# Numerical Simulation of Fluid-Structure Coupling for a Multi-Blade Vertical-Axis Wind Turbine
###### Abstract  
The aerodynamic characteristics of the vertical-axis wind turbine with three, four, five, and six blades are studied numerically. A coupling model of fluid flow and solid turbine blade is established to model the interactions between air and wind turbine. The pressure distribution and blade deformation affected by air are obtained and discussed. For the four wind turbines with different numbers of blades, the maximum pressure in the entire machine structure occurs at the variable angle position of the blades in the windward region under the same wind speed. Mainly due to the rapid airflow variation, complex turbulence, and significant influence of the wind field on the blades in this position, this part of the blades is prone to bending or damage. Under identical external wind field conditions, wind turbines with four and six blades exhibit significantly higher equivalent pressures on their surfaces compared to those with five and three blades. The maximum equivalent pressure of six blades can reach 3.161 \(\times\) 10\({}^{6}\) Pa. The maximum deformation of the blade basically occurs at the tip and four sides of the blade. The six-blade wind turbines withstand higher and non-uniform surface pressures on their blades, resulting in the largest deformation of up to 11.658 mm. On the other hand, the four-blade wind turbine exhibits the smallest deformation. The above conclusions provide theoretical guidance for the design and optimization of vertical-axis wind turbines. wind turbine; aerodynamic performance; fluid-structure coupling; numerical simulation 2023  
X]M.X.Z.Z. turbines, and it is also the main direction of current research [8; 9]. At present, according to the structure of wind turbines, they can be divided into vertical-axis wind turbines and horizontal-axis wind turbines. The development of horizontal-axis wind turbines has a relatively long history, and the technology is relatively mature, so currently, it holds a market share of around 97%. The number of formed wind turbine blades is generally two to three. The blades are installed radially along the wind turbine, and the shape of them is mostly airfoil-shaped. When operating normally, the rotating surface of the impeller is perpendicular to the wind direction. The wind turbine exhibits a relatively high starting torque, but it also boasts a high utilization coefficient of wind energy [10]. The development of vertical wind turbines started early. However, most researchers believe that vertical-axis wind turbines have lower wind efficiency compared to horizontal-axis wind turbines, so vertical-axis wind turbines develop relatively slowly. However, with the development of science and technology, the problems of horizontal-axis wind turbines began to be exposed, such as high cost, difficult maintenance, and so on. At this time, the vertical-axis wind turbine slowly began to receive attention. Researchers have started to study the aerodynamic performance of vertical-axis wind turbines and improve their appearance [11; 12; 13]. At present, there are mainly two methods for wind turbine research: experiments and numerical simulation. The experiments can be divided into field experiments, ground performance experiments, and wind tunnel experiments. Field experiments mainly use equipment to test and analyze the power and electrical quality of wind turbine units, and all data and experimental conditions must be carried out under actual conditions. While this method ensures maximum reliability in obtaining results, it often comes with high costs, and is difficult to guarantee 100% success of the experiments. Therefore, this method is not suitable for the initial research stage but is rather appropriate for assessing the reliability of results in the later stages of research. The practical application of wind turbines is to select appropriate blade parameters [14; 15] according to the local wind conditions. Conducting research solely through experiments poses challenges in terms of cost and time.