图4. 泡膨胀阶段实验与数值结果对比(数值计算的无量纲时间：0, 0.205, 0.384, 0.570, 0.718,每幅图的坐标范围是：$-1.5 \leqslant r \leqslant 1.5$, $ -1.5 \leqslant z \leqslant 2$,无量纲时间标识码 1.87ms,云图代表无量纲压力场)

Fig.4. Comparison between the experimental observation and numerical simulation for a bubble beneath a free surface during the expansion phase (the dimensionless times for the simulation are: 0, 0.205, 0.384, 0.570 and 0.718, respectively. Horizontal and vertical axes of each frame are $-1.5 \leqslant r \leqslant 1.5$ and $-1.5 \leqslant z \leqslant 2$, respectively. The time scale is 1.87ms. The contours denote the pressure fields)}