水下高速射流气泡变化过程数值研究

为研究水下高速射流气泡变化规律,采用VOF(Volume of Fluids)模型分别对水下等温高速气体射流和热高速气体射流动态流场进行了气水耦合数值求解。其中热射流考虑了汽化因素对气泡内气流场的影响,数值模拟了气泡的形成、发展、断裂及融合过程,揭示了气泡中压力和马赫数等参数的变化规律,得出了水下点火初期的流场特征。研究发现:在相同入口压力下,热射流产生气泡的空间尺度比等温射流产生的气泡空间尺度要小;气泡发展过程中会出现颈缩,也可能断裂,断裂与否取决于气泡颈缩处内外压差,气泡的颈缩与断裂是产生压力脉动的重要因素,并决定了压力峰的位置和大小,气泡断裂位置越靠近喷管出口,压力峰值越大,该压力峰值会影响火箭发动机尾流场特性。

Numerical study of the process of the evolution of bubble of high-speed jet underwater

To study the variation of bubble in underwater high-speed gas jet,the coupling numerical value results for the dynamic high-speed isothermal jet and thermal gas jet flow field was abtained by means of Volume of Fluids model.The effect of vaporization on the flow in the bubble is considered in terms of thermal jet.The formation,developing,fracture and fusion of bubble are properly simulated.The results show some regular patterns with the variation of the parameters such as pressure and Mach number in the bubble.It is found that with the same inlet pressure,the thermal jet flow displays events occurring on smaller spatial scales than observed in the isothermal jet flow.With the development of bubbles,it appears necking,and even fracture.Bubble fracture or not depends on the pressure difference between inside and outside of the location of bubble necking.The necking and fracture of bubble is an important factor in the pressure pulsation.They also determine the location and size of the peak press-ure.The more bubbles fracture location near the nozzle exit,the greater the peak pressure.The size of peak pressure affects the characteristics of wake field of rocket motor.