Research On Multiphase Flow Characteristics High Speed Water-entry For Moving Body Based On Overlapping Grid Technology

Coastal defense is an important guarantee for the country.As a powerful country in Asia,our country should strengthen its coastal defense effort and the research on marine defense armaments and weapon systems.The complex flow field involved in the process of high-speed water entry is the theoretical basis of high-speed cross-media missiles,super-cavitating torpedoes and other weapons,and it is provided with important engineering significance.In this paper,the method of numerical simulation is used to study the characteristics of the flow field of the small moving body at high speed and vertical water entry under the cross-flow conditions and the movement characteristics of the moving body.The main research contents and results of the paper are as follows:Based on the theory of homogeneous equilibrium flow,the VOF multiphase flow model,Schnerr and Sauer cavity model and realizable k-ε turbulence model are introduced,using the overlapping grid technology,a numerical calculation method for solving the vertical high-speed water entry of small moving bodies is established,and the method is compared with the literature to verify the effectiveness.The multi-phase flow characteristics of the moving body under high-speed vertical water entry under cross-flow conditions were studied,and the characteristics of the flow field,water entry trajectory and cavitation development during the water entry of the moving body were analyzed.The higher the water inlet speed and the density of the moving body,the greater the water depth.The peak value of the drag coefficient in the impact phase increases with the increase of the water inlet velocity,while the drag coefficient in the underwater stabilization phase is not greatly affected by the initial velocity and the density of the moving body.The peak pressure at the midpoint of the head of the moving body is directly related to the water inlet speed.The higher the water inlet speed,the greater the peak pressure.The multi-phase flow characteristics of the moving body under high-speed vertical water entry under cross-flow conditions were studied,and the flow field characteristics,water entry trajectory and cavitation development law during thewater entry of the moving body were analyzed.The presence of lateral flow leads to uneven pressure distribution on the head of the moving body,uneven water vapor content on both sides of the column section leads to the existence of lateral pressure difference,the side and yaw movements of the moving body occur,It is related;the cross flow has a promoting effect on the cavitation on the back flow side,and has an inhibitory effect on the cavitation on the oncoming flow side.The laws of water inlet velocity and cross-flow velocity on cavitation morphology,flow field structure and fluid dynamics are obtained.The water inlet velocity and cross-flow velocity affect the longitudinal and lateral development of cavitation morphology,respectively.The greater the water inlet velocity,the greater the peak pressure;and the greater the cross-flow velocity,the more uneven the head pressure distribution.The smaller the initial velocity,the greater the cross-flow velocity,and the greater the influence of the cross-flow on the lateral and yaw motion of the moving body at the same time.