Numerical study of airfoil used for helicopter rotor tip to investigate the enhancement in the aerodynamic characteristics using active flow control at forward flight conditions

Abstract

Helicopter forward flight is the most important state of flight due to time spent in this mode during the complete helicopter trip. In this study, a main rotor blade tip airfoil was simulated to obtain the effect of applying active flow control on the tip part of the rotor blade. A blowing excitation jet is applied to the leading edge of the airfoil just before the separation point with small momentum and high frequency to enhance the near wall boundary layer characteristic. This jet is used with different amplitude, frequency and excitation location from a leading edge to study the effect of this parameter. A numerical model is used to solve two different angles of attack and all results are compared with NACA report that used the same helicopter hub and airfoil. Results show good agreement with the experimental results and the chosen excitation parameter gives good enhancement to the performance of the airfoil used in the tip part of the helicopter blade in this mode of flight. Performance represented in lift and drag and lift to drag ratio shows improvement, reaching about 10% increase in lift and 30% decrease in drag, which means more than 50% change in lift to drag ratio. Furthermore, this study gives a good estimation of the best excitation location that is required for real application on the helicopter blade to improve of forward flight performance.