报告题目：Inertia Effects in Lopsided Elastic Dumbbell: Exponential-Time-Differencing (ETD) Schemes
报告时间：2026年05月20日，星期三，上午9:00 AM
报告地点：绣山楼，208会议室
主讲人：Prof. Nhan Phan-Thien, FAA，Department od Mechanical Engineering, National University of Singapore (NUS), Singapore 117575，Department of Engineering Mechanics, Zhejiang University, Hangzhou 310027
摘要：
Inertia effects in the Langevin dynamics of a lopsided elastic dumbbell are investigated using exponential-time-differencing (ETD) integrators for the corresponding stiff stochastic equations at small mass limit. Starting from the bead-level underdamped Langevin model, we formulate the dynamics in modal coordinates, highlighting two distinct friction scales: an additive friction 
controlling translation (
is the friction factor on bead i), and an effective internal friction given through 
controlling configurational relaxation, with relaxation time 
for a Hookean spring of stiffness H. We benchmark the ETD scheme against the popular Euler--Maruyama and overdamped Brownian dynamics using equilibrium statistics, time-domain autocorrelations, and frequency-domain power spectra of the end-to-end vector. When time is rescaled by 
, configurational and orientational relaxation curves collapse across asymmetry ratios of the dumbbell, showing that the dominant long-time structural dynamics remain close to the overdamped description. Inertial signatures live in short-time transients, high-frequency modifications of the configurational spectrum, and a transient coupling between translational and internal modes. This study provides a practical and accurate route for lopsided dumbbells across overdamped and weakly underdamped regimes, and clarifies how mass and friction asymmetry affect the translational and internal dynamics.[1]
Finally, if time permits, a personal view on AI in mechanics will be presented.
[1] Full paper in Lei Song, Dingyi Pan and Nhan Phan-Thien, Finite-inertia effects in Langevin dynamics of a lopsided elastic dumbbell using exponential-time differencing schemes, Transport Phenomena (2026), in press.
主讲人简介：
Prof. Nhan Phan-Thien, FAA (Nhan for short) is a professor emeritus at the University of Singapore. He is a fellow of the Australian Academy of Science (elected 1999), a fellow of the Asian Academy of Engineering and Technology (elected 2016), a Qiushi Distinguished Chair Professor, Zhejiang University (2018-20), Head of Mechanical Engineering Department (2016-19), Founding Chair in Bio Engineering, NUS (2001-04), Personal Chair Professor in Mechanical Engineering, Sydney University (1991-2000), Deputy Editor (2023-25), Senior Associate Editor (2023), Associate Editor (2016-2023), Physics of Fluids (AIP Publishing). Currently he is the Founding Deputy Editor, Transport Phenomena and Open Transport (de Gruyter Brill, Berlin). His research interests include rheology, computation mechanics, aerogels. His notable awards and prizes include Australian Centenary Medal (2003), Gordon Bell Prize, IEEE Computer Society (1997), Australian Society of Rheology Medal (1997), Edgeworth David Medal (1982). He was a visiting professor at many institutions, including a Senior Fulbright Scholar at CALTECH (1982-83).
