Calculation of Helicopter Airfoil Characteristics for High Tip-Speed Applications

The aerodynamic section characteristics of several helicopter profiles have been computed using the Reynolds-averaged, thin-layer Navier-Stokes equations, and an eddy-viscosity model to approximate boundary-layer turbulence. The calculations were performed over a wide range of Mach numbers, angles of attack, and Reynolds numbers, with particular emphasis on transonic separated flow conditions that are relevant to advancing blades in high-speed forward flight. An extensive study was made of the accuracy of the numerical code, ARC2D, and of the sensitivity of the results to the numerical parameters and approximations. Also, comparisons were made with a large body of experimental data. The numerical results reproduce the measured airfoil behavior across the transonic regime, and the details of the computed flow field provide new insights into transonic airfoil behavior.