Novel Tubercle Design for a Wind Turbine Blade Operating at Low Reynolds Number

2019 ◽  
Author(s):  
R. Deeksha ◽  
Mahesh K. Varpe
Keyword(s):  
Reynolds Number ◽  
Wind Turbine ◽  
Amplitude Ratio ◽  
Low Reynolds Number ◽  
Lift Coefficient ◽  
Leading Edge ◽  
Aerodynamic Performance ◽  
Operating Conditions ◽  
Operating Condition ◽  
Low Reynolds

Abstract Wind energy has become one of the vital sustainable energy resources and a leading contender to the renewable resources race. The need of extending the aerodynamic performance of a wind turbine paved the way for radical approaches in the design of wind turbine blades. One such promising technique is the adoption of passive flow controls like leading edge protuberance or tubercles. In this paper the aerodynamic performance of NACA0009 (baseline) superimposed with a leading edge protuberance is numerically investigated in the post-stall operating conditions. The investigation objective was to identify the optimum pitch to amplitude ratio of the protuberance in the post stall operating condition for a low Reynolds number of 5 × 104. Computational fluid dynamics computations were performed using κ-ω SST turbulence model. The optimum pitch to amplitude ratio was found to be 6 which enhanced the aerodynamic lift coefficient by 42% in the post stall operating condition. The lift is reduced at lower AOA but gets complement in the post stall operating conditions.

scholarly journals Aerodynamic Performance of Micro Aerial Wing Structures at Low Reynolds Number

2019 ◽  
Vol 11 (1) ◽  
pp. 107-120 ◽  
Author(s):  
Y. D. DWIVEDI ◽  
Vasishta BHARGAVA ◽  
P. M. V. RAO ◽  
Donepudi JAGADEESH
Keyword(s):  
Reynolds Number ◽  
Low Reynolds Number ◽  
Lift Coefficient ◽  
Reynolds Numbers ◽  
Aerodynamic Performance ◽  
Panel Method ◽  
Experiment Data ◽  
Wing Structures ◽  
Low Reynolds ◽  
Good Agreement

Corrugations are folds on a surface as found on wings of dragon fly insects. Although they fly at relatively lower altitudes its wings are adapted for better aerodynamic and aero-elastic characteristics. In the present work, three airfoil geometries were studied using the 2-D panel method to evaluate the aerodynamic performance for low Reynolds number. The experiments were conducted in wind tunnel for incompressible flow regime to demonstrate the coefficients of lift drag and glide ratio at two Reynolds numbers 1.9x104 and 1.5x105 and for angles of attack ranging between 00 and 160. The panel method results have been validated using the current and existing experiment data as well as with the computational work from cited literature. A good agreement between the experimental and the panel methods were found for low angles of attack. The results showed that till 80 angle of attack higher lift coefficient and lower drag coefficient are obtainable for corrugated airfoils as compared to NACA 0010. The validation of surface pressure coefficients for all three airfoils using the panel method at 40 angles of attack was done. The contours of the non-dimensional pressure and velocity are illustrated from -100 to 200 angles of attack. A good correlation between the experiment data and the computational methods revealed that the corrugated airfoils exhibit better aerodynamic performance than NACA 0010.

Effect of mach number on high-subsonic and low-Reynolds-number flows around airfoils

2020 ◽  
Vol 34 (14n16) ◽  
pp. 2040112
Author(s):  
Jian-Hua Xu ◽  
Wen-Ping Song ◽  
Zhong-Hua Han ◽  
Zi-Hao Zhao
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Reverse Flow ◽  
Separation Bubble ◽  
Low Reynolds Number ◽  
Lift Coefficient ◽  
Aerodynamic Performance ◽  
Attack Angle ◽  
Low Reynolds ◽  
Flow Vortex

High-subsonic and low-Reynolds-number flow is a special aerodynamic problem associated with near space propellers and Mars aircrafts. The flow around airfoils and the corresponding aerodynamic performance are different from the incompressible flow at low-Reynolds-number, due to complex shock wave-laminar separation bubble interaction. The objective of this paper is to figure out the effect of Mach number on aerodynamic performance and special flow structure of airfoil. An in-house Reynolds-averaged Navier–Stokes solver coupled with [Formula: see text] transition model is employed to simulate the flows around the E387 airfoil. The results show that the lift slope is larger than [Formula: see text] in the linear region. No stall occurs even at an attack angle of [Formula: see text]. With increase of Mach number, lift coefficient decreases when attack angle is below [Formula: see text]. However, once the angle of attack exceeds [Formula: see text], higher Mach number corresponds to higher lift coefficient. In addition, the strength and number of shock waves are very sensitive to Mach number. With increase of Mach number, the region of reverse flow vortex near transition location becomes smaller and finally disappears, while a new reverse flow vortex appears near the trailing edge and becomes larger.

Analysing and Optimizing the Aerodynamic Performance of Wind Turbine Blades Using Injected-Air Jets at Variable Frequency and Amplitude for Flow Control

2005 ◽  
Vol 29 (4) ◽  
pp. 331-339 ◽  
Author(s):  
Liu Hong ◽  
Huo Fupeng ◽  
Chen Zuoyi
Keyword(s):  
Wind Turbine ◽  
Turbine Blade ◽  
Lift Coefficient ◽  
Turbine Blades ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Aerodynamic Performance ◽  
Operating Conditions ◽  
Suction Surface ◽  
Air Jet

Optimum aerodynamic performance of a wind turbine blade demands that the angle of attack of the relative wind on the blade remains at its optimum value. For turbines operating at constant speed, a change in wind speed causes the angle of attack to change immediately and the aerodynamic performance to decrease. Even with variable speed rotors, intrinsic time delays and inertia have similar effects. Improving the efficiency of wind turbines under variable operating conditions is one of the most important areas of research in wind power technology. This paper presents findings of an experimental study in which an oscillating air jet located at the leading edge of the suction surface of an aerofoil was used to improve the aerodynamic performance. The mean air-mass flowing through the jet during each sinusoidal period of oscillation equalled zero; i.e. the jet both blew and sucked. Experiments investigated the effects of the frequency, momentum and location of the jet stream, and the profile of the turbine blade. The study shows significant increase in the lift coefficient, especially in the stall region, under certain conditions. These findings may have important implications for wind turbine technology.

The generation of tonal noise from sawtooth trailing-edge serrations at low Reynolds numbers

2016 ◽  
Vol 120 (1228) ◽  
pp. 971-983 ◽  
Author(s):  
D. J. Moreau ◽  
C. J. Doolan
Keyword(s):  
Reynolds Number ◽  
Low Reynolds Number ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Operating Conditions ◽  
Tonal Noise ◽  
Trailing Edge ◽  
Low Frequencies ◽  
Low Reynolds ◽  
Trailing Edge Serrations

ABSTRACTThe flow and noise created by sawtooth trailing-edge serrations has been studied experimentally at a low Reynolds number. Experiments have been performed on a flat-plate model with an elliptical leading edge and an asymmetrically bevelled trailing edge at Reynolds numbers of Rec = 1 × 105–1.3 × 105, based on chord. Wide serrations with a wavelength (λs) to amplitude (2h) ratio of λs/h = 0.6 were found to reduce the overall sound pressure level by up to 11dB. In contrast, narrower serrations with λs/h = 0.2 produce tonal noise and increase the overall noise level by up to 4dB. Intense vortices across the span of the trailing edge with narrow serrations are shown to be the source of tonal noise. Wide serrations reduce turbulent velocity fluctuations at low frequencies which explains the lower radiated noise. The narrow serrations that produce low Reynolds number tonal noise were shown previously to be effective at higher Reynolds numbers (Rec > 2 × 105), demonstrating that care is needed to fully understand the flow field over serrations for all intended operating conditions.

scholarly journals Numerical Study of Effect of Sawtooth Riblets on Low-Reynolds-Number Airfoil Flow Characteristic and Aerodynamic Performance

Processes ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 2102
Author(s):  
Xiaopei Yang ◽  
Jun Wang ◽  
Boyan Jiang ◽  
Zhi’ang Li ◽  
Qianhao Xiao
Keyword(s):  
Reynolds Number ◽  
Drag Reduction ◽  
Numerical Study ◽  
Low Reynolds Number ◽  
Aerodynamic Performance ◽  
Operating Conditions ◽  
Viscous Drag ◽  
Airfoil Flow ◽  
Low Reynolds ◽  
Reduction Effect

Riblets with an appropriate size can effectively restrain turbulent boundary layer thickness and reduce viscous drag, but the effects of riblets strongly depend on the appearance of the fabric that is to be applied and its operating conditions. In this study, in order to improve the aerodynamic performance of a low-pressure fan by using riblet technology, sawtooth riblets on NACA4412 airfoil are examined at the low Reynolds number of 1 × 105, and the airfoil is operated at angles of attack (AOAs) ranging from approximately 0° to 12°. The numerical simulation is carried out by employing the SST k–ω turbulence model through the Ansys Fluent, and the effects of the riblets’ length and height on aerodynamic performance and flow characteristics of the airfoil are investigated. The results indicate that the amount of drag reduction varies greatly with riblet length and height and the AOA of airfoil flow. By contrast, the riblets are detrimental to the airfoil in some cases. The most effective riblet length is found to be a length of 0.8 chord, which increases the lift and reduces the drag under whole AOA conditions, and the maximum improvements in both are 17.46% and 15.04%, respectively. The most effective height for the riblet with the length of 0.5 chord is 0.6 mm. This also improves the aerodynamic performance and achieves a change rate of 12.67% and 14.8% in the lift and drag coefficients, respectively. In addition, the riblets facilitate a greater improvement in airfoil at larger AOAs. The flow fields demonstrate that the riblets with a drag reduction effect form “the antifriction-bearing” structure near the airfoil surface and effectively restrain the trailing separation vortex. The ultimate cause of the riblet drag reduction effect is the velocity gradient at the bottom of the boundary layers being increased by the riblets, which results in a decrease in boundary thickness and energy loss.

scholarly journals Numerical Simulation Studies on Stall Suppression of a NACA0015 Airfoil

2021 ◽  
Vol 6 ◽  
pp. 23-31
Author(s):  
Biswash Shrestha ◽  
Nawraj Bhattarai
Keyword(s):  
Reynolds Number ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Constant Width ◽  
Low Reynolds Number ◽  
Lift Coefficient ◽  
Leading Edge ◽  
Ansys Fluent ◽  
Control Plate ◽  
Low Reynolds

This study aims to achieve an improved airfoil performance at low Reynolds number, and to determine the optimum position and size of rectangular cross-section burst control plate (BCP) to suppress stall in airfoil. The type of airfoil used in the present study is NACA0015 (National Advisory Committee for Aeronautics) airfoil with 200 mm of chord (c) length. Here, rectangular cross-section burst control plates with different sizes and at different locations are investigated numerically at the low Reynolds number of 1.6×105. Total of three positions (0.05c, 0.1c and 0.2c from the leading edge of airfoil), and four sizes (with heights 0.3 mm, 0.7mm, 1mm and 1.5 mm, and constant width 4 mm) of rectangular BCPs are simulated in ANSYS Fluent software using Transition SST model. The results indicate that the rectangular cross-section burst control plate is an effective device in the suppression of airfoil stall. For 0.7 mm and 1 mm height BCPs, the stall angle is postponed by 2° for all positions, while for 0.3 mm and 1.5 mm height BCPs, the reduction in sudden fall of lift can be observed but at the cost of reduction in maximum lift coefficient. Among various configurations, the 1mm height BCP located at 0.2c position is found to be most effective in the suppression of stall.

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