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Journal articles on the topic 'Airfoils'
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1
Giljarhus, K. E. T., G. S. Shariatpanahi, and O. A. Frøynes. "Computational investigation of the aerodynamic performance of reversible airfoils for a bidirectional tidal turbine." IOP Conference Series: Materials Science and Engineering 1201, no. 1 (November 1, 2021): 012003. http://dx.doi.org/10.1088/1757-899x/1201/1/012003.
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Abstract A reversible airfoil is an airfoil that has equal performance when the flow is reversed. Such airfoils are relevant for many different applications, including use in ventilation fans, helicopter rotors, wind turbines and tidal turbines. Compared to traditional airfoils, reversible airfoils have different performance characteristics and have been less explored in the scientific literature. This work investigates the aerodynamic performance of some selected reversible airfoils using computational fluid dynamics. The selected airfoils are based on existing NACA 6 profiles and a profile using B-spline parameterization. The results show reduced performance for the reversible airfoils compared to a unidirectional airfoil. Of the investigated airfoils, the B-spline airfoil has the highest performance, with a maximum aerodynamic efficiency which is 87 % of the unidirectional design.
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Chen, Haotian, Yijun Liu, and Yunuo Zhang. "Research on the Aerodynamic Performance of an Airfoil." Journal of Physics: Conference Series 2469, no. 1 (March 1, 2023): 012029. http://dx.doi.org/10.1088/1742-6596/2469/1/012029.
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Abstract Airfoils provide lift force for planes and keep planes flying in the atmosphere. Different airfoils have distinct performance characteristics based on their shapes, influencing the flying condition of planes and people’s safety. Therefore, an airfoil’s shape must be carefully studied and deliberated on because it’s an engineer’s professional duty to protect people’s safety with engineering knowledge. In this paper, physical and mathematical models are applied to analyze the shape and corresponding characteristics of an airfoil. Models, including Bernoulli’s Equation and Ideal gas Law, are applied, which are fundamental engineering models. Professional computational tools, including Matlab, are also utilized for the accuracy of data and plots and convenience in data analysis. As aeronautics technology keeps developing, more challenges will arise. Based on the data of existing airfoils, this paper also brings some considerations for the future of airfoil designs which are going to need to satisfy more flying conditions and types of aircraft.
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Wang, Quan, Boyang Liu, Cong Hu, Fengyun Wang, and Shuyi Yang. "Aerodynamic shape optimization of H-VAWT blade airfoils considering a wide range of angles of attack." International Journal of Low-Carbon Technologies 17 (December 28, 2021): 147–59. http://dx.doi.org/10.1093/ijlct/ctab092.
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Abstract The current H-type vertical axis wind turbine (VAWT) airfoils are from horizontal axis wind turbine airfoils or symmetry airfoils that are designed at one angle of attack (such as α = 6°) rather than different angles of attack. As a consequence, it cannot, to a certain extent, increase wind power efficiency. Therefore, an optimal method of H-type VAWT blade airfoils in different ranges of angles of attack is presented. It can be expressed by airfoil integrated function. Then, an optimized mathematical model in which the objective function is the average of tangential force coefficients is established. The particle swarm optimization algorithm coupled with RFOIL program is introduced to optimize the H-type VAWT airfoil profiles with high aerodynamic performance. The optimized results show that the new HVAWT-00153 airfoil is more suitable to VAWTs than the other two new airfoils and NACA-0015 airfoil. Besides, by using computational fluid dynamics technology, the superiority of HVAWT-00153 airfoil over NCAC-0015 airfoil is reviewed. The results indicate that the H-type VAWT with new HVAWT-00153 airfoils could exhibit larger torque coefficients and higher power coefficients than that of the original H-type VAWT with NACA-0015 airfoils. The maximum power coefficient can reach 0.362, increased by 8.45% compared with that of the original one. This study has a good guidance to how to design the H-type VAWT airfoils with high wind energy power.
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Chen, Xinying, Xinyu Cheng, and Junlu Tian. "Research on the pressure distribution under different airfoil types of aircraft." Journal of Physics: Conference Series 2441, no. 1 (March 1, 2023): 012005. http://dx.doi.org/10.1088/1742-6596/2441/1/012005.
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Abstract Airfoils produce life force for aircraft, which is the reason for planes flying in the sky. The formation of the airfoil depends on its shape, so airfoil designs play an important role in airplane designs. The airfoil design is also prioritized in the process of aircraft design, its speed of creating affecting the progress of the entire project. The goal of airfoil’s design is not simply to create “good” wings, because it does not exist. This means that when airfoils are adapting to a certain airflow or flying condition, their performance might not be satisfied due to environmental variations. Therefore, the application of Computational Fluid Dynamics (CFD) techniques and the Small Disturbance Equation, this study uses python to perform numerical analysis to simulate the surface pressure of the ideal wings under certain flying statues, and then applying a series of algorithms to calculate the shape of the target airfoils, which can find the most suitable airfoil shape under the flying circumstances. According to the researches, the best possible wings satisfying which the pressure below be as larger as possible than the pressure above to produce lift force, is f(x) = k*(x-1)∧4 for downside and f(x) = k*sin(pi(x-1)) for the top. Besides, after a series of calculations, this paper realized that the smaller the k value can be, the better fit it is to an ideal simulated airfoil shape.
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Chen, Ya Qiong, and Yue Fa Fang. "Research on Improved Method of Wind Turbine Airfoil S834 Based on Noise and Aerodynamic Performance." Applied Mechanics and Materials 744-746 (March 2015): 253–58. http://dx.doi.org/10.4028/www.scientific.net/amm.744-746.253.
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In this paper, aerodynamic performance and noise of the wind turbine airfoil are the optimization design goal and based on this, the optimization design method with multi-operating points and multi-objective of the airfoils is built. The Bezier curve is used in parametric modeling of the contour of the airfoil and the general equation for control points is deduced form the discrete points coordinates of the airfoil. The weigh distribution schemes for multi-objective and multi-operating points are integrated designed by treating the NREL S834 airfoil as the initial airfoils. The results show that the lift-to-drag ratio of the optimized airfoils has a improvement around the designed operating angle and the overall noise has a reduction compared with the initial airfoils, which means that the optimized airfoils get a better aerodynamic and acoustic performance.
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Xudong, Wang, Wang Licun, and Xia Hongjun. "An Integrated Method for Designing Airfoils Shapes." Mathematical Problems in Engineering 2015 (2015): 1–12. http://dx.doi.org/10.1155/2015/838674.
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A new method for designing wind turbine airfoils is presented in this paper. As a main component in the design method, airfoil profiles are expressed in a trigonometric series form using conformal transformations and series of polynomial equations. The characteristics of the coefficient parameters in the trigonometric expression for airfoils profiles are first studied. As a direct consequence, three generic airfoil profiles are obtained from the expression. To validate and show the generality of the trigonometric expression, the profiles of the NACA 64418 and S809 airfoils are expressed by the present expression. Using the trigonometric expression for airfoil profiles, a so-called integrated design method is developed for designing wind turbine airfoils. As airfoil shapes are expressed with analytical functions, the airfoil surface can be kept smooth in a high degree. In the optimization step, drag and lift force coefficients are calculated using the XFOIL code. Three new airfoils CQ-A15, CQ-A18, and CQ-A21 with a thickness of 15%, 18%, and 21%, respectively, are designed with the new integrated design method.
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TIAN, WEIJUN, FANGYUAN LIU, QIAN CONG, YURONG LIU, and LUQUAN REN. "STUDY ON AERODYNAMIC PERFORMANCE OF THE BIONIC AIRFOIL BASED ON THE SWALLOW'S WING." Journal of Mechanics in Medicine and Biology 13, no. 06 (December 2013): 1340022. http://dx.doi.org/10.1142/s0219519413400228.
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This paper demonstrates the design of the airfoil of small wind turbines, the bionic airfoil was inspired by the morphology of the swallow's extended wing. The wind tunnel tests on the bionic and standard airfoils NACA4412 were conducted, and the aerodynamic performances of the airfoils were numerically investigated. The results show that the bionic airfoil has better aerodynamic performance, the lift coefficient and lift-drag ratio are larger than those of the NACA4412; with the angle of attack increases, both the bionic and standard airfoils stall, but the stall characteristics of the bionic airfoil are better.
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Zhang, Qing, and Rongrong Xue. "Aerodynamic Exploration of Corrugated Airfoil Based on NACA0030 for Inflatable Wing Structure." Aerospace 10, no. 2 (February 13, 2023): 174. http://dx.doi.org/10.3390/aerospace10020174.
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The flow structures and surface pressure distributions on corrugated airfoils significantly differed from those on a conventional, smooth airfoil. An unsteady, two-dimensional computational simulation was carried out to investigate the flow behavior and associated aerodynamic performance of a group of corrugated airfoils with different levels of waviness at angles of attack from 0° to 20° with an interval of 2° at a low Reynolds number regime (Re = 1.2 × 105) and were quantitatively compared with those of its smooth counterpart. Time-averaged aerodynamic coefficients demonstrated that the corrugated airfoils have a lower lift and higher drag because of trapped vortices in the corrugations. The pressure drag of the corrugated airfoils was greater than that of the smooth airfoil. In contrast, the viscous drag of the corrugated airfoils was smaller than that of the smooth airfoil because the recirculation generated in the corrugation could reduce the viscous drag. The averaged velocity gradient in the boundary layer showed that the thickness of the boundary layer increased significantly for the corrugated airfoils because of recirculating flow caused by the small-standing vortices trapped in the valley of corrugations. The smoother the corrugated surface, the closer the aerodynamic characteristics are to those of the smooth airfoil.
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Zhu, Bao Li, Hui Pen Wu, and Tian Hang Xiao. "Study of Aerodynamic Interactions of Dual Flapping Airfoils in Tandem Configurations." Applied Mechanics and Materials 160 (March 2012): 301–6. http://dx.doi.org/10.4028/www.scientific.net/amm.160.301.
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The unsteady viscous flow fields of dual flapping airfoils in tandem configurations are simulated by a Navier-Stokes Solver based on dynamic deformable hybrid meshes. Aerodynamic interactions of three motion models are studied including flapping fore airfoil with fixed aft airfoil, two airfoils flapping in phase and out-of-phase. The results indicate that the aft airfoil in the wake of the flapping fore airfoil has great influence on the aerodynamic performance. When the fore airfoil flaps with a fixed aft airfoil, the thrust generation and thrust propulsive efficiency were enhanced by 65% and 44% respectively, compared to that of single flapping airfoil. When the two airfoils stoke in phase, the thrust generation is twice over that of single flapping airfoil. However the out-of-phase stroking has relatively much lower thrust.
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Chen, Ya Qiong, Yue Fa Fang, Sheng Guo, and Zhi Hong Chen. "Research on Correction to Fitting Factors of Shape Function and Convergence of Wind Turbine Airfoils." Applied Mechanics and Materials 705 (December 2014): 313–19. http://dx.doi.org/10.4028/www.scientific.net/amm.705.313.
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Based on the functional expression methods of wind turbine airfoils, the method of the correction to parameter factors of shape function by iterative calculation in the principle of making the residual error minimum between the fitting airfoil and the target airfoil is presented in this paper, which makes the fitting precision improved compared with the parametric representation of original airfoils. The method of the correction to parameter factors of shape function proposed in this paper is used for parametric representation of more than 20 kinds of typical airfoils and then the geometric and aerodynamic convergence are intensive studied. The results show that the minimal order of the integrated expression of airfoils is decreased by the proposed method in this paper and the mathematical models of airfoils which facilitate the unification of optimal design are established.
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Migliore, Paul, and Stefan Oerlemans. "Wind Tunnel Aeroacoustic Tests of Six Airfoils for Use on Small Wind Turbines*." Journal of Solar Energy Engineering 126, no. 4 (November 1, 2004): 974–85. http://dx.doi.org/10.1115/1.1790535.
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Aeroacoustic tests of seven airfoils were performed in an open jet anechoic wind tunnel. Six of the airfoils are candidates for use on small wind turbines operating at low Reynolds numbers. One airfoil was tested for comparison to benchmark data. Tests were conducted with and without boundary layer tripping. In some cases, a turbulence grid was placed upstream in the test section to investigate inflow turbulence noise. An array of 48 microphones was used to locate noise sources and separate airfoil noise from extraneous tunnel noise. Trailing-edge noise was dominant for all airfoils in clean tunnel flow. With the boundary layer untripped, several airfoils exhibited pure tones that disappeared after proper tripping was applied. In the presence of inflow turbulence, leading-edge noise was dominant for all airfoils.
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Wang, Quan, Pan Huang, Di Gan, and Jun Wang. "Integrated Design of Aerodynamic Performance and Structural Characteristics for Medium Thickness Wind Turbine Airfoil." Applied Sciences 9, no. 23 (December 2, 2019): 5243. http://dx.doi.org/10.3390/app9235243.
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The currently geometric and aerodynamic characteristics for wind turbine airfoils with the medium thickness are studied to pursue maximum aerodynamic performance, while the interaction between blade stiffness and aerodynamic performance is neglected. Combining the airfoil functional integration theory and the mathematical model of the blade cross-section stiffness matrix, an integrated design method of aerodynamic performance and structural stiffness characteristics for the medium thickness airfoils is presented. The aerodynamic and structural comparison of the optimized WQ-A300 airfoil, WQ-B300 airfoil, and the classic DU97-W-300 airfoil were analyzed. The results show that the aerodynamic performance of the WQ-A300 and WQ-B300 airfoils are better than that of the DU97-W-300 airfoil. Though the aerodynamic performance of the WQ-B300 airfoil is slightly reduced compared to the WQ-A300 airfoil, its blade cross-sectional stiffness properties are improved as the flapwise and edgewise stiffness are increased by 6.2% and 8.4%, respectively. This study verifies the feasibility for the novel design method. Moreover, it also provides a good design idea for the wind turbine airfoils and blade structural properties with medium or large thickness.
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Timmer, W. A., and R. P. J. O. M. van Rooij. "Summary of the Delft University Wind Turbine Dedicated Airfoils." Journal of Solar Energy Engineering 125, no. 4 (November 1, 2003): 488–96. http://dx.doi.org/10.1115/1.1626129.
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This paper gives an overview of the design and wind tunnel test results of the wind turbine dedicated airfoils developed by Delft University of Technology (DUT). The DU-airfoils range in maximum relative thickness from 15% to 40% chord. The first designs were made with the XFOIL code. The computer program RFOIL, which is a modified version of XFOIL featuring an improved prediction around the maximum lift coefficient and the capability of predicting the effect of rotation on airfoil characteristics, has been used to design the airfoils since 1995. The measured effect of Gurney flaps, trailing edge wedges, vortex generators (vg) and trip wires on the airfoil characteristics of various DU-airfoils is presented. Furthermore, a relation between the thickness of the airfoil leading edge and the angle-of-attack for leading edge separation is given.
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Li, Zhao, Guang-jun Yang, Xiao-yan Tong, and Feng Jiang. "A Parametric Design Method for Hybrid Airfoils for Icing Wind Tunnel Test." International Journal of Aerospace Engineering 2021 (April 20, 2021): 1–18. http://dx.doi.org/10.1155/2021/5594077.
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The size of aircraft models that can be tested in icing wind tunnels is limited by the dimensions of the facilities in present; it is an effective method to replace the large model with a hybrid airfoil to carry out the experiment. A design method of multiple control points for hybrid airfoil based on the similarity of flow field in the leading edge of airfoil is proposed. Aiming at generating the full-scale flow field and ice accretion on the leading edge, multiobjective genetic optimization algorithm is used to design the hybrid airfoil under different conditions by combining the airfoil parameterization and solution of spatial constraint. Pressure tests of hybrid airfoils are carried out and compared with the leading edge pressure of the corresponding full-scale airfoils. The design and experimental results show that the pressure coefficient deviation between the hybrid airfoils designed and the corresponding full-scale airfoil in the 15% chord length range of the leading edge is within 4%. Finally, the vortex distribution and ice accretion process of the two airfoils were simulated by the unsteady Reynolds-averaged-Navier–Stokes (URANS) equations and multistep ice numerical method; it is shown that the hybrid airfoil can provide the same vortex distribution and ice accretion with the full-scale airfoil.
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Xu, Rick E., and Zhe Wu. "Numerical Simulation of Flow Over Airfoil and Its Optimization." Journal of Physics: Conference Series 2441, no. 1 (March 1, 2023): 012004. http://dx.doi.org/10.1088/1742-6596/2441/1/012004.
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Abstract Airfoils are one of the most important factors in determining an airplane’s ability to fly. As such, their optimization holds important ramifications for the continual need to improve airplane performance. In this paper, the optimization of airfoil design is explored through numerical computational fluid dynamics. This paper first investigates the effects of Angle of Attack on airfoil lift/drag ratios, which is shown to have a significant influence on the performance of airfoils. Then, the effects from thickness are explored, and it is found that the influence of thickness is highly dependent on the specific shape of airfoil. In addition, in order to further improve airfoil aerodynamic performance, a type of modified airfoil with an additional tip is developed and simulated. The results indicate that airfoils with additional tips can perform better, but only with the proper combination of tip parameter values. For example, the modified airfoil with a tip of 0.03 L length at a 25° tip angle bested that same airfoil without an additional tip. Finally, it is found that the Backpropagation machine-learning algorithm, when trained with prior simulation data, can quickly predict lift and drag coefficients of airfoils. The results in this paper could facilitate the further optimization of airfoil design.
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Sunada, Shigeru, Akitoshi Sakaguchi, and Keiji Kawachi. "Airfoil Section Characteristics at a Low Reynolds Number." Journal of Fluids Engineering 119, no. 1 (March 1, 1997): 129–35. http://dx.doi.org/10.1115/1.2819098.
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The aerodynamic characteristics of airfoils operating at Re = 4 × 103 were examined, varying the parameters related to the airfoil shape such as thickness, camber, and roughness. Airfoils with good aerodynamic performance at this Re have the following shape characteristics: (1) they are thinner than airfoils for higher Re numbers, (2) they have a sharp leading edge, and (3) they have a camber of about five percent with its maximum camber at about mid-chord. The characteristics of airfoils are strongly affected by leading edge vortices. The measured two-dimensional airfoil characteristics indicate that the planform, which greatly affects the flight performance of the three-dimensional wing at high Reynolds numbers, has little effect on the flight performance at this Reynolds number.
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Yokoi, Yoshifumi. "Numerical Experiment of Flow Characteristics of Parallel Arrangement Two Symmetrical Airfoils." Applied Mechanics and Materials 798 (October 2015): 609–14. http://dx.doi.org/10.4028/www.scientific.net/amm.798.609.
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In this study, numerical experiment of flow around the close two airfoils which arranged in parallel with attack angle was performed. The aspect of flow and the instantaneous fluid force act on symmetrical airfoil (NACA0012) with attack angle were investigated using a vortex method at the Reynolds number Re=4.05×105, in ranges of the distance ratio L/c= 0.0, 0.25, 0.50 and 1.0 (here, L/c = 0.0 means single airfoil case) and the attack angle α = 0, 5, 10 and 15 degrees, (here, α =15 degree case is performed on single airfoil case only). As a result of calculations, in the case of two airfoils, the large lift was able to be obtained as compared with the single airfoil, but it was found in it that they are about 1.5 times in the case of single airfoil. And it was shown that the fluid force characteristic of each airfoil of two airfoils differs from the case of single airfoil.
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Gao, Ji, Rui Shan Yuan, Ming Hui Zhang, and Yong Hui Xie. "Numerical Study on Thrust Generation Performance of Plunging Airfoils." Applied Mechanics and Materials 312 (February 2013): 235–38. http://dx.doi.org/10.4028/www.scientific.net/amm.312.235.
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In this paper, the effects of angle of attack, camber and camber location on propulsion performance of flapping airfoils undergoing plunging motion were numerically studied at Re=20000 and h=0.175. The unsteady incompressible viscous flow around four different airfoil sections was simulated applying the dynamic mesh. The results show that the time averaged thrust coefficient CTmean and propulsive efficiency η of the symmetric airfoil decrease with the increasing angle of attack, and the variation of CTmean is more obvious than that of CPmean. Both CTmean and η for NACA airfoils studied in this paper decrease with the increasing camber and the difference between the propulsion performances of different airfoils is not obvious, and the thrust generation and power of various NACA airfoils gradually increase during the downstroke and decrease during the upstroke. Under the same conditions, the airfoil with a further distance between the maximum camber location and the chord of the leading edge leads to higher propulsive efficiency.
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Maleki Dastjerdi, Sajad, Kobra Gharali, Armughan Al-Haq, and Jatin Nathwani. "Application of Simultaneous Symmetric and Cambered Airfoils in Novel Vertical Axis Wind Turbines." Applied Sciences 11, no. 17 (August 30, 2021): 8011. http://dx.doi.org/10.3390/app11178011.
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Two novel four-blade H-darrieus vertical axis wind turbines (VAWTs) have been proposed for enhancing self-start capability and power production. The two different airfoil types for the turbines are assessed: a cambered S815 airfoil and a symmetric NACA0018 airfoil. For the first novel wind turbine configuration, the Non-Similar Airfoils 1 (NSA-1), two NACA0018 airfoils, and two S815 airfoils are opposite to each other. For the second novel configuration (NSA-2), each of the S815 airfoils is opposite to one NACA0018 airfoil. Using computational fluid dynamics (CFD) simulations, static and dynamic conditions are evaluated to establish self-starting ability and the power coefficient, respectively. Dynamic stall investigation of each blade of the turbines shows that NACA0018 under dynamic stall impacts the turbine’s performance and the onset of dynamic stall decreases the power coefficient of the turbine significantly. The results show that NSA-2 followed by NSA-1 has good potential to improve the self-starting ability (13.3%) compared to the turbine with symmetric airfoils called HT-NACA0018. In terms of self-starting ability, NSA-2 not only can perform in about 66.67% of 360° similar to the wind turbine with non-symmetric airfoils (named HT-S815) but the power coefficient of NSA-2 at the design tip speed ratio of 2.5 is also 4.5 times more than the power coefficient of HT-S815; the power coefficient difference between HT-NACA0018 and HT-S815 (=0.231) is decreased significantly when HT-S815 is replaced by NSA-2 (=0.076). These novel wind turbines are also simple.
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Feng, Fang, Shouyang Zhao, Chunming Qu, Yuedi Bai, Yuliang Zhang, and Yan Li. "Research on Aerodynamic Characteristics of Straight-Bladed Vertical Axis Wind Turbine with S Series Airfoils." International Journal of Rotating Machinery 2018 (2018): 1–13. http://dx.doi.org/10.1155/2018/8350243.
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Background. In order to investigate the effect of aerodynamic characteristics of S series airfoils on the straight-bladed vertical axis wind turbine (SB-VAWT), numerical simulations and wind tunnel experiments were carried out using a small SB-VAWT model with three kinds of blade airfoils, which are asymmetric airfoil S809, symmetric airfoil S1046, and NACA0018 used for performance comparison among S series. The aerodynamics characteristics researched in this study included static torque coefficient, out power coefficient, and rotational speed performance. The flow fields of these three kinds of blade under static and dynamic conditions were also simulated and analyzed to explain the mechanism effect of aerodynamic performance. According to the results, the SB-VAWT with airfoil S1046 has better dynamic aerodynamic characteristics than other two airfoils, while the SB-VAWT with airfoil S809 is better in terms of the static characteristics. As the most suitable airfoil for SB-VAWT, the S series airfoil is worth researching deeply.
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Zhao, Liangyu, and Shuxing Yang. "Influence of Thickness Variation on the Flapping Performance of Symmetric NACA Airfoils in Plunging Motion." Mathematical Problems in Engineering 2010 (2010): 1–19. http://dx.doi.org/10.1155/2010/675462.
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In order to investigate the impact of airfoil thickness on flapping performance, the unsteady flow fields of a family of airfoils from an NACA0002 airfoil to an NACA0020 airfoil in a pure plunging motion and a series of altered NACA0012 airfoils in a pure plunging motion were simulated using computational fluid dynamics techniques. The “class function/shape function transformation“ parametric method was employed to decide the coordinates of these altered NACA0012 airfoils. Under specified plunging kinematics, it is observed that the increase of an airfoil thickness can reduce the leading edge vortex (LEV) in strength and delay the LEV shedding. The increase of the maximum thickness can enhance the time-averaged thrust coefficient and the propulsive efficiency without lift reduction. As the maximum thickness location moves towards the leading edge, the airfoil obtains a larger time-averaged thrust coefficient and a higher propulsive efficiency without changing the lift coefficient.
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Bak, Christian, Anders S. Olsen, Andreas Fischer, Oliver Lylloff, Robert Mikkelsen, Mac Gaunaa, Jimmie Beckerlee, et al. "Wind tunnel benchmark tests of airfoils." Journal of Physics: Conference Series 2265, no. 2 (May 1, 2022): 022097. http://dx.doi.org/10.1088/1742-6596/2265/2/022097.
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Abstract This paper describes a benchmark of four airfoils in the Poul la Cour Tunnel (PLCT). The wind tunnel, the corrections used and the method of making adapters for the airfoils are also described. Very good agreement was in general observed between the measurements in PLCT and in other high quality wind tunnels. Some deviations were seen, but they were mainly attributed to the differences in separation on the airfoil. Apart from the benchmarking, this paper also highlights the challenges in testing airfoils in general such as obtaining 2D flow on thick airfoils that inherently shows separated flow and how to make adapters for airfoils tested in other wind tunnels.
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Xie, Huan, and Wei Zeng. "The Design Method of Airfoils for Variable-Pitch Wind Turbines Based on Knowledge Engineering." Advanced Materials Research 1030-1032 (September 2014): 1342–47. http://dx.doi.org/10.4028/www.scientific.net/amr.1030-1032.1342.
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In order to make good use of the previous design knowledge, the knowledge-based engineering ideas were introduced to the design of airfoils for variable-pitch wind turbines, a new design method for airfoil of wind turbine was formed. Firstly, the structure-behavior-function (SBF) model of airfoils design was derived. Secondly, the neural rules for airfoils design of variable-pitch wind turbines were deduced. Thirdly, the design method of airfoils structure for wind turbines based on case-based-reasoning (CBR) was establishment. And the dimensionless model based on case representation was set up, and the algorithm of geometric parameters design for airfoils based on CBR was proposed at last.
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Gigue`re, P., and M. S. Selig. "New Airfoils for Small Horizontal Axis Wind Turbines." Journal of Solar Energy Engineering 120, no. 2 (May 1, 1998): 108–14. http://dx.doi.org/10.1115/1.2888052.
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In a continuing effort to enhance the performance of small wind energy systems, one root airfoil and three primary airfoils were specifically designed for small horizontal axis wind turbines. These airfoils are intended primarily for 1–5 kW variable-speed wind turbines for both conventional (tapered/twisted) or pultruded blades. The four airfoils were wind-tunnel tested at Reynolds numbers between 100,000 and 500,000. Tests with simulated leading-edge roughness were also conducted. The results indicate that small variable-speed wind turbines should benefit from the use of the new airfoils which provide enhanced lift-to-drag ratio performance as compared with previously existing airfoils.
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Duz, Hasan, and Serkan Yildiz. "Numerical Performance Analyses of Different Airfoils for Use in Wind Turbines." International Journal of Renewable Energy Development 7, no. 2 (July 10, 2018): 151–57. http://dx.doi.org/10.14710/ijred.7.2.151-157.
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This study numerically investigated different types of high-performance airfoils in order to increase the efficiency of wind turbines. Performances of five airfoil types were numerically simulated at different attack angles (0 ° <α <20 °) and at different wind speeds (4, 8, 16 and 32 m/s). Numerical analysis shows that all airfoils achieve the highest performance at attack angles between 4o and 7o. Results also show that the performance of all airfoils increases in direct proportion to increase in wind speed with a low gradient. A new hybrid airfoil was generated by combining lower and upper surface coordinates of two high-performance airfoils which achieved the better results in pressure distribution. Numerical analysis shows that the hybrid airfoil profile performs up to 6% better than other profiles at attack angles between 4o and 7o while it follows the maximum performance curves closely at other attack anglesArticle History: Received January 16th 2018; Received in revised form June 5th 2018; Accepted June 15th 2018; Available onlineHow to Cite This Article: Duz, H and Yildiz, S. (2018) Numerical Performance Analyses of Different Airfoils for Use in Wind Turbines. Int. Journal of Renewable Energy Development, 7(2), 151-157.https://doi.org/10.14710/ijred.7.2.151-157
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Reham K. Jaafar, M. A. Abdelrahman, Mina G. Mourad, Adnan A. Ateeq, and M. Moawed. "Modified Trailing Edge Impact on the Aerodynamic Performance of Wind Turbine Airfoil." Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 91, no. 2 (February 11, 2022): 133–44. http://dx.doi.org/10.37934/arfmts.91.2.133144.
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One of the most important factors affecting wind turbine performance is the airfoil. The impact of the NACA 0012 trailing edge design on airfoil performance is investigated numerically in this paper. Computational fluid dynamics calculations are used to design and simulate the airfoils. The thick trailing edge is inclined to various angles to achieve further improvement in the lift/drag ratio and lift coefficient. The results reveal that, when compared with baseline airfoil, all the designed airfoils demonstrated higher lift coefficients. The lift coefficient increases with the angle of the inclined trailing edge. The maximum lift coefficient improvement inclined airfoil is 74%. In addition, the lift/drag ratio increases with the increase of the inclined angle, and the maximum improvement ratio reaches 39.495% for the inclined airfoil with Ꝋ=15º. Any further increase in the inclined angle decreases the lift/drag ratio as a result of drag increase. This study contributes toward the design of efficient wind turbine airfoils.
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Wang, Shunshun, and Zheng Guo. "Robust Optimization of Natural Laminar Flow Airfoil Based on Random Surface Contamination." Applied Sciences 12, no. 17 (August 31, 2022): 8757. http://dx.doi.org/10.3390/app12178757.
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Natural laminar-flow (NLF) airfoils are one of the most promising technologies for extending the range and endurance of aircrafts. However, there is a lack of methods for the optimization of airfoils based on the surface contamination that destroys the laminar flow. In order to solve this problem, a robust optimization process is proposed using the Non-dominated Sorting genetic algorithm- II (NSGA-II) evolutionary algorithm, and Monte Carlo simulation combined with an aerodynamic calculation software Xfoil. Firstly, the airfoil is optimized normally and the aerodynamic performance of optimized airfoil under surface contamination is analyzed. Then, the original airfoil is robustly optimized under random surface contamination based on the assumption that its locations follow triangular and uniform probability distributions. Finally, all the optimized results and original airfoil are compared. It is found that robust optimization reduces the sensitivity of the airfoil to random surface contamination, hence, improving the robustness of the airfoil. The proposed methods make it possible to improve the aerodynamic performance of NLF airfoils considering surface contamination.
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Raj Mohamed, Mohamed Arif, Rajesh Yadav, and Ugur Guven. "Flow separation control using a bio-inspired nose for NACA 4 and 6 series airfoils." Aircraft Engineering and Aerospace Technology 93, no. 2 (January 25, 2021): 251–66. http://dx.doi.org/10.1108/aeat-08-2019-0170.
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Purpose This paper aims to achieve an optimum flow separation control over the airfoil using a passive flow control method by introducing a bio-inspired nose near the leading edge of the National Advisory Committee for Aeronautics (NACA) 4 and 6 series airfoil. In addition, to find the optimised leading edge nose design for NACA 4 and 6 series airfoils for flow separation control. Design/methodology/approach Different bio-inspired noses that are inspired by the cetacean species have been analysed for different NACA 4 and 6 series airfoils. Bio-inspired nose with different nose length, nose depth and nose circle diameter have been analysed on airfoils with different thicknesses, camber and camber locations to understand the aerodynamic flow properties such as vortex formation, flow separation, aerodynamic efficiency and moment. Findings The porpoise nose design that has a leading edge with depth = 2.25% of chord, length = 0.75% of chord and nose diameter = 2% of chord, delays the flow separation and improves the aerodynamic efficiency. Average increments of 5.5% to 6° in the lift values and decrements in parasitic drag (without affecting the pitching moment) for all the NACA 4 and 6 series airfoils were observed irrespective of airfoil geometry such as different thicknesses, camber and camber location. Research limitations/implications The two-dimensional computational analysis is done for different NACA 4 and 6 series airfoils at low subsonic speed. Practical implications This design improves aerodynamic performance and increases the structural strength of the aircraft wing compared to other conventional high lift devices and flow control devices. This universal leading edge flow control device can be adapted to aircraft wings incorporated with any NACA 4 and 6 series airfoil. Social implications The results would be of significant interest in the fields of aircraft design and wind turbine design, lowering the cost of energy and air travel for social benefits. Originality/value Different bio-inspired nose designs that are inspired by the cetacean species have been analysed for NACA 4 and 6 series airfoils and universal optimum nose design (porpoise airfoil) is found for NACA 4 and 6 series airfoils.
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Hassani, M., M. Bazazzadeh, and M. D. Manshadi. "Effects of Splitting Airfoil’s Aspect Ratio on the Control of Separation and Loss Distribution in a Distortion Generator." International Journal of Aerospace Engineering 2022 (July 16, 2022): 1–20. http://dx.doi.org/10.1155/2022/1177112.
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The effects of aspect ratio (AR: opposite diameter to width) reduction on the total pressure loss distribution of horizontally arranged splitting airfoils are investigated experimentally and numerically. The array arrangement of airfoils is proposed as a novel distortion generator mechanism. The upgrade feasibility study of the single airfoil loss repeatability in combined pattern was the aim of the present research. Modification of 90° splitting airfoil as a representative of the airfoils category with AR > 1 was a corrective approach to eliminate or delay the downstream wake axis rotation destructive effects on the combined loss predictability. The results of the modified airfoil (single and multiple arrangements) wake simulations based on hybrid turbulence model demonstrate a good agreement with wind tunnel measurements. It was observed that the aspect ratio reduction below the limiting value of “1” for selected opening angle provides the quasi-2D behavior of downstream flow structure related to AR < 1 airfoil category along with relatively higher value of loss related to AR > 1 category. Elimination of the side separation for modified 90° airfoil and the resulting similarity of maximum loss lobes positioning in arrangement of airfoils lead to the reduction of combined flow structure complexity and the improvement of loss predictability. It has appeared that combined loss pattern of the triple arrangement of the airfoils can be reconstructed from dual arrangement, and it can be reproduced from a single pattern in a hierarchical process. Concerning the maximum loss coefficient “values,” an overprediction of velocity recovery rate was observed in simulation results at the fully developed wake region that led to approximately 15% lower maximum loss values in comparison with the experiments.
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Mikhailov, Yu S., and Yu G. Stepanov. "SIMULATION OF 2D FLOW AROUND OF AIRFOILS AT LOW-SPEED WIND TUNNEL WITH OPEN JET TEST-SECTION." Civil Aviation High TECHNOLOGIES 22, no. 1 (February 27, 2019): 51–62. http://dx.doi.org/10.26467/2079-0619-2019-22-1-51-62.
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At present, there is a great interest in the development of new airfoils for wind turbines and high-lift wings of unmanned aerial vehicles (UAV). The requirements for such airfoils differ from conventional aircraft airfoils, because of structural reasons and extreme operating conditions. So, wind turbine airfoils operate frequently under fully separated flow when stall is used for power regulation at high wind speeds. At the same time design of airfoils for wings UAV poses the problem of availability of high-lift at low Reynolds number. Modern airfoils are to a large extent developed from numerical methods. However, the complex flow conditions such as separation at high angles of attack, laminar separation bubbles and the transition from laminar to turbulent flow are difficult to predict accurately. Hence, testing of airfoils at a two-dimensional condition is an important phase in airfoil design. The development and validation of a 2D testing facility for investigation of single and multi-element airfoils in the wind tunnel Т-102 with open test section are considered in this article. T-102 is a continuous-operation, closed-layout wind tunnel with two reverse channels. The test section has an elliptical cross-section of 4 ×2,33 m and a length of 4 m. Two big flat panels of the L × H=3 ×3,9 m size installed upright on balance frame aligned with the free stream are used for simulating two-dimensional flow in the tunnel test section. The airfoil section in the layout of a rectangular wing is mounted horizontally between flat panels with minimum gaps to ensure 2D flow conditions. The aerodynamic forces and pitch moment acting on the model were measured by wind tunnel balance. To determine boundary corrections for a new test section of wind tunnel, the experimental investigation of three geometrically similar models has been executed. The use of boundary corrections has provided good correlation of the test data of airfoil NACA 6712 with the results obtained from the wind tunnel except for lift and drag coefficient values at high angles of attack.
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Xiao, Qianhao, Jun Wang, Boyan Jiang, Yanyan Ding, and Xiaopei Yang. "Study on Nonlinear Correlation in Modal Coefficients of the Bionic Airfoil." Machines 11, no. 1 (January 10, 2023): 88. http://dx.doi.org/10.3390/machines11010088.
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Applying bionic airfoils is essential in enlightening the design of rotating machinery and flow control. Dynamic mode decomposition was used to reveal the low dimensional flow structure of Riblets, Seagull, and Teal bionic airfoils at low Reynolds numbers 1×105 and is compared with NACA4412 airfoils. The attack angle of the two-dimensional airfoil is 19°, and the SST k-ω turbulence model and ANSYS fluent were used to obtain the transient flow field data. The sparse identification of nonlinear dynamics reveals the nonlinear correlation between modal coefficients and establishes manifold dynamics. The results show that the bionic airfoil and NACA4412 airfoil have the same type of nonlinear correlation, and the dimension and form of the minimum reduced-order model are consistent. The modal coefficients always appear in the manifold equation in pairs with a phase difference of 90°. The dimension of the manifold equation is two-dimensional, and the absolute value of the coefficient corresponds to the fundamental frequency of airfoil vortex shedding. The reconstructed flow field based on the manifold equation is highly consistent with the numerical simulation flow field, which reveals the accuracy of the manifold equation. The relevant conclusions of this study emphasize the unity of the nonlinear correlation of bionic airfoils.
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Al-Jaburi, Khider, and Daniel Feszty. "Fixed and rotary wing transonic aerodynamic improvement via surface-based trapped vortex generators." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 15 (June 12, 2019): 5522–42. http://dx.doi.org/10.1177/0954410019853902.
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A novel passive flow control concept for transonic flows over airfoils is proposed and examined via computational fluid dynamics. The control concept is based on the local modification of the airfoil's geometry. It aims to reduce drag or to increase lift without deteriorating the original lift and/or drag characteristics of the airfoil, respectively. Such flow control technique could be beneficial for improving the range or endurance of transonic aircraft or for mitigating the negative effects of transonic flow on the advancing blades of helicopter rotors. To explore the feasibility of the concept, two-dimensional computational fluid dynamics simulations of a NACA 0012 airfoil exposed to a freestream of Mach 0.7 and Re = 9 × 106 as well as of a NASA SC(3)−0712(B) supercritical airfoil exposed to a freestream of Mach 0.78 and Re = 30 × 106 were conducted. The baseline airfoil simulations were carefully verified and validated, showing excellent agreement with wind tunnel data. Then, 32 various local geometry modifications were proposed and systematically examined, all functioning as a trapped-vortex generator. The surface modifications were examined on both the upper and lower surfaces of the airfoils. The upper surface modifications demonstrated remarkable ability to reduce the strength of the shockwave on the upper surface of the airfoil with only a small penalty in lift. On the other hand, the lower surface modifications could significantly increase the lift-to-drag ratio for the full range of the investigated angles of attack, when compared to the baseline airfoil.
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Tanabi, Naser, Agesinaldo Matos Silva, Marcosiris Amorim Oliveira Pessoa, and Marcos Sales Guerra Tsuzuki. "Robust Algorithm Software for NACA 4-Digit Airfoil Shape Optimization Using the Adjoint Method." Applied Sciences 13, no. 7 (March 28, 2023): 4269. http://dx.doi.org/10.3390/app13074269.
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Optimizing the aerodynamic shape of an airfoil is a critical concern in the aviation industry. The introduction of flexible airfoils has allowed the shape of the airfoil to vary, depending on the flight conditions. Therefore, in this study, we propose an algorithm that is capable of robustly optimizing the shape of the airfoil based on variable parameters of the airfoil and flight conditions. The proposed algorithm can be understood as an optimization method, which employs the adjoint method, a powerful tool for estimating the sensitivity of the model output to the input in numerous studies. From an aerodynamic perspective, the development of shape geometry is a crucial step in airfoil development. The study used NACA-4 digit airfoils as input for the initial assumption and the range of shape change. The optimal shape was found using the proposed algorithm by defining one NACA profile as the initial value and another NACA profile as the limit for the optimized shape, considering the aerodynamic coefficients and flight conditions. However, morphing airfoils have certain deformation limitations. As an innovation in the algorithm, bounds were defined for the shape change during optimization so that the result can be constructed within the capabilities of the morphing wing. These bounds can be adjusted (depending on the capabilities of the airfoils). To validate the proposed algorithm, the study compared it with a previous flow solver for the same airfoil.
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Reuben, Umunna J., Koju Hiraki, and Miyamoto Shohei. "AIRFOIL CONSIDERATIONS IN THE DESIGN OF HIGH PERFORMANCE, LOW REYNOLDS NUMBER PROPELLERS." International Journal of Research -GRANTHAALAYAH 6, no. 9 (September 30, 2018): 373–84. http://dx.doi.org/10.29121/granthaalayah.v6.i9.2018.1250.
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A propeller was designed using 2D airfoil data obtained from a panel method numeric code. The propeller was designed to operate at 75% chord based Reynolds number of 20k. At low Reynolds numbers <40k, there are no publicly available 2D airfoil force data largely because of inherent difficulty in their measurement. Theoretical prediction of the propeller’s peak efficiency was 0.67 while experiment results was 0.58. To improve the propeller efficiency by using better performing airfoils, six (6) airfoils of varying thickness and camber were studied. Three of the six airfoils were chosen and used in the design of three propellers - a single airfoil for each propeller design. The propellers were designed to operate at Reynolds number of 30k at 0.75 radius and the 2D airfoil force data used for the designs were obtained from a numeric code. Theoretical predictions of efficiency were all > 81% in each of the designed propellers.
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MA, Tuliang, Hairun XIE, and Jing WANG. "Pressure Distribution Prediction of Supercritical Airfoils at Multiple Flight Conditions Using Deep Learning Approach." Journal of Physics: Conference Series 2292, no. 1 (June 1, 2022): 012012. http://dx.doi.org/10.1088/1742-6596/2292/1/012012.
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Abstract Supercritical airfoils are commonly found in modern civil airplanes. Effective access to pressure distribution around an airfoil under various flight situations is vital for enhancing the quality of supercritical airfoils. With the rapid development of deep learning, the rise of neural networks has provided new powerful tools for obtaining pressure distribution quickly. This paper proposed a deep learning based model to predict the surface pressure distribution around a supercritical airfoil under multiple flight conditions. The airfoil geometry parameters and various flight conditions are taken as input, and the corresponding surface pressure distributions are taken as output. The statistical results show that the proposed method is accurate and generalized in predicting pressure distributions around supercritical airfoils. Our method, in particular, achieves accurate prediction results over the double shock or strong shock area, demonstrating its superiority in handling complex flows.
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Zhang, Yang, Bo Pang, Xiankai Li, and Gang Chen. "Aerodynamic Shape Optimization with Grassmannian Shape Parameterization Method." Energies 15, no. 20 (October 19, 2022): 7722. http://dx.doi.org/10.3390/en15207722.
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The conventional method of optimizing the aerodynamic performance of an airfoil heavily depends on the confines of the design space. The design variables create a non-normalized space that is fragmented into several different clusters of airfoils. An approach that is data-driven and deforms airfoils over a Grassmannian submanifold is utilized in the work that is being presented here. The affine deformation, which includes camber and thickness, can be uncoupled from the method that is currently in use, and the operations that are performed on the airfoil shape can be made smooth enough to prevent unreasonable shapes from being produced. The CST method is also a part of the current study so that a comparison can be made between the two. A new method to describe the airfoil geometries over the Grassmannian space was generated using a dataset that contained 7007 different shapes of airfoils. These two methods are used to parameterize the subsonic (NACA0012) and transonic (RAE2822) airfoils, and the new method cuts the number of design variables from twelve to six, resulting in a reduction in overall complexity. The findings demonstrate that the new method maintains a high degree of consistency regardless of the flow conditions.
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Ho, WH, and TH New. "Unsteady numerical investigation of two different corrugated airfoils." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 231, no. 13 (December 16, 2016): 2423–37. http://dx.doi.org/10.1177/0954410016682539.
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An unsteady, two-dimensional numerical study was conducted to investigate the aerodynamic and flow characteristics of two bio-inspired corrugated airfoils at Re = 14,000 and compared with those of a smooth NACA0010 airfoil. Mean aerodynamic results reveal that the corrugated airfoils have better lift performance compared to the NACA0010 airfoil but incur slightly higher drag penalty. Mean flow streamlines indicate that this favourable performance is due to the ability of the corrugated airfoils in mitigating large-scale flow separations and stall. Unsteady flow field results show persistent formations of small recirculating vortices that remain within the corrugations at 10° angle-of-attack or less for one of the corrugated airfoil and below 15° for the other. In contrast, the flow behaviour can be highly turbulent with regular pairings of large-scale flow separation vortices along the upper surface at higher angles-of-attack. This not only disrupts the small recirculating vortices and causes them to detach from the corrugated surfaces, but it gets increasingly dominant at higher angles-of-attack resulting in regular lift and drag oscillations. At the end of each cycle, there is a sudden ejection of flow perpendicular to the airfoil surface and these disruptions manifest themselves as “kinks” in the instantaneous lift and drag of the corrugated airfoils. Therefore instead of regular fluctuations, the lift and drag curves have additional undulations. Despite that, the corrugations are able to produce larger pressure differentials between the upper and lower surfaces than the smooth airfoil. The current study demonstrates the intricate relationships between different sharp surface corrugations and favourable aerodynamic performance. In particular, results from this paper supports earlier investigations that corrugated airfoils may be used to good effects even at low Reynolds numbers, where flow separations are more likely.
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Akbari, Vahid, Mohammad Naghashzadegan, Ramin Kouhikamali, and Wahiba Yaïci. "Comparative Study of the Blade Number and Airfoil Profile Impacts on the Twist/Chord Distribution of a Small Wind Turbine Blade." International Journal of Energy Research 2023 (August 18, 2023): 1–23. http://dx.doi.org/10.1155/2023/8164273.
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The blade number and airfoil profile effects on the blade shape of a small horizontal-axis wind turbine (SHWT) were investigated. For this purpose, the NACA4412, SG6042, and SG6043 airfoils, as well as 2, 3, and 4 blades, were considered. Then, two optimization processes were used: first, the blades were designed to maximize the power coefficient ( C p ), and then a multiobjective optimization that included both maximizing C p and maximizing the starting torque ( Q s ) was employed. The differential evolution (DE) algorithm was employed to perform the optimization, and the blade element momentum aerodynamic approach was used to conduct the relevant computations. Also, to ensure the performance of the optimal blades, the computational fluid dynamics method was employed as well. The findings revealed that regardless of the number of blades and the type of airfoil, raising the twist angle ( θ p ) and chord length ( c ) along the radial direction of the blade, especially at the root part, helps increase the Q s . It was observed that increasing the number of blades does not have a significant effect on the θ p distribution of the selected airfoils, but the c of the blades fitted with all three airfoils decreases. Regardless of the number of blades, while the geometry of blades utilizing the NACA4412 and SG6042 airfoils are close to each other, the blade with the SG6043 airfoil has the shortest c , which reduces the generated Q s of blades fitted with this airfoil. The results also establish that by increasing the number of blades from 2 to 3, the power coefficient ( C p ) of the blades fitted with all three airfoils increases, but by further increasing the number of blades from 3 to 4, the change in C p completely depends on the airfoil profile.
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Virk, Muhammad S. "Effect of Wind Turbine Blade Profile Symmetry on Ice Accretion." Applied Mechanics and Materials 863 (February 2017): 229–34. http://dx.doi.org/10.4028/www.scientific.net/amm.863.229.
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A multiphase numerical study has been carried out to understand the effects of wind turbine blade profile (airfoil) symmetry on resultant ice accretion. Two symmetric (NACA 0006 & 0012) and two non-symmetric airfoils (NACA 23012 & N-22) were used for this preliminary study. Based upon the airflow field calculations and super cooled water droplets collision efficiency, the rate and shape of accreted ice was simulated for rime ice conditions. Analysis showed higher air velocity along top surface of the non-symmetric airfoils as compared to symmetrical airfoils that also effects the droplet behavior and resultant ice growth. Results show that change in blade profile symmetry effects the resultant ice accretion. For symmetric airfoils, more streamlines ice shapes were observed along leading edge as compared to non- symmetric airfoils.
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Shi, Yayun, Xiayu Lan, Yiwen Wang, Tihao Yang, and Yan Liu. "Data Mining-Based Design Space Exploration and Optimization for Tandem Airfoils." International Journal of Aerospace Engineering 2023 (May 22, 2023): 1–18. http://dx.doi.org/10.1155/2023/3513507.
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The joined-wing configuration has great technical appeal for the development of next-generation SensorCraft. Research based on the simplified tandem airfoil system can improve understanding of the joined-wing configuration’s aerodynamic characteristics. We combine the adjoint-based aerodynamic shape optimization and self-organizing map- (SOM-) based data mining technology to reveal the flow interactions of tandem airfoils and aerodynamic characteristics from the perspective of the entire aerodynamic design space. The SOM is used to explore the correlation between relative position parameters and aerodynamic force coefficients of tandem airfoil systems. Results show that the drag coefficient at the defined range of lift coefficients has obviously positive linear correlation and greatly dependents on the value of decalage. The tandem airfoils with negative decalage around -2.7° have the smallest drag coefficients. Due to variations in the aerodynamic interaction strength, the drag coefficient of each airfoil changes from a linear law to a nonlinear law as airfoils approach each other. We then perform single-point aerodynamic shape optimization based on two sets of relative position parameters with different aerodynamic interaction strengths, and 1.8% and 1.28% drag reductions are obtained, respectively. Based on optimized airfoils, the SOM is used to reveal the distribution of drag variation in the design space constructed by relative position parameters. Results illustrate that the aerodynamic interference strength between the front and rear airfoils significantly affects the drag reduction mechanism, which results in the different distribution patterns of drag variation in design space.
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Caboni, Marco, Koen Boorsma, and Stoyan Kanev. "Development of thick airfoils for outboard sections and investigation into their application for large rotors." Wind Engineering 42, no. 3 (October 19, 2017): 177–93. http://dx.doi.org/10.1177/0309524x17736480.
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The use of thick airfoils toward the outboard part of horizontal axis wind turbine blades is a promising concept to reduce the cost of wind energy. In fact, thick airfoils have higher area moments of inertia than those of thin airfoils, normally employed toward the outboard part of the blade. Replacing thin airfoils with thicker ones would therefore allow one to improve the structural properties of the blade, reducing the mass needed to ensure its structural integrity. Conventional thick airfoils, however, are generally characterized by worse aerodynamic performance with respect to those of thin airfoils, which make them less attracting for their use toward the outboard part of the blade. The research reported in this paper deals with the development of an optimization system for the aerodynamic design of thick airfoils, aiming to improve their aerodynamic performance, and therefore making them more suitable for their usage toward the outboard part of the blade. In order to determine the effect of the use of thick airfoils towards outboard sections, a blade design incorporating a newly designed 30% thick airfoil is assessed both statically and dynamically. The results showed that mass reduction can be achieved with the use of ad hoc optimized thick airfoils with limited penalty in power production.
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Tang, Hui, Yulong Lei, Xingzhong Li, Ke Gao, and Yanli Li. "Aerodynamic Shape Optimization of a Wavy Airfoil for Ultra-Low Reynolds Number Regime in Gliding Flight." Energies 13, no. 2 (January 17, 2020): 467. http://dx.doi.org/10.3390/en13020467.
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The effect of the number of waves and the width of the ridge and valley in chord direction for a wavy airfoil was investigated at the angle of attack of 0 ∘ and Reynolds number of 10 3 through using the two-dimensional direct numerical simulation for four kinds of wavy airfoil shapes. A new method for parameterizing a wavy airfoil was proposed. In comparison with the original corrugated airfoil profile, the wavy airfoils that have more distinct waves show a lower aerodynamic efficiency and the wavy airfoils that have less distinct waves show higher aerodynamic performance. For the breakdown of the lift and drag concerning the pressure stress and friction stress contributions, the pressure stress component is significantly dominant for all wavy airfoil shapes concerning the lift. Concerning the drag, the pressure stress component is about 75 % for the wavy airfoils that have more distinct waves, while the frictional stress component is about 70 % for the wavy airfoils that have less distinct waves. From the distribution of pressure isoline and streamlines around wavy airfoils, it is confirmed that the pressure contributions of the drag are dominant due to high pressure on the upstream side and low pressure on the downside; the frictional contribution of the drag is dominant due to large surface areas of the airfoil facing the external flow. The effect of the angle of attack on the aerodynamic efficiency for various wavy airfoil geometries was studied as well. Aerodynamic shape optimization based on the continuous adjoint approach was applied to obtain as much as possible the highest global aerodynamic efficiency wavy airfoil shape. The optimal airfoil shape corresponds to an increase of 60 % and 62 % over the aerodynamic efficiency and the lift from the initial geometry, respectively, when optimal airfoil has an approximate drag coefficient compared to the initial geometry. Concerning an fixed angle of attack, the optimal airfoil is statically unstable in the range of the angle of attack from − 1 ∘ to 6 ∘ , statically quasi-stable from − 6 ∘ to − 2 ∘ , where the vortex is shedding at the optimal airfoil leading edge. Concerning an angle of attack passively varied due to the fluid force, the optimal airfoil keeps the initial angle of attack value with an initial disturbance, then quickly increases the angle of attack and diverges in the positive direction.
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Korakianitis, T. "Hierarchical Development of Three Direct-Design Methods for Two-Dimensional Axial-Turbomachinery Cascades." Journal of Turbomachinery 115, no. 2 (April 1, 1993): 314–24. http://dx.doi.org/10.1115/1.2929237.
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The direct and inverse blade-design iterations for the selection of isolated airfoils and gas turbine blade cascades are enormously reduced if the initial blade shape has performance characteristics near the desirable ones. This paper presents the hierarchical development of three direct blade-design methods of increasing utility for generating two-dimensional blade shapes. The methods can be used to generate inputs to the direct- or inverse-blade-design sequences for subsonic or supersonic airfoils for compressors and turbines, or isolated airfoils. The examples included for illustration are typical modern turbine cascades, and they have been designed by the direct method exclusively. The first method specifies the airfoil shapes with analytical polynomials. It shows that continuous curvature and continuous slope of curvature are necessary conditions to minimize the possibility of flow separation, and to lead to improved blade designs. The second method specifies the airfoil shapes with parametric fourth-order polynomials, which result in continuous-slope-of-curvature airfoils, with smooth Mach number and pressure distributions. This method is time consuming. The third method specifies the airfoil shapes by using a mixture of analytical polynomials and mapping the airfoil surfaces from a desirable curvature distribution. The third method provides blade surfaces with desirable performance in very few direct-design iterations. In all methods the geometry near the leading edge is specified by a thickness distribution added to a construction line, which eliminates the leading edge overspeed and laminar-separation regions. The blade-design methods presented in this paper can be used to improve the aerodynamic and heat transfer performance of turbomachinery cascades, and they can result in high-performance airfoils in very few iterations.
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Athul Krishna, S., and MR Aswin. "Comparative study over double wedge and biconvex airfoils for laminar flow using CFD." Journal of Physics: Conference Series 2272, no. 1 (July 1, 2022): 012003. http://dx.doi.org/10.1088/1742-6596/2272/1/012003.
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Abstract This paper is mainly focused on Supersonic Laminar Flow at Mach 3 for biconvex and double wedge airfoils. The coefficient of lift (Cl), coefficient of drag (Cd), and coefficient of moment along the respective airfoils are being analysed. The geometry of these is generated using the Designmodeler of ANSYS. Further, meshing is also achieved by ANSYS with around 50000 nodes which is satisfactory for the current flow analysis. The total number of iterations being set for the particular simulation is 1000. This article covers the approach of the Kutta-Joukowski theorem, from which we know that flow circulation impacts the lift of the airfoil and how it changes for biconvex and double wedge airfoils. Decisively, this paper delivers provides pressure, heat transfer, and velocity distribution for both the airfoils. This paper gives a comparative study of both the double wedge and the biconvex airfoils at MACH 3, zero angle of attack. The study will be analysing both the airfoils in 3D as well as in 2D.
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Abdessemed, Chawki, Yufeng Yao, Abdessalem Bouferrouk, and Pritesh Narayan. "Morphing airfoils analysis using dynamic meshing." International Journal of Numerical Methods for Heat & Fluid Flow 28, no. 5 (May 8, 2018): 1117–33. http://dx.doi.org/10.1108/hff-06-2017-0261.
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Purpose The purpose of this paper is to use dynamic meshing to perform CFD analyses of a NACA 0012 airfoil fitted with a morphing trailing edge (TE) flap when it undergoes static and time-dependent morphing. The steady CFD predictions of the original and morphing airfoils are validated against published data. The study also investigates an airfoil with a hinged TE flap for aerodynamic performance comparison. The study further extends to an unsteady CFD analysis of a dynamically morphing TE flap for proof-of-concept and also to realise its potential for future applications. Design/methodology/approach An existing parametrization method was modified and implemented in a user-defined function (UDF) to perform dynamic meshing which is essential for morphing airfoil unsteady simulations. The results from the deformed mesh were verified to ensure the validity of the adopted mesh deformation method. ANSYS Fluent software was used to perform steady and unsteady analysis and the results were compared with computational predictions. Findings Steady computational results are in good agreement with those from OpenFOAM for a non-morphing airfoil and for a morphed airfoil with a maximum TE deflection equal to 5 per cent of the chord. The results obtained by ANSYS Fluent show that an average of 6.5 per cent increase in lift-to-drag ratio is achieved, compared with a hinged flap airfoil with the same TE deflection. By using dynamic meshing, unsteady transient simulations reveal that the local flow field is influenced by the morphing motion. Originality/value An airfoil parametrisation method was modified to introduce time-dependent morphing and used to drive dynamic meshing through an in-house-developed UDF. The morphed airfoil’s superior aerodynamic performance was demonstrated in comparison with traditional hinged TE flap. A methodology was developed to perform unsteady transient analysis of a morphing airfoil at high angles of attack beyond stall and to compare with published data. Unsteady predictions have shown signs of rich flow features, paving the way for further research into the effects of a dynamic flap on the flow physics.
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Liao, Yan Ping, Li Liu, and Teng Long. "Investigation of Various Parametric Geometry Representation Methods for Airfoils." Applied Mechanics and Materials 110-116 (October 2011): 3040–46. http://dx.doi.org/10.4028/www.scientific.net/amm.110-116.3040.
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Abstract—This paper presents the investigation of typical parametric geometry representation methods for airfoils, namely, PARSEC method, orthogonal basis function method and CST method. The investigation assesses the fitting accuracy of these parametric methods for various airfoils including the symmetric airfoil, cambered airfoil and supercritical airfoil. The design variables of these parametric methods are solved by the methods of least squares fit. The fitting results show that the fitting accuracy of CST method is better than other parametric methods for airfoil. The aerodynamics analysis models of these typical parametric geometry representation methods for airfoil are constructed. The pressure distributions calculated for different parametric methods are compared with the corresponding experimental pressure distributions for the actual airfoil geometry.Keywords-orthogonal basis function; PARSEC; CST; fitting accuracy; pressure distributions
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Chen, Qing Yuan, Feng Lin Guo, and Jin Quan Xu. "Applications of a Coupled Methodology to the Wind Turbine Airfoils." Advanced Materials Research 516-517 (May 2012): 572–76. http://dx.doi.org/10.4028/www.scientific.net/amr.516-517.572.
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In this study, a coupled methodology is proposed for the aerodynamic behavior of wind turbine airfoils. The idea is to combine a Navier-Stokes solver with a free vortex model. The zone for the calculation of CFD is confined to the surrounding of the airfoil, whilst the free vortex model accounts for the far field of the airfoil. The flow around the airfoil is assumed to be two-dimensional (2D) incompressible fully turbulent flow, which is modeled by two equation turbulence models. The computed aerodynamic coefficients are presented for two wind turbine airfoils and compared with wind tunnel data.
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Chen, Hai, Lei He, Weiqi Qian, and Song Wang. "Multiple Aerodynamic Coefficient Prediction of Airfoils Using a Convolutional Neural Network." Symmetry 12, no. 4 (April 3, 2020): 544. http://dx.doi.org/10.3390/sym12040544.
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Both symmetric and asymmetric airfoils are widely used in aircraft design and manufacture, and they have different aerodynamic characteristics. In order to improve flight performance and ensure flight safety, the aerodynamic coefficients of these airfoils must be obtained. Various methods are used to generate aerodynamic coefficients. The prediction model is a promising method that can effectively reduce cost and time. In this paper, a graphical prediction method for multiple aerodynamic coefficients of airfoils based on a convolutional neural network (CNN) is proposed. First, a transformed airfoil image (TAI) was constructed by using the flow-condition convolution with the airfoil image. Next, TAI was combined with the original airfoil image to form a composite airfoil image (CAI) that is used as the input of the CNN prediction model. Then, the structure and parameters of the prediction model were designed according to CAI features. Finally, a sample set that was generated on the basis of the deformation of symmetrical airfoil NACA 0012 was used to train and test the prediction model. Simulation results showed that the proposed method based on CNN could simultaneously predict the pitch-moment, drag, and lift coefficients, and prediction accuracy was high.
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Gardner, A. D., K. Richter, H. Mai, A. R. M. Altmikus, A. Klein, and C. H. Rohardt. "Experimental Investigation of Dynamic Stall Performance for the EDI-M109 and EDI-M112 Airfoils." Journal of the American Helicopter Society 58, no. 1 (January 1, 2013): 1–13. http://dx.doi.org/10.4050/jahs.58.012005.
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An experimental investigation of the dynamic performance of two new rotor blade airfoils was undertaken in a transonic wind tunnel. The EDI-M109 and EDI-M112 airfoils were tested at 0.3 ≤ M≤ 0.5 for pitching motions with amplitude 0.5° ≤ α± ≤8° and frequencies 3.3 Hz ≤ f ≤ 45 Hz. The results show the dynamic stall performance of both new airfoils, and the effect of frequency, amplitude, and higher order pitching motion on these results is described. The pitching moment peak size was found to have an approximately linear correlation to the normalized mean angular velocity, and thus test cases with the same maximum angle of attack and oscillation frequency had similar dynamic stall qualities. The correlation between low aerodynamic damping for high-frequency, low-amplitude pitching motion, and poor dynamic stall performance is shown to be low. The pitching moment peak of the EDI-M112 airfoil is shown to be smaller for M = 0.3 and 0.4, and peak for the EDI-M109 airfoil is lower at M = 0.5. The dynamic performance of the airfoils is compared to the OA209.
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Zhang, Qiang, and Phillip M. Ligrani. "Wake Turbulence Structure Downstream of a Cambered Airfoil in Transonic Flow: Effects of Surface Roughness and Freestream Turbulence Intensity." International Journal of Rotating Machinery 2006 (2006): 1–12. http://dx.doi.org/10.1155/ijrm/2006/60234.
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The wake turbulence structure of a cambered airfoil is studied experimentally, including the effects of surface roughness, at different freestream turbulence levels in a transonic flow. As the level of surface roughness increases, all wake profile quantities broaden significantly and nondimensional vortex shedding frequencies decrease. Freestream turbulence has little effect on the wake velocity profiles, turbulence structure, and vortex shedding frequency, especially downstream of airfoils with rough surfaces. Compared with data from a symmetric airfoil, wake profiles produced by the cambered airfoils also have significant dependence on surface roughness, but are less sensitive to variations of freestream turbulence intensity. The cambered airfoil also produces larger streamwise velocity deficits, and broader wakes compared to the symmetric airfoil.