USE OF CFD FOR HULL FORM AND APPENDAGE DESIGN ASSESSMENT ON AN OFFSHORE PATROL VESSEL AND THE IDENTIFICATION OF A WAKE FOCUSING EFFECT

摘要

It is well known that high wake peaks and poor flow in the propeller plane can give rise to a number of undesirable effects, not least of which are early onset of cavitation, more developed cavitation at design speed and higher propeller induced hull pressures and erosion on propellers, rudders and A-brackets. Recent Model Experiment work undertaken by BMT on a Naval Type Vessel conducted both in a Wind Tunnel, a Model Test Tank and a Cavitation Tunnel has shown the importance of correct design of the Stern Appendages and has identified some interesting effects concerning wake peaks in the propeller plane and the influence on this of the design of the appendages. In particular, an effect has been found in which poorly designed appendages focus some of the hull boundary layer into the propeller plane giving rise to the high wake peaks observed in some cases. Correct alignment of the A-Bracket arms and the shaping of the A-Bracket Boss are also vital if local propeller inflow problems are to be avoided. This work has demonstrated the viability and importance of using CFD for early design assessment of hull and appendage hydrodynamic design. A wake focusing effect has been demonstrated and knowledge of this coupled with the ability to investigate the effect of design changes using CFD opens up the prospect in the future of advanced appendage design with better propeller inflow characteristics. This will lead to fast, quieter and more efficient vessel designs.