Fig. 20.

Variation of the average movement velocity of the bubble centroid in the first bubble oscillation period with $\gamma$ based on Fig. 16. The black scatter points and the red line have the same meaning as them in Fig. 16. The blue triangles are newly added experimental data points with smaller $\gamma$. And the black dashed line indicates $\gamma =0.50$. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)