An investigation of ship airwakes using Detached-Eddy Simulation

Computational Fluid Dynamics simulations of ship airwakes have been performed using Detached-Eddy Simulation (DES) on unstructured grids. A generic simple frigate shape (SFS2) and a Royal Navy Type 23 Frigate (T23) have been studied at several wind-over-deck (WOD) conditions. A comprehensive validation exercise has been performed, comparing CFD results of the airwake calculated for the SFS2 with high quality wind tunnel data provided by the National Research Council of Canada. Comparisons of mean quantities and velocity spectra show good agreement, indicating that DES is able to resolve the large-scale turbulent structures which can adversely impact helicopter–ship operations. An analysis of the airwake flow topology at headwind and Green 45° conditions highlights the dominant flow features over the flight deck and it is shown that significant differences exist between the two WOD angles. T23 airwake data has been compared to full-scale experimental results obtained at sea. It is shown that the inclusion of an atmospheric boundary layer velocity profile in the CFD computations improves the agreement with full-scale data. Qualitative comparison between the simple frigate shape and T23 airwakes shows that large-scale flow patterns are similar; but subtle differences exist, particularly at more oblique WOD angles.