Understanding ducted-rotor antitorque and directional control characteristics part I: Steady-state simulation

Despite decades of very successful yaw-control and antitorque applications, the aerodynamics of ducted rotors in low-power, near-edgewise flow conditions are not well understood. Motiv ated by phenomena discovered during the development of the RAH-66 Comanche's directional-axis control laws, a research program was mjtfertptl to use computational fluid dynamics to improve the understanding of the dynamic relationship between ductedrotor thrust and applied collective pitch, especially when the rotor is operating in near-edgewfae flight conditions. This paper is a presentation of the results of this study. Numerical solutions of the inviseid Filler equations were obtained for the flow over the Comanche fuselage with a uniform actuator disk and blade element models for the EANTAIL™ the main rotor is excluded in tins study. The solutions were obtained by running the modified PUMA2 (Parallel Unstructured Maritime Aerodynamics) compntational-fluid-dynamics code with an unstructured grid with 2.8 million tetrahedral cells. Excellent correlation between the calculations and a variety of static test data are presented and discussed. Subsequent efforts will examine the important aspects of the dynamics of the thrust response, and allow further comparisons with flight-test data.