報告人：賀冬冬

報告題目：Stretching of a highly viscous thread with temperature-dependent viscosity and surface tension

報告人簡介：同濟大學航空航天與力學學院博士

Dr. Dongdong He is an assistant Professor at School of Aerospace Engineering and Applied Mechanics, Tongji University.He received PhD in Applied Mathematics at York University (Canada) in 2012 under supervision of Prof. Huaxiong Huang.  Before joining Tongji University, he worked as a postdoctoral fellow at Department of Mathematics in City University of Hong Kong, his postdoc advisor is Prof. Jonathan, Wylie.Dr. He's research interests include Mathematical Modeling, Applied Asymptotic Analysis, Computational Fluid Mechanics and Numerical Methods for PDEs. He has published more than 10 refereed journal papers, which include publications in Journal of Fluid Mechanics, Physical Review E, Journal of Scientific Computing, Communications in Computational Physics, Nonlinear Dynamics, Computers & Mathematics with Application and etc

報告摘要:

In this talk, I will show our recent results for the extension of the highly viscous threads arising from the glass and polymer industrial processing.  We consider the evolution of a long and thin vertically-aligned axisymmetric viscous thread, which is attached to a solid wall at its upper end, experiences gravity and is pulled at its lower end by a fixed force. The thread experiences either heating or cooling by its environment. Both the viscosity and surface tension are assumed to be functions of temperature. A set of one-dimensional model is derived through the formal slender body asymptotic analysis. When inertia is completely neglected and the temperature of the environment is spatially uniform, we obtain analytic solutions for an arbitrary initial shape and temperature profile. In addition, we determine the criteria for whether the cross-section of a given fluid element will ever become zero and hence determine the minimum stretching force that is required for pinching. For non-zero Reynolds numbers, we show that the dynamics is subtly influenced by inertia and the pinching location is selected by a competition between three distinct mechanisms. In particular, for a thread with initially uniform radius and a spatially uniform environment but with a non-uniform initial temperature profile, pinching can occur either at the hottest point, at the points near large thermal gradients or at the pulled end, depending on the Reynolds number.

報告時間:2016年9月26日16:00-17:00

報告地點:科技樓南樓702