CFD Analysis of High-speed Cavitating Water Jet and Hydraulic Design of Jet Nozzle

将两流体三压气泡动力学模型与可压缩两相流计算相耦合，提出了一种适用于非定常空化流动计算的混合流气泡空化模型。空化流动的流体介质被视为液体和球形气泡的混合物，这些气泡被认为是均匀分散在液体中的。用Rayleigh-Plesset方程计算局部流场中气泡的平均半径，用气泡中气体的体积分数来评价气穴的大小。利用气液两相状态方程定义了两相混合物的可压缩性，并通过相平均建立了平均流动控制方程。将该方法应用于孔板喷管和风口喷管内的流动计算，验证了计算结果的可靠性。

A mixture-flow bubble-cavitation model is proposed for unsteady cavitating flow computation by coupling a Two-Fluid Three-Pressure bubble dynamics model and a compressible two-phase flow computation. The fluid media of cavitating flow is treated as a mixture of liquid and spherical gas bubbles, those are supposed to disperse in the liquid phase uniformly. The average bubble radius in a local flow field is calculated by Rayleigh-Plesset equation and cavitation is evaluated by the volume fraction of gas included in bubbles. State equations of liquid and gas phases are employed to define the compressibility of two-phase mixture and a set of mean flow governing equations is developed by phase-averaging. The method is applied to treat flows in an orifice nozzle as well as a venture nozzle and the reliability of computation results is confirmed.