Orthogonal blade-vortex interaction on a helicopter tail rotor

The orthogonal blade-vortex interaction has been simulated using unsteady Reynolds-averaged Navier-Stokes equations with turbulence closure equations. The cases investigated are relative to an interaction between a lifting blade at a high angle of attack and an orthogonal vortex that travels either head-on or at 45 deg to the leading edge. The numerical simulations have been performed at a Reynolds number of Re = 1.85 x 105 and a vortex Reynolds number of Re v = 105. The impact parameter is equal to 8, which places the interaction in the weak vortex regime. The initial axial velocity of the vortex is zero, but as the vortex travels a self-induced velocity causes the vortex to move axially well before the impact on the blade. The analysis is carried out on the vortex dynamics and on the blade aerodynamics. The data investigated include the behavior of the pressure field as the vortex advances, the distribution of vorticity, the interaction of the vortex with the blade and the wake, the flow separation at the blade surface, and the path lines of the flow. A comparison between the case of straight and oblique blade-vortex interaction indicates that the blade-vortex interaction pressure peak is less severe in the latter case. A comparison is also made for the corresponding aerodynamic force coefficients (lift and drag and normal force).