Zhang Wei, Katsuragi Hiroaki, Yamamoto Ken
Department of Earth and Space Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan.
Water Frontier Research Center (WaTUS), Tokyo University of Science, 6-3-1 Niijuku, Katsushika-ku, Tokyo 125-8585, Japan.
Soft Matter. 2024 Aug 7;20(31):6120-6130. doi: 10.1039/d4sm00386a.
Drop impact events on a wet granular bed show a rich variety by changing the substrate composition. We observe the drop impact onto dry/wet granular substrates with different grain sizes (50-400 μm) and water contents (0-22 vol%). Despite the fixed impactor conditions (impact velocity: 4.0 m s, water drop radius: 1.8 mm), the experiment reveals that the post-impact behaviors of both the impactor and target are strongly influenced by the substrate composition. We categorize these behaviors into several phases concerning liquid splashing and crater shapes left after the event. As these phases are relevant to each other, we measure the mechanical characteristics of the substrates and find that the onset of splashing and particle ejection is explained the fracture of the substrate. Furthermore, we discuss several timescales of the event to understand the phase separations in more detail. Consequently, we find that the splashing phase and the crater shape are determined by competition among the timescales of impact, penetration, and contact.
通过改变基底成分，液滴撞击湿颗粒床的事件呈现出丰富的多样性。我们观察了液滴对不同粒径（50 - 400μm）和含水量（0 - 22体积%）的干/湿颗粒基底的撞击。尽管撞击器条件固定（撞击速度：4.0 m/s，水滴半径：1.8 mm），但实验表明，撞击器和目标的撞击后行为都受到基底成分的强烈影响。我们将这些行为按照事件发生后液体飞溅和留下的坑洼形状分为几个阶段。由于这些阶段相互关联，我们测量了基底的力学特性，发现飞溅和颗粒喷射的起始可以用基底的破裂来解释。此外，我们讨论了该事件的几个时间尺度，以更详细地理解相分离。因此，我们发现飞溅阶段和坑洼形状是由撞击、渗透和接触的时间尺度之间的竞争决定的。
