Evaluating ship superstructure aerodynamics for maritime helicopter operations through CFD and flight simulation

Abstract

ABSTRACTThe unsteady air flow over and around the helicopter landing deck of a naval vessel is known to cause high pilot workload and to limit the helicopter's operational envelope for launch and recovery. Previous research has suggested that modifications to the ship's hangar edges can beneficially modify the flow over the deck. This paper examines the effectiveness of five hangar-edge modifications using computational fluid dynamics–generated airwakes and flight mechanics modelling, as well as piloted flight trials in a motion-base simulator. Results are presented, in terms of unsteady helicopter loads and pilot workload ratings, for modifications to the windward vertical rear edge of the hangar and with an oblique wind. The results demonstrate that while the airwake can be altered by superstructure modifications, the integrated effect of the altered airwake on the entire helicopter does not necessarily give the desired result; indeed of the five modifications tested, two were seen to be beneficial while three caused an increase in pilot workload compared with the unmodified hangar. Overall, the paper shows that the airwake can be modified by superstructure design changes, and that the effect on the helicopter can be measured through modelling and simulation. It is also demonstrated that making judgements on the severity of the airwake based on the aerodynamic flow field alone can be misleading. The benefit of these simulation tools is that they can be used during the ship design process to evaluate the effect of the superstructure aerodynamics, rather than wait until after the ship is built.