NAVIER-STOKES ANALYSIS OF TIME-DEPENDENT FLOWS ABOUT WIND TURBINES

摘要

This paper presents an overview of an effort that uses various Reynolds-averaged Navier-Stokes (RaNS) methods to analyze time-dependent flows about horizontal-axis wind turbines (HAWT). The geometrically complex wind turbine consisting of closely coupled fixed and rotating components and complex flow phenomena including boundary-layer transition, unsteady tower wakes, and rotor-tower interaction make it an extremely difficult problem. The RaNS methods for this effort include a two-dimensional incompressible method and a three-dimensional compressible method. Both make use of structured overset grids to facilitate the simulation of flows about complex geometry. Boundary-layer transition can have a large effect on a wind turbine flowfield simulation. Several transition models including the classical Michel's method and the e n method were incorporated into the flow solvers. The e n method coupled to the Baldwin-Barth one-equation turbulence model shows good agreement with the wind-tunnel measured transition locations and loading characteristics for wind-turbine airfoils. Turbulent and unsteady tower wake affects wind-turbine rotor performance, aerodynamic loads, and acoustic characteristics. Two-dimensional studies demonstrate the capability to accurately model the tower's shedding frequency and resultant flow features. Unsteady, three-dimensional RaNS computation of the NREL Combined Experiment Phase II rotor demonstrates the capability, requirements and deficiency of current numerical methods. The current method captures the wake interactions between the rotor and tower and provides insight into the details of the wind-turbine flowfield.