Numerical Study of the Stagger Angle Effect of a Circular Cylinder Installed in front of Returning Blade Toward the Vertical Axis Savonius Water Turbine Performance

This paper investigates numerically the effect of the circular cylinder's stagger angle variation installed in front of the returning blade on the performance of Savonius vertical axis water turbine. The numerical simulation uses Computational Fluid Dynamics using ANSYS 17.0 to solve the incompressible Unsteady Reynolds Averaged Navier-Stokes (URANS). Firstly, numerical model is verified by varying the grid size at TSR 1,078. Then numerical results are validated by existing experimental data, in this case the torque coefficients. The working fluid is in verification using air at Reynolds of 4.32 x10⁵ and convert to water fluid. Ratio of circular cylinder diameter to the turbine diameter (ds/D) is 0.5 at gap (S/D) of 0.95 with varying TSR of 0.3, 0.5, 0.7, 0.9, 1.1 and 1.3 and stagger angle (α) of 0, 30, 60 and 90 degree. The results show that the maximum power coefficient increases about 29.84% at a TSR of 0.9 for stagger angle of 60 degree.