Quasi-steady aeromechanic helicopter simulations using mid-fidelity aerodynamics

A numerical simulation process based on loosely coupling a helicopter flight mechanics code and a 3D panel and freewake aerodynamics method is extended for arbitrary steady flight states and quasi-steady maneuver analysis. First, the basic coupling procedure and their building blocks are introduced. Then, the extensions for arbitrary steady flight states are illustrated and a newly developed procedure for approximate maneuver simulations using a sequence of steady aeromechanically coupled simulations is presented. The aim of this procedure is to provide a rapid method for evaluation of loads, performance and stability in the helicopter design and development process. It includes an improved physics-based modeling of aerodynamic interactions as compared to low-fidelity aerodynamics models used in comprehensive codes. At the same time the computational effort is dramatically reduced as compared to highfidelity aerodynamics methods. Finally, validation results for the coupling procedure and first applications of the maneuver simulation process are shown. The computed results are compared with flight tests and blade element momentum theory based results. In many cases the solution accuracy can be significantly improved by using the coupled simulation procedure. But for maneuvers involving fast pilot inputs or considerable translational or rotationalaccelerations of the helicopter, the quasi-steady coupling approach is not suitable and an extension to fully unsteadyloose coupling or the implementation of a tight coupling approach is proposed