Direct numerical simulations of transient turbulent jets: vortex-interface interactions
Direct numerical simulations of transient turbulent jets: vortex-interface interactions
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DOI：
10.1017/jfm.2021.519
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发表时间：
2020-11
影响因子：
3.7
通讯作者：
C. Constante-Amores;L. Kahouadji;A. Batchvarov;Seungwon Shin;J. Chergui;D. Juric;O. Matar
中科院分区：
文献类型：
--
作者：
C. Constante-Amores;L. Kahouadji;A. Batchvarov;Seungwon Shin;J. Chergui;D. Juric;O. Matar
摘要界面分裂成级联的液滴及其随后的聚结是一个普遍的问题，对于大量的工业设置，如混合，分离和燃烧具有核心重要性。我们研究了通过一个圆柱形喷嘴引入到一个停滞的粘性相通过混合界面跟踪/level-set方法来考虑在三维笛卡尔域中的表面张力的液体射流的破碎。数值解的雷诺数（$Re$）和韦伯数（$We$）的范围。我们发现，方位角和流向涡分量之间的相互作用，导致不同的界面特征和流态在$Re$-$We$空间。结果表明，流向涡量对射流表面三维不稳定性的发展起着关键作用。在惯性控制制度在高$Re$和$我们$，我们暴露的细节的时空发展的旋涡结构影响的界面动力学。在射流的前缘处形成蘑菇状结构，从而在其内部产生液体片，该液体片经历破裂以形成液滴。这些液滴由于它们与占主导地位的涡旋结构的相互作用而在蘑菇状结构内旋转。此外，Kelvin-Helmholtz涡在注入点附近形成，在流向方向上变形，形成发夹涡，这反过来又触发了射流核心中界面波瓣的形成。叶片的变薄引起孔的产生，所述孔膨胀以形成液体线，所述液体线经历毛细管破裂以形成液滴。
Abstract The breakup of an interface into a cascade of droplets and their subsequent coalescence is a generic problem of central importance to a large number of industrial settings such as mixing, separations and combustion. We study the breakup of a liquid jet introduced through a cylindrical nozzle into a stagnant viscous phase via a hybrid interface-tracking/level-set method to account for the surface tension forces in a three-dimensional Cartesian domain. Numerical solutions are obtained for a range of Reynolds ($Re$) and Weber ($We$) numbers. We find that the interplay between the azimuthal and streamwise vorticity components leads to different interfacial features and flow regimes in $Re$–$We$ space. We show that the streamwise vorticity plays a critical role in the development of the three-dimensional instabilities on the jet surface. In the inertia-controlled regime at high $Re$ and $We$, we expose the details of the spatio-temporal development of the vortical structures affecting the interfacial dynamics. A mushroom-like structure is formed at the leading edge of the jet inducing the generation of a liquid sheet in its interior that undergoes rupture to form droplets. These droplets rotate inside the mushroom structure due to their interaction with the prevailing vortical structures. Additionally, Kelvin–Helmholtz vortices that form near the injection point deform in the streamwise direction to form hairpin vortices, which, in turn, trigger the formation of interfacial lobes in the jet core. The thinning of the lobes induces the creation of holes which expand to form liquid threads that undergo capillary breakup to form droplets.