热物理模型对空化泡崩溃末期第一次闭合特性的影响

Thermophysics model influence on the first closed characteristics of the collapse final stage of cavitation bubble

通过理论证明和数值计算,研究了不同的热物理模型对空化泡崩溃末期的各种特性参数的影响。结果指出,随着多方指数γ的增加,合外力功和动能的最大值逐渐降低,泡内最大温度值逐渐增加,最大压力值却是逐渐降低的;在空化泡崩溃闭合点,合外力功、动能以及半径到达最小值,同时温度和压力达到最大值,五者均具有同时刻性;空化泡被压缩至初始半径值点R=R0,该点是合外力功和动力的最大值所对应的驻点半径,同时,该点也是等温过程与绝热过程的分界点,空化泡从膨胀至最大半径然后被压缩至初始半径R=R0时刻为止的这段时间内是属于热力学等温过程,然后,空化泡从被压缩至初始半径开始到空化泡第一次崩溃闭合点即最小半径R=Rmin时刻为止,该过程是属于动力学绝热过程;对于泡内气体为空气的空化泡在同一空化过程中,在不同阶段分别采用不同的热物理模型,在热力学等温过程期间多方指数取γ=1.0,在动力学绝热过程期间多方指数取γ=1.3～1.4之间较为合理。

Using the theoretical proof and numerical computation methods, this paper investigates the impact of different thermophysics models on the characteristics of cavitation bubble at the end, and analyzes their graphics, data and its local detail. The results show that with the increase of the polytropic index y, the maximum combined external force and kinetic energy are gradually reduced, the maximum temperature inside the cavitation bubble is gradually increased, and the maximum pressure is gradually reduced. At the collapse closed point of cavitation bubble, the combined work force, kinetic energy and the radius reach the minimum value, at the same time, the temperature and pressure come to the maximal value, and all five of them have the simultaneity characteristics. When the cavitation bubble is compressed to the initial radius point R=Ro, this point is the corresponding stagnation radius of combined external force and kinetic energy, at the same time, this point is also the demarcation point of isothermal process and the adiabatic process. This cavitation process is called the thermodynamics isothermal process including the begin of cavitation bubble expansion to the maximum radius and the compressed to the original radius point R=R0. After that, from the beginning of cavitation bubble compressed to the initial radius until to the first time collapse closed point of cavitation bubble, that is the cavitation bubble radius reach the minimum radius R = Rmin, this process is called dynamics adiabatic process. At the same cavitation process of air cavitation bubble, the different thermophysics models of cavitation bubble are adopted at different stages. During the stage of thermodynamics isothermal process, the polytropic ratio of y is taken equal to 1. 0. During the dynamics adiabatic process, the polytropic ratio of y is taken equal to 1.3 - 1.4 which are more reasonable