Effects of blade tip flow on aerodynamic characteristics of straight-bladed vertical axis wind turbines

Abstract

Straight-bladed vertical axis wind turbines (SB-VAWTs) are increasingly recognized as a favorable choice for wind energy systems in both urban and offshore environments. This study examines the effects of the blade tip flow on the aerodynamic characteristics of SB-VAWTs by numerical simulation. The analysis employs a comprehensive set of 84 models, varying in parameters such as rotor diameters, blade chord lengths, tip speed ratios, blade aspect ratios (ARs), and airfoil types. Initially, the blade is modeled using the finite division method, followed by a comprehensive three-dimensional URANS numerical simulation. A comprehensive analysis of the aerodynamic performance across the blade span is conducted to quantify the effects of the blade tip flow. The findings indicate that, in addition to causing losses, the tip flow also encourages reattachment of the separated flow onto the blade surface, especially under conditions of stronger flow separation. The influence of the tip flow reduces with a higher AR for AR less than 8. However, when AR surpasses 8, the effect of tip flow stabilizes. This study will serve as a valuable reference for the design of SB-VAWTs and lay the groundwork for future research on blade tip optimization.