Nuermical Studies On The Evolutional Supercaviting Flows Of A High-speed Underwater Moving Object

Researchs on underwater high-speed weapons has become an important way for countries to enhance their own military strength.One of the biggest obstacles to develop underwater weapons comes from the resistance during navigation.When the projectile is sailing underwater,the resistance will not only cause its speed to drop rapidly,but also greatly reduce the weapon’s lethality.Supercavitation technology can solve this problem well.In this paper,both the natural supercavitation flow and the ventilated supercavitation flow of the missile are studied and analyzed.First of all,the grid independence was verified.In the two working conditions of natural supercavitation and ventilation supercavitation,the influence of turbulence models and algorithm methods on numerical calculation were analyzed and compared,and the RNG k-e turbulence model and the PISO algorithm were found to be the most effective way to obtain precise results.This laid the foundation for subsequent calculations.And then,numerical study of the natural supercavitation flow is carried out in both two-dimensional and three-dimensional.The influence of cavitation number on the morphology of supercavitation,the evolution process of natural supercavitation,and the drag reduction ability of supercavitation are analyzed.It is found that the size of the cavity increases with the decrease of the cavitation number,and the size of the cavity in three dimensions is smaller than that in two dimensions;the occurrence of cavitation starts at the head of the projectile and increases along the surface of the projectile with time.In later development,breakage occurred at the place where the pressure suddenly increased;the resistance to the missile during the navigation was mostly derived from the differential pressure resistance.The drag coefficient when there is supercavitation is much lower than that when there is no one.At lower speed,much area of the missile body surface is in direct contact with water,and the role of frictional resistance cannot be ignored.In the end,the supercavitation flow under artificial ventilation is studied.In order to find out which factor will make big different influence on the cavitation shape and drag reduction effect,we take both the ventilation mass and the ventilation angle into consideration.Also,we connected two cavities in series and analyzed the changes in the flow field.The calculation shows that the size of the cavitation increases with the increase of the ventilation,but too much ventilation will make the supercavity shape extremely unstable and cause a large collapse;proper ventilation can significantly reduce the navigation resistance to the projectile,but too much ventilation will make it increases;the discrete data is curve-fitted,and the change law between the ventilation volume and the resistance coefficient is found to be consistent;as the ventilation angle increases,the thickness of the cavity increases,while the length decreases,and the resistance coefficient first decreases and then increases;the tail jet has an obvious take-away effect on the flow field at the tail of the projectile,and has little impact on the flow field in front of the tail nozzle.