Numerical study on aerodynamic performance of a ducted tail rotor in hover and sideward flight

Abstract

The present paper examines the aerodynamic performance of a ducted tail rotor in hover and sideward flight conditions using high-fidelity CFD methods. The wake features, flow separation, and aerodynamic force pulsation of a full-scale SA365N1 ducted tail rotor model under different flight conditions are compared. The coupling influence mechanism of the sideward inflow, wake flow, and shroud shielding on the aerodynamic loads of the ducted tail rotor are revealed through numerical evaluation of variations in collective pitch and sideward flight speed. Special attention is dedicated to studying the wake recirculation phenomenon and thrust breakdown of the ducted tail rotor during right sideward flight, in order to analyze the flight speed boundary that notably affect the aerodynamic performance. It is found that the duct effectively shields the tail rotor from intricate vortex interference during right sideward flight, thus averting tail rotor failure. Additionally, when the ratio of right sideward flight speed to hover equivalent induced velocity is below 0.2, it results in favorable recirculation and enhanced shroud thrust. However, increasing the speed ratio results in a reduction in duct thrust. If the right sideward flight speed becomes excessive, it induces a vortex ring state, resulting in failure of the shroud aerodynamics and a significant decline in the overall aerodynamic performance of ducted tail rotor.