Computational analysis of a shrouded small scale vertical axis wind turbine

In this research work, the numerical study of a VAWT (bare and shrouded) is presented. First, a 2 m high three bladed H-rotor vertical turbine, with a radius of 1.045 m was designed. The three blades are constructed using the NACA 0015 airfoil sections. The wind speed is constant and equal to 10 m/s, while the rotational speed ranges from 70 to 143 rpm and from 286 to 621 rpm for the bare turbine and the shrouded turbine case, respectively. The shroud designed for this project has a total length of 7.012 m, a rectangular cross section all over its body, inlet and outlet areas both equal to 2.2x3.255 m 2 , flat top and bottom walls and curved side walls. The area ratio for both converging and diverging sections of the shroud is 1.453. Full threedimensional transient CFD simulations were carried out for the modeling of the flow around the rotor, through the shroud and through the full rotor – shroud arrangement. The computational domain consisted of two regions with different frames of reference (a stationary and a rotating). Each simulation concerned a different rotational speed. All the simulations were performed using the commercial CFD software package ANSYS CFX. The standard k-e turbulence model was used for the simulations. Detailed flow analysis results are presented, dealing with the various investigated test cases. By varying the rotational speed of the turbine the power coefficient versus tip speed ratio curves were obtained. The results showed that there is a significant improvement in the performance of the wind turbine.