Numerical Study of Helicopter Rotors in a Ship Airwake

摘要

Operating helicopters in a naval environment is challenging because it imposes a pilot workload significantly higher than that during land-based operations. The aerodynamic interaction between the aircraft and the ship wake is known to play an important role in increasing the pilot workload, hence reducing the aircraft capability as a result of maintaining safety. As a further step toward numerical prediction of ship/helicopter operational limitations, computational-fluid-dynamics simulations are conducted for the Canadian Patrol Frigate. The effect of the rotor is included in the simulation, first using an actuator-disc method together with steady calculations, then using rotor blades and the unsteady Reynolds-averaged Navier-Stokes equations. Results using the actuator-disc method demonstrate the importance of coupling effects on the wake and rotor inflow when the rotor is operating close to the ship and therefore the invalidity of superposition methods. The case of a Sea King helicopter main rotor hovering above the deck just before touchdown is reproduced to overcome the limitations of steady calculations and the actuator-disc method. Predictions of rotor thrust compare well with the experimental data available and give confidence in the results. The findings highlight the differences in rotor loading between forward flight and near-deck operation. The possibility of using such simulations for determining safe flight envelopes is discussed as part of the future work.