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为了说明非定常空化的流动机理,该文采用数值与实验相结合的方法对绕三维水翼片状和云状空化流动结构进行了研究。实验在高速水洞中进行,采用高速录像技术观测了片状和云状空化阶段的空穴形态。数值计算基于均相流模型,汽液混合区域密度由质量传输方程调节。利用商业软件二次开发技术引入准确描述空化流场非定常特性的FBM湍流模型,进行绕三维水翼的数值模拟,获得了随时间变化的空穴形态、压力和速度分布等流场结构。与实验结果对比发现,数值计算结果与实验基本一致。在片状空化阶段,空穴稳定地附着在水翼表面,只有空穴尾部不断的有小空泡团沿着翼弦方向脱落。在云状空化阶段,清楚得描述了空穴的产生-发展-脱落-溃灭的准周期性变化,并准确地捕捉到空泡脱落时,附着在翼型前端的U型空穴和翼展方向不同强度的反向射流,脱落的空泡由翼型中前部旋涡状脱落。
In order to illustrate the mechanism of unsteady cavitation flow, a three-dimensional hydrofoil and a cloud-like cavitation flow structure are studied by a combination of numerical and experimental methods. Experiments were carried out in high-speed water tunnels. High-speed video recording techniques were used to observe the cavity morphology in lamellar and cloud-like cavitation phases. Based on the homogeneous flow model, the density of the vapor-liquid mixing zone is adjusted by the mass transfer equation. The FBM turbulence model, which accurately describes the unsteady behavior of cavitation flow field, is introduced by the commercial software secondary development technology. The numerical simulation of the three-dimensional hydrofoil is performed. The flow field structure such as cavity shape, pressure and velocity distribution is obtained. Compared with the experimental results, it is found that the numerical results are basically consistent with the experiment. In the sheet cavitation stage, the holes are stably attached to the surface of the hydrofoil, and only the small cavities continue to fall along the chordal direction at the tail of the holes. In the cloud-like cavitation phase, the quasi-periodic change of hole generation-development-exfoliation-collapse is clearly described and it is accurately captured that when the cavities fall off, the U-shaped holes and the wings attached to the front of the airfoil Reverse jet with different intensity in the exhibition direction. The falling vacuoles fall off from the front of the airfoil.