This paper presents the three-dimensional (3D) flow analysis around a horizontal axis wind turbine using pseudo-compressibility method combined with overset grid method. The computational results of 3D Navier-Stokes solution agree with two-dimensional (2D) ones of corresponding relative angle of attack at the middle span. However, it is found that the angle of attack at near the tip region is predicted to be smaller than that derived with 2D simulation which neglects the effect of tip vortex. The data obtained with the proposed algorithm of Computational Fluid Dynamics (CFD) are compared with the Blade Element and Momentum theory (BEM) data for a given angle of attack at each span section. Both sets of data are in good agreement with each other at the middle span position. Both BEM and CFD are able to analyze the down wash effect induced by a tip vortex and other variance of bound vortex in the span wise direction. However, the BEM underestimates the angle of attack at the hub and tip side where 3D flow effects are strong. In other words, the BEM estimates larger induced velocity than CFD.
The wake behind a wind turbine in the Atmospheric Boundary Layer (ABL) is investigated using a numerical simulation method. From the view of cost effectiveness, collective installation (wind farm) is desired because it can save the total length of the power transmission lines and the labor cost for maintenance. However, the wake from the upwind wind turbine may significantly reduces the power production of the downstream wind turbine and cause large load variations on the blades. Numerical methods based on Computational Fluid Dynamics (CFD) are efficient to investigate the structures and characteristics of the wind turbine wakes. In this study, the relationship between the velocity profile of the ABL and the wake vortex breakdown is discussed. It is found that the vortex breakdown occurs faster in the ABL flow conditions.
This study aims to design low-noise wind turbine blades by assessing some methods to predict wind turbine noise. This paper focuses on aerodynamic noise and analyzes wind turbine noise by using semi-empirical methods. The study reveals the difference of sound pressure level of aerodynamic noise. BPM model using XFOIL shows reducing noise by the control of rotating speed.
This present study focuses on the noise caused by the passing of the turbulent boundary layer over the trailing edge of the blade. The purpose of this study is to consider a low-noise-turbine blade by showing a correlation between sectional shape of trailing edge and high frequency noise from trailing edge. And furthermore, it aims to clarify the noise-generating mechanism by investigating behaviors of vortices generated from some trailing edges of NACA0012 using unsteady numerical analysis.
