An assessment of the scalings for the streamwise evolution of turbulent quantities in wakes produced by porous objects

Lingkan, Elizabeth H.; Buxton, O. R. H.

doi:10.1016/j.renene.2023.03.101

Renewable Energy

2023

DOI: 10.1016/j.renene.2023.03.101

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An assessment of the scalings for the streamwise evolution of turbulent quantities in wakes produced by porous objects

Elizabeth H. Lingkan

O. R. H. Buxton

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2024

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Cited by 3 publications

References 23 publications

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Influence of incoming turbulent scales on the wind turbine wake: A large-eddy simulation study

Vahidi,

Porté-Agel

2024

Physics of Fluids

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In this study, we aim to investigate the influence of inflow turbulent length scales on wind turbine wakes. For this purpose, large-eddy simulations of the wake of a wind turbine are performed under neutral atmospheric conditions with different boundary layer heights. Different inflow turbulent scales are generated by varying the boundary layer height, while a systematic approach is proposed to ensure that all the simulations have the same total turbulence intensity at the hub level. First, we study the simulations without the turbine to analyze the inflow scale variations and ensure a fairly constant rotor-averaged total turbulence intensity among the cases. Next, we investigate the influence of the inflow turbulent scales on the simulations with the turbine. We find that larger inflow scales in three flow directions lead to a faster wake recovery. For analytical wake modeling, the physics-based model that includes the effect of inflow integral scales is more accurate in capturing the wake expansion. Regarding wake dynamic characteristics, larger inflow turbulent scales tend to produce more wake meandering behind the turbine in both lateral and vertical directions. It is observed that the vertical-to-lateral wake center standard deviation ratio is fairly constant for all the cases. In addition, we study the turbulent momentum fluxes and their divergence to understand the role of inflow scales in the wake recovery mechanism.

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Influence of incoming turbulent scales on the wind turbine wake: A large-eddy simulation study

Vahidi,

Porté-Agel

2024

Physics of Fluids

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A new RANS-based added turbulence intensity model for wind-farm flow modelling.

Delvaux,

Van Der Laan,

Terrapon

2024

J. Phys.: Conf. Ser.

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This work aims to alleviate the memory requirements of the recent wake engineering model described in Criado Risco et al. [1]. The original model relies on a RANS-based look-up table of three-dimensional velocity deficit and added turbulence intensity fields computed for a stand-alone turbine under a wide variety of conditions. The objective is to develop an alternative to the model of Criado Risco et al. [1], particularly in terms of added turbulence intensity, for which little research has been carried out to date. To achieve this, a one-dimensional analytical expression is fitted to the look-up table and generalized to higher dimensions. The turbulence intensity model is then coupled to a velocity deficit model and implemented in PyWake, an open-source wake engineering software. Overall, the new turbulence intensity model is found to provide a reliable description of the RANS look-up table data while reducing by half the memory requirements of the original model. This conclusion is extended to multiple wake situations, for which this work also establishes a direct link between the adequate superposition method and the definition chosen to describe the added turbulence intensity in the wake.

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Influence of freestream turbulence and porosity on porous disk-generated wakes

Bourhis,

Buxton

2024

Phys. Rev. Fluids

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This study aims to evaluate the effect of freestream turbulence (FST) on wakes produced by disks with different porosity. The wakes are exposed to various freestream turbulence “flavors,” where turbulence intensity and integral length scale are independently varied. The turbulent wakes are interrogated through hot-wire anemometry from 3 to 15 diameters downstream of the disks. It is found that disks with low porosity behave similarly to a solid body, in terms of both entrainment behavior and scaling laws for the centerline mean velocity evolution. Far from the disks, the presence of FST reduces both the wake growth rate and entrainment rate, with a clear effect of both turbulence intensity and integral length scale. As porosity increases, these “solid body” FST effects gradually diminish and are reversed above a critical porosity. The entrainment behavior in disk-generated wakes is significantly influenced by the presence of large-scale coherent structures, which act as a shield between the wake and the surrounding flow, thus impeding mixing in the near wake. We found that higher porosity, turbulence intensity, or integral length scale weakens the energy content of these structures, thereby limiting their influence on wake development to a shorter distance downstream of the disk. This, in turn, potentially reduces the influence of large-scale engulfment on the overall entrainment mechanism to a shorter distance downstream of the disks as well. For low-porosity disks, freestream turbulence intensity initially promotes near-wake growth through the suppression of large-scale structures; however, farther downstream, the wakes grow faster when the background is nonturbulent. Published by the American Physical Society 2024

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An assessment of the scalings for the streamwise evolution of turbulent quantities in wakes produced by porous objects

Cited by 3 publications

References 23 publications

Influence of incoming turbulent scales on the wind turbine wake: A large-eddy simulation study

Influence of incoming turbulent scales on the wind turbine wake: A large-eddy simulation study

A new RANS-based added turbulence intensity model for wind-farm flow modelling.

Influence of freestream turbulence and porosity on porous disk-generated wakes

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