Investigation Of Ship Airwake And Rotor Aerodynamics Based On DES

Ship superstructures consist of a series of blunt bodies, which will generate turbulent airwake in the condition of ship motion or wind blowing. Large-scale flow separations and backflows are formed in the flow field. Meanwhile, different scales of vortices make the flow field more complicated. Shipborne helicopters have great tactical value to the navy, and extra effort has been paid to develop and research on them. Highly unsteady ship airwake is a threat to the helicopter maneuvering. Also the rotation of the rotor itself is likely to produce complicated turbulence, which will cause the change of the load when interacting with ship airwake, and further result in the change of the lift. This situation brings difficulties to the pilot and endangers the flight.In this paper, the characteristics of the ship airwake is investigated with CFD method. Rather than using traditional RANS method, DES method is adopted to investigate the transitional flow field. Transitional data is sampled at a certain frequency. Through processing the transitional data, a mean flow field is obtained, which shows a significant accuracy when compared with the experimental results. Furthermore, DES provides a direct way to observe the transitional vortices, flow separation and reattach. Therefore, it is proven that DES is better than RANS in solving ship airwake.Building on the successful application of DES in solving ship airwake, isolated rotor flow field and the ship-rotor coupling flow field are investigated. The results show that when the velocity field of the airwake, the topology of the vortices, the pressure distribution of the blades and other traits of the flow field are significantly influenced by the interaction between the ship and the rotor. Moreover, the lift generated by the rotor decreases 29.42% when it is in the ship airwake.Through the research presented in this paper, it is believed that DES is superior than RANS in solving ship airwake. Also analyzed is the traits of the ship airwake, the ship-rotor interaction, and the change of the performance of the rotor in it.