Research On Drag-reduction Principle And Hull Design Of Double M-ship Channel

The M-boat first appeared on the Venice river in Italy and was named for the letter "M" that resembles the cross section of its hull.The M-boat made from central main hull、rigid side walls on either side,and the channel between them composition.The excellent performance of the M-boat is due to its special structure.The central main hull adopts a pointed bow with a deep draft and a stern with a shallow draft.The rigid side skirts on both sides can not only absorb the bow wave generated by the central main row during the voyage,but also form a lift channel with the central main row.When M-boat are sailing at high speed,the high-pressure water-air two-phase flow mixture in the lift channel provides dynamic lift for M-boat,which makes most of the boats lift from the surface of the water,reduces the wet area of M-boat,and thus reduces the resistance.Based on the M-boat on the Venice river,a number of surface high-speed planing hull have been developed by the type M shipping company of San Diego,funded by the U.S.combat ship renewal office.Among them,"Stiletto",a double M-type channel planing hull with parallel double-m structure,has the characteristics of high sailing speed,small wave and good stealth performance.At present,there are few researches on m-type ships in China.In this paper,the bottom channel is redesigned on the basis of Stiletto,which is a double M-type break-stage channel planing hull.In this paper,a series of modules of Maxsurf software are used to analyze the large dip stability,resistance,effective power and seawall resistance of the double m-type break-stage channel planing hull,and the basic sailing performance of this type planing hull is obtained.In this paper,the commercial CFD software STAR-CCM+ is used to carry out CFD numerical simulation of this type of planing hull,and the ship traveling wave cloud plot,bottom pressure cloud plot and bottom water and air two-phase flow distribution cloud plot of this type of planing hull are obtained at different speeds.The numerical simulation of STAR-CCM+ software can preliminarily understand the sailing state and resistance of this type of planing hull at different sailing speeds,and provide a basis for the subsequent improvement and optimization of the ship.This paper also makes a comparative analysis with the double M-type channel planing hull without break-stage.The following conclusions can be drawn from various analyses of double M-type break-stage channel plaaning hull:1、The body design of the double M-type break-stage channel planing hull basically meets the low resistance requirement of the planing hull at high speed.2、Through the analysis of the bottom pressure cloud plot,the water-gas two-phase flow mixture distribution cloud plot,the ship traveling wave cloud plot and the total resistance value of the planing hull,the following can be obtained: When the sailing speed is less than 7kn,the glider is in the running state of drainage;When the sailing speed is greater than 7kn and less than 10 kn,the glider is in the semi-drained and semiglider sailing state;When the sailing speed is greater than 10 kn,the glider is in the gliding state.3、When using STAR-CCM+ for numerical simulation,the number of grids has a great influence on the calculation results.4、According to the results of computer simulation,the double M-type channel planing hull with no break-stage has better rapidity and drag reduction performance.