Sub-Hinze scale bubble production in turbulent bubble break-up
Sub-Hinze scale bubble production in turbulent bubble break-up
复制标题
DOI：
10.1017/jfm.2021.243
复制
发表时间：
2021-04-29
影响因子：
3.7
通讯作者：
Deike, Luc
中科院分区：
文献类型：
--
作者：
Riviere, Alienor;Mostert, Wouter;Deike, Luc
本文通过对两相不可压Navier-Stokes方程的直接数值模拟，研究了气泡在均匀各向同性湍流中的破碎。我们通过在物理空间中施加力来产生湍流，一旦达到统计稳定状态，就引入气泡。我们进行了大型模拟系综，以研究韦伯数（湍流力和表面张力之比）对气泡破裂动力学和统计学（包括子气泡尺寸分布）的影响，并讨论了获得独立于结果的数值要求网格大小。我们描述了临界韦伯数，低于该值时不发生破裂，以及相关的欣泽尺度d（h）。在韦伯数接近稳定条件（初始气泡尺寸d（0）接近d（h）），我们观察到二元和三元破裂，导致气泡主要在0.5d（h）和d（h）之间，这是局部规模生产过程的特征。对于大韦伯数（d（0）> 3d（h）），我们观察到气泡半径范围很广，在0.1d（h）和0.3d（h）之间有许多子气泡，比母气泡小一个数量级。父气泡和子气泡之间的尺度分离是规模非局部的生产过程的特征。这些亚欣兹尺度气泡的形成机制与快速的大变形和连续的破裂有关：序列中的第一次破裂留下高度变形的气泡，这些气泡将再次破裂，而不会恢复球形形状并产生一系列小得多的气泡。我们讨论了应用这种情况下的子欣泽泡沫破碎波的生产。
We study bubble break-up in homogeneous and isotropic turbulence by direct numerical simulations of the two-phase incompressible Navier-Stokes equations. We create the turbulence by forcing in physical space and introduce the bubble once a statistically stationary state is reached. We perform a large ensemble of simulations to investigate the effect of the Weber number (the ratio of turbulent and surface tension forces) on bubble break-up dynamics and statistics, including the child bubble size distribution, and discuss the numerical requirements to obtain results independent of grid size. We characterize the critical Weber number below which no break-up occurs and the associated Hinze scale d(h). At Weber number close to stable conditions (initial bubble sizes d(0) approximate to d(h)), we observe binary and tertiary break-ups, leading to bubbles mostly between 0.5d(h) and d(h), a signature of a production process local in scale. For large Weber numbers (d(0) > 3d(h)), we observe the creation of a wide range of bubble radii, with numerous child bubbles between 0.1d(h) and 0.3d(h), an order of magnitude smaller than the parent bubble. The separation of scales between the parent and child bubble is a signature of a production process non-local in scale. The formation mechanism of these sub-Hinze scale bubbles relates to rapid large deformation and successive break-ups: the first break-up in a sequence leaves highly deformed bubbles which will break again, without recovering a spherical shape and creating an array of much smaller bubbles. We discuss the application of this scenario to the production of sub-Hinze bubbles under breaking waves.