CFD predictions of the influence of external airflow on helicopter operations when operating from ship flight decks

A CFD model of a hovering helicopter main rotor is developed to examine airflow in the presence of ship structures and side winds. The rotor is modelled by modifying the governing Navier-Stokes equations in the region of the disc. The extra terms added to the governing equations apply a downforce to the fluid; these forces are independent of the flow around the rotor and equal to the helicopter weight. The boundaries of the computational domain are also modified in order to generate a physically correct solution. Flow solutions in both two and three dimensions are achieved using the commercial flow solver CFX 4.1. The flow solutions exhibit very good correlation with established momentum and power principles. In order to model helicopter operations from a ship's flight deck, typically a frigate, the rotor is modelled at several positions above a ship profile. Cross winds are applied to the computational domain. The thrust of the rotor is held constant and the resulting flow solutions are calculated. The power exerted at the rotor is obtained and compared to the ideal hover condition and computational flow solution