CFD Assessment of the Helicopter and Ground Obstacles Aerodynamic Interference

The helicopter is a very versatile flying machine that is often required to operate in confined areas or close to vertical obstacles such as buildings, ships and mountain walls. Therefore, the aerodynamic interaction between a helicopter and the surrounding obstacles has recently become a promising research topic in the rotorcraft field. In the present paper, the behaviour of a helicopter operating in the proximity of a ground obstacle is investigated using numerical simulations. Calculations were performed on the geometry used at Politecnico di Milano to carry out a systematic experimental study of the helicopter/obstacles aerodynamic interference. High-accuracy steady calculations were carried out using a compressible Navier-Stokes solver developed in-house. In this framework, an actuator disk model is used to reproduce the rotor effects. Blade loads prescribed on the actuator disk were computed using a low-accuracy aerodynamic solver based on the strip theory. The solvers were coupled through a weak coupling algorithm that allowed to find more realistic load maps in the rotor disk modifying the initial inflow prescribed by the strip theory using induced velocities provided by the Navier-Stokes solver. Numerical results were validated using experimental data and enabled to achieve a detailed insight about the aerodynamic interaction occurring when a helicopter is operating near a ground obstacle.