STUDYING THE EFFECT OF NUMBER OF BLADES ON THE AERODYNAMIC PERFORMANCE OF A VENTURI EFFECT FLUID TURBINE (VEFT) BY NUMERICAL SIMULATION

Vertical-axis wind turbines (VAWTs) are a type of wind turbine where the main rotor shaft is set vertically. A commercial VAWT with two different designs, i.e., 4-blade and 8-blade is numerically simulated and the effect of number of blades on the aerodynamic characteristics is investigated. Commercial software (ANSYS FLUENT (TM) 12.1.4) is used for simulations. The simulations are performed with stationary blades as well as rotating blades with different rotation speeds up to 10 rad/s while the k-epsilon model is used for simulation of turbulent air flow around VAWT. The location and magnitude of the maximum air velocity and dynamic pressure are determined from the relevant contours and the results are compared. The fundamentals of the flow physics in the close proximity of the rotor and the wake are investigated by numerical simulations. The magnitude of the net torque generated by VAWT is also calculated and the results are compared. The results show that increasing the number of blades increases the magnitude of the torque generated by VAWT and, therefore, increases the efficiency of the wind turbine. However, a VAWT with a higher number of blades is more expensive due to higher design and manufacturing costs. Accordingly, there is an optimum design with respect to efficiency and capital investment. The current study offers a practical and inexpensive method to find such an optimum design and can be applied to both horizontal-axis and vertical-axis wind turbines.