| Cavitation dynamics is an important issue in shipping engineering,water conservancy projects and environmental engineering.The cavitation produced by underwater multiple jets is complicated by various forces,such as resistance,pressure,lift and so on.It is often accompanied by rupture and fusion at the same time when significant deformation occurs.In this paper,the problem of multiple jets under the flat surface is studied by method of experiment and numerical simulation.The main research work includes the following aspects:An experimental method for studying the characteristics of gas-liquid flow in porous emitter is established based on a ventilated circulating water tunnel.The experimental scheme,experimental model and testing system are designed.Based on the Fluent software,the Multi fluid VOF model is introduced into the Euler multiphase flow model,and the basic theory of turbulence model is used to establish the numerical simulation method for the flow characteristics of multiple jets gas,and the experimental verification is obtained.The experimental and numerical simulation of gas-liquid flow characteristics of single hole jet under water is carried out.The bubble morphology of a single hole jet under water is studied by the method of experiment.The influence of the velocity and pressure ratio on the cavitation form is analyzed.The dimensionless number of the cavitation forms is obtained.Secondly,the influence of the transverse flow and pressure ratio on the flow coefficient of the single hole is studied,and the change mechanism of flow coefficient is analyzed.The characteristics of single hole jet flow field under water are studied by numerical calculation,and the pressure field,velocity field and vorticity field are analyzed.It is found that under the center of the hole,there is a peak of pressure in the bias flow measurement and partial back flow measurement.The peak velocity appears at the center of the hole,and the double vortex tube is formed under the shear force,and the vorticity gradually decreases along the direction of the flow.Experimental and numerical studies on the characteristics of gas-liquid flow in underwater multiple jets are carried out.Through the experimental method,the bubble morphology of the underwater multiple jets is first studied.The variation of the fusion point with the transverse flow velocity and pressure ratio of the single row of double and double row four hole vacuoles is analyzed.Secondly,the flow coefficient of a single row of double holes and the double rows of four holes is studied by the transverse flow and pressure ratio.The change of the flow coefficient of the single row and double holes is found.The flow coefficient of the first row hole is less than that of second row holes,and with the increase of the pressure ratio,the flow coefficient of the first row of holes approaches to the second row of holes gradually.The characteristics of underwater multiple jets flow field are studied by numerical calculation,and the pressure field,velocity field and vorticity field are analyzed.It is found that there is pressure peak at the center of the first row under the center of the hole,and there is a pressure peak in the backflow measurement.The second row of holes has a pressure peak below the center of the hole.The peak velocity of the first row hole appears in the backflow measurement of the center deviation of the hole,and the velocity peak value of the second row holes is basically at the center of the hole.Double vortex tubes are generated in the two rows of holes before and after,and the vortex tubes generated by the second rows of holes are larger than the first row holes. |
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