Estimation of power performances and flow characteristics for a Savonius rotor by vortex particle method

Abstract

This study investigates the implementation of the vortex particle method (VPM) with the goal of efficiently and accurately estimating the power performances and flow characteristics for a Savonius rotor. The accuracy and efficiency of simulation methods are critical for the reliable design of Savonius rotors. Among various approaches, VPM is chosen because it can be flexibly incorporated with selfcorrection techniques, and the distribution of bound vortex particles can effectively represent complex geometries. In this work, a double-trailing-edge-wake-modeling vortex particle method (DTVPM) is presented to extend the working range of VPM for dealing with large rotating amplitudes and high tip speed ratios (TSRs). DTVPM addresses asymmetrical torque predictions for a Savonius rotor without gap width. However, DTVPM performs poorly at high TSRs due to the absence of viscous effects near the surface. To capture complex wake structures, such as reverse flow structures, the viscous correction for tip vortices is suggested. The current research focuses on the implementation and validation of DTVPM for predicting torque coefficients and wake patterns, as well as comparisons to OpenFOAM results. Twodimensional and incompressible flow is estimated at λ = 0.2-1.2. For the studied cases, a maximum power coefficient is obtained at λ ≈ 0:8, consistent with published experimental data. In addition, the process of trailing-edge vortices generation and detachment is captured by DTVPM. The comparison results between OpenFOAM and DTVPM show that DTVPM allows to efficiently simulate a Savonius rotor without any empirical parameters. DTVPM will help to improve existing engineering models for wind energy fields.double-trailing-edge-wake-modeling, flow characteristics, power performances, Savonius rotor, vortex particle method | INTRODUCTIONThe Savonius rotor is one of the simplest wind turbines, consisting of at least two curved blades. Each blade has two sharp edges. Many geometrical parameters affect the operation of Savonius rotor, such as number of blades, gap width, number of stages, and blade shape. Early experimental

Identifying some regularities of the aerodynamics around wind turbines with a vertical axis of rotation

“…The advantage of using wind turbines with a vertical axis of rotation is the generation of electricity due to the possibility of self-starting and the absence of dependence on the wind direction on the example of the Savonius rotor [13]. But these installations have a disadvantage in the form of low efficiency, and the negative torque generated on the return blade limits its use in a large mastshab.…”

“…Article [13] presents the results of a numerical study of the energy and flow characteristics for a Savonius rotor using the vortex particle method (DTVPM). It is shown that DTVPM makes it possible to effectively model the Savonius rotor without any empirical parameters.…”

Performance analysis of an idealized Darrieus–Savonius combined vertical axis wind turbine

“…Jin et al 16 investigated 2D unsteady flows around polygons using a vortex method. Pan et al 17 implemented the vortex particle method to simulate transient blade forces and wake fields around the turbine. The kinematic models are quite complex due to the necessity of solving the unsteadiness of flow.…”