| Trans-medium weapon applies in scenarios when water surface penetration is needed,it makes possible the weapon’s motion in different mediums in a single launch.The trans-medium weapons are thus more popular in effectively penetrating defense and accomplishing the surface-submarine integrated attacking task.As a result,it is believed to be a promising weapon.To fulfill the above tasks,the trans-medium weapon needs to enter water at a high speed.However,there are many unclear issues during the waterentry process.Thus,the studies on projectile high-speed water-entry problem is of highly significance in both theoretical and industrial area.At present,high-speed water-entry problem is still a relatively new research direction,and we all still unknown of a number of its physical mechanisms.Past research usually carried out experiments or numerical simulations based on a specific application scenario in order to achieve empirical results,the systematisms of which is relatively weak.As a result,the treasure of physical phenomena in the high-speed entry problem remains to be discovered.The high-speed water entry process involves complex gas-liquid-solid threephase multi-physical field coupling problems,while its flow field has obvious nonlinear characteristics.The problem is difficult to solve by analytical methods.Numerical methods are capable of solving the problem.Two-dimensional Euler based high-precision numerical method is developed in the present work.The weighted-essential-non-oscillation scheme is used to solve the governing equations,Level-Set method is used combining with the ghost fluid method to capture the material interface,and modified Schimidt model is employed to emulate the cavitation phenomenon.The present numerical method is validated by a variety of numerical cases,according to which,the high-speed water-entry process simulated can be reasonably revealed.The water-entry process of planar-fronted,conical-fronted,chamfered-fronted and round-fronted bullets are simulated using the present numerical method.Complex flow phenomena are observed,their underlying physics are analyzed,and the payload variations during the water-entry process are presented based on the essential flow mechanisms.Orthogonal test and range analysis are conducted,bullet water-entry process simulation with multi-parameter combinations are performed,the influences of each parameter on the water-entry process are obtained,and quantitative correlations between the parameters and the bullet water-entry performance are deduced.We also derived empirical formulas of these performance.The results shows that,with the application of Euler method,the complex flow field of high-speed water-entry problem can be clearly captured.The load of the projectile during impact is also obtained.This article laid a solid foundation for further high-speed entry researches. |
