Turbulence and the Isolated Wind Turbine

Boundary-Layer Meteorol

2016

The wake characteristics of a wind turbine in a turbulent boundary layer under neutral stratification are investigated systematically by means of large-eddy simulations. A methodology to maintain the turbulence of the background flow for simulations with open horizontal boundaries, without the necessity of the permanent import of turbulence data from a precursor simulation, was implemented in the geophysical flow solver EULAG. These requirements are fulfilled by applying the spectral energy distribution of a neutral boundary layer in the wind-turbine simulations. A detailed analysis of the wake response towards different turbulence levels of the background flow results in a more rapid recovery of the wake for a higher level of turbulence. A modified version of the Rankine-Froude actuator disc model and the blade element momentum method are tested as wind-turbine parametrizations resulting in a strong dependence of the near-wake wind field on the parametrization, whereas the far-wake flow is fairly insensitive to it. The wake characteristics are influenced by the two considered airfoils in the blade element momentum method up to a streamwise distance of 14D (D = rotor diameter). In addition, the swirl induced by the rotation has an impact on the velocity field of the wind turbine even in the far wake. Further, a wake response study reveals a considerable effect of different subgrid-scale closure models on the streamwise turbulent intensity.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Impact of Neutral Boundary-Layer Turbulence on Wind-Turbine Wakes: A Numerical Modelling Study

Boundary-Layer Meteorol

2016

“…The interaction of the ABL turbulence with wind turbine wakes is only poorly understood due to the complexity of the ABL (Naughton et al (2011), Emeis (2013), Emeis (2014)). This paper can be considered as an investigation to prepare LESs of wind turbine wakes subject towards realistic 65 ABL regimes.…”

mentioning

confidence: 99%

“…In most of the numerical simulations of an individual wind turbine, however, an NBL is assumed (e.g. Wu and Porté-Agel (2011), Porté-Agel 80 et al (Chapel Hill, 2010), Naughton et al (2011), Englberger and Dörnbrack (2015)). There are approaches considering the SBL ) or the CBL ) in a one-way nested Weather Research and Forecasting (WRF)-LES simulation.…”

mentioning

confidence: 99%

The impact of the diurnal cycle of the atmospheric boundary layer on physical variables relevant for wind energy applications

2016

Preprint

Abstract. This paper provides a quantification of the temporal evolution of physical variables in the atmospheric boundary layer (ABL) relevant for wind energy applications. For this purpose, we use the unique dataset gathered during the BLLAST (Boundary Layer Late Afternoon and Sun- This results in a quantification of the diurnal cycle influence on the vertical wind shear, the stratifi-10 cation and the turbulence intensity in the atmosphere. Further, the impact of different heterogeneous surface conditions on shear near the surface layer of the ABL is investigated.

Impact of the Diurnal Cycle of the Atmospheric Boundary Layer on Wind-Turbine Wakes: A Numerical Modelling Study

Boundary-Layer Meteorol

2017

The wake characteristics of a wind turbine for different regimes occurring throughout the diurnal cycle are investigated systematically by means of large-eddy simulation. Idealised diurnal cycle simulations of the atmospheric boundary layer are performed with the geophysical flow solver EULAG over homogeneous and heterogeneous terrain. Under homogeneous conditions, the diurnal cycle significantly impacts the low-level wind shear and atmospheric turbulence. A strong vertical wind shear and veering with height occur in the nocturnal stable boundary layer and in the morning boundary layer, whereas the atmospheric turbulence is much larger in the convective boundary layer and in the evening boundary layer. The increased shear under heterogeneous conditions changes these wind characteristics, counteracting the formation of the night-time Ekman spiral. The convective, stable, evening, and morning regimes of the atmospheric boundary layer over a homogeneous surface as well as the convective and stable regimes over a heterogeneous surface are used to study the flow in a wind-turbine wake. Synchronized turbulent inflow data from the idealized atmospheric boundary-layer simulations with periodic horizontal boundary conditions are applied to the wind-turbine simulations with open streamwise boundary conditions. The resulting wake is strongly influenced by the stability of the atmosphere. In both cases, the flow in the wake recovers more rapidly under convective conditions during the day than under stable conditions at night. The simulated wakes produced for the nighttime situation completely differ between heterogeneous and homogeneous surface conditions. The wake characteristics of the transitional periods are influenced