图7. 气泡 ($Re \approx 700$)碰撞前垂直速度下降垂直速度下降比值$V_{\rm C}/V_{y\max}$ ($S^{\ast } =1.04$
Fig. 7. The vertical velocity decrease ratio $V_{\rm C}/V_{y\max}$ before bubble collision ($S^{\ast } =1.04$)