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为了研究轴对称体非定常空化的脉动特性,采用高速全流场显示技术和动态测力系统实验研究了绕半球型和平头轴对称体的非定常空化流场及其动力特性。实验在闭式水洞中进行,采用高速摄影的方法观察了在不同空化数下绕半球型和平头轴对称体的空穴形态,总结了在不同空化数下空泡形态的脉动特性;测量了轴对称体受到的阻力,并对阻力信号进行了时频分析,得到了轴对称体阻力在非定常空化阶段的时频特征。结果表明:空泡形态及其对应的动力特征随着空化数的变化存在明显的非定常特性,空化流场形态与动力特征频率存在高度的相关性。并且不同头型轴对称体的脉动特性存在明显的差异,半球型轴对称体空泡流动的脉动主要是空泡尾部的高频小脱落引起的,而平头轴对称体的空泡流脉动成分主要是大尺度的漩涡空泡团的周期性脱落,空化流场的低频特征频率与空泡的大断裂相对应。
In order to study the pulsating characteristics of unsymmetrical cavitation of axisymmetric bodies, the unsteady cavitation flow field and its dynamic characteristics of hemispherical and trunnion symmetric bodies are experimentally studied by using high-speed full flow field display technology and dynamic force measurement system. The experiments were carried out in closed water tunnels. The hole shapes of the hemispherical and trunnion symmetry bodies under different cavitation numbers were observed by high-speed photography. The pulsation characteristics of the cavities under different cavitation numbers were summarized. The resistance of the axisymmetric body was measured and the time-frequency analysis of the resistance signal was carried out. The time-frequency characteristics of axial symmetry body resistance in the unsteady cavitation stage were obtained. The results show that the cavitation bubble shape and its corresponding dynamic characteristics have obvious unsteady characteristics with the change of cavitation number. There is a high correlation between the cavitation flow field shape and the dynamic characteristic frequency. And the pulsation characteristics of the different axial symmetry bodies are obviously different. The pulsation of the hemispherical axisymmetric body cavitation flow is mainly caused by the high frequency small exfoliation of the tail of the hollow shaft, whereas the pulsating composition of the bubble axial flow symmetry body is mainly Is the periodic shedding of large-scale vortex bubble clusters. The low-frequency characteristic frequency of cavitation flow field corresponds to the large fracture of the bubble.