CFD Analysis for the Performance of Gurney Flap on Aerofoil and Vertical Axis Turbine Yan Yan 1 , Eldad Avital 2 , John Williams 3 School of Engineering and Materials Science Queen Mary University of London 327 Mile End Road London E1 4NS UK Email: yan.yan@qmul.ac.uk 1 , e.avital@qmul.ac.uk 2 , j.j.r.williams@qmul.ac.uk 3 Theodosios Korakianitis Parks College of Engineering, Aviation and Technology Saint Louis University, St Louis,USA Email: korakianitis@alum.mit.edu Abstract—A numerical study was carried out to investigate the effects of a Gurney flap on the aerodynamics performance of the NACA 0018 aerofoil and an associated three-blades rotor of a H-type Darrieus wind turbine. The flow fields around a single aerofoil and the Vertical Axis Wind Turbine (VAWT) rotor are studied using URANS. The height of Gurney flap ranges from 1% to 5% of the aerofoil chord length. The flow fields around a single aerofoil and the Vertical Axis Wind Turbine (VAWT) rotor are simulated using URANS. The results show that the Gurney flap can increase the lift and lift-to-drag ratio of the aerofoil. As a result, adding a Gurney flap can significantly improve the power coefficient of the VAWT at low tip speed ratio, where it typically gives low power production. The causing mechanism is discussed in detail —Gurney flap, CFD, wind turbine, aerofoil I. INTRODUCTION With the development of industry and economy, the demand for energy has rapidly grown in recent years. Fossil fuel, such as coal and oil, has supported industrial growth in the last century. However, the excessive consumption of fossil fuels has made humanity face an increasing pressure of energy shortage and environment problems, such as global warming and acidic rain. This energy crisis has become a global challenge. The need for alternative environmental friendly energy sources is more acute than ever before Wind power is one of the most popular renewable energy sources, because of its wide distribution around the globe. A wind turbine can produce electricity by transforming the kinetic energy from wind to the mechanical and electrical energy. Unlike fossil fuels, it produces very little or no greenhouse gas at all, and thus can help efforts in reducing global warming. Manuscript received March 4, 2018; revised April 8, 2019. Because of the increasing importance of wind energy, improvement in efficiency of wind turbines is of priority, leading to growing research in this area. There are two types of wind turbines, Horizontal Axis Wind Turbine (HAWT) and Vertical Axis Wind Turbine (VAWT). The former is more popular compared to the latter one, due to its higher aerodynamic power coefficient. However, VAWTs offer some unique advantages that HAWTs do not have. The power production of VAWTs is independent of the incoming direction of the flow. In addition, VAWTs can be deployed to a wide range of wind velocity and produce lower noise. They have relatively simpler mechanical structures and are easier to maintain than HAWTs. Wind turbine efficiency is mainly determined by the blade shape. The aerofoils are the basic element of the blade. They have significant influence on the aerodynamic performance of the turbine. Nowadays, many methods, such as optimizing blade shape [1, 2], adding intelligent control system and improving the configuration of generator, are available to improve the aerodynamics of wind turbine and overcome the drawbacks. Among them, flow control of wind turbine blades is one of the widely used techniques to improve the power coefficient of the rotor. The Gurney flap, which is named after its inventor, an American race car driver legend Dan Gurney [3], is a simple but effective passive control device for an aerofoil. Various studies have been carried out to understand the performance of the aerofoil with a Gurney flap and its application on aircrafts and land vehicles. However, its application on the wind turbine blade has not been much investigated. In the following, the analysis of aerodynamic performance of the Gurney flap on H-type Darrieus wind turbine blade is presented. Detailed flow features around aerofoils is also be discussed. International Journal of Mechanical Engineering and Robotics Research Vol. 8, No. 3, May 2019 © 2019 Int. J. Mech. Eng. Rob. Res 385 doi: 10.18178/ijmerr.8.3.385-392 Index Terms