Numerical analysis of aerodynamic performance of rotors with leading edge slats

Abstract

A three dimensional compressible Navier-Stokes analysis capable of computing flows around wings and rotors with partial-span flaps or slats is described. This analysis is cast in a moving body-fitted coordinate system permitting arbitrary motion of the solid surfaces to be directly modeled. This methodology is validated through several single and multi-element rotor and wing configurations. The analysis is subsequently applied to two helicopter rotors. The effects of leading edge slats on the aerodynamic performance of these rotors in hover is studied. It is demonstrated that leading edge slats can significantly improve the hover performance at high pitch settings, with an increase in thrust and a reduction in torque. At low pitch settings, the slats were found to be detrimental to the rotor performance. Many practical issues such as surface imperfections, proper sealing of the slat during retraction, control loads and other implementation aspects should be carefully evaluated in the event of a practical design of a slat. However, in the present study only the aerodynamic effects of slats are addressed and no practical issues are considered.