报告题目：Arrested retraction of a drop by a yield-stress fluid

报 告 人：Miguel Moyers-Gonzalez（新西兰坎特伯雷大学）

报告时间：2026年11月18日

报告地点：数学楼301教室

报告摘要：Many everyday materials, such as toothpaste, mayonnaise, concrete and lava, behave like solids under small stresses and flow only once the stress exceeds a critical value, the yield stress. Mathematically, this turns the equations of fluid motion into a nonlinear, non-smooth problem with unknown free boundaries separating flowing and rigid regions. In this talk I will introduce these fluids from scratch, assuming no background in fluid mechanics, and use them to study a simple question. Surface tension pulls an elliptical drop toward a circle, but a yield stress can stop it. How large must the yield stress be, and does it matter whether the drop or the surrounding fluid carries it? The key idea is that yield-stress dissipation, like dry friction, is one-homogeneous. This leads to a variational characterisation of the threshold, and a single simple trial motion gives an explicit lower bound in terms of complete elliptic integrals. Finite element computations confirm the predicted behaviour. Arrest is decided by a global energy balance rather than by the curvature at any single point. Joint work with Keetley Rate and Mingfeng Qiu (University of Canterbury).

报告人简介：Miguel Moyers-Gonzalez 博士是新西兰坎特伯雷大学数学与统计足球吧 副教授、副院长（主管学术），负责该足球吧 与足球吧 合作项目的学术监督。此前，他曾任英国杜伦大学数学科学系讲师，并在蒙特利尔大学应用数学实验室担任 CRM 博士后研究员两年。他在加拿大不列颠哥伦比亚大学数学系和应用数学研究所完成研究生学业，其博士论文荣获加拿大应用与工业数学学会（CAIMS）2005 年度 Cecil Graham 博士论文奖。 他的研究方向是连续介质力学问题的数学建模与计算建模，特别是非牛顿流体与屈服应力流体、界面流动，以及熔岩和冰川等地球物理流动。