Study On Flow Characteristics Of Ventilated Cavitation Around An Cylinder With Peripheral Multi-holes In Unsteady Exceeding Water Process

The high-velocity vehicle is prone to natural cavitation in the underwater sailing stage,which will affect the structural strength and stability of the vehicle.At present,the most effective way to solve this problem is active ventilation.Through gas-holes or seams,gas is discharged to control ventilated cavitation for making the vehicle stable and controllable.Therefore,in this paper,numerical simulation is used to study the evolution of ventilated cavitation during this process.Firstly,verification of this numerical method is needed and the numerical model,which is the same size of experimental model,is established to simulate the same process as the experiment.Through the comparative analysis of experimental bubble formation photographed by a proper high-speed camera and numerical bubble formation calculated by Fluent,the verification could be finished.Secondly,the numerical model of the cylinder with a single gas-hole moving vertically upwards in the water is established and the vertical movement is simulated to obtain physical quantities of this single bubble like the formation of it,the internal and external pressure,the velocity field and so on.Also,the formula of bubble internal pressure is given and the trend is verified.After changing the gas flow rate and the cylinder speed,the rule of the location and time of the bubble breakage is given.Give different gas flow rate and acceleration of the cylinder to obtain the influence of these two parameters on the evolution of this single bubble.Finally,the numerical models of the cylinder with two vertical gas-holes and three circumferential gas-holes moving vertically upwards in the water are established and the vertical movement is simulated to obtain the change of physical quantities of multi-bubbles.Compared with the shape and size of the single bubble generated from the single gas-hole,the interaction law of bubbles is obtained.Changing the gas flow rate and the acceleration of the cylinder,the two parameters on the bubble formation,pressure and other physical quantity and multi-bubbles fracture and fusion are obtained.