Study On Hydrodynamic Optimization Of Full-formed Ship Afterbody Based On Numerical Calculation Of Viscous Flow

Full-formed ship is the main ship form in today's cargo carrier, and research on such ship's lines is of great importance. This paper mainly deals with afterbody lines of full-formed ships. For usual single-screw ship, afterbody lines affect the propulsion efficiency much more than the viscous resistance, the design of ship stern is then to make a good starting point for propeller, thus improve the propulsion efficiency. Comparing with U- and V-shaped stern, the incorporation of stern bulb on full-formed ship could provide more uniform circumferential wake distribution at propeller disk, which on one hand reduces the propulsion deduction, increases the propulsion efficiency and on the other hand, stern vibration would be reduced by the decrease of propeller exciting force. But because of the complicated match of stern bulb with afterbody lines, it's not an easy job concerning design of afterbody lines.Numerical calculation has been playing an important role in ship's hydrodynamic optimization. For ship stern flows, viscous flow calculation has to be taken, in which solving the Reynolds-averaged Navier-Stokes equation (RANS method) is quite normal. By constructing proper turbulence model, RANS method has proved to be very successful in practical engineering applications. PARNASSOS is such a RANS code dedicated to predict the steady turbulence flow around ship hulls with very fast calculation speed and good precision. Full-scale calculation is PARNASSOS'another main characteristic.In this paper, two bulk carriers and one tanker are chosen as models for the calculation. Various transformations of afterbody lines including stern bulb, section lines and profile are generated. All calculations are done using PARNASSOS at scantling draught and its corresponding speed. Both model and full scale calculation are performed. Analysis is finally made with respect to both resistance and wake field quality. It hopes that this paper can provide some useful information on the hydrodynamic optimization of full-formed ship.