Study of the efficiency of a computer code to analyze the performance of a rotating machine: application on a Savonius wind turbine

Abstract

The wind turbine is one of the sources of renewable energies very solicited to solve global energy problems. Among the various technologies of a rotor, that of a Savonius wind turbine is technically best suited in developing sending countries. Despite its weakness in performance, it has some advantages exploitable both on its mechanical torque and on its starting speed. In this work, we tested the effectiveness of a computer code that we designed to increase its efficiency before multiplying it. To do this, the numerical simulation of the aerodynamic performances of a vertical axis wind turbine of the Savonius type was chosen in order to validate our code. The Computational Fluid Dynamic (CFD) code, which is designed in Fortran, makes it possible to give fine predictions on the profiles of pressure fields, velocities and some aerodynamic characteristic variables of the wind turbine (moment, mechanical torque, shock wave, turbulence, ...) characterizing the performance of a rotating machine. The numerical resolution method adopted in this analysis is that of explicit finite difference. The Lax discretization scheme at two-time steps followed by addition of corrected artificial (numerical) viscosity was used. The spatiotemporal precision is in two orders, whose stability is dictated by the so-called CFL (Current Friedrich Levy) condition which imposes a constraint on the time step Δt. A detailed study of the results obtained and phenomena developed all around the blade have been made in order to draw conclusions.