Simulation of a rotocraft in turbulent flows

Abstract

Accurate simulation of helicopters in an at-sea-shipboard environment is desired to provide realistic operating envelopes without incurring the enormous cost of real-time flight tests. This study examines the simulation of rotorcraft in turbulent flow by looking at previous attempts at helicopter-ship interfacing, current efforts in this area, and what will be needed in the future. Part of this study is devoted to the construction of an analytic model of the "tunnel strike" problem of the CH-46 Sea Knight helicopter that is based on measurements made over the flight deck of a model ship. A computer model was constructed, with the aim of modeling the "tunnel strike" during engagement aboard AOR type ships. The remainder of this study is concerned with the simulation of the motion of a helicopter in the turbulent wake of a DD-963 class ship. Results show that a sixth order transfer function can filter white noise to accurately model the turbulence spectra at specific points along a helicopter glide path in the wake. While a tunnel strike could not be successfully modeled using DYSCO software, a simple blade-element program was developed to show the aerodynamic forces on the rotor blades in a specific flow field over an AOR class ship flight deck. That program shows the location and magnitude of the aerodynamic forces contributing to the flapping of the rotor blades, which results in the rotor blades impacting the fuselage.