NUMERICAL INVESTIGATION OF A LARGE DIAMETER PROPELLER EMERGENCE RISK FOR A VESSEL IN WAVES

Although a Large Diameter Propeller (LDP) has a significant potential to improve a vessel propulsive efficiency, it may have a higher risk of propeller emergence and thus thrust reduction relative to a conventional propeller. The instantaneous propeller submergence can be considered as the main factor in the inception of the propeller emergence when the interaction between a running propeller and free-surface are disregarded. Therefore, accurate prediction of the ship motions and the hull wake in the vicinity of the propeller play a significant role in the propeller emergence risk assessment. In an earlier investigation, the authors of the current paper have carried out a comprehensive study on the seakeeping performance of the LDP vessel employing a Fully Non-linear Unsteady Potential Flow Panel Code in which a selected number of critical operating conditions with respect to the risk of propeller emergence have been identified. The objective of this paper is to further investigate the selected critical operating conditions by a higher fidelity approach which also takes the viscous effects into account. To this end, an Unsteady Reynolds-Averaged Navier-Stokes (URANS) solver is used for studying the seakeeping performance of the LDP vessel. The propeller is not modeled in the simulations. A good agreement is seen between the computed motions and resistance in regular head waves and the measurements data. Also, the results are compared to those from the potential flow simulations.