Lattice Boltzmann simulations of droplet breakup in confined and time-dependent flows
Lattice Boltzmann simulations of droplet breakup in confined and time-dependent flows
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DOI：
10.1103/physrevfluids.5.033607
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发表时间：
2019-10
影响因子：
2.7
通讯作者：
F. Milan;Luca Biferale;M. Sbragaglia;F. Toschi
中科院分区：
文献类型：
--
作者：
F. Milan;Luca Biferale;M. Sbragaglia;F. Toschi
本文通过多分量晶格玻尔兹曼算法研究了一般时变流动中的液滴动力学和破裂，重点研究了流动的启动条件。我们首先通过两种不同的方案研究了受限振荡剪切流中液滴的破裂。在一种设置中，我们从最初的球形液滴开始，突然打开流动（“激波法”）；在另一种方案中，我们也从最初的球形液滴开始，但在再次增加流动幅度之前，我们通过允许液滴在每次增加幅度时松弛到稳态来逐步增加流动幅度（“松弛法”）。这两种方案产生了截然不同的分手场景。这两种方案之间的不匹配还研究了流动拓扑、约束程度和流体惯性的变化。所有的结果都表明，在极端的约束条件下，弛豫协议可以驱动液滴进入亚稳态，只有在非常强烈的流动振幅下才会破裂，但它们的稳定性容易受到外部扰动的影响，比如振荡驱动力。
We study droplet dynamics and breakup in generic time-dependent flows via a multicomponent Lattice Boltzmann algorithm, with emphasis on flow start up conditions. We first study droplet breakup in a confined oscillatory shear flow via two different protocols. In one set up, we start from an initially spherical droplet and turn on the flow abruptly ("shock method"); in the other protocol, we start from an initially spherical droplet as well, but we progressively increase the amplitude of the flow, by allowing the droplet to relax to the steady state for each increase in amplitude, before increasing the flow amplitude again ("relaxation method"). The two protocols are shown to produce substantially different breakup scenarios. The mismatch between these two protocols is also studied for variations in the flow topology, the degree of confinement and the inertia of the fluid. All results point to the fact that under extreme conditions of confinement the relaxation protocols can drive the droplets into metastable states, which break only for very intense flow amplitudes, but their stability is prone to external perturbations, such as an oscillatory driving force.