Simulation of Helicopter Shipboard Operations with Spatial Velocity Gradients in the Ship's Airwake

A mathematical model of a generic helicopter that captures essential helicopter-ship's airwake dynamics (e.g. fuselage dynamics, blade flapping and lead/lagging, interactional aerodynamic effects of the ship's airwake) has been developed in the implicit nonlinear ODE form for control design and evaluation. A procedure in which the ship's airwake characteristics with spatial velocity gradients are integrated into the rotor blade dynamics is described using polynomial interpolations from available CFD data. A simulation of the automatic lateral reposition toward the ship in 30-deg wind-over-deck condition is performed using model predictive control. Comparisons between different assumptions about the uniform/spatial gradient airwake velocities over the main rotor disk of the helicopter are also presented. It is ascertained that severe spatial velocity gradients from the ship's airwake can increase the rotor blade loading and vibration, as well as the control workload to accomplish the mission.