Numerical Simulations of Vertical-Axis Wind Turbine Blades

2011 ◽  
Author(s):  
B. D. Plourde ◽  
J. P. Abraham ◽  
G. S. Mowry ◽  
W. J. Minkowycz
Keyword(s):  
Wind Tunnel ◽  
Numerical Simulations ◽  
Large Scale ◽  
Turbine Blades ◽  
Vertical Axis ◽  
Test Facility ◽  
Wing Design ◽  
In Situ Tests ◽  
Initial Design

A recent research project has been focused on the design, manufacture, and testing of novel, vertical-axis turbines which can be directly attached to existing structures (such as communication towers) for local power generation, particularly in areas of the world where grid-connected electricity is unavailable. The proposed turbine has undergone a multitude of design stages, including the wing design, prototype fabrication, wind-tunnel testing, and manufacture. This report discusses the initial design process utilized to create the turbine wing. That process relied upon numerical simulations of the unsteady flow patterns which occur when the wing rotates. Results from the simulation were used to modify the wing design and significant improvements in performance were realized. Based on wind-tunnel tests, improvements on the order of 300% were obtained, compared to the initial design. Improvements of this magnitude have allowed the progression from prototype testing to large-scale manufacturing. The simulations allowed the implementation of novel design features such as preferentially deployed vents which allowed an increase of torque and a decrease of transverse loads. Results from the simulation were compared with experimental results obtained from a wind-tunnel test. In addition, data was extracted from an in situ test facility which was installed with wind-speed and data acquisition equipment. It was found that the results of the simulation were in close agreement with both the results from the wind tunnel and the in situ tests. The congruence gave added confidence to the veracity of the simulations.

scholarly journals Evaluation of Stiffness and Dynamic Properties of a Mine Shaft Steelwork Structure through In Situ Tests and Numerical Simulations

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 664
Author(s):  
Jacek Jakubowski ◽  
Przemysław Fiołek
Keyword(s):  
Numerical Simulations ◽  
Dynamic Properties ◽  
Vertical Motion ◽  
Load Test ◽  
Mode Shapes ◽  
Dynamic Amplification Factor ◽  
In Situ Tests ◽  
Mine Shaft ◽  
Numerical Investigations

A mine shaft steelwork is a three-dimensional frame that directs the vertical motion of conveyances in mine shafts. Here, we conduct field and numerical investigations on the stiffness and dynamic properties of these structures. Based on the design documentation of the shaft, materials data, and site inspection, the steelwork’s finite element model, featuring material and geometric non-linearities, was developed in Abaqus. Static load tests of steelwork were carried out in an underground mine shaft. Numerical simulations reflecting the load test conditions showed strong agreement with the in situ measurements. The validated numerical model was used to assess the dynamic characteristics of the structure. Dynamic linear and non-linear analyses delivered the natural frequencies, mode shapes, and structural response to dynamic loads. The current practices and regulations regarding shaft steelwork design and maintenance do not account for the stiffness of guide-to-bunton connections and disregard dynamic factors. Our experimental and numerical investigations show that these connections provide considerable stiffness, which leads to the redistribution and reduction in bending moments and increased stiffness of the construction. The results also show a high dynamic amplification factor. The omission of these features implicates an incorrect assessment of the design loads and can lead to over- or under-sized structures and ultimately to shortened design working life or failure.

Detailed Analysis of the Wake Structure of a Straight-Blade H-Darrieus Wind Turbine by Means of Wind Tunnel Experiments and Computational Fluid Dynamics Simulations

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Alessandro Bianchini ◽  
Francesco Balduzzi ◽  
Giovanni Ferrara ◽  
Lorenzo Ferrari ◽  
Giacomo Persico ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Wind Tunnel ◽  
Wind Turbines ◽  
Large Scale ◽  
Vertical Axis ◽  
Performance Estimation ◽  
Small Scale ◽  
Dynamics Simulations

Darrieus vertical axis wind turbines (VAWTs) have been recently identified as the most promising solution for new types of applications, such as small-scale installations in complex terrains or offshore large floating platforms. To improve their efficiencies further and make them competitive with those of conventional horizontal axis wind turbines, a more in depth understanding of the physical phenomena that govern the aerodynamics past a rotating Darrieus turbine is needed. Within this context, computational fluid dynamics (CFD) can play a fundamental role, since it represents the only model able to provide a detailed and comprehensive representation of the flow. Due to the complexity of similar simulations, however, the possibility of having reliable and detailed experimental data to be used as validation test cases is pivotal to tune the numerical tools. In this study, a two-dimensional (2D) unsteady Reynolds-averaged Navier–Stokes (U-RANS) computational model was applied to analyze the wake characteristics on the midplane of a small-size H-shaped Darrieus VAWT. The turbine was tested in a large-scale, open-jet wind tunnel, including both performance and wake measurements. Thanks to the availability of such a unique set of experimental data, systematic comparisons between simulations and experiments were carried out for analyzing the structure of the wake and correlating the main macrostructures of the flow to the local aerodynamic features of the airfoils in cycloidal motion. In general, good agreement on the turbine performance estimation was constantly appreciated.

Development of a CFD Methodology to Reproduce the Effects of Macro Turbulence on Wind Turbines and its Application to the Particular Case of a VAWT

2019 ◽  
Author(s):  
Francesco Balduzzi ◽  
Marco Zini ◽  
Giovanni Ferrara ◽  
Alessandro Bianchini
Keyword(s):  
Wind Tunnel ◽  
Wind Turbines ◽  
Large Scale ◽  
Maximum Level ◽  
Vertical Axis ◽  
Navier Stokes ◽  
Energy Yield ◽  
Vertical Axis Wind Turbine ◽  
Energy Applications ◽  
Wind Tunnel Data

Abstract Based on existing reports and databases, most of the installations in highly turbulent sites in fact fail to reach the expected energy yield, resulting in still or underperforming turbines that also give bad press for the technology. A better understanding of the real performance of wind turbines under highly turbulent conditions is then pivotal to ensure the economic viability of new installations. To this end, the possible use of Computational Fluid Dynamics (CFD) techniques could provide notable benefits, reducing the time-to-market and the cost with respect to experiments. On the other hand, it is intrinsically not easy to reproduce properly intense and large-scale turbulence with the techniques of common use for research and industry (e.g. CFD unsteady RANS), while the only methods that are granted to do so (e.g. DNS or LES) are often not computationally affordable. Moving from this background, this study presents the development a numerical strategy to exploit at their maximum level the capabilities of an unsteady Reynolds-Averaged Navier-Stokes (RANS) approach in order to reproduce fields of macro turbulence of use for wind energy applications. The study is made of two main parts. In the first part, the numerical methodology is discussed and assessed based on real wind tunnel data. The benefits and drawbacks are presented also in comparison to other existing methods. In the second part, it has been used to simulate the behavior under turbulence of a H-Darrieus vertical-axis wind turbine, for which unique wind tunnel data were available. The simulations, even if preliminary, showed good matching with experiments (e.g. confirming the increase of power), showing then the potential of the method.

Aerodynamic Measurements on a Vertical Axis Wind Turbine in a Large Scale Wind Tunnel

2010 ◽  
Author(s):  
L. Battisti ◽  
L. Zanne ◽  
S. Dell’Anna ◽  
V. Dossena ◽  
B. Paradiso ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Flow Field ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Large Scale ◽  
Fluid Dynamic ◽  
Vertical Axis ◽  
Vertical Axis Wind Turbine ◽  
Aerodynamic Optimization ◽  
Vertical Axis Wind Turbines

This paper presents the first results of a wide experimental investigation on the aerodynamics of a vertical axis wind turbine. Vertical axis wind turbines have recently received particular attention, as interesting alternative for small and micro generation applications. However, the complex fluid dynamic mechanisms occurring in these machines make the aerodynamic optimization of the rotors still an open issue and detailed experimental analyses are now highly recommended to convert improved flow field comprehensions into novel design techniques. The experiments were performed in the large-scale wind tunnel of the Politecnico di Milano (Italy), where real-scale wind turbines for micro generation can be tested in full similarity conditions. Open and closed wind tunnel configurations are considered in such a way to quantify the influence of model blockage for several operational conditions. Integral torque and thrust measurements, as well as detailed aerodynamic measurements were applied to characterize the 3D flow field downstream of the turbine. The local unsteady flow field and the streamwise turbulent component, both resolved in phase with the rotor position, were derived by hot wire measurements. The paper critically analyses the models and the correlations usually applied to correct the wind tunnel blockage effects. Results evidence that the presently available theoretical correction models does not provide accurate estimates of the blockage effect in the case of vertical axis wind turbines. The tip aerodynamic phenomena, in particular, seem to play a key role for the prediction of the turbine performance; large-scale unsteadiness is observed in that region and a simple flow model is used to explain the different flow features with respect to horizontal axis wind turbines.

Detailed Analysis of the Wake Structure of a Straight-Blade H-Darrieus Wind Turbine by Means of Wind Tunnel Experiments and CFD Simulations

2017 ◽  
Author(s):  
Alessandro Bianchini ◽  
Francesco Balduzzi ◽  
Giovanni Ferrara ◽  
Lorenzo Ferrari ◽  
Giacomo Persico ◽  
...  
Keyword(s):  
Experimental Data ◽  
Wind Tunnel ◽  
Wind Turbines ◽  
Large Scale ◽  
Vertical Axis ◽  
Performance Estimation ◽  
Small Scale ◽  
Horizontal Axis Wind Turbines ◽  
Floating Platforms ◽  
Physical Phenomena

Darrieus Vertical Axis Wind Turbines (VAWTs) have been recently identified as the most promising solution for new types of applications, such as small-scale installations in complex terrains or offshore large floating platforms. To improve their efficiencies further and make them competitive with those of conventional horizontal axis wind turbines, a more in depth understanding of the physical phenomena that govern the aerodynamics past a rotating Darrieus turbine is needed. Within this context, Computational Fluid Dynamics (CFD) can play a fundamental role, since it represents the only model able to provide a detailed and comprehensive representation of the flow. Due to the complexity of similar simulations, however, the possibility of having reliable and detailed experimental data to be used as validation test cases is pivotal to tune the numerical tools. In this study, a two-dimensional U-RANS computational model was applied to analyze the wake characteristics on the mid plane of a small-size H-shaped Darrieus VAWT. The turbine was tested in a large-scale, open-jet wind tunnel, including both performance and wake measurements. Thanks to the availability of such a unique set of experimental data, systematic comparisons between simulations and experiments were carried out analyzing the structure of the wake, and correlating the main macro-structures of the flow to the local aerodynamic features of the airfoils in cycloidal motion. In general, good agreement on the turbine performance estimation was constantly appreciated.

Wind-Tunnel Tests of Vertical-Axis Wind Turbine Blades

2011 ◽  
Author(s):  
B. D. Plourde ◽  
J. P. Abraham ◽  
G. S. Mowry ◽  
W. J. Minkowycz
Keyword(s):  
Power Generation ◽  
Wind Tunnel ◽  
Turbine Blade ◽  
Vertical Axis ◽  
Cellular Communication ◽  
Wing Design ◽  
Ongoing Research ◽  
Wind Speeds ◽  
Wide Range ◽  
Communication Towers

An ongoing research project is investigating the potential of locating vertical-axis wind turbines (WT) on remote, off-grid cellular communication towers. The goal of the WT is to provide local power generation to meet the electrical needs of the tower. While vertical-axis devices are less efficient than their more traditional horizontal-axis counterparts, they provide a number of practical advantages which make them a suitable choice for the present situation. First, the direction of their axis is aligned with the existing tower and its rotation does not interfere with the tower structure. Second, vertical-axis devices are much less susceptible to the direction of wind and they do not require control-systems to ensure they are oriented correctly. Third, vertical-axis turbines have very low start-up wind speeds so that they generate power over a wide range of speeds. Fourth, since vertical-axis turbines rotate at a slower speed compared with horizontal counterparts, they impart a lessened vibration load to the tower. These facts, collectively, make the vertical-axis turbine suitable for the proposed application. The design process involved a detailed initial design of the turbine blade using computational methods. Next, a trio of designs was evaluated experimentally in a large, low-speed wind tunnel. The wind tunnel is operated by the University of Minnesota’s St. Anthony Falls Fluid Laboratory. The tunnel possesses two testing sections. The larger section was sufficient to test a full-size turbine blade. Accounting was taken of the blockage effect following the tests. The experiments were completed on (1) a solid-wing design (unvented), (2) a slotted-wing design (vented), and (3) a capped-and-slotted design (capped). Conditions spanned a wide range of wind speeds (4.5–11.5 m/s). The turbines were connected to electronics which simulated a range of electrical loads. The tested range was selected to span the expected range of resistances which will be found in practice. It was discovered that over a range of these wind speeds and electrical resistances, slots located on the wings result in a slight improvement in power generation. On the other hand, the slotted-and-capped design provided very large increases in performance (approximately 200–300% compared with the unvented version). This large improvement has justified commercialization of the product for use in powering remote, off-grid cellular communication towers.

Development of a Computational Fluid Dynamics Methodology to Reproduce the Effects of Macroturbulence on Wind Turbines and Its Application to the Particular Case of a VAWT

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Francesco Balduzzi ◽  
Marco Zini ◽  
Giovanni Ferrara ◽  
Alessandro Bianchini
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Tunnel ◽  
Wind Turbines ◽  
Large Scale ◽  
Maximum Level ◽  
Vertical Axis ◽  
Energy Yield ◽  
Vertical Axis Wind Turbine ◽  
Wind Tunnel Data

Abstract Based on existing reports and databases, most of the installations in highly turbulent sites in fact fail to reach the expected energy yield, resulting in still or underperforming turbines that also give bad press for the technology. A better understanding of the real performance of wind turbines under highly turbulent conditions is then pivotal to ensure the economic viability of new installations. To this end, the possible use of computational fluid dynamics (CFD) techniques could provide notable benefits, reducing the time-to-market and the cost with respect to experiments. On the other hand, it is intrinsically not easy to reproduce properly intense and large-scale turbulence with the techniques of common use for research and industry (e.g., CFD unsteady Reynolds-averaged Navier–Stokes (URANS)), while the only methods that are granted to do so (e.g., direct numerical simulation (DNS) or large eddy simulation (LES)) are often not computationally affordable. Moving from this background, this study presents the development of a numerical strategy to exploit at their maximum level the capabilities of an unsteady RANS approach in order to reproduce fields of macroturbulence of use for wind energy applications. The study is made of two main parts. In the first part, the numerical methodology is discussed and assessed based on real wind tunnel data. The benefits and drawbacks are presented also in comparison to other existing methods. In the second part, it has been used to simulate the behavior under turbulence of a H Darrieus vertical-axis wind turbine, for which unique wind tunnel data were available. The simulations, even if preliminary, showed good matching with experiments (e.g., confirming the increase of power), showing then the potential of the method.

Background-Oriented Schlieren Imaging for Full-Scale and In-Flight Testing

2014 ◽  
Vol 59 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Markus Raffel ◽  
James T. Heineck ◽  
Edward Schairer ◽  
Friedrich Leopold ◽  
Kolja Kindler
Keyword(s):  
Wind Tunnel ◽  
Large Scale ◽  
Flight Testing ◽  
Tip Vortices ◽  
Wide Range ◽  
Spatial Coordinates ◽  
Blade Tip ◽  
Natural Formation ◽  
Background Oriented Schlieren

Background-oriented schlieren (BOS) methods suited for large-scale and in-flight testing are presented with special emphasis on the detection and tracing of blade tip vortices in situ. Retroreflective recording and photogrammetric epipolar analysis for the computation of the vortices' spatial coordinates in the wind tunnel are described. Feasibility and fidelity of reference-free BOS in conjunction with natural formation backgrounds and related evaluation methods are discussed, additionally, illustrating their simplicity and robustness. Results of successful image acquisition from a chaser aircraft are presented allowing vortex wakes to be identified at a wide range of flight attitudes, including complex maneuvers.

Laterally Loaded Piles With Wings: In Situ Testing With Cyclic Loading From Varying Directions

2013 ◽  
Author(s):  
Christina Rudolph ◽  
Jürgen Grabe
Keyword(s):  
Large Scale ◽  
Load Level ◽  
Lateral Loading ◽  
Offshore Wind ◽  
In Situ Tests ◽  
Laterally Loaded Piles ◽  
Offshore Wind Turbines ◽  
Loading Direction ◽  
Laterally Loaded

The application of piles as foundations for offshore wind turbines yields new requirements for the design. Wind and waves induce a cyclic lateral loading on the pile which changes direction corresponding to the meteorological conditions. Cyclic lateral loading on piles results in accumulated displacements, depending on the cyclic load level and load characteristics. The deformation can increase significantly due to a varying loading direction. Under such loading conditions the pile can drift sideways even if the loading is symmetric. Wings attached to the pile shortly below the seabed have been known to reduce deformations on laterally loaded piles as they locally enlarge the diameter on which the soil resistance is activated. They also change the cross-section of the pile from a circular shape to a star-shape. This might reduce the drifting of the pile. A series of large-scale in-situ tests has been carried out in order to identify the effects of changing loading direction as well as the applicability of winged piles to reduce deformations. Two tubular steel piles (one of them equipped with wings) have been installed and subjected to high-cyclic lateral loading from varying directions. In this paper the in-situ tests and their results are presented.

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