Abstract
We have investigated the effects of the rotating blades of an upwind-type three-blade horizontal-axis wind turbine (HAWT) on the basic characteristics of aerodynamic forces acting on its tower by conducting improved delayed detached-eddy simulations (DESs). Three tip-speed ratios were considered for the operating conditions of the HAWT: λ = 3 (low), λ = 6 (optimum), and λ = 10 (high). The diversion of the flow approaching the tower by the rotating blades and the low-pressure region that formed downwind of the blades significantly affected the aerodynamic forces acting on the tower. For example, the azimuth angle around the tower at which the pressure reached a maximum at each height shifted significantly in the direction of the movement of the blade passing the tower because of the diversion of the flow by the blades. Fluctuations in the lift force of the tower were significantly larger than those in its drag force because of the low-pressure region downwind of the blades.
Highlights
When designing a wind turbine, it is important to avoid the excitation of resonant oscillations of the wind turbine tower by rotor thrust fluctuations at the blade-passing frequency or, to a lesser extent, at the rotational frequency
As a first step toward clarifying the effects of aerodynamic forces acting on the tower of a wind turbine on the vibratory characteristics of the tower, we investigated the effects of the rotating blades of an upwind-type horizontal-axis wind turbine (HAWT) on the basic aerodynamic characteristics of the tower
As aa first first step step toward toward clarifying clarifying the the effects effects of of aerodynamic aerodynamic forces forces acting acting on on the the tower tower of of aa wind wind turbine on the vibratory characteristics of the tower, we investigated the effects of the rotating turbine on the vibratory characteristics of the tower, we investigated the effects of the rotating blades blades of an upwind-type three-blade on the basic characteristics of the aerodynamic forces of an upwind-type three-blade
Summary
When designing a wind turbine, it is important to avoid the excitation of resonant oscillations of the wind turbine tower by rotor thrust fluctuations at the blade-passing frequency or, to a lesser extent, at the rotational frequency. Using the HAWT with a downwind configuration, Zahle et al [13] showed that the rotor had a strong effect on the tower shedding frequency, causing vortex lock-in at the upper part of the tower under certain flow conditions They suggested the possibility that these lock-in phenomena were due to numerical artifacts of the RANS turbulence model. As a first step toward clarifying the effects of aerodynamic forces acting on the tower of a wind turbine on the vibratory characteristics of the tower, we investigated the effects of the rotating blades of an upwind-type HAWT on the basic aerodynamic characteristics of the tower (e.g., the drag, lift, and pressure coefficients) This was done by conducting CFD simulations with the improved delayed detached-eddy simulation (IDDES) model [14], which is a hybrid RANS-LES model, of the wind flow around the wind turbine and its tower at low, optimum, and high tip-speed ratios
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