An extended actuator cylinder model: Actuator‐in‐actuator cylinder (AC‐squared) model

Tavernier, Delphine De; Ferreira, Carlos

doi:10.1002/we.2340

Cited by 7 publications

(11 citation statements)

References 14 publications

(18 reference statements)

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“…For example, for a single VAWT, the “inside” and “downwind” regions must be defined. This requirement is compounded when the AC method is used to treat multiple turbines 12,13 . For example, when two concentric turbines were studied, 5 regions had to be defined.…”

Section: Discussionmentioning

confidence: 99%

“…It is these shortcomings that led to the development of the venerable AC model that has long been used to study the performance of VAWTs 3,10–12 . This is still a dynamic method where an ideal steady flow is under the influence of forces restricted to an infinitesimally thin surface.…”

Section: Introductionmentioning

confidence: 99%

“…This is in contrast to the multi‐turbine extensions of the AC method, which require explicit delineation of different flow regions. This requirement is compounded when one turbine is in the wake of another 12,13 …”

Section: Introductionmentioning

confidence: 99%

“…9 It is these shortcomings that led to the development of the venerable AC model that has long been used to study the performance of VAWTs. 3,[10][11][12] This is still a dynamic method where an ideal steady flow is under the influence of forces restricted to an infinitesimally thin surface. However, unlike streamtube models, the AC model explicitly solves the Euler momentum equation in two dimensions to fully resolve the flow details through the cross section of a Darrieus VAWT.…”

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confidence: 99%

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Numerical method for steady ideal 2‐D flows of finite vorticity with applications to vertical‐axis wind turbine aerodynamics

Nikiforov

Rahman

2022

Wind Energy

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This paper presents a new method for approximately modeling 2-D ideal steady fluid flows with finite vorticity induced by actuator curves of arbitrary shape. An actuator curve is an infinitesimally thin region containing a body force density acting on the flow, while the rest of the flow is force-free. The approach can be used for any flow satisfying this description, but, like other actuator methods, it is naturally suited for modeling turbines or propellers. We derive a weak formulation of the governing equations in the Lagrange streamfunction ψ and solve it using finite elements. Compared to related methods such as the actuator cylinder (AC) approach, our formulation is uniquely suited for computations involving wake-wake or wake-turbine interactions. We validate the method by computing the flow through a single Darrieus vertical-axis wind turbine (VAWT) and comparing with previous work. To demonstrate the ability to simulate interacting actuators of arbitrary configuration, we simulate a three-VAWT array. The turbines are modeled in a freestream, and the loading is chosen to represent ideal airfoils. The standard VAWT results are consistent with previous work, validating the method. The three-VAWT array demonstrates a higher efficiency than the single VAWT (0.56 vs. 0.52), with differing optmal tip speed ratios for the upwind and downwind turbines (upwind: 3.9, downwind: 3.1.The optimum for a single turbine is 3.6). The flow field of the three-VAWT array shows expected features such as an acceleration of flow between the two counterrotating upwind turbines.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Numerical method for steady ideal 2‐D flows of finite vorticity with applications to vertical‐axis wind turbine aerodynamics

Nikiforov

Rahman

2022

Wind Energy

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“…These experimental techniques require large-scale facilities and precise measurement systems, which, in general, are expensive. Analytic and semi-empirical techniques such as the Streamtube model [11,12], free wake vortex models [13][14][15], and cylinder and line actuator models [16][17][18], among others, are considered simple to implement but highly dependent on experimental data. The most common computational technique used in the simulation of Vertical Axis Turbines (VAT) is Computational Fluid Dynamics (CFD) in which the governing equations of the dynamics of flow are solved in a computational domain that needs to be discretized in elements (Control volumes).…”

Section: Introductionmentioning

confidence: 99%

Comparison of Sliding and Overset Mesh Techniques in the Simulation of a Vertical Axis Turbine for Hydrokinetic Applications

Mejia

Escorcia

et al. 2021

Processes

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The application of Computational Fluid Dynamics (CFD) to energy-related problems has increased in the last decades in both renewable and conventional energy conversion processes. In recent years, the application of CFD in the study of hydraulic, marine, tidal, and hydrokinetic turbines has focused on the understanding of the details of the complex turbulent flow and also in improving the prediction of the performance of these devices. There are several complexities involved in the simulation of Vertical Axis Turbine (VAT) for hydrokinetic applications. One of them is the necessity of a dynamic mesh model. Typically, the model used in the simulation of these devices is the sliding mesh technique, but in recent years the fast development of the overset (also known as chimera) mesh technique has caught the attention of the academic community. In the present paper, a comparison between these two techniques is done in order to establish their advantages and disadvantages in the two-dimensional simulation of vertical axis turbines. The comparison was done not only for the prediction of performance parameters of the turbine but also for the capabilities of the models to capture complex flow phenomena in these devices and computational costs.

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Intracycle RPM control for vertical axis wind turbines

Sadman Sakib,

Todd Griffith,

Hossain

et al. 2023

Wind Energy

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The wind energy market is currently dominated by horizontal axis wind turbines (HAWTs); however, vertical axis wind turbines (VAWTs) are emerging as a design alternative, especially for deep‐water offshore siting due to their low center of gravity, ease of access to drivetrain components, and overall simplicity. Due to the absence of a pitch mechanism in large‐scale Darrieus VAWTs, stall control has often been used to manage power and loads. Introducing a pitching mechanism in H‐type VAWTs has been studied, but this diminishes the mechanical simplicity advantage, and the use of a pitching mechanism in a large‐scale Darrieus‐type VAWT is not practical. This work examines an innovative, alternative method to control the rotor dynamics of a large‐scale 5 MW VAWT to maximize power while constraining loads without introducing any new or complex mechanical elements. This control strategy is termed intracycle revolution per minute (RPM) control, where the rotational speed of the turbine is allowed to vary in an optimal fashion with the azimuthal location of blades as opposed to typical constant RPM operation. An optimization framework is formulated for an open‐loop optimal control problem and solved to maximize power subject to constraints on aerodynamic design loads. Results are presented to demonstrate the benefits and the performance limits of intracycle RPM control for large‐scale 5 MW Darrieus VAWTs, namely, (1) power production (quantified in terms of AEP) that can be increased subject to baseline load limits and (2) opportunities to significantly increase AEP or decrease loads via intracycle RPM control that are examined for both two‐bladed and three‐bladed VAWTs.

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An extended actuator cylinder model: Actuator‐in‐actuator cylinder (AC‐squared) model

Cited by 7 publications

References 14 publications

Numerical method for steady ideal 2‐D flows of finite vorticity with applications to vertical‐axis wind turbine aerodynamics

Numerical method for steady ideal 2‐D flows of finite vorticity with applications to vertical‐axis wind turbine aerodynamics

Comparison of Sliding and Overset Mesh Techniques in the Simulation of a Vertical Axis Turbine for Hydrokinetic Applications

Intracycle RPM control for vertical axis wind turbines

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