Dynamic Stall: The Case of the Vertical Axis Wind Turbine

1986 ◽  
Vol 108 (2) ◽  
pp. 140-145 ◽  
Author(s):  
A. Laneville ◽  
P. Vittecoq
Keyword(s):  
Experimental Investigation ◽  
Reynolds Number ◽  
Leading Edge ◽  
Vertical Axis ◽  
Dynamic Stall ◽  
Speed Ratio ◽  
Vertical Axis Wind Turbine ◽  
Airfoil Surface ◽  
Helicopter Blade ◽  
Tip Speed Ratio

This paper presents the results of an experimental investigation on a driven Darrieus turbine rotating at different tip speed ratios. For a Reynolds number of 3.8 × 104, the results indicate the presence of dynamic stall at tip speed ratio less than 4, and that helicopter blade aerodynamics can be used in order to explain some aspects of the phenomenon. It was observed that in deep stall conditions, a vortex is formed at the leading edge; this vortex moves over the airfoil surface with 1/3 of the airfoil speed and then is shed at the trailing edge. After its shedding, the vortex can interact with the airfoil surface as the blade passes downstream.

scholarly journals Dynamic Stall of a Vertical-Axis Wind Turbine and Its Control Using Plasma Actuation

Energies ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3738 ◽  
Author(s):  
Lu Ma ◽  
Xiaodong Wang ◽  
Jian Zhu ◽  
Shun Kang
Keyword(s):  
Wind Turbine ◽  
Tangential Force ◽  
Vertical Axis ◽  
Dynamic Stall ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Vertical Axis Wind Turbine ◽  
Dbd Plasma ◽  
Tip Speed Ratio ◽  
Plasma Actuation

In this paper, a dynamic stall control scheme for vertical-axis wind turbine (VAWT) based on pulsed dielectric-barrier-discharge (DBD) plasma actuation is proposed using computational fluid dynamics (CFD). The trend of the wind turbine power coefficient with the tip speed ratio is verified, and the numerical simulation can describe the typical dynamic stall process of the H-type VAWT. The tangential force coefficient and vorticity contours of the blade are compared, and the regular pattern of the VAWT dynamic stall under different tip speed ratios is obtained. Based on the understanding the dynamic stall phenomenon in flow field, the effect of the azimuth of the plasma actuation on the VAWT power is studied. The results show that the azimuth interval of the dynamic stall is approximately 60° or 80° by the different tip speed ratio. The pulsed plasma actuation can suppress dynamic stall. The actuation is optimally applied for the azimuthal position of 60° to 120°.

scholarly journals Effect of solidity on the dynamic behaviour of the Darrieus turbine with leading-edge protuberance

2021 ◽  
Vol 850 (1) ◽  
pp. 012038
Author(s):  
U Lokesh ◽  
N Kirthika ◽  
K Madhu Madhan ◽  
C B Maheswaran ◽  
S Ramaswami ◽  
...  
Keyword(s):  
Wind Energy ◽  
Wind Turbine ◽  
Dynamic Behaviour ◽  
Leading Edge ◽  
Vertical Axis ◽  
Speed Ratio ◽  
Experimental Measurements ◽  
Vertical Axis Wind Turbine ◽  
Tip Speed Ratio ◽  
Vortex Induced Vibrations

Abstract The dynamic behaviour of the straight–type Darrieus turbine with leading-edge protuberance (LEP) was analysed under various solidity ratios at several tip speed ratios through experiments. The Darrieus turbine is a type of Vertical Axis Wind Turbine (VAWT) which uses wind energy to generate electricity. This type of turbine was subjected to vortex-induced and buffeting types of vibrations. These vibrations were more sensitive to the number of blades and tip speed ratios. Based on the experimental measurements, the results revealed that, at a low tip speed ratio, the four-bladed turbine exhibits lesser vortex-induced vibrations than those of the three and five-bladed turbines. However, at a high tip speed ratio, the three-bladed configuration operates well against the vortex-induced vibrations. In the case of buffeting, a three-bladed turbine diminishes the dynamic oscillations at both low and high tip speed ratios, whereas the four and five-bladed turbines induce dynamic oscillations at slightly higher amplitudes. However, the amplitude of buffeting is smaller than those of vortex-induced vibrations.

Numerical Investigations on the Use of Multi-Element Airfoils for Vertical Axis Wind Turbine Configurations

2013 ◽  
Author(s):  
Elhadji A. A. Bah ◽  
Lakshmi N. Sankar ◽  
Jechiel I. Jagoda
Keyword(s):  
Wind Turbines ◽  
Vertical Axis ◽  
Dynamic Stall ◽  
Speed Ratio ◽  
Single Element ◽  
Ratio Analysis ◽  
Vertical Axis Wind Turbine ◽  
Tip Speed Ratio ◽  
Pressure Distributions ◽  
Vertical Axis Wind Turbines

Vertical axis wind turbines (VAWT) have a relatively simple, rugged construction compared to HAWTs. However, vertical-axis wind turbines have numerous challenges that may hinder their performance. For instance they are strongly affected by dynamic stall at low tip speed ratios. A significant part of the kinetic energy contained in the oncoming wind is lost in swirl and vortices. As a result, VAWTs have a lower power production and efficiency compared to HAWTs. In an effort to alleviate the adverse effects of dynamic stall phenomena, the present study explores the use of two-element airfoils. A comparative study of single element and dual element VAWT configurations for representative VAWT turbines is given. The benefits of dual-element configurations are analyzed through a detailed flow visualization study of the single and two-element VAWT configurations at various azimuthal locations for a representative tip speed ratio. Analysis of these qualitative phenomena is complemented by a discussion on quantitative data for torque, surface pressure distributions, and airloads.

Numerical Research on the Characteristics of Lift-Drag Type Vertical Axis Wind Turbine

2012 ◽  
Vol 189 ◽  
pp. 448-452
Author(s):  
Yan Jun Chen ◽  
Guo Qing Wu ◽  
Yang Cao ◽  
Dian Gui Huang ◽  
Qin Wang ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Vertical Axis ◽  
Chord Length ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Vertical Axis Wind Turbine ◽  
Tip Speed Ratio ◽  
Middle Range ◽  
Parabolic Form ◽  
Cfd Method

Numerical studies are conducted to research the performance of a kind of lift-drag type vertical axis wind turbine (VAWT) affected by solidity with the CFD method. Moving mesh technique is used to construct the model. The Spalart-Allmaras one equation turbulent model and the implicit coupled algorithm based on pressure are selected to solve the transient equations. In this research, how the tip speed ratio and the solidity of blade affect the power coefficient (Cp) of the small H-VAWT is analyzed. The results indicate that Cp curves exhibit approximate parabolic form with its maximum in the middle range of tip speed ratio. The two-blade wind turbine has the lowest Cp while the three-blade one is more powerful and the four-blade one brings the highest power. With the certain number of blades, there is a best chord length, and too long or too short chord length may reduce the Cp.

scholarly journals Kontrol Angle of Attack untuk Optimasi Daya padaVertical Axis Wind Turbine Tipe Darrieus

2020 ◽  
Vol 8 (3) ◽  
pp. 492
Author(s):  
WAHYU AULIA NURWICAKSANA ◽  
BUDHY SETIAWAN ◽  
IKA NOER SYAMSIANA ◽  
SEPTYANA RISKITASARI
Keyword(s):  
Wind Turbine ◽  
Angle Of Attack ◽  
Vertical Axis ◽  
Speed Ratio ◽  
Trial And Error ◽  
Proportional Integral Derivative ◽  
Vertical Axis Wind Turbine ◽  
Average Efficiency ◽  
Proportional Integral ◽  
Tip Speed Ratio

ABSTRAKVAWT (Vertical Axis Wind Turbine) tipe Darrieus NACA0015 merupakan salah satu model dari turbin angin yang bekerja dengan menggunakan angin sebagai sumber penggerak. Namun dari hasil pengamatan, kecepatan angin yang ada tidak konstan setiap saat. Sehingga dari permasalahan ini perlu suatu kontrol yaitu dengan mengendalikan sudut kerja blade VAWT yang dikenal dengan kontrol angle of attack (AoA). Prinsip kerja kontrol AoA yaitu sudut blade diatur agar VAWT bekerja secara optimum dan dapat meningkatkan efisiensi. Metode kontrol AoA menggunakan PID (Proportional–Integral–Derivative) dengan memberikan nilai trial and error pada Kp, Ki, Kd. VAWT ini menggunakan konstanta TSR (Tip Speed Ratio) yaitu 4. Hasil dari penelitian ini yaitu daya yang dihasilkan VAWT dengan kontrol AoA mendapatkan rata-rata efisiensi sebesar 5.16%, sedangkan VAWT tanpa kontrol mendapatkan efisiensi sebesar 3.49%. Sehingga dapat disimpulkan bahwa dengan kontrol AoA, rata-rata efisiensi dayanya naik sebesar 1.67% dari yang tanpa kontrol.Kata Kunci: Kontrol Angle of Attack (AoA), VAWT, TSR, Efisiensi ABSTRACTVAWT (Vertical Axis Wind Turbine) type Darrieus NACA0015 is one model of a wind turbine that works by using wind as a source of propulsion. Conditions from observations, wind speeds that are not constant every time. So from this problem needs control VAWT by controlling the working angle of the VAWT blade is the angle of attack control (AoA). The principle AoA control is that the blade angle adjusted so that the VAWT works optimally and can improve the efficiency. AoA control method uses PID (Proportional-Integral-Derivative) by providing trial and error values for Kp, Ki, Kd. VAWT uses TSR (Tip Speed Ratio) constant which is 4. The results of this research, VAWT with AoA control get an average efficiency of 5.16%, while without control gets an average efficiency of 3.49%. So it can be concluded that with AoA control, the average power efficiency increases by 1.67% from those without control.Keywords: Angle of Attack (AoA) Control, VAWT, TSR, Efficiency

Savonius Wind Turbine Performances on Wind Concentrator

2017 ◽  
Vol 8 (1) ◽  
pp. 376
Author(s):  
Dygku. Asmanissa Awg. Osman ◽  
Norzanah Rosmin ◽  
Nor Shahida Hasan ◽  
Baharruddin Ishak ◽  
Aede Hatib Mustaamal@Jamal ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Electrical Power ◽  
Vertical Axis ◽  
Angular Speed ◽  
Speed Ratio ◽  
Vertical Axis Wind Turbine ◽  
Air Compressor ◽  
Tip Speed Ratio ◽  
Savonius Wind Turbine ◽  
Air Streams

The air streams from the outlet of an air compressor can be used to generate electricity. For instance, if a micro-sized Vertical-Axis Wind-Turbine (VAWT) is installed towards the airflow, some amount of electricity can be generated before being stored in a battery bank. The research’s objectives are to design, fabricate and analyze the performance of Helical Savonius VAWT blade rotors, which is tested with and without using a wind concentrator. The Helical Savonius VAWT is tested at 0 cm without the concentrator, whereas the blade rotor is tested at concave-blade position when using the concentrator. The blade and the wind concentrator designs were based on the dimensions and the constant airflow of the air compressor. The findings suggested that the blade produced its best performance when tested using wind concentrator at concave-blade position in terms of angular speed (<em>ω</em>), tip speed ratio (<em>TSR</em>) and the generated electrical power (<em>P</em><em><sub>E</sub></em>). The findings concluded that the addition of wind concentrator increases the airflow which then provided better performances on the blades.

Numerical evaluation of optimum tip speed ratio for darrieus type vertical axis wind turbine

2020 ◽  
Vol 33 ◽  
pp. 4719-4722
Author(s):  
E. Leelakrishnan ◽  
M. Sunil Kumar ◽  
S. David Selvaraj ◽  
N. Sundara Vignesh ◽  
T.S. Abhesheka Raja
Keyword(s):  
Wind Turbine ◽  
Numerical Evaluation ◽  
Vertical Axis ◽  
Speed Ratio ◽  
Vertical Axis Wind Turbine ◽  
Tip Speed Ratio

An Experimental Study of the Aerodynamics and Performance of a Vertical Axis Wind Turbine in a Confined and Unconfined Environment

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Vincenzo Dossena ◽  
Giacomo Persico ◽  
Berardo Paradiso ◽  
Lorenzo Battisti ◽  
Sergio Dell'Anna ◽  
...  
Keyword(s):  
Experimental Study ◽  
Wind Tunnel ◽  
Wind Turbine ◽  
Vertical Axis ◽  
Tip Vortex ◽  
Speed Ratio ◽  
Vertical Axis Wind Turbine ◽  
Tip Speed Ratio ◽  
And Performance ◽  
Power Curves

This paper presents the results of a wide experimental study on an H-type vertical axis wind turbine (VAWT) carried out at the Politecnico di Milano. The experiments were carried out in a large-scale wind tunnel, where wind turbines for microgeneration can be tested in real-scale conditions. Integral torque and thrust measurements were performed, as well as detailed aerodynamic measurements to characterize the flow field generated by the turbine downstream of the rotor. The machine was tested in both a confined (closed chamber) and unconfined (open chamber) environment, to highlight the effect of wind tunnel blockage on the aerodynamics and performance of the VAWT under investigation. The experimental results, compared with the blockage correlations presently available, suggest that specific correction models should be developed for VAWTs. The experimental thrust and power curves of the turbine, derived from integral measurements, exhibit the expected trends with a peak power coefficient of about 0.28 at tip-speed ratio equal to 2.5. Flow measurements, performed in three conditions for tip speed ratio equal to 1.5, 2.5, and 3.5, show the fully three-dimensional character of the wake, especially in the tip region where a nonsymmetrical wake and tip vortex are found. The unsteady evolution of the velocity and turbulence fields further highlights the effect of aerodynamic loading on the wake unsteadiness, showing the time-dependent nature of the tip vortex and the onset of dynamic stall for tip speed ratio lower than 2.

Numerical Modeling of Vertical Axis Wind Turbines

2014 ◽  
Author(s):  
Teresa Parra-Santos ◽  
Armando Gallegos-Muñoz ◽  
Miguel A. Rodriguez-Beneite ◽  
Cristobal Uzarraga-Rodriguez ◽  
Francisco Castro-Ruiz
Keyword(s):  
Mechanical Energy ◽  
Vertical Axis ◽  
The Self ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Vertical Axis Wind Turbine ◽  
Tip Speed Ratio ◽  
Vertical Axis Wind Turbines ◽  
Selection Of ◽  
Rotor Axis

This paper aims to predict the performance of Vertical Axis Wind Turbine (VAWT), hence the modeling of kinetic energy extraction from wind and its conversion to mechanical energy at the rotor axis, is carried out. The H-type Darrieus turbine consists of three straight blades with shape of aerofoil attached to a rotating vertical shaft. The criterion on the selection of this kind of turbines, despite its reduced efficiency, is the easy manufacture in workshops. A parametric study has been carried out to analyze the camber effect on the non dimensional curves of power coefficient so that the self starting features as well as the range of tip speed ratio of operation could be predicted.

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