Citation: Zheng, H.-D.; Zhang, B.;
Wang, S.-B.; Zhou, G.-Z. Effects of
Blade Numbers on Wind-Induced
Fatigue Lives of Straight-Bladed
Vertical-Axis Wind-Turbine Tower
Bases. Metals 2022, 12, 321. https://
doi.org/10.3390/met12020321
Academic Editors:
Alberto Campagnolo and
Alberto Sapora
Received: 18 December 2021
Accepted: 4 February 2022
Published: 11 February 2022
Publisher’s Note: MDPI stays neutral
with regard to jurisdictional claims in
published maps and institutional affil-
iations.
Copyright: © 2022 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
Article
Effects of Blade Numbers on Wind-Induced Fatigue Lives of
Straight-Bladed Vertical-Axis Wind-Turbine Tower Bases
Hua-Dong Zheng
1,
*, Bo Zhang
2
, Sheng-Bin Wang
2
and Guan-Zheng Zhou
3
1
School of Civil Engineering and Architecture, Wuhan University of Technology, Wuhan 430074, China
2
Changjiang Survey, Planning, Design and Research Co., Ltd., Wuhan 430074, China;
zhangbo@cjwsjy.com.cn (B.Z.); wangshengbin@cjwsjy.com.cn (S.-B.W.)
3
Department of Civil Engineering, The University of Hong Kong, Hong Kong 999077, China;
zhougz21@connect.hku.hk
* Correspondence: zhenghd18@mails.tsinghua.edu.cn
Abstract:
Vertical-axis wind turbines (VAWTs) are being reconsidered as a complementary technology
to the more commercially used horizontal-axis wind turbines (HAWTs) because of their economical
installation and maintenance. The selection of the blade numbers is one of the crucial concerns for
VAWTs. This study focuses on the effects of the blade numbers on the fatigue lives of VAWT tower
bases subjected to wind loading. Three straight-bladed VAWTs, with the same solidity ratios but
different blade numbers, varying from two to four, were designed. The aerodynamic loading incurred
by the VAWTs was computed using the corrected double-disk multistreamtube (DMS) model. The
dynamic equations of the turbine systems were solved using the explicit central difference method.
Then, a fatigue assessment model, including the crack-initiation and crack-propagation stages,
was developed for the turbine tower bases. The results indicate that the three- and four-bladed
VAWTs always presented better performances than the two-bladed VAWT in terms of the fatigue life.
Moreover, increasing the number of blades from two to three improves the fatigue life of the tower
base more than increasing it from three to four at lower wind speeds, while the latter is the more
effective way to improve the tower-base fatigue life at higher wind speeds.
Keywords:
vertical-axis wind turbine; fatigue; crack propagation; blade numbers; aerodynamic loading
1. Introduction
Wind energy is the fastest growing renewable clean energy source. At the end of
2019, the global wind capacity was already up to 651 GW, which provided the world with
5.3% [
1
] of its electric energy needs. In 2020, the new global wind power installations
were at 90 GW, which brought the total wind capacity to 743 GW [
2
]. With the increasing
development of wind energy projects, there has been much research on novel solutions
and, in some cases, reviews of previous work in order to revitalize these solutions using
new techniques. Vertical-axis wind turbines (VAWTs) belong to the latter category. VAWTs
peaked during the 1970s and 1990s, and then gradually faded out after that period because
horizontal-axis wind turbines (HAWTs) were thought to have higher power coefficients [
3
];
however, there has recently been renewed interest in VAWTs, beginning in the 2010s. The
reason is that VAWTs have several unique advantages, such as much lower noise levels,
simpler power generation systems, and much higher structural stabilities compared to
HAWTs [4].
A typical VAWT consists of a steel tower and a rotor with several blades. When
wind travels through turbines, the rotors rotate in order to harvest wind energy. In this
process, the aerodynamic loading incurred by the rotors periodically acts on VAWTs, which
greatly affects the fatigue lives of the structures. In order to accurately assess the fatigue
damage, it is necessary to perform time-domain simulations for the dynamic responses of
VAWTs. Although there are several commercially available software packages that are able
Metals 2022, 12, 321. https://doi.org/10.3390/met12020321 https://www.mdpi.com/journal/metals
