An Investigation Of The Ventilated Cavitating Flow

Two physical processes in water flow will produce low density cavities composed of the vapor or the gas. One is the vaporization caused by the high speed flow when the local pressure falls below a saturation value. The other is the ventilation by injecting noncondensable gas. When the cavity length approaches or exceeds the character length, a supercavitating flow occurs. It results in the multiphase flow of gas, vapor and water in the near-wall region of underwater vehicle except its head which touches with water only. The ventilated supercavitating flow relates to the complex flow phenomenon and mechanism, such as multiphase flow, turbulence, mass transfer, compressibility and unsteadiness.Recently, a great breakthrough was made in the aspect of the underwater weapon development with high-speed by applying the technique of ventilation to reduce the drag and break the velocity limitation. The research on the ventilated supercavitating flow is in the elementary phase at home. It is in urgent need of further pertinent study.In this dissertation, some key problems about ventilated cavitating flow, including the cavity morphology, flow structure, stability and reducing drag mechanism, were investigated using the theoretical analysis, mechanical test and numerical simulation.Firstly, the test models, ventilation system and measurement system were designed according to the requirement on researches using the existing experimental facility and measuring instruments. By adjusting the upstream velocity, pressure, angle of attack, ventilation rate, cavitator shape etc, experiments were conducted systematically to study the flow characteristics, mechanism and the rule of the ventilated cavitating flows in water tunnels...