The work is focused on numeric analysis of compressible flow around National Renewable Energy Laboratory (NREL) phase VI wind turbine blade airfoil S809. Although wind turbine airfoils are low Reynolds number airfoils, a reasonable investigation of compressible flow under extreme condition might be helpful. A subsonic flow (mach no. ) has been considered for this analysis and the impacts of this flow under seven different angles of attack have been determined. The results show that shock takes place just after the mid span at the top surface and just before the mid span at the bottom surface at zero angle of attack. Slowly the shock waves translate their positions as angle of attack increases. A relative translation of the shock waves in upper and lower face of the airfoil are presented. Variation of Turbulent viscosity ratio and surface Y+ have also been determined. A k-ω SST turbulent model is considered and the commercial CFD code ANSYS FLUENT is used to find the pressure coefficient (Cp) as well as the lift (CL) and drag coefficients (CD). A graphical comparison of shock propagation has been shown with different angle of attack. Flow separation and stream function are also determined. 1. Introduction According to the US Department of Energy the combustion of fossil fuels results in a net increase of 10.65 billion ton of atmospheric carbon dioxide every year [1] which has an enormous impact on environmental imbalance. As a result more focus on conversion of energy from alternate source has been given for the last few decades. In near future wind will be the most reliable green energy in the history of mankind. The field of wind energy started to develop in 1970s after the oil crisis, with a large infusion of research money in the United States, Denmark, and Germany to find alternative resource of energy especially wind energy [2]. To design the blade of a wind turbine proper assessment of aerodynamic characteristics of airfoil plays the most important role. The most effective way to design the blade is to have accurate experimental data set for the correct airfoil. But such data set are not always available and the designer must rely on calculated data such as simulated data generated by large-scale CFD code. Recent applications of CFD to solve the Navier Stokes equations for wind-turbine airfoils are reflected in the works of Chang et al. [3]. They used their in-house code to solve the 2D flow field around the S805 and S809 airfoils with attached flow and the S809 airfoil with separated flow. Computations were made with the Baldwin-Lomax, Chein’s
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