利用数值映射技术,首次与高精度的失稳测量结果进行了定量分析。他们的线性稳定性分析表明,在临界球半径R = 0.926 mm以上,在2%的实验值范围内,气泡在水中的直线路径在周期性扰动(Hopf分叉)下变得不稳定。虽然以前认为气泡尾迹变得不稳定,但课题组现在证明了一种新的机制,基于流动和气泡变形之间的相互作用。
据介绍,文艺复兴时期以来就有文献记载,在水中上升的气泡一旦超过临界大小,就会偏离其笔直、稳定的路径,执行周期性之字形或螺旋运动。然而,不稳定气泡上升现象一直没有定量描述,其物理机制也一直存在争议。
附:英文原文
Title: Path instability of an air bubble rising in water
Author: Herrada, Miguel A., Eggers, Jens G.
Issue&Volume: 2023-1-17
Abstract: It has been documented since the Renaissance that an air bubble rising in water will deviate from its straight, steady path to perform a periodic zigzag or spiral motion once the bubble is above a critical size. Yet, unsteady bubble rise has resisted quantitative description, and the physical mechanism remains in dispute. Using a numerical mapping technique, we for the first time find quantitative agreement with high-precision measurements of the instability. Our linear stability analysis shows that the straight path of an air bubble in water becomes unstable to a periodic perturbation (a Hopf bifurcation) above a critical spherical radius of R=0.926 mm, within 2% of the experimental value. While it was previously believed that the bubble’s wake becomes unstable, we now demonstrate a new mechanism, based on the interplay between flow and bubble deformation.
DOI: 10.1073/pnas.2216830120
Source: https://www.pnas.org/doi/10.1073/pnas.2216830120