Abstract
Abstract. A procedure to propagate longitudinal transient gusts through a flow field by using the resolved-gust approach is implemented in the URANS solver THETA. Both the gust strike of a 1−cos() gust and an extreme operating gust following the IEC 61400-1 standard are investigated on the generic NREL 5 MW wind turbine at rated operating conditions. The impact of both gusts on pressure distributions, rotor thrust, rotor torque, and flow states on the blade are examined and quantified. The flow states on the rotor blade before the gust strike at maximum and minimum gust velocity are compared. An increased blade loading is detectable in the pressure coefficients and integrated blade loads. The friction force coefficients indicate the dynamic separation and re-attachment of the flow during the gust. Moreover, a verification of the method is performed by comparing the rotor torque during the extreme operating gust to results of FAST rotor code.
Highlights
The origins of applying computational fluid dynamics (CFD) to wind turbine rotors date back to the 1990s when Soerensen and Hansen (1998) applied EllipSys3D to a wind turbine. Soerensen and Hansen (1998) solved the Reynoldsaveraged Navier–Stokes (RANS) equations and applied the Menter shear stress transport (SST) k − ω turbulence model to a full-scale wind turbine
The study presented the validation of the resolved-gust approach that was implemented in the unsteady RANS (URANS) solver THETA
1. the wind speed is constant in height and time; 2. the gust velocity is constant in height; 3. the gust transport velocity is equal to speed of sound which is infinite; 4. the boundary conditions of the flow domain are chosen to prevent the flow from escaping sideways
Summary
The origins of applying computational fluid dynamics (CFD) to wind turbine rotors date back to the 1990s when Soerensen and Hansen (1998) applied EllipSys3D to a wind turbine. Soerensen and Hansen (1998) solved the Reynoldsaveraged Navier–Stokes (RANS) equations and applied the Menter shear stress transport (SST) k − ω turbulence model to a full-scale wind turbine. The origins of applying computational fluid dynamics (CFD) to wind turbine rotors date back to the 1990s when Soerensen and Hansen (1998) applied EllipSys3D to a wind turbine. In 2002 the National Renewable Energy Laboratory (NREL) performed the Unsteady Aerodynamic Experiment (UAE) (Hand et al, 2001), which has long been the reference for several CFD computations. Johansen et al (2002) presented a detached eddy simulation (DES) on the NREL UAE phase VI blade to demonstrate the capabilities of predicting flow separation. The experiment has been widely used for URANS solver validation for example by Duque et al (2003), Le Pape and Lecanu (2004), Yelmule and Anjuri (2013), Lynch and Smith (2013), Oe et al (2014), and Länger-Möller (2017)
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