Turbulent boundary layer statistics at very high Reynolds number

Vallikivi, Margit; Hultmark, Marcus; Smits, Alexander J.

doi:10.1017/jfm.2015.273

Cited by 115 publications

(81 citation statements)

References 43 publications

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“…In this context, Hutchins and Marusic [64] showed how the energy of the turbulent structures in the overlap region increases with R e , becoming comparable with the energy in the near-wall region. This was also observed in the experiments by Vallikivi et al [65] on high-pressure ZPG boundary layers up to R e 𝜃 ≃ 223 × 10 3 , which start to exhibit a prominent outer peak in the streamwise velocity fluctuation profile, of a magnitude comparable to the one of the inner peak. However, a proper assessment of these effects would require investigations of numerical and experimental nature at much higher Reynolds numbers and over a wider range of pressure gradients, in order to properly isolate Reynolds-number and pressure-gradient effects.…”

Section: Turbulence Statisticssupporting

confidence: 80%

Pressure-Gradient Turbulent Boundary Layers Developing Around a Wing Section

Vinuesa

Hosseini

Hanifi

et al. 2017

Flow Turbulence Combust

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A direct numerical simulation database of the flow around a NACA4412 wing section at R e c = 400,000 and 5∘ angle of attack (Hosseini et al. Int. J. Heat Fluid Flow 61, 117–128, 2016), obtained with the spectral-element code Nek5000, is analyzed. The Clauser pressure-gradient parameter β ranges from ≃ 0 and 85 on the suction side, and from 0 to − 0.25 on the pressure side of the wing. The maximum R e 𝜃 and R e τ values are around 2,800 and 373 on the suction side, respectively, whereas on the pressure side these values are 818 and 346. Comparisons between the suction side with zero-pressure-gradient turbulent boundary layer data show larger values of the shape factor and a lower skin friction, both connected with the fact that the adverse pressure gradient present on the suction side of the wing increases the wall-normal convection. The adverse-pressure-gradient boundary layer also exhibits a more prominent wake region, the development of an outer peak in the Reynolds-stress tensor components, and increased production and dissipation across the boundary layer. All these effects are connected with the fact that the large-scale motions of the flow become relatively more intense due to the adverse pressure gradient, as apparent from spanwise premultiplied power-spectral density maps. The emergence of an outer spectral peak is observed at β values of around 4 for λ z ≃ 0.65δ 99, closer to the wall than the spectral outer peak observed in zero-pressure-gradient turbulent boundary layers at higher R e 𝜃. The effect of the slight favorable pressure gradient present on the pressure side of the wing is opposite the one of the adverse pressure gradient, leading to less energetic outer-layer structures.

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Section: Turbulence Statisticssupporting

confidence: 80%

Pressure-Gradient Turbulent Boundary Layers Developing Around a Wing Section

Vinuesa

Hosseini

Hanifi

et al. 2017

Flow Turbulence Combust

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“…The facility is designed to support static pressures up to 233 bar and free-stream velocities of 10 m/s. This facility has been used in previous work on horizontal and vertical axis wind turbines [8,2], as well as two-dimensional airfoil tests [9], zero-pressure-gradient turbulent boundary layers [10], and high-Reynolds number studies in the wake of a suboff model [11,12]. Further details regarding this facility can be found in those studies.…”

Section: Experiments Descriptionmentioning

confidence: 99%

Rotor solidity effects on the performance of vertical-axis wind turbines at high Reynolds numbers

Miller

Subrahmanyam

Kelly

et al. 2018

J. Phys.: Conf. Ser.

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Abstract.Vertical Axis Wind Turbines have yet to see wide-spread use as a means of harvesting the kinetic energy of the wind. This may be due in part to the difficulty in modeling the relatively complex flow field and hence performance of these units. Additionally, similar to Horizontal Axis Wind Turbines, VAWTs are difficult to properly test in a conventional wind tunnel. Typically Reynolds numbers cannot be matched or the turbine geometry must be altered, limiting the applicability of the results. Presented in the following is a set of experiments in a specialized, high-pressure wind tunnel used to achieve high Reynolds numbers with a small-scale model. The performance change of this model is investigated at two different solidities and over nearly a decade of Reynolds numbers (based on diameter: 600, 000 ≤ Re D ≤ 5 × 10 6 ). The nondimensional power coefficient displays behavior consistent with Reynolds number invariance, regardless of solidity. In addition, the change in performance as this limit is approached also shows no direct dependence on the solidity for the VAWT geometry used in this study. The results of this work have direct application for modeling and simulation efforts concerning the performance of new VAWT designs. IntroductionDespite continued research effort over the past several decades, vertical axis wind turbines (VAWTs) have yet to see wide-spread acceptance in the commercial wind industry. The flow field created by a VAWT has proven to be much more difficult to model than that of a similarly sized horizontal axis wind turbine (HAWT). This difficulty arises from the highly three-dimensional flow field created by each turbine blade and the turbulent, asymmetric wake shed behind the units. However, from an experimental and computational point of view, the governing nondimensional parameters for both HAWTs and VAWTs remain the same:

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“…Figures 9a and 9b show the correlation coefficients of the turbulent signals with streamwise wavelength greater than 0.3δ and 3δ, respectively. It should be noted that the turbulent signals with streamwise wavelength more than 0.3δ are principally related to LSMs and VLSMs (Hutchins & Marusic, 2007a;Kovasznay et al, 1970), and the turbulent signals with streamwise wavelength greater than 3δ are principally related to VLSMs (Monty et al, 2007;Vallikivi et al, 2015). As can be seen from Figure 9, the correlation coefficients of the turbulent signals with streamwise wavelength larger than 0.3δ and 3δ are greater than 0.5 and 0.7 between 0.9 and 30 m, respectively, which further indicates that our predictive model is effective for the prediction of the large-scale turbulent signals in the near-neutral ASL.…”

Section: 1029/2018jd029052mentioning

confidence: 99%

A Predictive Model for the Streamwise Velocity in the Near‐Neutral Atmospheric Surface Layer

Han

Liu

et al. 2019

JGR Atmospheres

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For the reconstruction of the streamwise velocity field in the high‐Reynolds‐number (Reτ ≈ Ο(106)) near‐neutral atmospheric surface layer (ASL), a predictive model was proposed in our work. In our model, the streamwise velocity time series at each height are predicted by the superposition of mean velocity, small‐scale turbulent signals, and large‐scale turbulent signals. All the parameters used by our model have clear physical meaning. In addition, the parameters can be directly determined by the experiment that is easy to be achieved in the ASL. The model can predict the streamwise velocity between 0.9 and 30 m in the near‐neutral ASL based only on single‐point‐measured large‐scale streamwise velocity signal. For example, mean velocity, turbulence intensity, and power spectrum of streamwise velocity can be predicted by the new model. Furthermore, the streamwise velocity time series predicted by the new model have a good correlation with the directly measured results, especially for large‐scale structures. It indicates that our model can be used to reconstruct the streamwise velocity field in the logarithmic region of the near‐neutral ASL, and our model is an important complement to the Marusic‐Mathis‐Hutchins model.

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Turbulent boundary layer statistics at very high Reynolds number

Cited by 115 publications

References 43 publications

Pressure-Gradient Turbulent Boundary Layers Developing Around a Wing Section

Pressure-Gradient Turbulent Boundary Layers Developing Around a Wing Section

Rotor solidity effects on the performance of vertical-axis wind turbines at high Reynolds numbers

A Predictive Model for the Streamwise Velocity in the Near‐Neutral Atmospheric Surface Layer

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