A Wind-Tunnel Investigation of Wind-Turbine Wakes: Boundary-Layer Turbulence Effects

By Leonardo P. Chamorro, Fernando Port'e-Agel. 2009

533 citations recorded by the source corpus.

Wind-tunnel experiments were performed to study turbulence in the wake of a model wind turbine placed in a boundary layer developed over rough and smooth surfaces. Hot-wire anemometry was used to characterize the cross-sectional distribution of mean velocity, turbulence intensity and kinematic shear stress at different locations downwind of the turbine for both surface roughness cases. Special emphasis was placed on the spatial distribution of the velocity deficit and the turbulence intensity, which are important factors affecting turbine power generation and fatigue loads in wind energy parks. Non-axisymmetric behaviour of the wake is observed over both roughness types in response to the non-uniform incoming boundary-layer flow and the effect of the surface. Nonetheless, the velocity deficit with respect to the incoming velocity profile is nearly axisymmetric, except near the ground in the far wake where the wake interacts with the surface. It is found that the wind turbine induces a large enhancement of turbulence levels (positive added turbulence intensity) in the upper part of the wake. This is due to the effect of relatively large velocity fluctuations associated with helicoidal tip vortices near the wake edge, where the mean shear is strong. In the lower part of the wake, the mean shear and turbulence intensity are reduced with respect to the incoming flow. The non-axisymmetry of the turbulence intensity distribution of the wake is found to be stronger over the rough surface, where the incoming flow is less uniform at the turbine level. In the far wake the added turbulent intensity, its positive and negative contributions and its local maximum decay as a power law of downwind distance (with an exponent ranging from −0.3 to −0.5 for the rough surface, and with a wider variation for the smooth surface). Nevertheless, the effect of the turbine on the velocity defect and added turbulence intensity is not negligible even in the very far wake, at a distance of fifteen times the rotor diameter.

Subfields: Aerospace Engineering, Computational Mechanics, Environmental Engineering

View Paper: https://www.semanticscholar.org/paper/4cca185b5e481af29fc657bc0013ddcd390316e9

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Citations in the corpus

Effects of Thermal Stability and Incoming Boundary-Layer Flow Characteristics on Wind-Turbine Wakes: A Wind-Tunnel Study (2010, methodology): “As pointed out by Chamorro and Porte-Agel (2009) , the relatively high turbulence levels of the incoming flow precludes a noticeable effect of the tip vortices at the bottom tip height (result not shown here).”
Review of computational fluid dynamics for wind turbine wake aerodynamics (2011, methodology): “Porté-Agel et al. prescribed the surface shear stress and heat ﬂux by adopting a time-dependent variant of Monin–Obukhov similarity theory.”
Dynamic wind loads and wake characteristics of a wind turbine model in an atmospheric boundary layer wind (2012, background): “…as hot-wire anemometry, hot-film anemometry, and laser Doppler velocimetry, to conduct flow velocity measurements at limited points of interest (Alfredsson and Dahlberg 1979; Tsustui and Matsumya 1987; Ebert and Wood 1997; Vermeer 2001; Medici and Alfredsson 2006; Chamorro and Porte-Agel 2009).”
Development and validation of a new two-dimensional wake model for wind turbine wakes (2015, methodology): “The first two test cases are based on the meteorological mast measurements from the Sexbierum wind farm (Cleijne, 1993) and the Nibe site (Taylor, 1990).”
Atmospheric Turbulence Effects on Wind-Turbine Wakes: An LES Study (2012, background): “This behavior is consistent with the experimental results reported by Chamorro and Porté-Agel [6] and Zhang et al.”
Wind-Turbine Wakes in a Convective Boundary Layer: A Wind-Tunnel Study (2013, methodology): “…flow on the wind-turbine wake structure have been studied through wind-tunnel experiments and numerical simulations (e.g., Whale et al. 2000; Vermeer 2001; Medici and Alfredsson 2006; Chamorro and Porté-Agel 2009, 2010; Hancock and Pascheke 2010; Porté-Agel et al. 2011; Wu and Porté-Agel 2011).”
Wind-Turbine and Wind-Farm Flows: A Review (2019, background): “…wind-tunnel experiments have also been performed to study the interaction between turbulent boundary-layer flows and wind turbines or farms (e.g., Chamorro and Porté-Agel 2009, 2011; Cal et al. 2010; Lebron et al. 2012; Aubrun et al. 2013; Tian et al. 2013; Hancock and Pascheke 2014; Hamilton et…”
Large-Eddy Simulation of Wind-Turbine Wakes: Evaluation of Turbine Parametrisations (2011, background): “More recently, Chamorro and Porté-Agel (2009) carried out a wind-tunnel experiment to study the wake of a miniature wind turbine placed in a boundary layer developed over different surface roughness conditions.”