In efficiency remains the main problem with VAWT (Vertical Axis Wind Turbine). One method to improve wind turbine efficiency is to reduce the negative moment or increase the positive moment. In this study,five kinds of rotating speeds and three kinds of wind speeds were used to
simulate and analyse air flow over a VAWT. The finite volume method
with turbulent and sliding mesh models were employed to simulate the
flowfield. The results indicate that the separation bubble disappears on the upside of the blade when the blade is rotating into the upwind, and highest differential pressure occurs near to the leading edge of the blade.Moreover, when the differential pressure is higher, the moment is greater,and the moment increases when inflow speed and rotating speed are both increasing. The output moment is similar when the tip speed ratio is
identical. The selection of the tip speed radio is 1.25 when the blade chord is 1 and the radius is 2.