Howard A. Stone教授学术报告
主 题：Elementary flows with surprising responses: (I) Biofilms and flow and (II) Trapping of bubbles in stagnation point flows
时 间：9:00-11:00，2013年8月19日（周一）
地 点：机械A楼F210 会议室
主讲人：Prof. Howard A. Stone, Mechanical and Aerospace Engineering, Princeton University
摘 要：
In this talk we describe two distinct problems that we have studied whereseemingly modest variations in an elementary channel flow produce neweffects. First, we investigate some influences of flow on biofilms. Inparticular, we identify the formation of biofilm streamers, which arefilaments of biofilm extended along the central region of a channel flow,and show how these filaments are capable of causing catastrophicdisruption and clogging of industrial, environmental and medical flowsystems. We present a mathematical model to rationalize the rapid growthof the streamer. Second we consider flow in a T-junction, which is perhapsthe most common element in many piping systems. The flows are laminar buthave high Reynolds numbers, typically Re=100-1000. It seems obvious thatany particles in the fluid that enter the T-junction will leave followingthe one of the two main flow channels. Nevertheless, we report experimentsthat document that bubbles and other low density objects can be trapped atthe bifurcation. The trapping leads to the steady accumulation of bubblesthat can form stable chain-like aggregates in the presence, for example,of surfactants, or give rise to a growth due to coalescence. Ourthree-dimensional numerical simulations rationalize the mechanism behindthis phenomenon.
报告人简介：
In 2008, Stone was the winner of the inaugural Batchelor Prize sponsored by the Journal of Fluid Mechanics for the breadth and depth of his research over a 10-year period (1998-2007) and for his widely acknowledged leadership in fluid mechanics generally. Stone did his undergraduate studies at University of California at Davis and earned his Ph.D. at Caltech. He joined the Harvard faculty in 1989 after spending one year as a post-doctoral fellow in the Department of Applied Mathematics and Theoretical Physics at Cambridge University.His research has been concerned with a variety of fundamental problems in fluid motions dominated by viscosity, so-called low Reynolds number flows, and has frequently featured a combination of theory, computer simulation and modeling, and experiments to provide a quantitative understanding of the flow phenomenon under investigation. Stone's studies have also been directed toward heat transfer and mass transfer problems involving convection, diffusion and surface reactions. He has made contributions to a wide range of problems involving effects of surface tension, buoyancy, fluid rotation, and surfactants. He has also studied problems concerning the flow of lipid bilayers and monolayers, and has investigated the motions of particles suspended in such interfacial layers.In 2000, Stone was named a Harvard College Professor, an appointment established in 1997 to honor outstanding service to undergraduate education. He credited his students for making teaching enjoyable: "They have been a source of questions, insights, and continued learning for me." The following quote, he said, summarizes his philosophy of teaching: "‘The sickness of man lies in his fondness for playing teacher to others. Thus in a world full of gurus, I claim merely the title of a guide, to be dismissed at the end of the journey.’”