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Influence of Flap Parameters on the Aerodynamic Performance of a Wind-Turbine airfoil

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Fluid Dynamics & Materials Processing 2024年第4期20卷 771-786页

作者： Yuanjun Dai Jingan Cui Baohua Li Cong Wang Kunju Shi Mechanical College Shanghai DianJi UniversityShanghai201306China College of Energy Engineering Xinjiang Institute of TechnologyUrumqi830091China

A numerical method has been used to analyze the flow field related to a NACA 0015 airfoil with and without a flap and assess the influence of the flap height and angle on the surface pressure coefficient,lift coefficient,and drag coefficient.The numerical results demonstrate that the flap can effectively improve the lift coefficient of the airfoil;however,at small attack angles,its influence is significantly reduced.When the angle of attack exceeds the critical stall angle and the flap height is 1.5%of the chord length,the influence of the flap becomes very evident.As the flap height increases,the starting point of the separation vortex gradually moves forward and generates a larger wake vortex.Optimal aerodynamic characteristics are obtained for 1.5%(of the chord length)flap height and a 45°flap angle;in this case,the separation vortex is effectively reduced.

关键词： airfoil flap height flap angle lift-drag ratio aerodynamic characteristics

Mechanism of the electromagnetic force to control hydrodynamic noise from an airfoil model and its action mode

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Chinese Journal of Acoustics 2024年第2期43卷 173-198页

作者： LIU Yongwei WANG Lu QIN Qikai ZHENG Penghui SHANG Dejiang National Key Laboratory of Underwater Acoustic Technology Harbin Engineering UniversityHarbin 150001 Key Laboratory of Marine Information Acquisition and Security(Harbin Engineering University) Ministry of Industry and Information TechnologyHarbin 150001 College of Underwater Acoustic Engineering Harbin Engineering UniversityHarbin 150001

A method is proposed to control the flow and reduce the hydrodynamic noise by applying the constant electromagnetic force into the boundary layer. The flow and sound fields from an airfoil model with and without the electromagnetic force are calculated. Results show that along the flow direction, electromagnetic force can delay the flow separation on the airfoil surface, suppress small discrete vortices, reduce turbulent fluctuation pressure on the airfoil surface, and decrease the hydrodynamic noise. The change law of the hydrodynamic noise effect reduced by the electromagnetic force is summarized in terms of the Reynolds number, attack angle, and electromagnetic effective parameters.Based on the numerical calculation results, an actual model is experimentally measured in the water circulating tank to validate the abovementioned effect. Since the transition area pressure of the airfoil model is the lowest and the area is limited, the application of electromagnetic force into this area can achieve the lowest noise effect and decrease the power consumption. The effect of the magnetic leak is analyzed. The results provide a new method for the suppression of hydrodynamic noise in airfoil models.

关键词： airfoil noise flow

Experimental investigation of shock-buffet criteria on a pitching airfoil

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Chinese Journal of Aeronautics 2022年第7期35卷 179-191页

作者： Mehran MASDARI Aghil ZEINALZADEH Mohammad Ali ABDI Mohammad Reza SOLTANI Faculty of New Sciences and Technologies University of TehranTehran ***Iran Department of Aerospace Engineering Sharif University of TechnologyTehran 11365-11155Iran Department of Aeronautical and Astronomical Engineering University of WashingtonSeattleWAUSA

An experimental investigation of the shock-buffet phenomenon subject to unsteady pitching supercritical airfoil around its quarter chord has been conducted in a transonic wind tunnel.The model was equipped with pressure taps connected to the fast response pressuretransducers.Measurements were conducted at different free-stream Mach number from 0.61 to0.76.The principle goal of this investigation was to experimentally discuss the shock-buffet criterion over a SC(2)-0410 supercritical pitching related to the hysteresis loops of total drag and trailing edge pressure,the behaviour of the shock wave foot location,the pressure distribution over the upper surface,and by implementing the wavelet analysis of the normal force.To ensure capturing the buffet phenomenon by utilizing these criteria,a pressure port has been drilled exactly at the trailing edge of the airfoil where its output was used to detect the buffet phenomenon for different conditions.Visual representation of the flow using the shadow graph flow visualization technique for different test cases is further used to illustrate the unsteady shock wave motion.A comparative analysis of experimental measurements shows that the conducted criteria confirm each other when the buffet phenomenon occurs at the position of the oscillating cycle.

关键词： airfoil Buffeting Experimental analysis Hysteresis loops Pitching motion Shock wave Wavelet analysis

Interactive Effects of Wind Tunnel Sidewalls on Flow Structures around 2D airfoil Model

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Journal of Thermal Science 2023年第2期32卷 708-717页

作者： BAI Jingyan ZHANG Lei YANG Ke ZHAO Daiqing XU Jianzhong Guangzhou Institute of Energy Conversion Chinese Academy of SciencesGuangzhou 510650China Institute of Engineering Thermophysics Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China Key laboratory of CAS for Wind Utility Chinese Academy of SciencesBeijing 100190China

This paper presents the effect of wind tunnel sidewalls on the wind turbine airfoils with experimental and numerical methods.The test is carried out in a low-speed wind tunnel at Re=2.62×10^(5).Pressures acting on the airfoil surface are measured by a multiport pressure device.And,the oil flow visualization technique is used to investigate the flow field characteristics of the airfoil surface.Then,a numerical simulation was conducted with the measurement results.As a result,it is clarified the flow structures on the airfoil surface depend strongly on the angles of attack and the sidewalls.At small angles of attack,the three-dimensional separation caused by the interaction between the sidewall boundary layer and the airfoil boundary layer is very small,and only appears near the junction of the airfoil model and the sidewall.This corner separation becomes large with the increase of the angle of attack.At the middle part of the testing model,the boundary layer flow evolves into three-dimensional separation,i.e.,stall cell,when the separation develops to an appreciate extent.The stall phenomenon will further spread from the center line to sidewalls with the increase of the angle of attack;and then,its development will be limited by the sidewall boundary layer separation.Comparably,the simulation shows that the sidewall make the pressure coefficient Cpdecrease,and proper boundary condition can maintain two-dimensional flow at large angles of attack by eliminating the influence of corner vortices.

关键词： airfoil experiment sidewall corner vortex stall cell airfoil-wall junction

Design and Structure Optimization of Plenum Chamber with airfoil Baffle to Improve Its Outlet Velocity Uniformity in Heat Setting Machines

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Journal of Donghua University(English Edition) 2023年第5期40卷 515-524页

作者：钱淼魏鹏郦林子杰向忠胡旭东 Zhejiang Provincial Key Lab of Modern Textile Machinery School of Mechanical EngineeringZhejiang Sci-Tech UniversityHangzhou 310018China

The plenum chamber of a heat setting machine is a key structure for distributing hot air to different air channels.Its outlet velocity uniformity directly determines the heating uniformity of textiles,significantly affecting the heat setting performance.In a traditional heat setting machine,the outlet airflow maldistribution of the plenum chamber still exists.In this study,a novel plenum chamber with an airfoil baffle was established to improve the uniformity of the velocity distribution at the outlet in a heat setting machine.The structural influence of the plenum chamber on the velocity distribution was investigated using a computational fluid dynamics program.It was found that a chamber with a smaller outlet partition thickness had a better outlet velocity uniformity.The structural optimization of the plenum chamber was conducted using the particle swarm optimization algorithm.The outlet partition thickness,the transverse distance and the longitudinal distance of the optimized plenum chamber were 20,686.2 and 274.6 mm,respectively.Experiments were carried out.The experimental and simulated results showed that the optimized plenum chamber with an airfoil baffle could improve the outlet velocity uniformity.The air outlet velocity uniformity index of the optimized plenum chamber with an airfoil baffle was 4.75%higher than that of the plenum chamber without an airfoil baffle and 5.98%higher than that of the conventional chamber with a square baffle in a commercial heat setting machine.

关键词： velocity distribution uniformity structure optimization numerical simulation airfoil plenum chamber heat setting

Leading-edge flow separation control over an airfoil using a symmetrical dielectric barrier discharge plasma actuator

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Chinese Journal of Aeronautics 2019年第5期32卷 1190-1203页

作者： Xin ZHANG Huaxing LI Yong HUANG Kun TANG Wanbo WANG School of Aeronautics Northwestern Polytechnical University Low Speed Aerodynamics Institute China Aerodynamics Research and Development Center

In order to promote an in-depth understanding of the mechanism of leading-edge flow separation control over an airfoil using a symmetrical Dielectric Barrier Discharge(DBD) plasma actuator excited by a steady-mode excitation, an experimental investigation of an SC(2)-0714 supercritical airfoil with a symmetrical DBD plasma actuator was performed in a closed chamber and a low-speed wind tunnel. The plasma actuator was mounted at the leading edge of the airfoil.Time-resolved Particle Image Velocimetry(PIV) results of the near-wall region in quiescent air suggested that the symmetrical DBD plasma actuator could induce some coherent structures in the separated shear layer, and these structures were linked to a dominant frequency of f0= 39 Hz when the peak-to-peak voltage of the plasma actuator was 9.8 kV. In addition, an analysis of flow structures without and with plasma actuation around the upper side of the airfoil at an angle of attack of18° for a wind speed of 3 m/s(Reynolds number Re = 20000) indicated that the dynamic process of leading-edge flow separation control over an airfoil could be divided into three stages. Initially, this plasma actuator could reinforce the shedding vortices in the separated shear layer. Then, these vortical structures could deflect the separated flow towards the wall by promoting the mixing between the outside flow with a high kinetic energy and the flow near the surface. After that, the plasma actuator induced a series of rolling vortices in the vicinity of the suction side of the airfoil, and these vortical structures could transfer momentum from the leading edge of the airfoil to the separated region, resulting in a reattachment of the separated flow around the airfoil.

关键词： airfoil Dielectric Barrier Discharge(DBD) Flow control Particle Image Velocimetry(PIV) Plasma actuator

Numerical simulation of airfoil flows with a turbulence model

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航空动力学报 2014年第2期29卷 475-480页

作者： GAO Lin JIANG Li-jun CUI Shu-xin GAO Ge National Key Laboratory of Science and Technology on Aero-Engine Aero-thermodynamics School of Energy and Power EngineeringBeijing University of Aeronautics and Astronautics

Turbulent flows over AS240and NACA4412airfoil were simulated numerically using a two-equation turbulence model named k-ξmodel.The predictions of velocity profiles and the pressure coefficient of airfoil AS240at 8°/19°attack angle and NACA4412at 13.87°attack angle were calculated.The results were compared with those using k-εand k-ω models,as well as experimental data.It indicates that the newk-ξmodel offers more realistic prediction than the other two models.The main finding shows that the newk-ξmodel is good at predicting separated flows around airfoils,and it captures the flow feature of pressure-induced separation adequately.All calculations are implemented as per openFOAM 1.7.1(open source field operation and manipulation).

关键词： turbulence airfoil incompressible separation openFOAM

Experimental and numerical investigation of the influence of roughness and turbulence on LUT airfoil performance

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Acta Mechanica Sinica 2019年第6期35卷 1178-1190页

作者： Shoutu Li Ye Li Congxin Yang Xiaobo Zheng Qing Wang Yin Wang Deshun Li Wenrui Hu School of Energy and Power Engineering Lanzhou University of TechnologyLanzhou 730050China Gansu Provincial Technology Centre for Wind Turbines Lanzhou 730050China Key Laboratory of Fluid Machinery and Systems Lanzhou 730050China Lab of Multiple Function Towing Tank School of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong UniversityShanghai 200240China State Key Laboratory of Ocean Engineering School of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong UniversityShanghai 200240China Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration Shanghai Jiao Tong UniversityShanghai 200240China Key Laboratory of Hydrodynamics(Ministry of Education) Shanghai Jiao Tong UniversityShanghai 200240China Institute of Mechanics Chinese Academy of SciencesBeijing 100080China

Vertical-axis wind turbines(VAWTs)have been widely used in urban environments,which contain dust and experience strong turbulence.However,airfoils for VAWTs in urban environments have received considerably less research attention than those for horizontal-axis wind turbines(HAWTs).In this study,the sensitivity of a new VAWT airfoil developed at the Lanzhou University of Technology(LUT)to roughness was investigated via a wind tunnel experiment.The results show that the LUT airfoil is less sensitive to roughness at a roughness height ofairfoil decreases with increasing roughness height.Furthermore,the loads on the LUT airfoil during dynamic stall were studied at different turbulence intensities using a numerical method at a tip-speed ratio of 2.Before the stall,the turbulence intensity did not considerably affect the normal or tangential force coefficients of the LUT airfoil.However,after the stall,the normal force coefficient varied obviously at low turbulence intensity.Moreover,as the turbulence intensity increased,the normal and tangential force coefficients decreased rapidly,particularly in the downwind region of the VAWT.

关键词： airfoil Dynamic load Roughness Vertical-axis wind turbines(VAWTs) Wind tunnel experiment

Experimental study of the boundary layer over an airfoil in plunging motion

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Acta Mechanica Sinica 2012年第2期28卷 372-384页

作者： F.Rasi Marzabadi M.R.Soltani Aerospace Research Institute TehranIran Department of Aerospace Engineering Sharif University of TechnologyTehranIran

This is an experimental study on the bound- ary layer over an airfoil under steady and unsteady conditions. It specifically deals with the effect of plunging oscil- lation on the laminar/turbulent characteristics of the bound- ary layer. The wind tunnel measurements involved surface- mounted hot-film sensors and boundary-layer rake. The ex- periments were conducted at Reynolds numbers of 0.42 x 106 to 0.84 X l06 and the reduced frequency was varied from 0.01 to 0.11. The results of the quasi-wall-shear stress as well as the boundary layer velocity profiles provided impor- tant information about the state of the boundary layer over the suction surface of the airfoil in both static and dynamic cases. For the static tests, boundary layer transition occurred through a laminar separation bubble. By increasing the an- gle of attack, disturbances and the transition location moved toward the leading edge. For the dynamic tests, earlier transi- tion occurred with increasing rather than decreasing effective angle of attack. The mean angle of attack and the oscillating parameters significantly affected the state of the boundary layer. By increasing the reduced frequency, the boundary layer transition was promoted to the upstroke portion of the equivalent angle of attack, but the quasi skin friction coeffi- cient was decreased.

关键词： Boundary layer Unsteady - Plunging Wind tunnel airfoil