Evaluation of Rans Turbulence Models for Turbulent Flow over Nrel S809 Airfoil

Abstract

In this presented work, a numerical investigation was conducted to evaluate the performance of RANS turbulence models implemented in ANSYS CFX to predict flow field and aerodynamic characteristics of the NREL S809 Airfoil. The simulations were carried out with ANSYS CFX R18.2 (academic version). The blade geometry was simplified into a 2D airfoil and the flow analysis around the profile was conducted at various angles of attack equal to 0°, 5.13°, 9.22°, 11.24° and 20.15°, at a constant and same Reynolds number equal to 2x106. In this paper, the turbulence flow patterns and separation around the profile were represented using the most turbulence models used in CFD codes, the standard k-ε and its modifications RNG k-ε. The moment coefficient (Cm), the lift coefficient (Cl) and the drag coefficient (Cd) were determined and plotted as a function of the angle of attack. The pressure distributions around this profile, for each angle of attack, were also presented. The results and the plots obtained have shown good agreements with published experimental results. From the simulations, the two turbulence models provided near prediction to the experimental values at low angle of attacks, but over predict the Cd values. Calculations have also shown that the standard k-ɛ model and RNG k-ɛ model produced similarly results but with partly differences in pressure magnitude.

Keywords

• NREL S809 Airfoil,CFD simulations,RANS turbulence models,Aerodynamic characteristics

References

1. ANSYS, Inc. (2017). ANSYS CFX Reference Guide. Release 18.2 academic version. Butterfield, C. P., Scott, G., & Musial, W. (1992). Comparison of wind tunnel airfoil performance data with wind turbine blade data. Journal of solar energy engineering, 114(2), 119-124. Chang, Y. L., Yang, S. L., & Arici, O. (1996). Flow field computation of the NREL S809 airfoil using various turbulence models (No. CONF-960154-). American Society of Mechanical Engineers, New York, NY (United States). Guerri, O., Bouhadef, K., & Harhad, A. (2006). Turbulent flow simulation of the NREL S809 airfoil. Wind Engineering, 30(4), 287-301. Hartwanger, D., & Horvat, A. (2008, June). 3D modelling of a wind turbine using CFD. In NAFEMS Conference, United Kingdom. Launder, B. E. & Spalding, D. B. (1974). The numerical computation of turbulent flows. Computer methods in applied mechanics and engineering, 3(2),269–289. Wang, H., Zhang, B., Qiu, Q., & Xu, X. (2017). Flow control on the NREL S809 wind turbine airfoil using vortex generators. Energy, 118, 1210-1221. Wolfe, W. P. and Ochs, S. S., CFD calculations of S809 aerodynamic characteristics, AIAA-97-09 Yakhot, V. S. A. S. T. B. C. G., Orszag, S. A., Thangam, S., Gatski, T. B., & Speziale, C. G. (1992). Development of turbulence models for shear flows by a double expansion technique. Physics of Fluids A: Fluid Dynamics, 4(7), 1510-1520.