| Enhancing ship speed not only enhances maritime military power,but also promotes the development of economic and trade,energy conservation and emission reduction.However,ship resistance seriously restricts the enhancement of ship speed,so find a way to effectively reduce the ship navigation resistance has been a research hotspot in domestic and international.In this paper,the hull structure of the Double-M craft was designed and improved,and the 2-DOF motion of the Double-M craft in Static water was numerically simulated using Star ccm+ software.The sailing characteristics of Double-M craft was studied,and the effects of the broken-staged structure and its height on the drag performance of the Double-M craft were mainly investigated.The combined broken-staged-air reduction technique technology was proposed,and the effect of the technique on the drag reduction of the Double-M craft and the drag reduction principle were investigated in focus.Research findings as follows:(1)The Double-M craft sails smoothly at low and high speeds,but needs to experience a large undulation of motion before entering the high-speed gliding state.The broken stage improves the characteristics of the Double-M craft such as pressure and water-air distribution,while increasing the amplitude of hull movement.Unlike conventional boats,the frictional resistance of the Double-M craft at low speeds accounts for a small percentage of the total resistance,which increases with the speed of the hull.(2)Within the design speeds,the maximum drag reduction rate of the broken stage is 7.574%,but the broken stage increases the viscous pressure resistance while reducing the frictional resistance of the hull,making the viscous pressure resistance the main drag in the full speed range of the broken-staged double-M craft.The essence of the effective drag reduction of the broken stage structure is that the reduction in frictional drag is greater than the increase in viscous drag,although the height of the broken stage must not exceed a certain limit,otherwise the lifting effect of the dynamic lift on the hull will be ineffective.(3)The injection of air at the broken stage can effectively reduce the viscous pressure resistance increased by the broken stage,and the analysis suggests that the air injected to a certain extent destroys the conditions for the creation of the viscous pressure resistance field of the hull,and this destruction effect is more obvious at high speeds.The injection of air at the broken stage reduces the resistance of the broken-staged hull by up to 14.505%.(4)The combined broken-stage-air group reduction technology has successfully achieved the reduction of total drag at high speeds on the Double-M craft through divisional drag reduction,with a maximum drag reduction rate of 20.981% and a corresponding frictional drag reduction of 51.948% under working conditions.This technology realizes and promotes the cross-integration of drag reduction technologies and their development,providing ideas and experience to guide future research on drag reduction technologies. |
