Examensarbete

This master thesis work has been performed at Rolls Royce on one of their propulsion systems the MermaidTM pod. The main purpose of the work is to produce a conceptual design of a fin that reduces the momentum around the steering axis of the pod as far as possible. First a literature study was carried out. This included effects on fin fitted pods, recovery of rotational energy, economics and rules from classification societies. Then the fin was analysed both hydrodynamically and mechanically. The hydrodynamic analysis was performed with linear theory which has been compared with tests results performed by Rolls Royce. The structural analysis, which is based on numerical methods, covered structural arrangement of the fin including interfaces between the pod and the fin. A fin with a NACA 0015 profile, a cord of 1.5 meters, an average length of 1.35 meters and fasten to the pod with a short interface seem to be the best solution considering hydrodynamics, mechanics and economics. The fin should be mounted as far back on the pod as possible at a six a clock position. The size of the fin is dependant of the size of the pod.