Prof. Peng-Sheng Wei
Prof. Peng-Sheng Wei
National Sun Yat-Sen University, Chinese Taipei
Title: Solute Convection on Pore Formation during Solidification
A transport model is proposed to predict entrapment of a bubble during unidirectional upward solidification. Pore formation and its shape in solid influence not only microstructure of materials, but also contemporary issues of various sciences of biology, engineering, foods, geophysics and climate change, etc. In this study, COMSOL computer code is used to solve conservation equations of mass, momentum, energy and solute concentration in liquid, gas and solid phases satisfied by their interfacial conditions. It shows that strong convection results in pore growth toward downstream direction. However, time for bubble entrapment depends on the ratio between square of concentration boundary layer thickness and solute diffusivity. Solute diffusion is therefore the mechanism responsible bubble entrapment, where the bubble growth rate and vertical velocity component of fluid at the bubble cap are found to be of the same order of magnitude. Predicted contact angle and apex radius of the bubble cap agree with that predicted by the Abel’s equation and Young-Laplace equation, respectively.
Dr. Peng-Sheng Wei received Ph.D. in Mechanical Engineering Department at University of California, Davis, in 1984. He has been a professor in the Department of Mechanical and Electro-Mechanical Engineering of National Sun Yat-Sen University, Kaohsiung, Taiwan, since 1989. Dr. Wei has contributed to advancing the understanding of and to the applications of electron and laser beam, plasma, and resistance welding through theoretical analyses coupled with verification experiments. Investigations also include studies of their thermal and fluid flow processes, and formations of the defects such as humping, rippling, spiking and porosity. Dr. Wei has published more than 80 journal papers, given keynote or invited speeches in international conferences more than 50 times. He is a Fellow of AWS (2007), and a Fellow of ASME (2000). He also received the Outstanding Research Achievement Awards from both the National Science Council (2004), and NSYSU (1991, 2001, 2004), the Outstanding Scholar Research Project Winner Award from National Science Council (2008), the Adams Memorial Membership Award from AWS (2008), the Warren F. Savage Memorial Award from AWS (2012), and the William Irrgang Memorial Award from AWS (2014). He has been the Xi-Wan Chair Professor of NSYSU since 2009, and Invited Distinguished Professor in the Beijing University of Technology, China, during 2015-2017.