Benjamin Cazzolato | University of Adelaide (original) (raw)
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Papers by Benjamin Cazzolato
Renewable Energy, 2017
The mechanisms responsible for swishing and thumping noises generated by wind turbines are unclea... more The mechanisms responsible for swishing and thumping noises generated by wind turbines are unclear and the existence of which have significantly affected the perception of wind energy by the community. To better understand the nature of this noise source, this study, for the first time, investigates the correlation between the potential noise generation mechanisms in wind farms and the characteristics of the perceived noise reported by residents in the vicinity of the farms in survey data. Published reports and measurements show that in addition to the perceived noise near the turbines, the thumping noise, in general, is perceived far downstream of the turbines. Normal swish perceived in a short distance from a wind turbine, especially in the cross-wind directions, can be explained by the convective amplification and directivity of the trailing edge noise. As will be discussed in this article, there exists strong evidence that the dominant mechanism of wind farm noise is associated with amplitude modulation of the aerodynamic noise by the eddies generated when the turbine blade partially stalls or due to an interaction with the turbine wake. This hypothesis is primarily based on the low frequency characteristics of the stall and also the distance and direction of the noise propagation. Moreover, it is hypothesised that the wake supplements this effect as it results in refraction and modulation of the emitted noise.
Renewable Energy, 2018
In an array of wind turbines, the interaction of the downstream machines with the wakes from the ... more In an array of wind turbines, the interaction of the downstream machines with the wakes from the upstream ones results in a reduction in the overall wind farm performance. Turbine wakes are a major source of turbulence which exerts fluctuating loads on the blades of the downstream turbines, resulting in the generation of noise and fatigue of the turbine blades. There are many semi-empirical wind turbine wake models in the literature. This paper, develops a fully numerical model of wind turbine wakes using CFD by means of a Large Eddy Simulation (LES). The new LES model is tested against experimental data, showing very good agreement. The advantages of the LES model compared to the available semi-empirical models in the literature are discussed and it is shown that the LES model is very accurate compared to the conventional semi-empirical wake models usually used in the industry. Moreover, the LES model is used as a benchmark to compare the accuracy of these semi-empirical models; it is shown that the model proposed by Jensen can predict the velocity deficit most accurately among the semi-empirical models, while the highest degree of accuracy in the wake expansion is achieved by using the Larsen model.
Journal of Wind Engineering and Industrial Aerodynamics, 2014
ABSTRACT Wind farms have recently been reported to produce a noise signature that is described as... more ABSTRACT Wind farms have recently been reported to produce a noise signature that is described as possessing a “thumping” quality. Measurements of these signatures are limited and their effects are debated but their effect on public opinion and complaints make them a concern for researchers in this field. Proposed reasons for these noise signatures include amplitude modulation, interference patterns and wake–rotor interaction. This paper discusses these effects and concludes that wake–rotor interaction plays a role by causing variations in turbulent-inflow noise and dynamic stall. The current state of research into stall noise and wind turbine wake structure is also reviewed and it is concluded that the available information and collected data on wind turbine wake are insufficient to determine how strong this role is. More information on the velocity and turbulence fields in the wake of horizontal-axis wind turbines as well as a characterisation of the noise produced by an airfoil experiencing dynamic stall is required in order to make a full assessment of rotor–wake contributions to wind farm noise.
Experimental Thermal and Fluid Science, 2014
International Journal of Computational Fluid Dynamics, 2014
ABSTRACT Skin friction drag reduction in the turbulent boundary layer has high potential benefits... more ABSTRACT Skin friction drag reduction in the turbulent boundary layer has high potential benefits which have been a subject of much interest. From general point of view this Paper gives an overview of various methods to control the turbulent boundary layer. Primary section of the paper highlights the importance of skin friction drag reduction in turbulent boundary layers, followed by brief discussion of turbulence and Reynolds shear stress production process in the near wall region. Since there are several ways to suppress the instabilities, which naturally occur in the turbulent boundary layer, lots of control techniques have been investigated in next sections. The present article provides an up-to-date summary of passive and active mechanisms responsible for viscous drag reduction. Furthermore, the implications of previous controller and the success or limitations of various methods are discussed.
Journal of Renewable and Sustainable Energy, 2014
AIAA Aerospace …, Jan 1, 2009
Page 1. American Institute of Aeronautics and Astronautics 092407 1 An Investigation on the Appli... more Page 1. American Institute of Aeronautics and Astronautics 092407 1 An Investigation on the Application of DBD Plasma Actuators as Pressure Sensors Benjamin J. Chartier1, Maziar Arjomandi2 and Benjamin S. Cazzolato3 ...
… , IEEE Transactions on, Jan 1, 2005
![Research paper thumbnail of Corrigendum to: Theoretical design parameters for a quasi-zero stiffness magnetic spring for vibration isolation [J. Sound Vib. 326 (1-2)(2009) 88-103]](https://attachments.academia-assets.com/42522905/thumbnails/1.jpg)
](Journal of Sound …, Jan 1, 2011
personal.mecheng.adelaide.edu.au
Conference of the Australian Acoustical Society, 2013
A recently-published equation for calculating the force between coaxial cylindrical magnets is pr... more A recently-published equation for calculating the force between coaxial cylindrical magnets is presented in simplified form. The revised equation is now very compact: it is defined with fewer parameters and contains fewer terms than the original equation. The new equation is purely real, unlike the original which contained imaginary components. As a result of the simplifications, the new equation is demonstrably faster to evaluate than the original, improving its utility for parametric optimization. A reference implementation is provided for Matlab and Mathematica.
Conference of the Australian Acoustics Society, 2013
In this paper, a variety of analytical/integral methods are compared for calculating the axial fo... more In this paper, a variety of analytical/integral methods are compared for calculating the axial force between a cylindrical magnet and a “thick” solenoid that consists of many turns both radially and axially. Two newly developed techniques are introduced: one being numerical integration-based and the other completely analytical. These are compared to two other techniques, each shown to have various advantages in different contexts. One method in particular is introduced that is shown to be the most computationally efficient in the majority of actuator designs. This method is then used to optimize a typical “sleeve-type” magnet-coil actuator based on the cost function of peak force, and it is shown that optimal values of wire thickness and magnet-coil geometry can be chosen based on desired coil impedance and magnet volume.
In this paper a non-contact magnetic spring design is presented that uses inclined magnets to pro... more In this paper a non-contact magnetic spring design is presented that uses inclined magnets to produce an adjustable relationship between load force and dynamic stiffness. With appropriate choice of parameters, the spring may either operate with a range of constant natural frequency against variable load forces, or a positive stiffness in one horizontal direction may be achieved in addition to having a positive vertical stiffness. Dynamic simulations are presented to assess the non-linear stability of a planar three degree of freedom version of the system; cross-coupling between horizontal and rotation motion is shown to compromise passive stability, in which case passive constraints or active control must be used to avoid instability. The design is scalable in that using larger magnets increases the load bearing capacity and decreases the natural frequency of the system.
Renewable Energy, 2017
The mechanisms responsible for swishing and thumping noises generated by wind turbines are unclea... more The mechanisms responsible for swishing and thumping noises generated by wind turbines are unclear and the existence of which have significantly affected the perception of wind energy by the community. To better understand the nature of this noise source, this study, for the first time, investigates the correlation between the potential noise generation mechanisms in wind farms and the characteristics of the perceived noise reported by residents in the vicinity of the farms in survey data. Published reports and measurements show that in addition to the perceived noise near the turbines, the thumping noise, in general, is perceived far downstream of the turbines. Normal swish perceived in a short distance from a wind turbine, especially in the cross-wind directions, can be explained by the convective amplification and directivity of the trailing edge noise. As will be discussed in this article, there exists strong evidence that the dominant mechanism of wind farm noise is associated with amplitude modulation of the aerodynamic noise by the eddies generated when the turbine blade partially stalls or due to an interaction with the turbine wake. This hypothesis is primarily based on the low frequency characteristics of the stall and also the distance and direction of the noise propagation. Moreover, it is hypothesised that the wake supplements this effect as it results in refraction and modulation of the emitted noise.
Renewable Energy, 2018
In an array of wind turbines, the interaction of the downstream machines with the wakes from the ... more In an array of wind turbines, the interaction of the downstream machines with the wakes from the upstream ones results in a reduction in the overall wind farm performance. Turbine wakes are a major source of turbulence which exerts fluctuating loads on the blades of the downstream turbines, resulting in the generation of noise and fatigue of the turbine blades. There are many semi-empirical wind turbine wake models in the literature. This paper, develops a fully numerical model of wind turbine wakes using CFD by means of a Large Eddy Simulation (LES). The new LES model is tested against experimental data, showing very good agreement. The advantages of the LES model compared to the available semi-empirical models in the literature are discussed and it is shown that the LES model is very accurate compared to the conventional semi-empirical wake models usually used in the industry. Moreover, the LES model is used as a benchmark to compare the accuracy of these semi-empirical models; it is shown that the model proposed by Jensen can predict the velocity deficit most accurately among the semi-empirical models, while the highest degree of accuracy in the wake expansion is achieved by using the Larsen model.
Journal of Wind Engineering and Industrial Aerodynamics, 2014
ABSTRACT Wind farms have recently been reported to produce a noise signature that is described as... more ABSTRACT Wind farms have recently been reported to produce a noise signature that is described as possessing a “thumping” quality. Measurements of these signatures are limited and their effects are debated but their effect on public opinion and complaints make them a concern for researchers in this field. Proposed reasons for these noise signatures include amplitude modulation, interference patterns and wake–rotor interaction. This paper discusses these effects and concludes that wake–rotor interaction plays a role by causing variations in turbulent-inflow noise and dynamic stall. The current state of research into stall noise and wind turbine wake structure is also reviewed and it is concluded that the available information and collected data on wind turbine wake are insufficient to determine how strong this role is. More information on the velocity and turbulence fields in the wake of horizontal-axis wind turbines as well as a characterisation of the noise produced by an airfoil experiencing dynamic stall is required in order to make a full assessment of rotor–wake contributions to wind farm noise.
Experimental Thermal and Fluid Science, 2014
International Journal of Computational Fluid Dynamics, 2014
ABSTRACT Skin friction drag reduction in the turbulent boundary layer has high potential benefits... more ABSTRACT Skin friction drag reduction in the turbulent boundary layer has high potential benefits which have been a subject of much interest. From general point of view this Paper gives an overview of various methods to control the turbulent boundary layer. Primary section of the paper highlights the importance of skin friction drag reduction in turbulent boundary layers, followed by brief discussion of turbulence and Reynolds shear stress production process in the near wall region. Since there are several ways to suppress the instabilities, which naturally occur in the turbulent boundary layer, lots of control techniques have been investigated in next sections. The present article provides an up-to-date summary of passive and active mechanisms responsible for viscous drag reduction. Furthermore, the implications of previous controller and the success or limitations of various methods are discussed.
Journal of Renewable and Sustainable Energy, 2014
AIAA Aerospace …, Jan 1, 2009
Page 1. American Institute of Aeronautics and Astronautics 092407 1 An Investigation on the Appli... more Page 1. American Institute of Aeronautics and Astronautics 092407 1 An Investigation on the Application of DBD Plasma Actuators as Pressure Sensors Benjamin J. Chartier1, Maziar Arjomandi2 and Benjamin S. Cazzolato3 ...
… , IEEE Transactions on, Jan 1, 2005
Journal of Sound …, Jan 1, 2011
personal.mecheng.adelaide.edu.au
Conference of the Australian Acoustical Society, 2013
A recently-published equation for calculating the force between coaxial cylindrical magnets is pr... more A recently-published equation for calculating the force between coaxial cylindrical magnets is presented in simplified form. The revised equation is now very compact: it is defined with fewer parameters and contains fewer terms than the original equation. The new equation is purely real, unlike the original which contained imaginary components. As a result of the simplifications, the new equation is demonstrably faster to evaluate than the original, improving its utility for parametric optimization. A reference implementation is provided for Matlab and Mathematica.
Conference of the Australian Acoustics Society, 2013
In this paper, a variety of analytical/integral methods are compared for calculating the axial fo... more In this paper, a variety of analytical/integral methods are compared for calculating the axial force between a cylindrical magnet and a “thick” solenoid that consists of many turns both radially and axially. Two newly developed techniques are introduced: one being numerical integration-based and the other completely analytical. These are compared to two other techniques, each shown to have various advantages in different contexts. One method in particular is introduced that is shown to be the most computationally efficient in the majority of actuator designs. This method is then used to optimize a typical “sleeve-type” magnet-coil actuator based on the cost function of peak force, and it is shown that optimal values of wire thickness and magnet-coil geometry can be chosen based on desired coil impedance and magnet volume.
In this paper a non-contact magnetic spring design is presented that uses inclined magnets to pro... more In this paper a non-contact magnetic spring design is presented that uses inclined magnets to produce an adjustable relationship between load force and dynamic stiffness. With appropriate choice of parameters, the spring may either operate with a range of constant natural frequency against variable load forces, or a positive stiffness in one horizontal direction may be achieved in addition to having a positive vertical stiffness. Dynamic simulations are presented to assess the non-linear stability of a planar three degree of freedom version of the system; cross-coupling between horizontal and rotation motion is shown to compromise passive stability, in which case passive constraints or active control must be used to avoid instability. The design is scalable in that using larger magnets increases the load bearing capacity and decreases the natural frequency of the system.