Selection of Airfoils for Straight-Bladed Vertical Axis Wind Turbines Based on Desirable Aerodynamic Characteristics

2008 ◽  
Author(s):  
Mazharul Islam ◽  
M. Ruhul Amin ◽  
David S.-K. Ting ◽  
Amir Fartaj
Keyword(s):  
Urban Areas ◽  
Lift Coefficient ◽  
Vertical Axis ◽  
Aerodynamic Characteristics ◽  
Performance Indices ◽  
Niche Markets ◽  
Design Changes ◽  
Stall Angle ◽  
Lift And Drag ◽  
Selection Of

Selection of the airfoil is crucial for better aerodynamic performance and dimensions of a smaller-capacity SB-VAWT which can compete with conventional energy sources in niche markets like urban areas and off-grid remote applications for diversified applications. Airfoil related design changes also have the potential for increasing the cost effectiveness of VAWTs. Recently, Islam et. al [1] have identified the desirable features of an ideal airfoil for smaller capacity SB-VAWT to improve its starting characteristics and overall performance. They have shortlisted several aerodynamic characteristics of the desirable airfoil. Based on these desirable aerodynamic characteristics, an attempt has been made in this paper to shortlist ten prospective candidate airfoils for smaller-capacity SB-VAWT. This is done using both experimental and analytical characteristics. Nine performance indices have been defined in this paper in light of desirable aerodynamic characteristics to select best performing airfoil. These performance indices are utilized for considering the following desirable aerodynamic characteristics: (i) stall angle at low Reynolds number, (ii) width of the drag bucket, (iii) zero-lift-drag coefficient, (iv) Cl/Cd ratio, (v) maximum lift-coefficient, (vi) deep-stall angle, (vii) roughness sensitivity, (viii) trailing edge noise generation, and (ix) pitching moment. Here, Cl and Cd are coefficients of lift and drag respectively. After determining the value of the performance indices and rating of the candidate airfoils, the most promising airfoil is selected. Among the ten candidate airfoils, overall rating of NASA LS(1)-0417 has been found to be the best.

Computational Analysis of Airfoil Merging and its Effect on Performance of Lift Based Vertical Axis Wind Turbine

2016 ◽  
Author(s):  
Akshay Basavaraj
Keyword(s):  
Reynolds Number ◽  
Wind Turbine ◽  
Lift Coefficient ◽  
Turbine Blades ◽  
Vertical Axis ◽  
Aerodynamic Characteristics ◽  
Vertical Axis Wind Turbine ◽  
Low Wind Speed ◽  
Naca 0012 ◽  
Selection Of

In regions of low wind speed, overcoming the starting torque of a Vertical Axis Wind Turbine (VAWT) becomes a challenge aspect. In order to overcome this adversity, careful selection of airfoils for the turbine blades becomes a priority. This paper tries to address the issue utilizing an approach wherein by observing the effect of merging two airfoils. Two airfoils which are of varying camber and thickness are merged and their aerodynamic characteristics are evaluated using the software XFOIL 6.96. For a variation in angle of attack from 0 to 90°, aerodynamic analysis is done in order to observe the behavior of one quarter of the entire VAWT cycle. An objective function is developed so as to observe the maximum possible torque generated by these airfoils at Reynolds number varying from 15,000–120,000. Due to change in the value of CL observed at Low Reynolds Number using commercial CFD softwares, multiple objective functions are utilized to observe the behavior over a range of Reynolds number. An experimental co-relation between the cut-in velocity and the lift-coefficient of the airfoils is developed in order to predict the cut-in velocity of the interpolated airfoils. The airfoils used for this paper are NACA 0012, NACA 0018, FX 66 S196, Clark Y (smooth), PT 40, SD 7032, A 18, SD 7080, SG 6043 and SG 6040.

scholarly journals Investigation of a NACA0012 Finite Wing Aerodynamics at Low Reynold’s Numbers and 0º to 90º Angle of Attack

2019 ◽  
Author(s):  
Shahrooz Eftekhari ◽  
Abdulkareem Shafiq Mahdi Al-Obaidi
Keyword(s):  
Drag Force ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Poor Performance ◽  
Aerodynamic Characteristics ◽  
Airfoil Surface ◽  
Wing Geometry ◽  
Stall Angle ◽  
Finite Wing ◽  
Lift And Drag

The aerodynamic characteristics of a NACA0012 wing geometry at low Reynold’s numbers and angle of attack ranging from 0º to 90º are investigated using numerical simulations and the results are validated by wind tunnel experiments. Further experiments are conducted at low Reynold’s numbers of 1 × 105, 2 × 105 and 3 × 105. Findings of the study show a similar trend for the lift and drag coefficients at all the investigated Reynold’s numbers. The lift coefficient is linearly increased with angle of attack until it reaches its maximum value at 32º which is the stall angle. It is observed that further increment in angle of attack results in decrement of lift coefficient until it reaches its minimum value at 90º angle of attack. The drag force acting on the airfoil increases as the angle of attack is increased and increment in the drag force results in change of laminar flow to turbulent flow. As the turbulence gets higher the flow starts to separate from the airfoil surface due to eddies generated by turbulence. Hence, the lift force generated by the wing is reduced and drag force is increased simultaneously, which results in poor performance of the wing.

Numerical Study on Aerodynamic Characteristics of NACA0015

2013 ◽  
Vol 302 ◽  
pp. 640-645
Author(s):  
Su Jeong Lee ◽  
Eui Chul Jeong ◽  
Hee Chang Lim
Keyword(s):  
Pressure Distribution ◽  
Numerical Study ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Vertical Axis ◽  
Aerodynamic Characteristics ◽  
Surface Pressure Distribution ◽  
Maximum Value ◽  
Stall Angle ◽  
Near Wall

In this study, a numerical simulation is made to understand the effect of the angle of attack on a NACA airfoil, which will be used for a basic shape to apply for making the vertical axis Darius wind turbine. The near-wall y+ value which is less than 1 is known to be most desirable for a near-wall modeling. Therefore, this study is aiming to observe the variation and find the optimized value of y+. The Reynolds number used in this study was 360,000, where the chord length and the velocity were 0.12m and 43.8m/s, respectively. Generally, the lift coefficient of the airfoil tends to increase as the angle of attack increases and it decreases substantially at the stall angle and then it decreases. As expected, the lift coefficient increases rapidly from 0 to 10° and then after the sudden drop of the lift (i.e., the stall) at around 10 to 16° depending on the y+ value. In this paper, it seems to be reliable and appropriate to use y+ value close to 1. From the surface pressure distribution, from the result obtained the ratio of pressure distribution of maximum value to the minimum value was 1.89and these peaks move forward to backward as the angle of attack increases.

Wind Tunnel Experimental Study of Wind Turbine Airfoil Aerodynamic Characteristics

2012 ◽  
Vol 260-261 ◽  
pp. 125-129
Author(s):  
Xin Zi Tang ◽  
Xu Zhang ◽  
Rui Tao Peng ◽  
Xiong Wei Liu
Keyword(s):  
Wind Tunnel ◽  
Wind Turbine ◽  
Lift Coefficient ◽  
Turbine Blades ◽  
Aerodynamic Characteristics ◽  
Wind Turbine Blades ◽  
High Lift ◽  
Minimum Drag ◽  
Stall Angle ◽  
High Reynolds

High lift and low drag are desirable for wind turbine blade airfoils. The performance of a high lift airfoil at high Reynolds number (Re) for large wind turbine blades is different from that at low Re number for small wind turbine blades. This paper investigates the performance of a high lift airfoil DU93-W-210 at high Re number in low Re number flows through wind tunnel testing. A series of low speed wind tunnel tests were conducted in a subsonic low turbulence closed return wind tunnel at the Re number from 2×105to 5×105. The results show that the maximum lift, minimum drag and stall angle differ at different Re numbers. Prior to the onset of stall, the lift coefficient increases linearly and the slope of the lift coefficient curve is larger at a higher Re number, the drag coefficient goes up gradually as angle of attack increases for these low Re numbers, meanwhile the stall angle moves from 14° to 12° while the Re number changes from 2×105to 5×105.

scholarly journals Effect of Leading-Edge Bulges on Aerodynamic Characteristics of Bionic Wingsail

2021 ◽  
Author(s):  
Chen Li ◽  
Peiting Sun ◽  
Hongming Wang
Keyword(s):  
Stokes Equations ◽  
Lift Coefficient ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Suction Surface ◽  
Ansys Fluent ◽  
Navier Stokes Equations ◽  
Extension Direction ◽  
Lift And Drag

The leading-edge bulges along the extension direction are designed on the marine wingsail. The height and the spanwise wavelength of the protuberances are 0.1c and 0.25c, respectively. At Reynolds number Re=5×105, the Reynolds Averaged Navier-Stokes equations are applied to the simulation of the wingsail with the bulges thanks to ANSYS Fluent finite-volume solver based on the SST K-ω models. The grid independence analysis is carried out with the lift and drag coefficients of the wingsail at AOA = 8° and AOA=20°. The results show that while the efficiency of the wingsail is reduced by devising the leading-edge bulges before stall, the bulges help to improve the lift coefficient of the wingsail when stalling. At AOA=22° under the action of the leading-edge tubercles, a convective vortex is formed on the suction surface of the modified wingsail, which reduces the flow loss. So the bulges of the wingsail can delay the stall.

scholarly journals Numerical Analysis of the Aerodynamic Characteristics of NACA-4312 Airfoil

2020 ◽  
Vol 01 (02) ◽  
pp. 29-36
Author(s):  
Md Rhyhanul Islam Pranto ◽  
Mohammad Ilias Inam
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Lift Coefficient ◽  
Turbulence Models ◽  
Aerodynamic Characteristics ◽  
Numerical Results ◽  
Ansys Fluent ◽  
Coefficient Increase ◽  
Lift And Drag ◽  
Lift And Drag Coefficient

The aim of the work is to investigate the aerodynamic characteristics such as lift coefficient, drag coefficient, pressure distribution over a surface of an airfoil of NACA-4312. A commercial software ANSYS Fluent was used for these numerical simulations to calculate the aerodynamic characteristics of 2-D NACA-4312 airfoil at different angles of attack (α) at fixed Reynolds number (Re), equal to 5×10^5 . These simulations were solved using two different turbulence models, one was the Standard k-ε model with enhanced wall treatment and other was the SST k-ω model. Numerical results demonstrate that both models can produce similar results with little deviations. It was observed that both lift and drag coefficient increase at higher angles of attack, however lift coefficient starts to reduce at α =13° which is known as stalling condition. Numerical results also show that flow separations start at rare edge when the angle of attack is higher than 13° due to the reduction of lift coefficient.

scholarly journals Analysis on Flow Field Characteristics of Airfoil in Pitching Motion

2021 ◽  
Vol 2076 (1) ◽  
pp. 012069
Author(s):  
Rui Yin ◽  
Jing Huang ◽  
Zhi-Yuan He
Keyword(s):  
Flow Field ◽  
Drag Coefficient ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Decisive Role ◽  
Aerodynamic Characteristics ◽  
Pitching Motion ◽  
Maximum Value ◽  
Flow Field Characteristics ◽  
Lift And Drag

Abstract Based on CFD, the flow field characteristics of NACA4412 airfoil are analyzed under pitching motion, and its aerodynamic characteristics are interpreted. The results show that streamline changes on the upper surface of the airfoil play a decisive role in the aerodynamic characteristics. The interaction between the vortex leads to fluctuations in the lift and drag coefficients. Under a big angle of attack, the secondary trailing vortex on the upper surface of the airfoil adheres to the trailing edge of the airfoil, resulting in an increased drag coefficient. Under a small angle of attack, the secondary trailing vortex can break away from the airfoil. The lift coefficient reaches the maximum value of 2.961 before the airfoil is turned upside down, and the drag coefficient reaches the maximum value of 1.515 after the airfoil is turned upside down, but the corresponding angles of attack of the two are equal.

Surface Modifications for Improved Maneuverability and Performance of an Aircraft

2011 ◽  
Author(s):  
Deepanshu Srivastav ◽  
K. N. Ponnani
Keyword(s):  
Surface Modifications ◽  
Boundary Layer Separation ◽  
Aerodynamic Characteristics ◽  
Aircraft Wing ◽  
Pressure Drag ◽  
Wing Model ◽  
Study Results ◽  
Stall Angle ◽  
And Performance ◽  
Lift And Drag

The work describes a comparative study of aerodynamic characteristics of an aircraft wing model with and without surface modifications to it. The surface modifications that are considered here are outward dimples on the wing model. In the present study, results of computational fluid dynamics (CFD) analysis are presented showing variance in lift and drag of modified wing models at different angle of attacks. Dimples on the surface aircraft wing model doesn’t affect much the pressure drag since it’s already aerodynamic in shape but it can affect the angle of stall. This project verifies if the dimples that reduce a golf ball’s drag, can also increase an airplane’s critical angle of stall. Dimples delay the boundary layer separation by creating more turbulence over the surface. The airfoil profile considered here is NACA-0018 with uniform cross-section throughout the length of airfoil. Subsonic flows are considered for the study. The CAD model is prepared in CatiaV5 R18 and simulations are carried out in Comsol 3.4 and Comsol 4.0. The overall aim of the study is improved maneuverability and performance of an aircraft. The results justify the increase in the overall lift and reduction in drag of the aircraft, also change of stall angle with different surface modifications on the wing model is observed.

Impact of Gurney Flaplike Strips on the Aerodynamic and Vortex Flow Characteristic of a Reverse Delta Wing

2016 ◽  
Vol 138 (6) ◽  
Author(s):  
T. Lee
Keyword(s):  
Vortex Flow ◽  
Delta Wing ◽  
Lift Coefficient ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Force Balance ◽  
Vortex Control ◽  
Lift Curve ◽  
Lift And Drag ◽  
The Impact

The impact of Gurney flaplike strips, of different geometric configurations and heights, on the aerodynamic characteristics and the tip vortices generated by a reverse delta wing (RDW) was investigated via force-balance measurement and particle image velocimetry (PIV). The addition of side-edge strips (SESs) caused a leftward shift of the lift curve, resembling a conventional trailing-edge flap. The large lift increment overwhelmed the corresponding drag increase, thereby leading to an improved lift-to-drag ratio compared to the baseline wing. The lift and drag coefficients were also found to increase with the strip height. The SES-equipped wing also produced a strengthened vortex compared to its baseline wing counterpart. The leading-edge strips (LESs) were, however, found to persistently produce a greatly diffused vortex flow as well as a small-than-baseline-wing lift in the prestall α regime. The downward LES delivered a delayed stall and an increased maximum lift coefficient compared to the baseline wing. The LESs provide a potential wingtip vortex control alternative, while the SESs can enhance the aerodynamic performance of the RDW.

Dynamic stall of an airfoil with different mounting angle of gurney flap

2020 ◽  
Vol 92 (7) ◽  
pp. 1037-1048
Author(s):  
Mehran Masdari ◽  
Milad Mousavi ◽  
Mojtaba Tahani
Keyword(s):  
Lift Coefficient ◽  
Oscillation Amplitude ◽  
Vertical Axis ◽  
Aerodynamic Performance ◽  
Dynamic Stall ◽  
Content Type ◽  
Naca0012 Airfoil ◽  
Gurney Flap ◽  
Stall Angle ◽  
Axis Length

Purpose One of the best methods to improve wind turbine aerodynamic performance is modification of the blade’s airfoil. The purpose of this paper is to investigate the effects of gurney flap geometry and its oscillation parameters on the pitching NACA0012 airfoil. Design/methodology/approach This numerical solution has been carried out for different cases of gurney flap mounting angles, heights, reduced frequencies and oscillation amplitudes, then the results were compared to each other. The finite volume method was used for the discretization of the governing equations, and the PISO algorithm was used to solve the equations. Also, the “SST” was adopted as the turbulence model in the simulation. Findings In this paper, the different parameters of gurney flap were investigated. The results showed that the best range of gurney flap height are between 1 and 3.2% of chord and the best ratio of lifting to drag coefficient is achieved in gurney flap with an angle of 90° relative to the chord direction. The dynamic stall angle of the airfoil with gurney flap decreases were compared to without gurney flap. Earlier LEV formation can be one of the main reasons for decreasing the dynamic stall angle of the airfoil with gurney flap. Increasing the reduced frequency and oscillation amplitude causes rising of maximum lift coefficient and consequently lift curve slope. Moreover, gurney flap with mounting angle has a lower hinge moment than the gurney flap without mounting angle but with the same vertical axis length. So, there is more complexity in structural design concerning the gurney flap without mounting angle. Practical implications Improving aerodynamic efficiency of airfoils is vital for obtaining more output power in VAWTs. Gurney flaps are one of the best mechanisms to increase the aerodynamic performance of the airfoil and increases the efficiency of VAWTs. Originality/value Investigating the hinge moment on the connection point of the airfoil, gurney flap and try to compare the gurney flap with and without angle.

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