| Swirling flow exists in various hydraulic machinery.Because of the pressure reduction caused by swirling flow,cavitation occurs and it compromises the hydraulic performance of hydraulic machinery seriously.Based on the National Natural Science Foundation of China,a visual experimental platform of swirling flow has been designed and set up.Visualization of swirling flow cavitation vortex rope and the experimental study of pressure fluctuation has been carried out,and the shape of cavitation vortex rope and the characteristics of pressure fluctuation induced by cavitation vortex rope under different working conditions are clarified.The Large Eddy Simulation(LES)method was used to simulate the cavitation vortex rope.(1)A visual experimental platform of swirling flow has been designed and set up.Based on the investigation of the existing literature,the core experimental section has been designed according to the generation condition of the cavitation and swirling,the pipeline system of the experimental deciv e has been designed and processed.High-speed image acquisition experiment of swirling cavitation vortex rope was carried out.The formation and development mechanism of different vortices were observed by controlling the experimental conditions.The tempo ral and spatial evolution characteristics of vortices have been analyzed.The development trends of different vortices have been expounded,and the unstable phenomena caused by the transformation of different vortex rope has been expounded.(2)An experimental study on the pressure fluctuation of the swirling cavitation vortex rope was carried out.By measuring the characteristics of the pressure fluctuation upstream and downstream,the influence of the different development behaviors of the vortex rope on the pressure fluctuation has been analyzed,the influence of the formation and development of the vortex rope on the pressure has been explained,and the characteristics of the pressure fluctuation induced by the vortex rope in time and frequency domain have been analyzed.(3)The spatio-temporal evolution mechanism of cavitation vortices has been studied by numerical simulation.The LES method is used to simulate the cavitation vortex rope,and the flow information,such as streamline distribution and phas e transfer rate have been obtained.The spatial and temporal distribution of vorticity and the main factors affecting the vorticity distribution have been analyzed by the method of vorticity analysis.The time-varying law of vorticity was obtained by transient calculation,and the influence factors of the vorticity distribution and the shape of vortices have been expounded.In this study,the visual experimental platform of swirling flow has been designed and built,and the spatiotemporal evolution mechanis m of the vortex rope has been studied by numerical simulation,the formation and development mechanism of the vortex has been investigated,and the spatiotemporal evolution law of the vortex was expounded,the influence factors of pressure fluctuation and instability caused by vortex rope are revealed,which is meaningful to restrain the instability caused by swirling cavitation vortex rope. |
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