scholarly journals Application of Simultaneous Symmetric and Cambered Airfoils in Novel Vertical Axis Wind Turbines

2021 ◽  
Vol 11 (17) ◽  
pp. 8011
Author(s):  
Sajad Maleki Dastjerdi ◽  
Kobra Gharali ◽  
Armughan Al-Haq ◽  
Jatin Nathwani
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Vertical Axis ◽  
Dynamic Stall ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Vertical Axis Wind Turbines ◽  
Good Potential ◽  
Computational Fluid Dynamics Cfd ◽  
Naca0018 Airfoil

Two novel four-blade H-darrieus vertical axis wind turbines (VAWTs) have been proposed for enhancing self-start capability and power production. The two different airfoil types for the turbines are assessed: a cambered S815 airfoil and a symmetric NACA0018 airfoil. For the first novel wind turbine configuration, the Non-Similar Airfoils 1 (NSA-1), two NACA0018 airfoils, and two S815 airfoils are opposite to each other. For the second novel configuration (NSA-2), each of the S815 airfoils is opposite to one NACA0018 airfoil. Using computational fluid dynamics (CFD) simulations, static and dynamic conditions are evaluated to establish self-starting ability and the power coefficient, respectively. Dynamic stall investigation of each blade of the turbines shows that NACA0018 under dynamic stall impacts the turbine’s performance and the onset of dynamic stall decreases the power coefficient of the turbine significantly. The results show that NSA-2 followed by NSA-1 has good potential to improve the self-starting ability (13.3%) compared to the turbine with symmetric airfoils called HT-NACA0018. In terms of self-starting ability, NSA-2 not only can perform in about 66.67% of 360° similar to the wind turbine with non-symmetric airfoils (named HT-S815) but the power coefficient of NSA-2 at the design tip speed ratio of 2.5 is also 4.5 times more than the power coefficient of HT-S815; the power coefficient difference between HT-NACA0018 and HT-S815 (=0.231) is decreased significantly when HT-S815 is replaced by NSA-2 (=0.076). These novel wind turbines are also simple.

scholarly journals Dynamic stall in vertical axis wind turbines: scaling and topological considerations

2018 ◽  
Vol 841 ◽  
pp. 746-766 ◽  
Author(s):  
Abel-John Buchner ◽  
Julio Soria ◽  
Damon Honnery ◽  
Alexander J. Smits
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Vortex Shedding ◽  
Turbine Blades ◽  
Vertical Axis ◽  
Dynamic Stall ◽  
Speed Ratio ◽  
Vertical Axis Wind Turbine ◽  
Wind Turbine Blades ◽  
Vertical Axis Wind Turbines

Vertical axis wind turbine blades are subject to rapid, cyclical variations in angle of attack and relative airspeed which can induce dynamic stall. This phenomenon poses an obstacle to the greater implementation of vertical axis wind turbines because dynamic stall can reduce turbine efficiency and induce structural vibrations and noise. This study seeks to provide a more comprehensive description of dynamic stall in vertical axis wind turbines, with an emphasis on understanding its parametric dependence and scaling behaviour. This problem is of practical relevance to vertical axis wind turbine design but the inherent coupling of the pitching and velocity scales in the blade kinematics makes this problem of more broad fundamental interest as well. Experiments are performed using particle image velocimetry in the vicinity of the blades of a straight-bladed gyromill-type vertical axis wind turbine at blade Reynolds numbers of between 50 000 and 140 000, tip speed ratios between $\unicode[STIX]{x1D706}=1$ to $\unicode[STIX]{x1D706}=5$, and dimensionless pitch rates of $0.10\leqslant K_{c}\leqslant 0.20$. The effect of these factors on the evolution, strength and timing of vortex shedding from the turbine blades is determined. It is found that tip speed ratio alone is insufficient to describe the circulation production and vortex shedding behaviour from vertical axis wind turbine blades, and a scaling incorporating the dimensionless pitch rate is proposed.

scholarly journals An experimental study of the optimal design parameters of a wind power tower used to improve the performance of vertical axis wind turbines

2018 ◽  
Vol 10 (9) ◽  
pp. 168781401879954
Author(s):  
Soo-Yong Cho ◽  
Sang-Kyu Choi ◽  
Jin-Gyun Kim ◽  
Chong-Hyun Cho
Keyword(s):  
Experimental Study ◽  
Optimal Design ◽  
Wind Turbine ◽  
Wind Power ◽  
Wind Turbines ◽  
Vertical Axis ◽  
Power Coefficient ◽  
Design Parameters ◽  
Vertical Axis Wind Turbine ◽  
Vertical Axis Wind Turbines

In order to augment the performance of vertical axis wind turbines, wind power towers have been used because they increase the frontal area. Typically, the wind power tower is installed as a circular column around a vertical axis wind turbine because the vertical axis wind turbine should be operated in an omnidirectional wind. As a result, the performance of the vertical axis wind turbine depends on the design parameters of the wind power tower. An experimental study was conducted in a wind tunnel to investigate the optimal design parameters of the wind power tower. Three different sizes of guide walls were applied to test with various wind power tower design parameters. The tested vertical axis wind turbine consisted of three blades of the NACA0018 profile and its solidity was 0.5. In order to simulate the operation in omnidirectional winds, the wind power tower was fabricated to be rotated. The performance of the vertical axis wind turbine was severely varied depending on the azimuthal location of the wind power tower. Comparison of the performance of the vertical axis wind turbine was performed based on the power coefficient obtained by averaging for the one periodic azimuth angle. The optimal design parameters were estimated using the results obtained under equal experimental conditions. When the non-dimensional inner gap was 0.3, the performance of the vertical axis wind turbine was better than any other gaps.

scholarly journals Numerical Investigations of the Effects of the Rotating Shaft and Optimization of Urban Vertical Axis Wind Turbines

Energies ◽  
2018 ◽  
Vol 11 (7) ◽  
pp. 1870 ◽  
Author(s):  
Lidong Zhang ◽  
Kaiqi Zhu ◽  
Junwei Zhong ◽  
Ling Zhang ◽  
Tieliu Jiang ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Suction Side ◽  
Vertical Axis ◽  
Power Coefficient ◽  
Small Scale ◽  
Physical Parameters ◽  
Rotating Shaft ◽  
Vertical Axis Wind Turbines ◽  
Negative Effect

The central shaft is an important and indispensable part of a small scale urban vertical axis wind turbines (VAWTs). Normally, it is often operated at the same angular velocity as the wind turbine. The shedding vortices released by the rotating shaft have a negative effect on the blades passing the wake of the wind shaft. The objective of this study is to explore the influence of the wake of rotating shaft on the performance of the VAWT under different operational and physical parameters. The results show that when the ratio of the shaft diameter to the wind turbine diameter (α) is 9%, the power loss of the wind turbine in one revolution increases from 0% to 25% relative to that of no-shaft wind turbine (this is a numerical experiment for which the shaft of the VAWT is removed in order to study the interactions between the shaft and blade). When the downstream blades pass through the wake of the shaft, the pressure gradient of the suction side and pressure side is changed, and an adverse effect is also exerted on the lift generation in the blades. In addition, α = 5% is a critical value for the rotating shaft wind turbine (the lift-drag ratio trend of the shaft changes differently). In order to figure out the impacts of four factors; namely, tip speed ratios (TSRs), α, turbulence intensity (TI), and the relative surface roughness value (ks/ds) on the performance of a VAWT system, the Taguchi method is employed in this study. The influence strength order of these factors is featured by TSRs > ks/ds > α > TI. Furthermore, within the range we have analyzed in this study, the optimal power coefficient (Cp) occurred under the condition of TSR = 4, α = 5%, ks/ds = 1 × 10−2, and TI = 8%.

Power performance enhancement of vertical axis wind turbines by a novel gurney flap design

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Milad Mousavi ◽  
Mehran Masdari ◽  
Mojtaba Tahani
Keyword(s):  
Wind Turbines ◽  
Vertical Axis ◽  
Dynamics Simulation ◽  
Power Coefficient ◽  
Lower Amount ◽  
Speed Ratio ◽  
Power Performance ◽  
Content Type ◽  
Vertical Axis Wind Turbines ◽  
Gurney Flap

Purpose Nowadays flaps and winglets are one of the main mechanisms to increase airfoil efficiency. This study aims to investigate the power performance of vertical axis wind turbines (VAWT) that are equipped with diverse gurney flaps. This study could play a crucial role in the design of the VAWT in the future. Design/methodology/approach In this paper, the two-dimensional computational fluid dynamics simulation is used. The second-order finite volume method is used for the discretization of the governing equations. Findings The results show that the gurney flap enhances the power coefficient at the low range of tip speed ratio (TSR). When an angled and standard gurney flap case has the same aerodynamic performance, an angled gurney flap case has a lower hinge moment on the junction of airfoil and gurney flap which shows the structural excellence of this case. In all gurney flap cases, the power coefficient increases by an average of 20% at the TSR range of 0.6 to 1.8. The gurney flap cases do not perform well at the high TSR range and the results show a lower amount of power coefficient compare to the clean airfoil. Originality/value The angled gurney flap which has the structural advantage and is deployed to the pressure side of the airfoil improves the efficiency of VAWT at the low and medium range of TSR. This study recommends using a controllable gurney flap which could be deployed at a certain amount of TSR.

Wind tunnel and numerical study of multi-storey vertical axis wind turbines with different configurations

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Abhijeet M. Malge ◽  
Prashant Maruti Pawar
Keyword(s):  
Wind Tunnel ◽  
Wind Turbine ◽  
Wind Power ◽  
Wind Turbines ◽  
Numerical Study ◽  
Research Work ◽  
Vertical Axis ◽  
Power Coefficient ◽  
Content Type ◽  
Vertical Axis Wind Turbines

Purpose Three different configurations of vertical axis wind turbines (VAWT) were fabricated by changing the storey height and their orientations. The purpose of this study is to find the effect of storey height and orientation on the performance of wind turbines. The multistory VAWT has three storeys. The first configuration had increased middle storey height, with 0–90-0 orientation of blades. Wherein the second turbine had equal storey heights. The third configuration had increased middle storey height with 0–120-240 orientation of blades. The blades were tested numerically and experimentally. Design/methodology/approach In this research work, prototypes of innovative multistory VAWT were built with different configurations and orientations. Three configurations of three-storey VAWT were fabricated by varying the height of storey of turbines. The orientations were made by keeping the storeys orthogonal to each other. Multistory VAWT was tested numerically and experimentally. ANSYS Fluent was used for computational fluid dynamic analysis of VAWT. K-epsilon model was used for numerical analysis of wind turbine. Experimentation was carried out in a wind tunnel for different tip speed ratios (TSR). Findings The three configurations of innovative multistory VAWT were tested numerically and experimentally for different TSR. It has been found that the VAWT with equal storey height had a better performance as compared to the other two configurations with increased middle storey height. The power coefficient of equal storey height VAWT was about 22%, wherein the power coefficient of turbines with reduced upper and lower storey height was between 5%–8% Research limitations/implications The research work of multi-storey VAWT is very novel and original. The findings of the research will contribute to the existing work done in the field of VAWT. This will help other researchers to have insight into the development of multistory VAWT. The effect of storey height and configuration of multi-storey VAWT is studied numerically and experimentally, which concludes that the performance of equal storey is superior as compared to other configurations. Practical implications The multi-storey concept of VAWT was developed to counter the problem of wind direction. The blades of each storey were arranged orthogonal to each other. This helped to harness wind power irrespective of the direction of the wind. This will make the VAWT more sustainable and financially viable for domestic use. Social implications The turbines are specially designed for remotely located housed in rural areas where the power grid is not yet reached. Users can install the turbine on their rooftop and harness wind power of 100 W capacity. This will help them to make their life easy. Originality/value This research work is very original and first of a kind. The multistory concept of the wind turbine was checked for the effect of storey height and orientations of blades on its performance. Different configurations and orientations of the vertical axis were designed and developed for the first time.

scholarly journals Viscous Flow and Dynamic Stall Effects on Vertical-Axis Wind Turbines

1995 ◽  
Vol 2 (1) ◽  
pp. 1-14 ◽  
Author(s):  
A. Allet ◽  
I. Paraschivoiu
Keyword(s):  
Wind Turbines ◽  
Stokes Equations ◽  
Control Volume ◽  
Numerical Procedure ◽  
Vertical Axis ◽  
Dynamic Stall ◽  
Staggered Grid ◽  
Speed Ratio ◽  
Vertical Axis Wind Turbines ◽  
Control Volume Approach

The present paper describes a numerical method, aimed to simulate the flow field of vertical-axis wind turbines, based on the solution of the steady, incompressible, laminar Navier-Stokes equations in cylindrical coordinates. The flow equations, written in conservation law form, are discretized using a control volume approach on a staggered grid. The effect of the spinning blades is simulated by distributing a time-averaged source terms in the ring of control volumes that lie in the path of turbine blades. The numerical procedure used here, based on the control volume approach, is the widely known “SIMPLER” algorithm. The resulting algebraic equations are solved by the TriDiagonal Matrix Algorithm (TDMA) in the r- and z-directions and the Cyclic TDMA in the 0-direction. The indicial model is used to simulate the effect of dynamic stall at low tip-speed ratio values. The viscous model, developed here, is used to predict aerodynamic loads and performance for the Sandia 17-m wind turbine. Predictions of the viscous model are compared with both experimental data and results from the CARDAAV aerodynamic code based on the Double-Multiple Streamtube Model. According to the experimental results, the analysis of local and global performance predictions by the 3D viscous model including dynamic stall effects shows a good improvement with respect to previous 2D models.

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°.

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.

Design Criteria on Sizing and Material Selection of SB-VAWTS

2013 ◽  
Author(s):  
Mojtaba Ahmadi-Baloutaki ◽  
Rupp Carriveau ◽  
David S-K. Ting
Keyword(s):  
Wind Turbines ◽  
Material Selection ◽  
Vertical Axis ◽  
Moment Of Inertia ◽  
Power Coefficient ◽  
Design Parameters ◽  
Speed Ratio ◽  
Design Criteria ◽  
Vertical Axis Wind Turbines ◽  
Selection Of

A design methodology has been presented on the sizing and material selection of straight-bladed vertical axis wind turbines. Several design parameters such as turbine power coefficient, blade tip speed ratio, rotor solidity factor, blade aspect ratio and rotor moment of inertia have been analyzed. Material selection and its relevant design criteria have also been discussed for different parts of a straight-bladed vertical axis wind turbines with three blades and two supporting arms per blade. The number of the supporting arms and their optimum locations have been determined via minimizing the bending moments on the blade. A comparative study has also been performed to examine the effect of blade density and turbine H/D ratio on the rotor moment of inertia. It was found that the turbine rotational speed increases as blade density decreases and this increase is larger at higher turbine H/D ratio.

scholarly journals Aeroacoustics behavioral study of Savonius wind turbine

2021 ◽  
Vol 2128 (1) ◽  
pp. 012033
Author(s):  
Maymouna Malainine ◽  
Amany Khaled ◽  
Sameh M Shabaan
Keyword(s):  
Wind Turbine ◽  
Vertical Axis ◽  
Sound Level ◽  
Aerodynamic Noise ◽  
Navier Stokes ◽  
Speed Ratio ◽  
Residential Areas ◽  
Vertical Axis Wind Turbines ◽  
Computational Fluid Dynamics Cfd ◽  
Savonius Wind Turbine

Abstract Vertical Axis Wind Turbines (VAWTs) are appropriate for use in populated areas. If VAWTs were installed at residential areas, the generated aerodynamic noise can be harmful in a way or another. Therefore, in the present study, the aero-acoustics of the conventional Savonius Wind turbine was investigated using Computational Fluid Dynamics (CFD). Both the Unsteady Reynolds-averaged Navier-Stokes (URANS) equations and impermeable Ffowcs Wiliams and Hawkings (FW-H) equation were simultaneously solved. The effect of speed ratio was also studied. The results indicate that; the pressure is inversely proportional to the speed ratio. Additionally, the velocity has been increased due to the increase of the tip speed ratio. Finally, it has improved that for the majority of receivers, the overall sound level increases with increasing speed ratio.

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