Estimating the Aerodynamic Coefficients of a Savonius Rotor Blade Profile Developed Through the Simplex Search Method

The Savonius rotor, a type of vertical-axis wind turbine, seems to be promising for small-scale power generation. Most of the studies conducted so far have focused on the evaluation of torque and power coefficients (CT, CP) of the rotor. This paper aims at analyzing the aerodynamic drag and lift coefficients (CD, CL) of a Savonius rotor blade profile that is generated by the simplex search method to maximize its CP. The optimization is carried out by coupling the numerical simulations with the simplex search method. The optimized blade profile thus obtained is symmetric about its axis, where one half is created through a natural cubic spline curve using three points. Two-dimensional (2D) unsteady numerical simulations have been conducted by adopting ANSYS FLUENT solver to examine the CD and CL of the optimized blade profile at an inlet air velocity of 7.30 m/s. The shear stress transport (SST) k-ω turbulence model is used to solve the transient Reynolds-averaged Navier-Stokes (RANS) equations. The aerodynamic analysis is performed over a range of tip speed ratios (TSRs). The total pressure, velocity magnitudes, and the turbulent intensity contours of the optimized blade profile are generated and studied at different angles of rotation. The CD and CL of the blade profile are investigated for a complete rotation with an increment of 1°. At TSR = 0.8, the optimized profile shows a CDmax of 1.91 at an angle of rotation of 54°, while CDmin is found to be 0.45 at an angle 147°.

Aerodynamic Analysis of Novel Savonius Rotor

Wind is a renewable form of energy that holds vital solutions to energy crisis that will be faced in the possible future. Apart from the viable lift based turbines that we have been working on, research can be done on drag based turbines that can be installed in urban areas for short power requirements. The research aims at developing a novel design for Savonius type rotor which will help to improve the power producing characteristics of the turbine. CFD fluent analysis will help in analysis of the proposed blade shape. The results explain how the combination of elliptical profiled blade improves coefficient of power for Savonius type rotor. Keywords: Aerodynamics, Wind Energy, Savonius, VAWT, Wind Turbine

Computational Fluid Dynamics Study of a Modified Savonius Rotor Blade by Universal Consideration of Blade Shape Factor Concept

This work aims to investigate computationally the performance of Savonius vertical axis wind turbine having a new design feature for its blade geometry. The proposed design is based on a universal consideration of blade shape factor concept for the Savonius rotor blade. A blade shape factor ranges from zero to infinity, or vice versa, is considered in a single blade of the modified Savonius rotor. This means that each point in the two-dimensional blade profile of the suggested blade design has a single value of blade shape factor that is defined based on the dimensions of conventional semi-circular blade. The computational results of the proposed blade shape design, having blade shape factor varying from infinity to zero, showed an improvement in turbine performance as compared to conventional blade shape design. Moreover, increasing the operating range of Savonius wind turbine is expected.

Dependence of Power Characteristics on Savonius Rotor Segmentation

Savonius rotors are large and heavy because they use drag force for propulsion. This leads to a larger investment in comparison to horizontal axis wind turbine (HAWT) rotors using lift forces. A simple construction of the Savonius rotor is preferred to reduce the production effort. Therefore, it is proposed here to use single-segment rotors of high elongation. Nevertheless, this rotor type must be compared with a multi-segment rotor to prove that the simplification does not deteriorate the effectiveness. The number of segments affects the aerodynamic performance of the rotor, however, the results shown in the literature are inconsistent. The paper presents a new observation that the relation between the effectiveness of single- and multi-segment rotors depends on the wind velocity. A single-segment rotor becomes significantly more effective than a four-segment rotor at low wind speeds. At high wind speeds, the effectiveness of both rotors becomes similar.

Dynamics of a Wheeled Cart Driven by a Savonius Rotor

Savonius rotor is one of relatively wide-spread type of wind turbines. The rotation rate of this rotor is considerably lower than that of horizontal axis wind turbines and Darrieus wind turbines. However, it starts rotating at small wind speeds, doesn’t require any additional devices to ensure its re-orientation in case of change of the wind direction, and generates a rather large torque. Therefore, it is suitable for use as a drive in different mechanical and electromechanical systems. In the present paper, dynamics of rectilinear motion of a wheeled cart is studied, which is driven by Savonius rotor installed on it. It is assumed that the wind makes a certain constant angle with the line, along which the cart moves. The aerodynamic load upon the rotor is described with an empirical model, in the context of which the aerodynamic characteristics (aerodynamic torque, drag and lateral force coefficients) are represented as Fourier series with respect to the rotor revolution angle, the coefficients of the series being functions of the rotor tip speed ratio (dimensionless angular speed). Experiments were performed in the subsonic wind tunnel of the Institute of Mechanics of Lomonosov Moscow State University intended to measure aerodynamic characteristics of the rotor at different wind speeds and rotor angular speeds. Based on experimental data, functions were proposed that approximately describe the dependence of the above mentioned coefficients upon the tip speed ratio. The obtained dependences were used for analysis of dynamics of the cart driven by the Savonius rotor. The equations of motion are averaged with respect to the angle of revolution of rotor. Steady solutions of this averaged system are studied. It is shown that, for certain values of parameters, there exist two attracting steady motions corresponding to different directions of the cart velocity. Cart dynamics in the context of the full system of equations of motion is compared with its dynamics in the context of the averaged system.