Study Of The Numerical Method For High-speed Cavitation Flow

Cavitation is a kind of phenomenon that vapor cavity or vapor bubble appears in liquidphase at some specific conditions. When an object as a high-speed movement in a liquid orthe liquid in high-speed flow around the object, the high-speed promote cavitationgenerated, cavitation also greatly affect the hydrodynamic characteristics of the object.Develop a reasonable model applied to simulation the complex cavitation flow athigh-speed, it’s not only of great theoretical significance but also of wide application valueson engineering. This dissertation is aimed at researching the cavitation flow characteristicsand numerical methods at high speed around the disc cavitator. The primary researchingcontents and results are as follows:In order to research the differences in cavity shape, flow filed structure and dragcharacteristics, two different turbulence models are compared and analyzed based on theexperimental results. The results show, In the standard k-model, the resistance against thedisc cavitator and cavity shape are stable, pressure, velocity and vorticity field are verticallysymmetrical, which is difference with the experiment results. In the FBM model and theexperiment, the resistance against the disc cavitator show the same fluctuation law, and themean of the resistance are very close, and the cavity shape are shown togeneration-development-shedding cyclical.Establish a high-speed cavitation flow model. In this model, the compressibility of themedium as the theoretical basis, and take into the energy equation and cavitation modelwhich was modified. The high-speed cavitation flow model in low-speed incompressiblecalculation is researched based on the experimental results. The results show, thehigh-speed cavitation flow model can well capture the generation-development-sheddingcycle process of the cavity shape, the resistance obtained by the numerical and theexperiment are very close. The high-speed cavitation flow model in high-speedcompressible calculation is researched based on the potential flow theory, the slender bodytheory and the semi-empirical formula. The results show, the cavity shape of the numericalis consistent with the results of the1/3theory, the potential flow theory and thesemi-empirical formula, confirm the conclusion that the contour of the front cavity shapewhich is unrelated with the cavitation number. Under the condition of the mach number isconstant, confirm the conclusion that the cavity slenderness ratio decrease as the cavitation number increase in the slender body theory, and confirm the conclusion that the dragcoefficient increase as the cavitation number increase in the potential flow theory.The mach number has a great influence on the flow filed characteristics around thedisc cavitator, under the condition of the cavitation number is constant, confirm theconclusion that the cavity slenderness ratio and the drag coefficient increase as the machnumber increase, and the corresponding maximum pressure and the maximum mixeddensity in the flow filed increase, the corresponding minimum mixed density in the flowfiled decrease.The cavitation number has a great influence on the flow filed characteristics aroundthe disc cavitator, under the condition of the mach number is constant, the correspondingminimum density in the flow filed decrease and the cavity slenderness ratio increase as thecavitation number increase.