Simulation and testing of helicopter-ship aerodynamic interaction

Abstract

Development of a high-fidelity simulation environment, suitable for Helicopter-Ship Dynamic Interface testing has shown numerous advantages with respect to at-sea test campaigns. To correctly replicate the workload of the pilot, it is crucial to model the unsteady loads caused by complex aerodynamic interaction between airwake of the ship and inflow of the rotor. This paper aims to investigate the behaviour of the unsteady aerodynamic loads on a scaled-helicopter operating in the airwake of a generic frigate model. A series of wind tunnel tests have been conducted to characterise the unsteady loading for a wide range of wind speeds, directions and positions of the helicopter over the deck. A stern landing trajectory was simulated by trimming the rotor at different positions along an oblique path towards the landing spot. The unsteady measurements have been used to evaluate a numerical model developed by integrating the time-accurate CFD airwake of the isolated ship into the simulation environment. The numerical and experimental results show similar behaviour, as moving towards the landing spot the unsteadiness is increased. However, the numerical model underestimates the unsteadiness in most of the test points and the difference becomes more significant when testing with a 60_ wind-angle. Furthermore, a fully dynamic landing maneuver was tested in the wind tunnel to evaluate the effect of the approach velocity of the helicopter on the unsteady loads. In comparison to the measurements at fixed positions, the effect of approach velocity was found to be more significant when testing with the wind from the port side compare to the headwind condition.