应TYC234CC太阳成集团官网陈文礼教授和陈冠斌副研究员的邀请，韩国釜山国立大学（Pusan National University），韩国翰林院院士、Journal of Visualization主编Kyung Chun Kim教授将于2026年04月07日到04月21问我校，并作报告，欢迎感兴趣的师生参加。
报告时间：2026年04月14日 9:30-11:00
报告地点：TYC234CC太阳成集团官网303会议室
报告主题：Velocity Jump of Newtonian Droplets in Viscoelastic Fluids: Analytical and Experimental Study
Abstract
This study presents a combined analytical and experimental investigation into the rising dynamics of Newtonian droplets in viscoelastic fluids, focusing on discontinuous transitions in droplet velocity. Although velocity jumps have been observed in gas bubbles, this work is the first systematic investigation of the phenomenon in Newtonian droplets. Analytically, a triple-perturbation approach is developed using Reynolds, Deborah, and capillary numbers as expansion parameters. The surrounding viscoelastic medium is modeled using the nonlinear-Giesekus constitutive equation. The analysis reveals that increasing Deborah number intensifies and reorients normal stresses—particularly the polar (𝜃-direction) and hoop components—along the droplet interface. These stresses migrate rearward with increasing elasticity, resulting in localized elongational flows and concentrated radial stresses near the rear stagnation point, which indicates the onset of elastic instabilities. Experimentally, Newtonian droplets are introduced into a variety of exterior fluids: (i) quasilinear Boger fluids, which are constant-viscosity viscoelastic solutions that isolate elastic effects, and (ii) a strongly nonlinear viscoelastic solution, which exhibits both high elasticity and significant shear-thinning behavior. Equivalent Newtonian fluids of matched viscosity are also used as controls. Viscoelastic fluids are solutions of polyacrylamide in the water-glycerin mixture. Across all experiments, the dimensionless ranges were Re ≈ 6 × 10−4 –4.59, De ≈ 0.057–0.802, and Ca ≈ 0.0026–0.638, framing the scope of applicability. The experimental observations challenge the classical expectation of smooth droplet motion and demonstrate that Newtonian droplets in viscoelastic environments can exhibit sharp, weak, or no velocity jumps, depending on the balance between elasticity, viscosity, and deformability.
报告人Kyung Chun Kim教授简介
Prof. KC Kim received his BA degree at Pusan National University, Korea in 1979. He received MS and Ph.D degree at KAIST, Korea in 1981 and 1987 respectively. Since 1983, he is a professor at School of Mechanical Engineering in Pusan National University (PNU), Korea. He was invited as a visiting professor from Ottawa University in Canada for 1989-1990. He joined at the department of theoretical and applied mechanics in University of Illinois, Urbana-Champaign, USA as an invited professor for 1996-1997. He was invited as a special foreign professor from the University of Tokyo, Japan for 2009-2010. On the basis of his research outcomes, he became a member of National Academy of Engineering in Korea in 2004. He received the outstanding paper awards (1995, 2002) from KSME and KOSEF. In 2009 and 2016, he received the Academic award and the first Yeosong award from KSME. He received Nakayama award in 2012 and Asanuma award in 2014 based on contributions in world Visualization society. KC Kim was selected as a PNU Distinguished Professor in 2018. In 2019, he received Busan Science and Technology award.
Prof. KC Kim is currently serving as an Editor in Chief for Journal of Visualization. In 2020, he was selected as the director of Regional Leading Research Center for Eco-friendly Smart Ship. His research interests include: Turbulence, Two-Phase Flows, Flow Visualization, and Artificial Intelligence.
