2017
Miao, Weipao; Li, Chun; Pavesi, Giorgio; Yang, Jun; Xie, Xiaoyun
Investigation of wake characteristics of a yawed HAWT and its impacts on the inline downstream wind turbine using unsteady CFD Journal Article
In: Journal of Wind Engineering and Industrial Aerodynamics, vol. 168, iss. May, pp. 60-71, 2017, ISSN: 01676105.
Abstract | Links | BibTeX | Tags: CFD, Power Output, Wake deviation, Wind, Wind farm, Yaw
@article{Miao2017,
title = {Investigation of wake characteristics of a yawed HAWT and its impacts on the inline downstream wind turbine using unsteady CFD},
author = {Weipao Miao and Chun Li and Giorgio Pavesi and Jun Yang and Xiaoyun Xie},
url = {http://dx.doi.org/10.1016/j.jweia.2017.05.002},
doi = {10.1016/j.jweia.2017.05.002},
issn = {01676105},
year = {2017},
date = {2017-01-01},
urldate = {2017-01-01},
journal = {Journal of Wind Engineering and Industrial Aerodynamics},
volume = {168},
issue = {May},
pages = {60-71},
publisher = {Elsevier Ltd},
abstract = {Unsteady CFD simulations for influences of the yawed wake on the wake trajectory and the downstream wind turbine were carried out using the full rotor model (FRM) of a 5 MW wind turbine, in order to investigate the mechanism of wake deviation. A control strategy based on the yaw angle was adopted to skew the upstream wake trajectory, thereby avoiding the downstream wind turbine and improving the efficiency of whole wind farm power generation. In this paper, the commercial CFD software STAR-CCM+ was used to simulate the wind farm with two tandem wind turbines operating in the neutral atmospheric boundary layer (ABL) condition. The results show that the wind farm's total power increases when the upstream wind turbine applies a positive yaw angle intentionally. According to the analysis of velocity contours, wake centerlines and vortex structures, a counter-rotating blade tip vortex pair is observed to be responsible for the wake deviation effects. It also reveals that the influence of a yawed wake on the downstream wind turbine may be slightly underestimated in some empirical wake model.},
keywords = {CFD, Power Output, Wake deviation, Wind, Wind farm, Yaw},
pubstate = {published},
tppubtype = {article}
}
Unsteady CFD simulations for influences of the yawed wake on the wake trajectory and the downstream wind turbine were carried out using the full rotor model (FRM) of a 5 MW wind turbine, in order to investigate the mechanism of wake deviation. A control strategy based on the yaw angle was adopted to skew the upstream wake trajectory, thereby avoiding the downstream wind turbine and improving the efficiency of whole wind farm power generation. In this paper, the commercial CFD software STAR-CCM+ was used to simulate the wind farm with two tandem wind turbines operating in the neutral atmospheric boundary layer (ABL) condition. The results show that the wind farm's total power increases when the upstream wind turbine applies a positive yaw angle intentionally. According to the analysis of velocity contours, wake centerlines and vortex structures, a counter-rotating blade tip vortex pair is observed to be responsible for the wake deviation effects. It also reveals that the influence of a yawed wake on the downstream wind turbine may be slightly underestimated in some empirical wake model.
2014
Rossetti, Antonio; Pavesi, Giorgio; Ardizzon, Guido; Santolin, Alberto
Numerical Analyses of Cavitating Flow in a Pelton Turbine Journal Article
In: Journal of Fluids Engineering, vol. 136, iss. 8, pp. 081304, 2014, ISSN: 0098-2202.
Abstract | Links | BibTeX | Tags: Cavitation, CFD, Multiphase Flow, Pelton
@article{pop00014,
title = {Numerical Analyses of Cavitating Flow in a Pelton Turbine},
author = {Antonio Rossetti and Giorgio Pavesi and Guido Ardizzon and Alberto Santolin},
url = {http://fluidsengineering.asmedigitalcollection.asme.org/article.aspx?doi=10.1115/1.4027139 http://biomechanical.asmedigitalcollection.asme.org/article.aspx?articleid=1846558},
doi = {10.1115/1.4027139},
issn = {0098-2202},
year = {2014},
date = {2014-01-01},
urldate = {2014-01-01},
journal = {Journal of Fluids Engineering},
volume = {136},
issue = {8},
pages = {081304},
publisher = {… .asmedigitalcollection.asme.org},
abstract = {Erosion and wear of hydraulic surfaces are frequent problems in hydraulic turbines, which lead to a decrease of the performance in time and/or in extreme cases to the rotor mechanical failure. These circumstances have negative repercussions on the annual produced power due to the decay of the efficiency, the delivered power, and to the off line periods as result of ordinary and extraordinary hydraulic profiles maintenances. Consistently, the study of this wearing process is an important step to improve the impeller design, and to avoid or minimize the rise of extraordinary maintenance. While mechanical damages are well documented and studied, little information can be found on cavitation in Pelton turbines. In this paper, a CFD model was applied to study the cavitation mechanics on a Pelton turbine. A Pelton runner affected by pitting cavitation was taken as a test case. The bucket geometry was modeled and analyzed using unsteady Reynolds averaged Navier-Stokes (RANS) multiphase analyses. Numerical results allowed us to highlight the different vapor productions during the cut-in water jet processes by the bucket. Furthermore, a simple procedure to identify the locations of higher damage risk was presented and verified in the test case runner.},
keywords = {Cavitation, CFD, Multiphase Flow, Pelton},
pubstate = {published},
tppubtype = {article}
}
Erosion and wear of hydraulic surfaces are frequent problems in hydraulic turbines, which lead to a decrease of the performance in time and/or in extreme cases to the rotor mechanical failure. These circumstances have negative repercussions on the annual produced power due to the decay of the efficiency, the delivered power, and to the off line periods as result of ordinary and extraordinary hydraulic profiles maintenances. Consistently, the study of this wearing process is an important step to improve the impeller design, and to avoid or minimize the rise of extraordinary maintenance. While mechanical damages are well documented and studied, little information can be found on cavitation in Pelton turbines. In this paper, a CFD model was applied to study the cavitation mechanics on a Pelton turbine. A Pelton runner affected by pitting cavitation was taken as a test case. The bucket geometry was modeled and analyzed using unsteady Reynolds averaged Navier-Stokes (RANS) multiphase analyses. Numerical results allowed us to highlight the different vapor productions during the cut-in water jet processes by the bucket. Furthermore, a simple procedure to identify the locations of higher damage risk was presented and verified in the test case runner.
Ardizzon, Guido; Cavazzini, Giovanna; Pavesi, Giorgio
A new generation of small hydro and pumped-hydro power plants: Advances and future challenges Journal Article
In: Renewable and Sustainable Energy Reviews, vol. 31, pp. 746-761, 2014, ISSN: 13640321.
Abstract | Links | BibTeX | Tags: CFD, Hydropower, Optimal management strategies, Pumped-hydro energy storage plant, Small hydro power plant, Variable-speed pump-turbine
@article{Ardizzon2014a,
title = {A new generation of small hydro and pumped-hydro power plants: Advances and future challenges},
author = {Guido Ardizzon and Giovanna Cavazzini and Giorgio Pavesi},
url = {http://linkinghub.elsevier.com/retrieve/pii/S1364032113008575},
doi = {10.1016/j.rser.2013.12.043},
issn = {13640321},
year = {2014},
date = {2014-01-01},
journal = {Renewable and Sustainable Energy Reviews},
volume = {31},
pages = {746-761},
abstract = {Hydropower is not only a renewable and sustainable energy source, but its flexibility and storage capacity also makes it possible to improve grid stability and to support the deployment of other intermittent renewable energy sources such as wind and solar power. As a result, a renewed interest in pumped-hydro energy storage plants (PHES) and a huge demand for the rehabilitation of old small hydropower plants are emerging globally. As regards PHES, advances in turbine design are required to increase plant performance and flexibility and new strategies for optimizing storage capacity and for maximizing plant profitability in the deregulated energy market have to be developed. During the upgrading of old small hydropower plants, the main challenges to be faced are the design of new runners, that had to match the existing stationary parts, and the development of optimal sizing and management strategies to increase their economic appeal. This paper traces an overview of the prospects of pumped-hydro energy storage plants and small hydro power plants in the light of sustainable development. Advances and future challenges in both turbine design and plant planning and management are proposed. PHES and hybrid wind/solar-PHES are illustrated and discussed, as well as the limits and peculiarities of the new design strategies, based on computational fluid dynamics, for both PHES and small hydropower plants. ?? 2014 Elsevier Ltd.},
keywords = {CFD, Hydropower, Optimal management strategies, Pumped-hydro energy storage plant, Small hydro power plant, Variable-speed pump-turbine},
pubstate = {published},
tppubtype = {article}
}
Hydropower is not only a renewable and sustainable energy source, but its flexibility and storage capacity also makes it possible to improve grid stability and to support the deployment of other intermittent renewable energy sources such as wind and solar power. As a result, a renewed interest in pumped-hydro energy storage plants (PHES) and a huge demand for the rehabilitation of old small hydropower plants are emerging globally. As regards PHES, advances in turbine design are required to increase plant performance and flexibility and new strategies for optimizing storage capacity and for maximizing plant profitability in the deregulated energy market have to be developed. During the upgrading of old small hydropower plants, the main challenges to be faced are the design of new runners, that had to match the existing stationary parts, and the development of optimal sizing and management strategies to increase their economic appeal. This paper traces an overview of the prospects of pumped-hydro energy storage plants and small hydro power plants in the light of sustainable development. Advances and future challenges in both turbine design and plant planning and management are proposed. PHES and hybrid wind/solar-PHES are illustrated and discussed, as well as the limits and peculiarities of the new design strategies, based on computational fluid dynamics, for both PHES and small hydropower plants. ?? 2014 Elsevier Ltd.
2013
Pavesi, Giorgio; Rossetti, Antonio; Santolin, Alberto; Ardizzon, Guido
Numerical Analyses of a Cavitating Pelton Turbine Proceedings Article
In: 10th European Conference on Turbomachinery Fluid Dynamics and Thermodynamics, ETC 2013, pp. 1-12, 2013, ISSN: 24104833.
Abstract | BibTeX | Tags: Cavitation, CFD, Pelton Turbine
@inproceedings{Pavesi2013,
title = {Numerical Analyses of a Cavitating Pelton Turbine},
author = {Giorgio Pavesi and Antonio Rossetti and Alberto Santolin and Guido Ardizzon},
issn = {24104833},
year = {2013},
date = {2013-01-01},
urldate = {2013-01-01},
booktitle = {10th European Conference on Turbomachinery Fluid Dynamics and Thermodynamics, ETC 2013},
pages = {1-12},
abstract = {Erosive wear of hydro turbine runners is a complex phenomenon, which depends upon many parameters and which leads to a decrease of the performance in time and/or in extreme cases to the rotor mechanical failure. Consistently, the study of this wearing process is an important step to improve the impeller design, to avoid or minimize the rise of extraordinary maintenance. In the present paper the cavitation mechanics of a Pelton turbine was investigated using CFD analyses. A Pelton affected by pitting cavitation was taken as test case. The Pelton geometry was modelled and analyzed using unsteady Reynolds averaged Navier-Stokes (RANS) multiphase analyses. The homogeneous approach was used to describe the multiphase flow composed by water, water vapour and air. Numerical results discriminated the vapour production processes during the cut in of the bucket on the water jet. The design and the part load flow rates were analyzed and the cavitation process compared. A simple procedure to identify the locations of higher damage risk was presented and verified on the test case runner.},
keywords = {Cavitation, CFD, Pelton Turbine},
pubstate = {published},
tppubtype = {inproceedings}
}
Erosive wear of hydro turbine runners is a complex phenomenon, which depends upon many parameters and which leads to a decrease of the performance in time and/or in extreme cases to the rotor mechanical failure. Consistently, the study of this wearing process is an important step to improve the impeller design, to avoid or minimize the rise of extraordinary maintenance. In the present paper the cavitation mechanics of a Pelton turbine was investigated using CFD analyses. A Pelton affected by pitting cavitation was taken as test case. The Pelton geometry was modelled and analyzed using unsteady Reynolds averaged Navier-Stokes (RANS) multiphase analyses. The homogeneous approach was used to describe the multiphase flow composed by water, water vapour and air. Numerical results discriminated the vapour production processes during the cut in of the bucket on the water jet. The design and the part load flow rates were analyzed and the cavitation process compared. A simple procedure to identify the locations of higher damage risk was presented and verified on the test case runner.
Rossetti, Antonio; Pavesi, Giorgio
Comparison of different numerical approaches to the study of the H-Darrieus turbines start-up Journal Article
In: Renewable Energy, vol. 50, pp. 7-19, 2013.
Abstract | BibTeX | Tags: 3D effects, BEM, CFD, Darrieus, Self-start, VAWT
@article{Rossetti2013b,
title = {Comparison of different numerical approaches to the study of the H-Darrieus turbines start-up},
author = {Antonio Rossetti and Giorgio Pavesi},
year = {2013},
date = {2013-01-01},
urldate = {2013-01-01},
journal = {Renewable Energy},
volume = {50},
pages = {7-19},
abstract = {Self-start capability is an important feature of wind turbines. It allows to obtain simpler and cheaper turbines not actively controlled. Different approaches to describe the self-start of an H-blade Darrieus rotor are presented and compared in the present work. The Blade Element Momentum (BEM) approach was compared with two and three-dimensional CFD simulations. The tip-speed ratio versus power coefficient curves and the evolution of the trust forces over a blade revolution highlighted the limits and the strengths of each approach.The BEM model showed remarkable limits to describe to describe the self-start behaviour of the tested geometry. The principal limits of the BEM approach can be ascribed to the absence of well documented aerofoil databases for low Reynolds number and the inadequate modelling of dynamics effects. The 2D simulation allowed to highlight the unsteady features of the flow fields, and the presence of a complex vortices pattern which interact with the blade. Furthermore the comparison between 2D and 3D data demonstrated the importance of 3D effects such as secondary flows and tip effects. These effects were proved to have a positive effect on start-up, increasing the torque characteristic for tip-speed ratio of 1. The start-up capability of H-Darrieus appears to be influenced by many different factors, which include secondary flows, three-dimensional aerodynamic effects and the finite aspect-ratio of the blades. ?? 2012 Elsevier Ltd.},
keywords = {3D effects, BEM, CFD, Darrieus, Self-start, VAWT},
pubstate = {published},
tppubtype = {article}
}
Self-start capability is an important feature of wind turbines. It allows to obtain simpler and cheaper turbines not actively controlled. Different approaches to describe the self-start of an H-blade Darrieus rotor are presented and compared in the present work. The Blade Element Momentum (BEM) approach was compared with two and three-dimensional CFD simulations. The tip-speed ratio versus power coefficient curves and the evolution of the trust forces over a blade revolution highlighted the limits and the strengths of each approach.The BEM model showed remarkable limits to describe to describe the self-start behaviour of the tested geometry. The principal limits of the BEM approach can be ascribed to the absence of well documented aerofoil databases for low Reynolds number and the inadequate modelling of dynamics effects. The 2D simulation allowed to highlight the unsteady features of the flow fields, and the presence of a complex vortices pattern which interact with the blade. Furthermore the comparison between 2D and 3D data demonstrated the importance of 3D effects such as secondary flows and tip effects. These effects were proved to have a positive effect on start-up, increasing the torque characteristic for tip-speed ratio of 1. The start-up capability of H-Darrieus appears to be influenced by many different factors, which include secondary flows, three-dimensional aerodynamic effects and the finite aspect-ratio of the blades. ?? 2012 Elsevier Ltd.
