A double-multiple streamtube model for vertical axis wind turbines of arbitrary rotor loading

Ayati, Anis Awal; Steiros, Konstantinos; Miller, Mark A.; Subrahmanyam, D.; Hultmark, Marcus

doi:10.5194/wes-4-653-2019

Cited by 30 publications

(24 citation statements)

References 21 publications

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“…The second cause of wake asymmetry is a net cross-stream force on the blades (figure 6( d ), dashed line) resulting in a net acceleration of the flow (figure 6 e ); here this cross-stream force is measured, but it may also be estimated as in Ayati et al. (2019). This net forcing is explained as follows: power measurements on a single-bladed cross-flow turbine (Strom et al.…”

Section: Results and Analysis: Mean Flowmentioning

confidence: 89%

Near-wake dynamics of a vertical-axis turbine

2022

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Cross-flow, or vertical-axis, turbines are a promising technology for capturing kinetic energy in wind or flowing water and their inherently unsteady fluid mechanics present unique opportunities for control optimization of individual rotors or arrays. To explore the potential for beneficial interactions between turbines in an array, as well as to characterize important cycle-to-cycle variations, coherent structures in the wake of a single two-bladed cross-flow turbine are examined using planar stereo particle image velocimetry in a water channel experiment. There are three main objectives in the present work. First, the mean wake structure of this high chord-to-radius ratio rotor is described, compared with previous studies, and a simple explanation for observed wake deflection is presented. Second, the unsteady flow is then analysed via the triple decomposition, with the periodic component extracted using a combination of traditional techniques and a novel implementation of the optimized dynamic mode decomposition. The latter method is shown to outperform conditional averaging and Fourier methods, as well as uncover frequencies suggesting a transition to bluff-body shedding in the far wake. Third, vorticity and finite-time Lyapunov exponents are then employed to further analyse the oscillatory wake component. Vortex streets on both sides of the wake are identified, and their formation mechanisms and effects on the mean flow are discussed. Strong axial (vertical) flow is observed in vortical structures shed on the retreating side of the rotor where the blades travel downstream. Time-resolved tracking of these vortices is performed, which demonstrates that vortex trajectories have significant rotation-to-rotation variation within one diameter downstream. This variability suggests it would be challenging to harness or avoid such structures at greater downstream distances.

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Section: Results and Analysis: Mean Flowmentioning

confidence: 89%

Near-wake dynamics of a vertical-axis turbine

2022

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“…A new development in actuator modelling in general was introduced by Ayati [36] who utilised an extension of Rankie-Froude momentum theory proposed by Sterios and Hultmark which is valid for a much wide range of loading, and doesn't predict wake reversal for highly loaded situations. This approach seems very promising for the application of DMS at higher tip-speed ratios where the rotor loading is generally above the range at which Rankie-Froude momentum The tool developed in this paper utilises the correction factor proposed by Bhul.…”

Section: Streamline Curvaturementioning

confidence: 99%

Aerodynamic modelling of a novel vertical axis wind turbine concept

Morgan

Leithead

2022

J. Phys.: Conf. Ser.

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This paper introduces the X-Rotor, a hybrid vertical-horizontal axis turbine concept designed to lower the cost of energy in the floating offshore environment. The development of a double multiple streamtube (DMS) simulation tool is presented alongside a thorough discussion of the secondary correction factors included in the model. New corrections for streamline curvature effects applicable to an airfoil where the blade normal plane is not aligned with the rotor plane are derived. The DMS model is successfully validated against experimental data and against higher fidelity lifting line (LLT) simulations. Strong agreement is observed between the LLT simulations and the DMS simulations for both rotor averaged and azimuthally varying outputs, indicating that the DMS simulations can be used for future control simulations.

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“…Concerning long, flexible bridges, the problem was more complex because wind tends to produce large deflections (Figure 1). In such cases, analysis of scaled models in wind tunnels is a solution, but detailed analysis of wind effects on long bridges requires high-pressure, high Reynolds number wind tunnels, are very few (for instance, in Princeton University, USA; [8]). For these reasons, deflections of bridges of different types due to dynamic loads remained rather unknown, and regulations for bridge performance all around the world relied on model predictions and on certain empirical criteria (e.g., AASHTO 1997 [9]).…”

Section: Introductionmentioning

confidence: 99%

GNSS (GPS) Monitoring of Dynamic Deflections of Bridges: Structural Constraints and Metrological Limitations

Stiros

2021

Infrastructures

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The advent of modern geodetic satellite techniques (GNSS, including GPS) permitted to observe dynamic deflections of bridges, initially of long flexible ones, and more recently of short, essentially stiff bridges with modal frequencies > 1 Hz, and with small SNR (signal-to-noise ratio), even SNR < 1. This was an enormous progress, but not without problems. Apart from monitoring results consistent with structural models, experimental data and serviceability criteria, there exist some apparently unexplained cases of stiff bridges for which there have been claimed apparent dynamic deflections too large for common healthy structures. Summarizing previous experience, this article: (i) discusses structural constraints, experimental evidence, and serviceability limits of bridges as constraints to GNSS monitoring; (ii) examines a representative case of careful monitoring of a reinforced concrete road bridge with reported excessive dynamic deflections; and (iii) explains such deflections as a result of a double process generated by large reflective surfaces of passing vehicles near the antenna; first corruption/distortion of the satellite signal because of high-frequency dynamic multipath, and second, shadowing of some satellites; this last effect leads to a modified observations system and to instantaneously changed coordinates and deflections. In order to recognize and avoid such bias in GNSS monitoring, a strategy based on practical rules and structural constraints is presented.

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A double-multiple streamtube model for vertical axis wind turbines of arbitrary rotor loading

Cited by 30 publications

References 21 publications

Near-wake dynamics of a vertical-axis turbine

Near-wake dynamics of a vertical-axis turbine

Aerodynamic modelling of a novel vertical axis wind turbine concept

GNSS (GPS) Monitoring of Dynamic Deflections of Bridges: Structural Constraints and Metrological Limitations

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