Combined Numerical and Experimental Study on the Use of Gurney Flaps for the Performance Enhancement of NACA0021 Airfoil in Static and Dynamic Conditions

2020 ◽  
Author(s):  
Francesco Balduzzi ◽  
David Holst ◽  
Pier Francesco Melani ◽  
Felix Wegner ◽  
Christian Navid Nayeri ◽  
...  
Keyword(s):  
Wind Energy ◽  
Performance Enhancement ◽  
Vertical Axis ◽  
Hysteresis Cycle ◽  
Dynamic Conditions ◽  
Energy Applications ◽  
Gurney Flaps ◽  
Industrial Community ◽  
Sinusoidal Motion ◽  
The Impact

Abstract Power augmentation devices in wind energy applications have been receiving increasing interest from both the scientific and the industrial community. In particular, Gurney Flaps (GFs) showed a great potential thanks to the passive functioning, the simple construction and the possibility to add them as a retrofit to existing rotors. Within this context, the authors have performed an extended investigation on the lift increase capabilities of GFs for the well-known NACA 0021 airfoil, which has been used in several wind energy applications up to now. The present paper shows the results of a combined experimental and numerical analysis considering different geometrical configurations of the flaps under both static and dynamic conditions. Experimental data were first obtained for the AoA range of 180 degrees at a Reynolds number of 180 k to analyze the impact of three different geometrical configurations of the GF on the aerodynamic behavior. The geometrical configurations were defined by varying the length of the flap (1.4% and 2.5% of the chord) and its inclination angle with respect to the blade chord (90 degrees and 45 degrees). The experimental investigation involved also dynamic sinusoidal pitching movements at multiple reduced frequencies to evaluate the stall hysteresis cycle. An unsteady CFD numerical model was calibrated against wind tunnel data and then exploited to extend the investigation to a wider range of Reynolds numbers for dynamic AoA rates of change typical of vertical-axis wind turbines, i.e. characterized by higher reduced frequencies with a non-sinusoidal motion law.

Combined Numerical and Experimental Study on the Use of Gurney Flaps for the Performance Enhancement of NACA0021 Airfoil in Static and Dynamic Conditions

2020 ◽  
Author(s):  
Francesco Balduzzi ◽  
David Holst ◽  
Pier Francesco Melani ◽  
Felix Wegner ◽  
Christian Navid Nayeri ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Wind Energy ◽  
Full Range ◽  
Hysteresis Cycle ◽  
Technical Literature ◽  
Dynamic Conditions ◽  
Energy Applications ◽  
Gurney Flaps ◽  
Wide Range ◽  
The Impact

Abstract The use of power augmentation devices in wind energy applications has been receiving increasing interest from both the scientific and the industrial community. In particular, Gurney Flaps (GFs) showed a great potential thanks to the passive functioning, the simple construction and the possibility to add them as a retrofit to existing rotors. The possibility of having a high quality set of airfoil data for a wide range of both angle of attack (AoA) and Reynolds number is pivotal in the design phase of newly developed machines. Such data are usually available in the technical literature for smooth airfoils, while there is a lack of generalized results in case of airfoils with GFs. Within this context, the authors have performed an extended investigation on the lift increase capabilities of GFs for the well-known NACA 0021 airfoil, which has been used in several wind energy applications up to now. The present paper shows the results of a combined experimental and numerical analysis considering different geometrical configurations of the flaps under both static and dynamic conditions. Experimental data were first obtained for the AoA range of 180 degrees at a low value of Reynolds number (i.e. Re = 180 k) to analyze the impact of three different geometrical configurations of the GF on the aerodynamic behavior for the full range of incidence angles. The geometrical configurations were defined by varying the length of the flap (i.e. 1.4% and 2.5% of the chord length) and its inclination angle with respect to the blade chord (i.e. 90 degrees and 45 degrees). The experimental investigation involved also dynamic sinusoidal pitching movements at multiple reduced frequencies to evaluate the stall hysteresis cycle. Subsequently, an unsteady CFD numerical model was first calibrated against wind tunnel data at low values of the Reynolds number. Then, the virtual model was exploited to extend the investigation to a wider range of Reynolds number for dynamic AoA rates of change typical for example of vertical-axis wind turbines, i.e. characterized by higher reduced frequencies with a non-sinusoidal motion law.

Combined Numerical and Experimental Study on the Use of Gurney Flaps for the Performance Enhancement of NACA0021 Airfoil in Static and Dynamic Conditions

2021 ◽  
Author(s):  
Francesco Balduzzi ◽  
David Holst ◽  
Pier Francesco Melani ◽  
Felix Wegner ◽  
Christian Navid Nayeri ◽  
...  
Keyword(s):  
Experimental Study ◽  
Performance Enhancement ◽  
Dynamic Conditions ◽  
Gurney Flaps

Circulation Control Applied to Wind Turbines

2009 ◽  
Author(s):  
David McGrain ◽  
Gerald M. Angle ◽  
Jay P. Wilhelm ◽  
Emily D. Pertl ◽  
James E. Smith
Keyword(s):  
Wind Energy ◽  
Wind Turbines ◽  
Power Output ◽  
Alternative Energy ◽  
Vertical Axis ◽  
Limiting Factor ◽  
Circulation Control ◽  
Bird Populations ◽  
Horizontal Axis Wind Turbines ◽  
The Impact

The recent rise in fuel costs and global warming concerns have re-invigorated the search for alternative energy sources. Harnessing energy from the wind is a logical alternative; however the cost and efficiency of current wind turbines is a limiting factor. The use of an augmented Vertical Axis Wind Turbines (VAWTs) may become the superior choice to the more common Horizontal Axis Wind Turbines (HAWTs) that are usually associated with the harvesting of wind energy. HAWTs operate on the same principles as large airplane propellers, while VAWTs operate on lift and/or drag principles like an airplane wing or a sail on a boat. VAWTs are currently being investigated for use with circulation control to increase their potential power output. In this paper, two topics will be presented, a comparison between VAWTs and HAWTs for rotor diameter versus key turbine aspects and the impact of VAWTs on environmental concerns, such as bat and bird populations. The Center for Industrial Research Applications (CIRA) at West Virginia University (WVU) is currently developing a concept utilizing circulation control to increase the lift to drag ratio, maximizing the beneficial forces on the VAWT blade, allowing for improved wind energy production. For the comparison between VAWTs and HAWTs, there are currently 14 companies with a total of 34 wind turbines variations representing VAWTs and 11 companies with a total of 40 wind turbines representing HAWTs. Trend studies of VAWT and HAWT diameters to cut-in-speed, rated velocity, max velocity, power output (<100 kW), and power output (≥100 kW) were created to show the potential of VAWTs. A growing concern with wind energy is the impact on bat and bird populations. It is currently believed that VAWTs reduce the impact of wind energy by altering the interaction with the wind. If these benefits can be proven, then not only are VAWTs potentially more economical, but even more eco-friendly.

scholarly journals The impact of the diurnal cycle of the atmospheric boundary layer on physical variables relevant for wind energy applications

2016 ◽  
Author(s):  
Antonia Englberger ◽  
Andreas Dörnbrack
Keyword(s):  
Boundary Layer ◽  
Wind Energy ◽  
Atmospheric Boundary Layer ◽  
Diurnal Cycle ◽  
Vertical Wind Shear ◽  
Physical Parameters ◽  
Late Afternoon ◽  
Energy Applications ◽  
Physical Variables ◽  
The Impact

Abstract. This paper provides a quantification of the temporal evolution of physical variables in the atmospheric boundary layer (ABL) relevant for wind energy applications. For this purpose, we use the unique dataset gathered during the BLLAST (Boundary Layer Late Afternoon and Sunset Turbulence) field experiment to validate a large-eddy simulation (LES) model by simulating the complete diurnal cycle of the ABL. In this way, this contribution to the special issue of ACP "The Boundary-Layer Late Afternoon and Sunset Turbulence project" satisfies the purpose of the BLLAST experiment: to provide a dataset for the validation of numerical simulations aiming to study transient BL processes. For wind energy applications, we are investigating the behaviour of different physical parameters which are relevant in the height region where a wind turbine operates. This results in a quantification of the diurnal cycle influence on the vertical wind shear, the stratification and the turbulence intensity in the atmosphere. Further, the impact of different heterogeneous surface conditions on shear near the surface layer of the ABL is investigated.

Performance enhancement of Savonius wind turbine by blade shape and twisted angle modifications

2021 ◽  
pp. 095765092098794
Author(s):  
Ahmed M Nagib Elmekawy ◽  
Hassan A Hassan Saeed ◽  
Sadek Z Kassab
Keyword(s):  
Wind Turbine ◽  
Performance Enhancement ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Vertical Axis ◽  
Cfd Simulations ◽  
Sliding Mesh ◽  
Blade Shape ◽  
Rotor Shape ◽  
Twisting Angle

Three-dimensional CFD simulations are carried out to study the increase of power generated from Savonius vertical axis wind turbines by modifying the blade shape and blade angel of twist. Twisting angle of the classical blade are varied and several proposed novel blade shapes are introduced to enhance the performance of the wind turbine. CFD simulations have been performed using sliding mesh technique of ANSYS software. Four turbulence models; realizable k -[Formula: see text], standard k - [Formula: see text], SST transition and SST k -[Formula: see text] are utilized in the simulations. The blade twisting angle has been modified for the proposed dimensions and wind speed. The introduced novel blade increased the power generated compared to the classical shapes. The two proposed novel blades achieved better power coefficients. One of the proposed models achieved an increase of 31% and the other one achieved 32.2% when compared to the classical rotor shape. The optimum twist angel for the two proposed models achieved 5.66% and 5.69% when compared with zero angle of twist.

scholarly journals Optimal Design of Novel Blade Profile for Savonius Wind Turbines

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3484
Author(s):  
Tai-Lin Chang ◽  
Shun-Feng Tsai ◽  
Chun-Lung Chen
Keyword(s):  
Wind Energy ◽  
Drag Force ◽  
Wind Turbines ◽  
Rural Areas ◽  
Large Scale ◽  
Design Method ◽  
Angular Position ◽  
Vertical Axis ◽  
Blade Profile ◽  
Main Concept

Since the affirming of global warming, most wind energy projects have focused on the large-scale Horizontal Axis Wind Turbines (HAWTs). In recent years, the fast-growing wind energy sector and the demand for smarter grids have led to the use of Vertical Axis Wind Turbines (VAWTs) for decentralized energy generation systems, both in urban and remote rural areas. The goals of this study are to improve the Savonius-type VAWT’s efficiency and oscillation. The main concept is to redesign a Novel Blade profile using the Taguchi Robust Design Method and the ANSYS-Fluent simulation package. The convex contour of the blade faces against the wind, creating sufficient lift force and minimizing drag force; the concave contour faces up to the wind, improving or maintaining the drag force. The result is that the Novel Blade improves blade performance by 65% over the Savonius type at the best angular position. In addition, it decreases the oscillation and noise accordingly. This study achieved its two goals.

scholarly journals Evaluation of offshore wind power in the China sea

2021 ◽  
pp. 014459872199226
Author(s):  
Yu-chi Tian ◽  
Lei kou ◽  
Yun-dong Han ◽  
Xiaodong Yang ◽  
Ting-ting Hou ◽  
...  
Keyword(s):  
Wind Energy ◽  
Wind Power ◽  
Energy Development ◽  
Offshore Wind ◽  
Human Beings ◽  
Offshore Wind Power ◽  
Business Operation ◽  
Advantages And Disadvantages ◽  
Wind Energy Development ◽  
The Impact

With resource crisis and environmental crisis increasingly grim, many countries turn the focus to pollution-free and renewable wind energy resources, which are mainly used for offshore wind power generation, seawater desalination and heating, etc., on the premise that the characteristics of resources are fully grasped. In this study, the evaluation of offshore wind energy in offshore waters in China, as well as the advantages and disadvantages of existing studies were overviewed from four aspects: the spatial-temporal characteristics of wind energy, wind energy classification, the short-term forecast of wind energy and the long-term projection of wind energy, according to the research content and the future considerations about wind energy evaluation (evaluation of wind energy on islands and reefs, the impact of wind energy development on human health) were envisaged, in the hope of providing a scientific basis for the site selection and business operation ‘or military applications’ here (after business operation), etc. of wind energy development, ‘aritime navigation against environmental construction,’ here and also contributing to the sustainable development and health of human beings.

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