发表机构
The University of Manchester（曼彻斯特大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究通过直接数值模拟，发现弹粘性塑性液滴的重力驱动铺展起始由屈服区连通性控制，而非局部屈服，加速度和弹性分别调控转变条件与变形分配。
AI 中文摘要
控制弹粘性塑性液滴重力驱动铺展起始的物理机制仍不明确，因为材料不同区域可同时发生屈服、弹性变形和粘性耗散。为分离这些机制，我们对置于相同材料的薄前驱层上的大轴对称液滴进行直接数值模拟。每个液滴先在重力g作用下平衡，再承受大小可变的额外恒定向下加速度。液滴流变学由Saramito–Herschel–Bulkley模型描述。当增强外力下变形速率可忽略时，移除额外加速度，让液滴再次仅在重力作用下松弛，从而将全局变形分为可恢复和不可恢复分量。我们发现铺展并非仅因材料某些部分局部屈服而发生：在施加低加速度时，屈服区域仍局限于以类固态粘弹性基质为主的区域，产生的变形大多可恢复；当这些屈服区域连接形成从液滴内部到自由表面的连续流化路径时，才会观察到明显铺展，该路径允许径向物质传输。此转变所需加速度主要由屈服应力控制，而弹性通过调节屈服区域的范围和空间分布，控制可恢复变形与铺展之间的分配。
英文摘要
The physical mechanisms controlling the onset of gravity-driven spreading of elastoviscoplastic drops remain unclear because yielding, elastic deformation, and viscous dissipation can occur simultaneously in different regions of the material. To isolate these mechanisms, we perform direct numerical simulations of large axisymmetric drops resting on a thin precursor layer of the same material. Each drop is first equilibrated under gravity, $g$, before being subjected to an additional constant downward acceleration of varying magnitude. The drop rheology is described by the Saramito--Herschel--Bulkley model. Once the rate of deformation becomes negligible under the enhanced forcing, the additional acceleration is removed and the drop is allowed to relax again under gravity alone, enabling the global deformation to be separated into recoverable and unrecoverable components. We find that spreading does not occur simply because some portion of the material yields locally. At low imposed accelerations, yielded regions remain confined within a predominantly solid-like viscoelastic matrix, and the resulting deformation is mostly recoverable. Appreciable spreading is observed when these yielded regions connect to form a continuous fluidised pathway from the drop interior to the free surface, allowing radial material transport. The acceleration required for this transition is governed primarily by the yield stress, whereas elasticity controls the partition between recoverable deformation and spreading by regulating the extent and spatial distribution of yielded regions.
