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In recent years, various podded propulsors with an electrical propulsion system are being developed for the better hydrodynamic performance. Among them, the system with electric motors inside the pod is considered to be most promising. In Japan, the new type of a podded propulsor is under development now. This podded propulsor is equipped with contrarotating propellers(CRP) in order to achieve the high e.ciency and hence to recover the energy loss of an electric propulsion system. For the optimized design of ships with a podded propulsion system, methods for predicting hydrodynamic performances of a ship with a podded propulsor are required. CFD(Computational Fluid Dynamics) methods with an unstructured grid approach are expected to be the most powerful tool for this purpose, since it can analyze turbulent viscous .ows around a complex geometry. For the analysis of self propulsion condition by CFD methods, propeller e.ects should be taken into account in a Navier-Stokes solver. It can be done by the use of a body force distribution representing propeller e.ects. This approach has been applied to analysis of ship .ows with a propeller e.ect and generally showed good agreements with measured data. In this paper, the Navier-Stokes solver with an unstructured grid method is applied to the prediction of the performances of a ship with a podded propulsor. Fig.1 shows the numerical simulation of ship .ows with podded propulsor without a propeller e.ect. In Fig.2, the computed .ow pattern around a podded propulsor with a conventional propeller e.ect is depicted. The numerical results for ship .ows with a podded propulsor under CRPe.ects will be shown and compared with measured results. Also, the discussions will be made for the performances of the two ways of podded propulsor arrangement, a pusher type and a tractor type. Through these applications, capability of the numerical method is #demonstrated and hydrodynamic performances of podded propulsion system is discussed. |
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