increase the performance of swept back wings by the enhanced CL/CD ratio in the pre-stall AoA region. Interestingly, the flow separation region behind the centerline of tubercles and formation of Laminar Separation Bubbles (LSB) were asymmetric because of the sweep.

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5

Hansen, Kristy L., Nikan Rostamzadeh, Richard M. Kelso, and Bassam B. Dally. "Evolution of the streamwise vortices generated between leading edge tubercles." Journal of Fluid Mechanics 788 (January 12, 2016): 730–66. http://dx.doi.org/10.1017/jfm.2015.611.

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Sinusoidal modifications to the leading edge of a foil, or tubercles, have been shown to improve aerodynamic performance under certain flow conditions. One of the mechanisms of performance enhancement is believed to be the generation of streamwise vortices, which improve the momentum exchange in the boundary layer. This experimental and numerical study investigates the formation and evolution of these streamwise vortices at a low Reynolds number of $Re=2230$, providing insight into both the averaged and time-dependent flow patterns. Furthermore, the strength of the vortices is quantified through calculation of the vorticity and circulation, and it is found that the circulation increases in the downstream direction. There is strong agreement between the experimental and numerical observations, and this allows close examination of the flow structure. The results demonstrate that the presence of strong pressure gradients near the leading edge gives rise to a significant surface flux of vorticity in this region. As soon as this vorticity is created, it is stretched, tilted and diffused in a highly three-dimensional manner. These processes lead to the generation of a pair of streamwise vortices between the tubercle peaks. A horseshoe-shaped separation zone is shown to initiate behind a tubercle trough, and this region of separation is bounded by a canopy of boundary-layer vorticity. Along the sides of this shear layer canopy, a continued influx of boundary-layer vorticity occurs, resulting in an increase in circulation of the primary streamwise vortices in the downstream direction. Flow visualisation and particle image velocimetry studies support these observations and demonstrate that the flow characteristics vary with time, particularly near the trailing edge and at a higher angle of attack. Numerical evaluation of the lift and drag coefficients reveals that, for this particular flow regime, the performance of a foil with tubercles is slightly better than that of an unmodified foil.

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6

Pena, Blanca, Ema Muk-Pavic, Giles Thomas, and Patrick Fitzsimmons. "Numerical analysis of a leading edge tubercle hydrofoil in turbulent regime." Journal of Fluid Mechanics 878 (September 6, 2019): 292–305. http://dx.doi.org/10.1017/jfm.2019.611.

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This paper presents a numerical performance evaluation of the leading edge tubercles hydrofoil with particular focus on a fully turbulent flow regime. Efforts were focused on the setting up of an appropriate numerical approach required for an in-depth analysis of this phenomenon, being able to predict the main flow features and the hydrodynamic performance of the foil when operating at high Reynolds numbers. The numerical analysis was conducted using an improved delayed detached eddy simulation for Reynolds numbers corresponding to the transitional and fully turbulent flow regimes at different angles of attack for the pre-stall and post-stall regimes. The results show that tubercles operating in turbulent flow improve the hydrodynamic performance of the foil when compared to a transitional flow regime. Flow separation was identified behind the tubercle troughs, but was significantly reduced when operating in a turbulent regime and for which we have identified the main flow mechanisms. This finding confirms that the tubercle effect identified in a transitional regime is not lost in a turbulent flow. Furthermore, when the hydrofoil operates in the turbulent flow regime, the transition to a turbulent regime takes place further upstream. This phenomenon suppresses a formation of a laminar separation bubble and therefore the hydrofoil exhibits a superior hydrodynamic performance when compared to the same foil in the transitional regime.

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7

Fish, Frank E., Paul W. Weber, Mark M. Murray, and Laurens E. Howle. "Marine Applications of the Biomimetic Humpback Whale Flipper." Marine Technology Society Journal 45, no. 4 (July 1, 2011): 198–207. http://dx.doi.org/10.4031/mtsj.45.4.1.

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AbstractThe biomimetic approach seeks technological advancement through a transfer of technology from natural technologies to engineered systems. The morphology of the wing-like flipper of the humpback whale has potential for marine applications. As opposed to the straight leading edge of conventional hydrofoils, the humpback whale flipper has a number of sinusoid-like rounded bumps, called tubercles, which are arranged periodically along the leading edge. The presence of the tubercles modifies the water flow over the wing-like surface, creating regions of vortex generation between the tubercles. These vortices interact with the flow over the tubercle and accelerate that flow, helping to maintain a partially attached boundary layer. This hydrodynamic effect can delay stall to higher angles of attack, increases lift, and reduces drag compared to the post-stall condition of conventional wings. As the humpback whale functions in the marine environment in a Reynolds regime similar to some engineered marine systems, the use of tubercles has the potential to enhance the performance of wing-like structures. Specific applications of the tubercles for marine technology include sailboat masts, fans, propellers, turbines, and control surfaces, such as rudders, dive planes, stabilizers, spoilers, and keels.

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8

Chen, Shuling, Yan Liu, Changzhi Han, Shiqiang Yan, and Zhichao Hong. "Numerical Investigation of Turbine Blades with Leading-Edge Tubercles in Uniform Current." Water 13, no. 16 (August 13, 2021): 2205. http://dx.doi.org/10.3390/w13162205.

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Inspired by the tubercles on humpback whale flippers, leading-edge tubercles have been incorporated into the design of wings and turbine blades in an attempt to improve their hydrodynamic performance. Although promising improvements, especially in terms of the stall performance, have been demonstrated in the limited research that exists to date, the effectiveness of the leading-edge tubercles seems to be influenced by the base blade. This paper focuses on the introduction of sinusoidal leading-edge tubercles to a base blade developed from the classic NACA0018 airfoil, and numerically investigates the effectiveness of leading-edge tubercles on the hydrodynamics associated with the blade in uniform current with different attack angles. Both the macroscopic parameters, such as the lift and drag forces, and the micro-scale flow characteristics, including the vortex and flow separation, are analyzed. The results indicate that the leading-edge tubercles brings a significant influence on the hydrodynamic forces acting on the blade when subjected to an attack angle greater than 15°. This study also reveals the important role of the turbulence and flow separation on hydrodynamic loading on the blade and the considerable influence of the tubercles on such micro-scale flow characteristics. Although the conditions applied in this work are relatively ideal (e.g., the blade is fixed in a uniform flow and the end effect is ignored), the satisfactory agreement between the numerical and corresponding experimental data implies that the results are acceptable. This work builds a good reference for our future work on the hydrodynamic performance of tidal turbines which adopt this kind of blade for operating in both uniform and shearing currents.

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9

Zhang, Li Hong, Wei Jie Li, and Ji Xin Yin. "Numerical Simulation of Bionic Wing for Drag Reduction." Advanced Materials Research 602-604 (December 2012): 1761–64. http://dx.doi.org/10.4028/www.scientific.net/amr.602-604.1761.

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According to the presence of the rounded protuberances or tubercles located on the leading edge, a similar leading edge of humpback whale pectoral fin with the “paraganglioma” has been made on the leading edge of NACA63-210 wing, an bionic NACA63-210 airfoil is designed with convex-concaved leading edges, and the 3-dimensional flows around the bionic wing are simulated for the drag reduction purpose.

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10

Xingwei, Zhang, Zhou Chaoying, Zhang Tao, and Ji Wenying. "Numerical study on effect of leading‐edge tubercles." Aircraft Engineering and Aerospace Technology 85, no. 4 (June 28, 2013): 247–57. http://dx.doi.org/10.1108/aeat-feb-2012-0027.

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11

Keerthi, M. C., M. S. Rajeshwaran, Abhijit Kushari, and Ashoke De. "Effect of Leading-Edge Tubercles on Compressor Cascade Performance." AIAA Journal 54, no. 3 (March 2016): 912–23. http://dx.doi.org/10.2514/1.j054452.

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12

Asghar, Asad, Ruben E. Perez, Peter W. Jansen, and W. D. E. Allan. "Application of Leading-Edge Tubercles to Enhance Propeller Performance." AIAA Journal 58, no. 11 (November 2020): 4659–71. http://dx.doi.org/10.2514/1.j058740.

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13

Ng, BF, TH New, and R. Palacios. "Effects of leading-edge tubercles on wing flutter speeds." Bioinspiration & Biomimetics 11, no. 3 (April 12, 2016): 036003. http://dx.doi.org/10.1088/1748-3190/11/3/036003.

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14

Sisinni, Giuseppe, Domenico Pietrogiacomi, and Giovanni Paolo Romano. "Biomimetic Wings." Advances in Science and Technology 84 (September 2012): 72–77. http://dx.doi.org/10.4028/www.scientific.net/ast.84.72.

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An experimental analysis is performed in a wind tunnel on wings with wavy leading edge derived from humpback whale flippers. The major peculiarity of such flippers is given by the presence of several bumps placed along the leading edge, called tubercles, giving rise to a sort of wing with irregular wavy leading edge. Specifically, the important question to be solved is if the tubercles are able to delay wing stall and to attain higher lift in comparison to a standard wing without them. The present investigations employ different measurement techniques in order to evaluate the amount of possible gain, the potential drawbacks and the physics under such a phenomenon.

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15

Hansen, Kristy L., Richard M. Kelso, and Bassam B. Dally. "Performance Variations of Leading-Edge Tubercles for Distinct Airfoil Profiles." AIAA Journal 49, no. 1 (January 2011): 185–94. http://dx.doi.org/10.2514/1.j050631.

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16

Meng, Xuanshi, Afaq Ahmed Abbasi, Huaxing Li, Shiqing Yin, and Yuqi Qi. "Bioinspired Experimental Study of Leading-Edge Plasma Tubercles on Wing." AIAA Journal 57, no. 1 (January 2019): 462–66. http://dx.doi.org/10.2514/1.j057351.

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17

Utama, I. Ketut Aria Pria, Dendy Satrio, Mukhtasor Mukhtasor, Mehmet Atlar, Weichao Shi, Ridho Hantoro, and Giles Thomas. "Numerical simulation of foil with leading-edge tubercle for vertical-axis tidal-current turbine." Journal of Mechanical Engineering and Sciences 14, no. 3 (September 30, 2020): 6982–92. http://dx.doi.org/10.15282/jmes.14.3.2020.02.0547.

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The main disadvantage of the vertical-axis turbine is its low coefficient of performance. The purpose of this work was to propose a method to improve this performance by investigating the hydrodynamic forces and the flow-field of a foil that was modified with a sinusoidal leading-edge tubercle. NACA 63(4)021 was chosen as the original foil since it has a symmetrical profile that is suitable for use on a vertical-axis tidal-current turbine. The study was conducted using a numerical simulation method with ANSYS-CFX Computational Fluid Dynamics (CFD) code to solve the incompressible Reynolds-Averaged Navier-Stokes (RANS) equations. Firstly, the simulation results of the original foil were validated with available experimental data. Secondly, the modified foils, with three configurations of tubercles, were modelled. From the simulation results, the tubercle foils, when compared with the original foil, had similar lift performances at low Angles of Attack (0-8 degrees of AoA), lower lift performances at medium AoA (8-19 degrees) and higher lift performances at high AoA (19-32 degrees). A tubercle foil with Height/Chord (H/C) of 0.05 can maintain the static stall condition until 32 degrees. Therefore, a vertical-axis turbine with tubercle-blades provides an opportunity to increase its performance by extending the operational range for extracting energy in the dynamic stall condition.

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18

Aftab, Syed Mohammed Aminuddin, and Kamarul Arifin Ahmad. "NACA 4415 Wing Modification Using Tubercles - A Numerical Analysis." Applied Mechanics and Materials 629 (October 2014): 30–35. http://dx.doi.org/10.4028/www.scientific.net/amm.629.30.

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In this work, the characteristic design of the humpback whale flippers is incorporated and investigated on NACA 4415 airfoil at very low Mach number. The effect of Tubercle Leading Edge on NACA4415 airfoil has been studied. This novel study attempts to mimic the effect of tubercles on the airfoil wing to improve lift and delay stall. The results showed significant improvement in aerodynamic performance of TLE when compared to CW. TLE, in comparison to wing with vortex generators, performed better. An improvement in lift by about 13.6% was obtained contrary to only 6.3% increase in case of VG under same Reynolds number. In addition, it was also observed that incorporation of tubercles further delayed stall and continued to produce lift at high angle of attacks.

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19

Owen, Miles, and Abdelkader Frendi. "Towards the Understanding of Humpback Whale Tubercles: Linear Stability Analysis of a Wavy Flat Plate." Fluids 5, no. 4 (November 19, 2020): 212. http://dx.doi.org/10.3390/fluids5040212.

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The results from a temporal linear stability analysis of a subsonic boundary layer over a flat plate with a straight and wavy leading edge are presented in this paper for a swept and un-swept plate. For the wavy leading-edge case, an extensive study on the effects of the amplitude and wavelength of the waviness was performed. Our results show that the wavy leading edge increases the critical Reynolds number for both swept and un-swept plates. For the un-swept plate, increasing the leading-edge amplitude increased the critical Reynolds number, while changing the leading-edge wavelength had no effect on the mean flow and hence the flow stability. For the swept plate, a local analysis at the leading-edge peak showed that increasing the leading-edge amplitude increased the critical Reynolds number asymptotically, while the leading-edge wavelength required optimization. A global analysis was subsequently performed across the span of the swept plate, where smaller leading-edge wavelengths produced relatively constant critical Reynolds number profiles that were larger than those of the straight leading edge, while larger leading-edge wavelengths produced oscillating critical Reynolds number profiles. It was also found that the most amplified wavenumber was not affected by the wavy leading-edge geometry and hence independent of the waviness.

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20

Kemali, Harun, Ahmet Ziya Saydam, and Şebnem Helvacıoğlu. "Investigation of the Effect of Leading Edge Tubercles on Wingsail Performance." Journal of ETA Maritime Science 8, no. 1 (2020): 54–65. http://dx.doi.org/10.5505/jems.2020.60490.

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21

Shi, Weichao, Roslynna Rosli, Mehmet Atlar, Rosemary Norman, Dazheng Wang, and Wenxian Yang. "Hydrodynamic performance evaluation of a tidal turbine with leading-edge tubercles." Ocean Engineering 117 (May 2016): 246–53. http://dx.doi.org/10.1016/j.oceaneng.2016.03.044.

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22

Miklosovic, D. S., M. M. Murray, L. E. Howle, and F. E. Fish. "Leading-edge tubercles delay stall on humpback whale (Megaptera novaeangliae) flippers." Physics of Fluids 16, no. 5 (May 2004): L39—L42. http://dx.doi.org/10.1063/1.1688341.

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23

Kim, Heesu, Jooha Kim, and Haecheon Choi. "Flow structure modifications by leading-edge tubercles on a 3D wing." Bioinspiration & Biomimetics 13, no. 6 (October 26, 2018): 066011. http://dx.doi.org/10.1088/1748-3190/aae6fc.

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24

Zhang, Man, and Abdelkader Frendi. "Effect of airfoil leading edge waviness on flow structures and noise." International Journal of Numerical Methods for Heat & Fluid Flow 26, no. 6 (August 1, 2016): 1821–42. http://dx.doi.org/10.1108/hff-04-2015-0143.

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Purpose – The tubercles at the leading edge of Humpback Whale flippers have been shown to increase aerodynamic efficiency. The purpose of this paper is to compute the flow structures and noise signature of a NACA0012 airfoil with and without leading edge waviness, and located in the wake of a cylinder using the hybrid RANS-LES method. Design/methodology/approach – The mean flow Mach number is 0.2 and the angle of attack used is 2°. After benchmarking the method using existing experimental results, unsteady computations were then carried-out on both airfoil geometries and for a 2° angle of attack. Findings – Results from these computations confirmed the aerodynamic benefits of the leading edge waviness. Moreover, the wavy leading edge airfoil was found to be at least 4 dB quieter than its non-wavy counterpart. In-depth analysis of the computational results revealed that the wavy leading edge airfoil breaks up the large coherent structures which are then convected at higher speeds down the trough region of the waviness in agreement with previous experimental observations. This result is supported by both the two-point and space-time correlations of the wall pressure. Research limitations/implications – The limitations of the current findings reside in the fact that both the Reynolds number and the flow Mach number are low, therefore not applicable to aircrafts. In order to extend the study to practical aircrafts one needs huge grids and large computational resources. Practical implications – The results obtained here could have a huge implications on the design of future aircrafts and spacecrafts. More specifically, the biggest benefit from such redesign is the reduction of acoustic signature as well as increased efficiency in fuel consumption. Social implications – Reducing acoustic signature from aircrafts has been a major research thrust for NASA and Federal Aviation Administration. The social impact of such reduction would be improved quality of life in airport communities. For military aircrafts, this could results in reduced detectability and hence saving lives. Originality/value – Humpback Whales have been studied by various researchers to understand the effects of leading edge “tubercles” on flow structures. What is new in this study is the numerical confirmation of the effects of the tubercles on the flow structures and the resulting noise radiations. It is shown through the use of two-point correlations and space-time correlations that the flow structures in the trough area are indeed vortex tubes.

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25

Butt, Fahad Rafi, and Tariq Talha. "Numerical Investigation of the Effect of Leading-Edge Tubercles on Propeller Performance." Journal of Aircraft 56, no. 3 (May 2019): 1014–28. http://dx.doi.org/10.2514/1.c034845.

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26

Ni, Zao, Manhar Dhanak, and Tsung-chow Su. "Performance Characteristics of Airfoils with Leading-Edge Tubercles and an Internal Slot." AIAA Journal 57, no. 6 (June 2019): 2394–407. http://dx.doi.org/10.2514/1.j058145.

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27

Kumar, Vivek V., and Dilip A. Shah. "Application of Tubercles in Wind Turbine Blades: A Review." Applied Mechanics and Materials 867 (July 2017): 254–60. http://dx.doi.org/10.4028/www.scientific.net/amm.867.254.

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Due to the rapid depletion of conventional energy resources like fossil fuels and their harmful effects on the environment, there is an urgent need to seek alternative and sustainable energy sources. Wind energy is considered as one of the efficient source of energy which can be converted to useful form of energy like electrical energy. Though the field of wind engineering has developed in the recent era there is still scope for improvement in the effective utilization of energy. Energy efficiency in wind turbine is largely determined by the aerodynamics of the turbine blades and the characteristics of the turbulent fluid flow. The objective of this paper is to have a review on the improvement of Horizontal Axis Wind Turbine (HAWT) blade design by incorporating biomimetics into blades. Biomimetics is the field of science in which we adapt designs from nature to solve modern problems. The morphology of the wing-like flipper of the humpback whale (Megaptera novaeangliae) has potential for aerodynamic applications. Instead of straight leading edges like that of conventional hydrofoils, the humpback whale flipper has a number of sinusoidal rounded bumps, called tubercles arranged periodically along the leading edge. The presence of tubercles modifies the flow over the blade surface, creating vortices between the tubercles. These vortices interact with the flow over the tubercle and accelerate that flow, helping to maintain a partially attached boundary layer. This aerodynamic effect can delay stall to higher angles of attack, increase lift and reduce drag compared to the post-stall condition of conventional airfoils. The modified airfoil is characterized by a superior lift/drag ratio (L/D ratio) due to greater boundary layer attachment from vortices energizing the boundary layer.

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28

Baghdad, Mohammed, Abdelkader Nehmar, and Ahmed Ouadha. "Numerical simulation of the flow over a tubercled wing." MATEC Web of Conferences 307 (2020): 01036. http://dx.doi.org/10.1051/matecconf/202030701036.

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The objective of the present study is to carry out a numerical study of the flow around a NACA0021 modified wing by the incorporation of sinusoidal tubercles on its leading edge at a Reynolds number equal to 225,000. The SST k-ω turbulence model is used as closure to the incompressible governing equations. Runs have been performed for several attack angles. Results show that for lower angles of attack, tubercles reduce the drag coefficient with a slight increase in lift.

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29

Sudhakar, S., N. Karthikeyan, and P. Suriyanarayanan. "Experimental Studies on the Effect of Leading-Edge Tubercles on Laminar Separation Bubble." AIAA Journal 57, no. 12 (December 2019): 5197–207. http://dx.doi.org/10.2514/1.j058294.

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30

Stark, Callum, and Weichao Shi. "Hydroacoustic and hydrodynamic investigation of bio-inspired leading-edge tubercles on marine-ducted thrusters." Royal Society Open Science 8, no. 9 (September 2021): 210402. http://dx.doi.org/10.1098/rsos.210402.

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Underwater radiated noise (URN) has a negative impact on the marine acoustic environment where it can disrupt marine creature's basic living functions such as navigation and communication. To control the ambient ocean noise levels due to human activities, international governing bodies such as the International Maritime Organization (IMO) have issued non-mandatory guidelines to address this issue. Under such framework, the hydroacoustic performance of marine vehicles has become a critical factor to be evaluated and controlled throughout the vehicles' service life in order to mitigate the URN level and the role humankind plays in the ocean. This study aims to apply leading-edge (LE) tubercles of the humpback whales’ pectoral fins to a benchmark ducted propeller to investigate its potential in noise mitigation. This was conducted using CFD, where the high-fidelity improved delayed detached eddy simulations (IDDES) in combination with the porous Ffowcs-Williams Hawkings (FW-H) acoustic analogy was used to solve the hydrodynamic flow field and propagate the generated noise to the far-field. It has been found that the LE tubercles have shown promising noise mitigation capabilities in the far-field, where the OASPL at J = 0.1 was reduced to a maximum of 3.4 dB with a maximum of 11 dB reduction in certain frequency ranges at other operating conditions. Based on detailed flow analysis researching the fundamental vortex dynamics, this noise reduction is shown to be due to the disruption of the coherent turbulent wake structure in the propeller slipstream causing the acceleration in the dissipation of turbulence and vorticity-induced noise.

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31

Shi, Weichao, Mehmet Atlar, Rosemary Norman, Batuhan Aktas, and Serkan Turkmen. "Numerical optimization and experimental validation for a tidal turbine blade with leading-edge tubercles." Renewable Energy 96 (October 2016): 42–55. http://dx.doi.org/10.1016/j.renene.2016.04.064.

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32

Sudhakar, S., N. Karthikeyan, and L. Venkatakrishnan. "Influence of leading edge tubercles on aerodynamic characteristics of a high aspect-ratio UAV." Aerospace Science and Technology 69 (October 2017): 281–89. http://dx.doi.org/10.1016/j.ast.2017.06.031.

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33

Lu, Yu, Ziying Li, Xin Chang, Zhenju Chuang, and Junhua Xing. "An aerodynamic optimization design study on the bio-inspired airfoil with leading-edge tubercles." Engineering Applications of Computational Fluid Mechanics 15, no. 1 (January 1, 2021): 293–313. http://dx.doi.org/10.1080/19942060.2020.1856723.

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34

Kim, Jae Wook, Sina Haeri, and Phillip F. Joseph. "On the reduction of aerofoil–turbulence interaction noise associated with wavy leading edges." Journal of Fluid Mechanics 792 (March 3, 2016): 526–52. http://dx.doi.org/10.1017/jfm.2016.95.

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An aerofoil leading-edge profile based on wavy (sinusoidal) protuberances/tubercles is investigated to understand the mechanisms by which they are able to reduce the noise produced through the interaction with turbulent mean flow. Numerical simulations are performed for non-lifting flat-plate aerofoils with straight and wavy leading edges (denoted by SLE and WLE, respectively) subjected to impinging turbulence that is synthetically generated in the upstream zone (free-stream Mach number of 0.24). Full three-dimensional Euler (inviscid) solutions are computed for this study thereby eliminating self-noise components. A high-order accurate finite-difference method and artefact-free boundary conditions are used in the current simulations. Various statistical analysis methods, including frequency spectra, are implemented to aid the understanding of the noise-reduction mechanisms. It is found with WLEs, unlike the SLE, that the surface pressure fluctuations along the leading edge exhibit a significant source-cutoff effect due to geometric obliqueness which leads to reduced levels of radiated sound pressure. It is also found that there exists a phase interference effect particularly prevalent between the peak and the hill centre of the WLE geometry, which contributes to the noise reduction in the mid- to high-frequency range.

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35

ZHANG, RI-KUI, JIE-ZHI WU, and SHI-YI CHEN. "A NEW ACTIVE CONTROL STRATEGY FOR WIND-TURBINE BLADES UNDER OFF-DESIGN CONDITIONS." International Journal of Modern Physics: Conference Series 19 (January 2012): 283–92. http://dx.doi.org/10.1142/s2010194512008872.

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A new active control strategy for wind-turbine blades under off-design conditions has been investigated in this paper. According to our previous work, in comparison with the traditional straight leading-edge blade, a new kind of bionic blades with a sinusoidal leading edge can significantly enhance the turbine's power output at high speed inflows. However, the wavy leading-edge shape is unfavorable under the design operating conditions since an early boundary-layer separation is inevitable for a wind-turbine blade because of the geometric disturbances of the leading-edge tubercles. But for the present active control, the deflect in wavy leading-edge blades can be eliminated by introducing a series of small flat delta wings as the control units, since delta wings can also generate powerful leading-edge vortices. As a preliminary test, our numerical results show that, the shaft-torque fluctuation in the turbine's stall region can be improved from 27.8% for a straight leading-edge blade (no control) to 8.9% for the present active control; and by adjusting the control parameters, the control units nearly have not any negative effect on the blade's shaft torque under the design conditions. We believe that, as an auxiliary tool of the conventional control strategies, the present active control approach may be favorable to generate a more stable and more controllable power output for wind turbines under all operating conditions (even in the yawed inflows).

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36

Ni, Zao, Tsung-chow Su, and Manhar Dhanak. "An empirically-based model for the lift coefficients of twisted airfoils with leading-edge tubercles." AIP Advances 8, no. 4 (April 2018): 045123. http://dx.doi.org/10.1063/1.5023103.

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37

Shi, Weichao, Mehmet Atlar, and Rosemary Norman. "Detailed flow measurement of the field around tidal turbines with and without biomimetic leading-edge tubercles." Renewable Energy 111 (October 2017): 688–707. http://dx.doi.org/10.1016/j.renene.2017.04.053.

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38

Zheng, Tan, Xiao-Qing Qiang, Jin-Fang Teng, and Jin-Zhang Feng. "Study on the behavior of streamwise vortices formed between leading edge tubercles in a compressor cascade." Journal of Theoretical and Applied Mechanics 57, no. 3 (July 15, 2019): 617–29. http://dx.doi.org/10.15632/jtam-pl/109708.

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39

Wei, Zhaoyu, T. H. New, and Y. D. Cui. "An experimental study on flow separation control of hydrofoils with leading-edge tubercles at low Reynolds number." Ocean Engineering 108 (November 2015): 336–49. http://dx.doi.org/10.1016/j.oceaneng.2015.08.004.

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40

Wei, Zhaoyu, B. Zang, T. H. New, and Y. D. Cui. "A proper orthogonal decomposition study on the unsteady flow behaviour of a hydrofoil with leading-edge tubercles." Ocean Engineering 121 (July 2016): 356–68. http://dx.doi.org/10.1016/j.oceaneng.2016.05.043.

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41

Wei, Zhaoyu, T. H. New, Lian Lian, and Yanni Zhang. "Leading-edge tubercles delay flow separation for a tapered swept-back wing at very low Reynolds number." Ocean Engineering 181 (June 2019): 173–84. http://dx.doi.org/10.1016/j.oceaneng.2019.04.018.

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42

Papadopoulos, Charalampos, Vasilis Katsiadramis, and Kyros Yakinthos. "Numerical 3D study on the influence of spanwise distribution of tubercles on wings for UAV applications." MATEC Web of Conferences 304 (2019): 02014. http://dx.doi.org/10.1051/matecconf/201930402014.

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In this work, a 3D numerical study on the influence of the spanwise distribution of tubercles for UAV applications is presented. The idea of using tubercles in aeronautics comes from the humpback whale (Megaptera novaeangliae) which has a characteristic flipper, with a spanwise scalloped leading edge, creating an almost sinusoidal shape, consisting of bumps called tubercles. Early experimental research showed a great potential in enhancing the 3D aerodynamic characteristics of a wing. Most of the existing experimental results concern infinite wings (2D) models and are accompanied with substantial loss in lift and increase in drag in pre–stall region. On the other hand, finite models (3D) have displayed a better overall aerodynamic performance (increased lift and moment, but also decreased drag). At a range of Reynolds number between 500,000 and 1,000,000 (based on the mean chord of the flipper), tubercles act as virtual fences, introducing a pair of counter rotating vortices that delays the stall of the flipper, a phenomenon that the whales use to perform sharp turns and catch their prey. The aforementioned Reynolds number range is the same as the operational Reynolds number for typical Unmanned Aerial Vehicles (UAV). To assess the influence of the tubercles installation on UAV wings, a full 3D computational study is carried-out, with the use of CFD tools that at a first phase are validated and calibrated with available in the literature experimental data. Then, computations are performed, for different spanwise tubercles distributions. The results show that there is a noticeable potential on controlling the flow on the wings of a UAV operating in a Reynolds number range between 500,000 and 1,000,000 (based on UAV’s wing mean chord), which can lead to an aerodynamic performance and efficiency increase.

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Elsheikh, Mogeeb Elrahman. "Highly Flexible Wind Turbine Blades Utilizing Corrugated Surface Hinges." Coatings 11, no. 6 (May 26, 2021): 635. http://dx.doi.org/10.3390/coatings11060635.

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An anthropomorphic wind turbine blade was the suggested design that had a flexure hinge at root, middle, and tip regions. The inter-distances of the flexure hinges follow the Fibonacci sequence and resembled the natural finger through binding. Therefore, the present study designs various corrugated flexure hinges. NACA0012 is chosen as the basic airfoil for designing the corrugated flexure hinges with different geometrical profiles and leading edges. The designs are based on morphing technology and the main geometrical parameters of the corrugation, the pitch distance along the span and the height, are inspired by tubercles of the whale flippers. The study uses the finite element method to define the significant strength characteristics of each design flap-wise, edge-wise, torsional stiffness, and buckling resistance in order to assign the best fit corrugation profile for each region of the blade.

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Stark, Callum, Weichao Shi, and Mehmet Atlar. "A numerical investigation into the influence of bio-inspired leading-edge tubercles on the hydrodynamic performance of a benchmark ducted propeller." Ocean Engineering 237 (October 2021): 109593. http://dx.doi.org/10.1016/j.oceaneng.2021.109593.

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45

Chávez-Modena, M., J. L. Martínez, J. A. Cabello, and E. Ferrer. "Simulations of Aerodynamic Separated Flows Using the Lattice Boltzmann Solver XFlow." Energies 13, no. 19 (October 2, 2020): 5146. http://dx.doi.org/10.3390/en13195146.

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We present simulations of turbulent detached flows using the commercial lattice Boltzmann solver XFlow (by Dassault Systemes). XFlow’s lattice Boltzmann formulation together with an efficient octree mesh generator reduce substantially the cost of generating complex meshes for industrial flows. In this work, we challenge these meshes and quantify the accuracy of the solver for detached turbulent flows. The good performance of XFlow when combined with a Large-Eddy Simulation turbulence model is demonstrated for different industrial benchmarks and validated using experimental data or fine numerical simulations. We select five test cases: the Backward-facing step the Goldschmied Body the HLPW-2 (2nd High-Lift Prediction Workshop) full aircraft geometry, a NACA0012 under dynamic stall conditions and a parametric study of leading edge tubercles to improve stall behavior on a 3D wing.

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46

Taheri, Arash. "HYDRODYNAMIC ANALYSIS OF BIONIC CHIMERICAL WING PLANFORMS INSPIRED BY MANTA RAY EIDONOMY." Indonesian Journal of Engineering and Science 2, no. 3 (September 8, 2021): 011–29. http://dx.doi.org/10.51630/ijes.v2i3.25.

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In this paper, inspired by the external morphology of a manta ray (Mobula alfredi), four chimerical wing planforms are designed to assess its gliding performance. The planforms possess an arbitrary combination of extra hydrodynamic features like tubercles at the leading edge (L.E.) and trailing edge (T.E.) inspired by humpback whale's flippers and flukes, respectively, as longitudinal ridges inspired by whale shark's economy. In addition, another planform is designed to investigate the possible effects of manta ray's injuries (geometric deficiency) generated by predator's attacks or boat strikes on its locomotion (gliding) performance. In this regard, turbulent flow physics involved in the problem is numerically simulated at different angles of attack (AoA). High Reynolds number, 106, corresponding to the swimming of a juvenile manta ray at an average speed equals one m/s. The results show that the manta ray-inspired planform with L.E. undulations exhibits a superior performance at high AoAs than its other counterpart variants. In addition, the results demonstrate that injuries on the manta ray's body can noticeably modify hydrodynamics and, as a result corresponding hydrodynamical forces and moments acting on the swimming animal in the gliding phase.

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47

Feng, Feng, Xiang Ru Cheng, Xiang Yang Qi, and Xin Chang. "Hydrodynamic Performance of Leading-Edge Tubercle Three-Dimensional Airfoil." Applied Mechanics and Materials 152-154 (January 2012): 1509–15. http://dx.doi.org/10.4028/www.scientific.net/amm.152-154.1509.

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Based on RANS method, this paper studied leading-edge tubercle three-dimensional airfoil, which had effect on hydrodynamic performance of three-dimensional airfoil. Both section configurations of the two three-dimensional airfoil models were NACA0020 airfoil. The research method was numerical simulation. First, the leading-edge profile of the first airfoil model was normal. To get stalling angle of the first model, it analyzed hydrodynamic performance of the first model under different angle of attacks at Re=1.35*105. Then, the second model had a sinusoidal leading-edge profile. The second model chose the same Reynolds number. By comparison the numerical calculation results between the first and the second model, the stalling angle of second model delays 3°than the normal airfoil, and the lift coefficient of the second model increases 11.92% than the normal model. The results have laid the foundation for optimization design of leading-edge tubercle three-dimensional airfoil.

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48

Serson, Douglas, Julio R. Meneghini, and Spencer J. Sherwin. "Direct numerical simulations of the flow around wings with spanwise waviness." Journal of Fluid Mechanics 826 (August 10, 2017): 714–31. http://dx.doi.org/10.1017/jfm.2017.475.

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The use of spanwise waviness in wings has been proposed in the literature as a possible mechanism for obtaining improved aerodynamic characteristics, motivated by the tubercles that cover the leading edge of the pectoral flippers of the humpback whale. We investigate the effect of this type of waviness on the incompressible flow around infinite wings with a NACA0012 profile, using direct numerical simulations employing the spectral/hp method. Simulations were performed for Reynolds numbers of $Re=10\,000$ and $Re=50\,000$, considering different angles of attack in both the pre-stall and post-stall regimes. The results show that the waviness can either increase or decrease the lift coefficient, depending on the particular $Re$ and flow regime. We observe that the flow around the wavy wing exhibits a tendency to remain attached behind the waviness peak, with separation restricted to the troughs, which is consistent with results from the literature. Then, we identify three important physical mechanisms in this flow. The first mechanism is the weakening of the suction peak on the sections corresponding to the waviness peaks. This characteristic had been observed in a previous investigation for a very low Reynolds number of $Re=1000$, and we show that this is still important even at $Re=50\,000$. As a second mechanism, the waviness has a significant effect on the stability of the separated shear layers, with transition occurring earlier for the wavy wing. In the pre-stall regime, for $Re=10\,000$, the flow around the baseline wing is completely laminar, and the earlier transition leads to a large increase in the lift coefficient, while for $Re=50\,000$, the earlier transition leads to a shortening of the separation bubble which does not lead to an increased lift coefficient. The last mechanism corresponds to a sub-harmonic behaviour, with the flow being notably different between subsequent wavelengths. This allows the wing to maintain higher lift coefficients in some portions of the span.

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Aftab, S. M. A., and K. A. Ahmad. "CFD study on NACA 4415 airfoil implementing spherical and sinusoidal Tubercle Leading Edge." PLOS ONE 12, no. 8 (August 29, 2017): e0183456. http://dx.doi.org/10.1371/journal.pone.0183456.

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50

Guo, Chun-yu, Zuo-tian Zhang, Xu-xiang Cao, Tie-cheng Wu, and Yu-min Su. "Numerical and experimental studies of hydrodynamic performance of bionic leading-edge tubercle airfoil." Journal of Hydrodynamics 31, no. 6 (August 30, 2019): 1240–49. http://dx.doi.org/10.1007/s42241-019-0068-3.

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