The influence of the Reynolds number on the airfoils

Abstract

The wind speed is one of the major parameter influencing the design of the wind turbine, which varies widely over the different part of the country and globe. So, significant research is going on for the design of wind turbine for low, medium and high wind speed. Currently, many researchers have started designing small-scale horizontal axis wind turbines (HAWT) in world, to adapt their use to households. The advantage is reflected in the simple and affordable construction, uninterrupted operation and satisfactory power that wind turbines create. An airfoil is defined as the cross section of a body that is placed in an airstream in order to produce a useful aerodynamic force in the most efficient manner possible. The cross sections of wings, propeller blades, windmill blades, compressor and turbine blades in a jet engine, and hydrofoils are example of airfoils. A computational study has been conducted on various airfoils to simulate flows at different Reynolds numbers (Re) and wind speed to provide understanding and guidance for other low Reynolds-number designs. The numerical computational method used in this study is a boundary element method (BEM) which is implemented in software Qblade. It is an alternative deterministic method which incorporates a mesh that is only located on the boundaries of the domain and hence are attractive for free surface problems. The airfoils investigated in this study include NACA 4412, NACA 63-415 and S809. Performances such as power, power coefficient and tip speed ratio were compared.