An investigation of ship airwake phenomena using time-accurate CFD and piloted helicopter flight simulation

This paper describes the use of Computational Fluid Dynamics (CFD) data to improve the fidelity of helicopter-ship dynamic interface simulation. Time-accurate airwakes for the simple frigate shape (SFS2) and a Type 23 Frigate have been computed for a number of wind-overdeck (WOD) angles to provide a realistic flow field in which to perform simulated deck landings within the FLIGHTLAB flight simulation environment. CFD predictions show good agreement with both wind tunnel data and full scale at-sea experimental data. Results from piloted flight trials using the University of Liverpool full-motion simulator are presented in detail. Pilot workload ratings resulting from the trials have been used to generate two Ship-Helicopter Operating Limits (SHOL) diagrams for a Lynx-like helicopter: one operating from the SFS2 and the other from a Type 23 Frigate. Pilot control activity for several WOD cases has been analysed in order to identify the nature of the interactions between airwake turbulence and the helicopter aerodynamic model. It is shown that the location and magnitude of velocity fluctuations on the rotor disk have a significant impact on the control activity required to maintain station over the landing spot. This study builds on earlier work performed at Liverpool and provides a platform for such simulations being used to reduce at-sea trials, and to provide a safe environment for pilot training.