Numerical Study of Aerodynamic Performance of Airfoil with Variable Curvature Split Flap

Document Type : Regular Article


1 School of Energy and Power Engineering, University of Shanghai for Science and Technology 2, Shanghai, 200093, China

2 Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Hong Kong

3 National Key Laboratory of Science and Technology on Aerodynamic Design and Research, Xi’an, 710072, China



To further improve the lift-rising effect of the attached flap on an airfoil, based on the unique movement pattern of a fluke when a dolphin moves forward, this paper puts forward a novel attached split flap model with variable curvature. The lift-type vertical axis wind turbine's typical blade airfoil NACA 0018 is taken as the research object. First, the aerodynamic performance of the two-dimensional airfoil is simulated based on the SST k-ω turbulence model. The contrast between the simulation and the experimental results proves the correctness of the numerical simulation methods in this paper. Then, the effectiveness of split flap is verified, and the lift-rising principle is briefly analyzed. Finally, the parametric study is carried out based on the flap model with variable curvature proposed in this paper, and the lift-rising principle of the variable curvature split flap is analyzed in detail. The results indicate that, with the rise of the flap's curvature index, the airfoil's lift coefficient (Cl) integrated with the flap gradually increases accordingly and tends to a constant value. The bionic research in this paper can provide a comprehensive reference for the aerodynamic shape design of airfoil trailing edge flap and the further optimization of energy efficiency of rotating machinery or aviation.


Main Subjects

Atalay, K. D., B. Dengiz, T. Yavuz, E. Koç and Y. T. İç (2020). Airfoil–slat arrangement model design for wind turbines in fuzzy environment. Neural Computing and Applications 32, 13931-13939.##
Bénard, N., J. Jolibois and E. Moreau (2009). Lift and drag performances of an axisymmetric airfoil controlled by plasma actuator. Journal of Electrostatics 67(2), 133-139.##
Bianchini, A., F. Balduzzi, D. Di Rosa and G. Ferrara (2019). On the use of Gurney Flaps for the aerodynamic performance augmentation of Darrieus wind turbines. Energy Conversion and Management 184, 402-415.##
Daróczy, L., M. H. Mohamed, G. Janiga and D. Thévenin (2014). Analysis of the effect of a slotted flap mechanism on the performance of an H-Darrieus turbine using CFD. In Turbo Expo: Power for Land, Sea, and Air, American Society of Mechanical Engineers.##
Duong, N. T., M. Kashitani, M. Taguchi, K. Kusunose and Y. Takita (2020). Study on Aerodynamic Characteristics of Supersonic Biplane installed Split Flap by Wake Measurement. In AIAA Scitech 2020 Forum, Orlando, America, 0536.##
Fatahian, E., A. L. Nichkoohi, H. Salarian and J. Khaleghinia (2019). Comparative study of flow separation control using suction and blowing over an airfoil with/without flap. Sādhanā 44(11), 220.##
Feero, M. A., P. Lavoie and P. E. Sullivan (2017). Influence of synthetic jet location on active control of an airfoil at low Reynolds number. Experiments in Fluids 58(8), 99.##
Fish, F. E., T. M. Williams, E. Sherman, Y. E. Moon, V. Wu and T. Wei (2018). Experimental measurement of dolphin thrust generated during a tail stand using DPIV. Fluids 3(2), 33.##
Huang, S., Y. Hu and Y. Wang (2021). Research on aerodynamic performance of a novel dolphin head-shaped bionic airfoil. Energy 214, 118179.##
Kaul, U. K. and N. T. Nguyen (2014). Drag optimization study of variable camber continuous trailing edge flap (VCCTEF) using OVERFLOW. In 32nd AIAA Applied Aerodynamics Conference, Atlanta, America.##
Kim, N., M. Han, A. Iakovleva, H. Park, W. Chu and S. Ahn (2020). Hybrid Composite Actuator with Shape Retention Capability for Morphing Flap of Unmanned Aerial Vehicle (UAV). Composite Structures 112227.##
Kral, L. D. (2000). Active flow control technology. ASME Fluids Engineering Technical Brief 1-28.##
Kulhánek, R., Z. Pátek, P. Vrchota, P. Procházka and V. Uruba (2020). Experimental and CFD study of slotted Krueger flaps aerodynamics in critical locations. International Journal of Numerical Methods for Heat and Fluid Flow 31(2), 618-628.##
Kumar, Y., M. Paraschivoiu and I. Paraschivoiu (2010). Low reynolds number vertical axis wind turbine for mars. Wind Engineering 34(4), 461-476.##
Li, C. X., C. Zhang, R. X. Zhang and X. M. Ye (2020). Effect of gurney flap on performance and aeroacoustics of variable-pitch axial fans. AIAA Journal 58(6), 2546-2559.##
Liebeck, R. H. (1978). Design of subsonic airfoils for high lift. Journal of Aircraft 15(9), 547-561.##
Liu, Y. and L. Tan (2018). Method of C groove on vortex suppression and energy performance improvement for a NACA0009 hydrofoil with tip clearance in tidal energy. Energy 155, 448-461.##
Melton, L. P., N. W. Schaeffler, C. Yao and A. Seifert (2005). Active control of flow separation from supercritical airfoil leading-edge flap shoulder. Journal of Aircraft 42(5), 1142-1149.##
Pawsey, N. C. K. (2002). Development and Evaluation of Passive Variable-Pitch Vertical Axis Wind Turbines. Ph. D. Thesis, University of New South Wales, Sydney, Australia.##
Post, M. L. and T. C. Corke (2006). Separation control using plasma actuators: dynamic stall vortex control on oscillating airfoil. AIAA journal 44(12), 3125-3135.##
Schaefer, L. (2008). Fin structure and function.
Urnes, J. and N. Nguyen (2013). A mission adaptive variable camber flap control system to optimize high lift and cruise lift to drag ratios of future n+3 transport aircraft. In 51st AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, Dallas, America, 0214.##
Velasco, D., O. L. Mejia and S. Laín (2017). Numerical simulations of active flow control with synthetic jets in a Darrieus turbine. Renewable Energy 113, 129-140.##
Wang, H., B. Zhang, Q. Qiu and X. Xu (2017). Flow control on the NREL S809 wind turbine airfoil using vortex generators. Energy 118, 1210-1221.##
Wang, Y., G. Li, S. Shen, D. Huang and Z. Zheng (2018). Influence of an off-surface small structure on the flow control effect on horizontal axis wind turbine at different relative inflow angles. Energy 160, 101-121.##
Weick, F. E. and R. C. Platt (1933). Wind-tunnel tests on model wing with fowler flap and specially developed leading-edge slot. NASA Technical Reports Server 1-30.##
Zhang, L., J. Gu, K. Hu, H. Zhu, J. Miao, X. Li and Z. Wang (2021). Influences of trailing edge split flap on the aerodynamic performance of vertical axis wind turbine. Energy Science and Engineering 9(1), 101-115.##
Zhang, W., Z. Zhang, Z. Chen and Q. Tang (2017). Main characteristics of suction control of flow separation of an airfoil at low Reynolds numbers. European Journal of Mechanics-B/Fluids 65, 88-97.##
Zhou, Y., L. Hou and D. Huang (2017). The effects of Mach number on the flow separation control of airfoil with a small plate near the leading edge. Computers and Fluids 156, 274-282.##
Zhu, H., W. Hao, C. Li and Q. Ding (2019). Numerical study of effect of solidity on vertical axis wind turbine with Gurney flap. Journal of Wind Engineering and Industrial Aerodynamics 186, 17-31.##