The standard k-ε eddy viscosity model is the most commonly used model in computational fluid dynamics and perform well in application, but less effective for flows with high mean shear rate or massive separation. An non-linear eddy viscosity k-ε model was developed to compensate the deficit, in which the Cμ determined by an expression of shear strain rate rather than a constant on the base of experimental and DNS data. Two-dimensional CFD simulations were carried out by proposed NL k-ε model and standard k-ε model for wind-turbine airfoil S809 with the general purpose CFD code ANSYS CFX 12.1. Results show that standard k-ε can predict the flow around the airfoil for angles of attack with attached flow, but is not qualified for flow at angles of attack with strong flow separation, whereas non-linear k-ε model can improve the accuracy of the performance coefficients to some extent, and when large flow separation generates, non-linear k-ε model can improve the accuracy of pressure distribution around the airfoil and simulate the flow separation more correctly.

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