Performance evaluation and shape improvement of a novel vertical-axis autorotation current turbine

A new type of vertical-axis turbine called the vertical-axis autorotation current turbine (VAACT) has been investigated experimentally and numerically. This novel turbine utilizes the autorotation phenomenon to extract kinetic energy and is characterized by a higher moment of inertia and a flapped blade. The main objective of the present work is to further improve the efficiency of this turbine type by improving the original shape. First, through a comparison of experimental and numerical results under specific conditions, the accuracy of the three-dimensional (3D) detached eddy simulation (DES) used in the present study is validated. The free surface effect on the average rotation velocity and efficiency is found to be insignificant when the fluctuation of the free surface is small. Then, shape improvement based on response surface methodology (RSM) incorporated into computational fluid dynamics (CFD) simulations is performed. The inner length and flapped angle are selected as shape variation parameters. Finally, the optimal parameters of an inner length of 10.8 cm and a flapped angle of 47.2 degrees, corresponding to a maximum mean power coefficient of 0.1545, are found and verified. The improvement methodology adopted in this paper greatly reduces the number of required sampling points compared to other optimization algorithms, such as genetic algorithms, which confirms the potential of the resource-intensive 3D DES method as a computational tool.