Hydrodynamic Performance Analysis Of A 22000 DWT Multi-purpose Vessel

Duet to the depression of international shipping market,the transportation price has dropped a lot of,and the operating costs of shipping enterprises keep high.To save fuel consumption has become a hot issue and common goal for the ship owners and ship designers.Since their simple structure,low cost,simple installation,remarkable energy saving effect,the additional hydrodynamic energy saving devices of ship have attracted too much attention in the hydrodynamic area of shipbuilding and ship design.Regarding as a 22000 DWT multipurpose bulk carrier(MPV)as the research object in this paper,numerical simulations about the ship models with different combinations of energy saving devices have been carried out.Observed data from model testing have also been taken into account to amend the setting of numerical simulation and vivificate the results from numerical simulation.The research contents are shown as follows:Firstly,the resistance coefficient of the MPV with different speed was calculated based on CFD method.Comparing the results with those from towing tank model testing,it has been found that the calculation results agree well with the observed data from HSVA tank.It has been proved that the result from numerical simulation is reliable and effective.Subsequently,the patterns of stern hull nominal wake field are investigated,after the several scales of ship model size have been determined.The variation characteristics of the wake fraction according to different angles at various radius of the propeller disk are obtained as well.Secondly,numerical simulations of propeller in open water condition have also been carried out.By comparing various hydrodynamic parameters obtained from numerical simulation and open water model test respectively,the effectively of this numerical simulation method had been verified again.The hydrodynamic performance of rudder ball device affiliated to ship-rudder system has been studied.By comparing the hydrodynamic parameter,velocity and pressure profiles,some conclusions have been drawn about the variation rule of the wake field attributed to propeller,and propeller propulsion efficiency attributed to the rudder-rudder ball.Finally,the numerical simulations concerning hull-propeller-rudder have been accomplished.Various parameters from numerical simulation,such as ship model resistance,propeller thrust,torque and resultant force of hull-propeller-rudder show good agreement with those from towing tank self propulsion model test.Based on the well performed numerical simulation method and model settings,the effectively of additional energy saving devices such as rudder ball,thrust fin and Mewis compensation tube have also been considered.It has been proved that rudder ball maybe helpful to increase the boosting effect and reduce the resistance coefficient subsequently.In addition,the thrust fin and Mewis compensation tub maybe enhance this effect successively.It has been found that combination of those three energy saving devices is the best,rather than two combination of them or single being adopted.Based on the analysis of pressure contours,velocity contours and streamline in the stern,the energy saving mechanisms of various devices have been discussed.