时 间：2019年7月8日上午 9:00-10:00
题 目：The characteristics of flow around six in-line circular cylinders at low Reynolds numbers
Flow past a circular cylinder has attracted significant amount of attention in fluid mechanics community due to its interesting phenomena and close relationship with industrial applications. When the number of cylinder is increased, the flow becomes more complex. This work investigates the characteristics of the flow field around a group of circular cylinders arranged in in-line configuration. A series of two-dimensional numerical simulations are carried out to simulate the flow for Reynolds number in the range of 40 to 180 and gap to diameter ratio from 0.5 to 18. According to the vortex shedding characteristics around the six cylinders, a flow regime map is proposed where the flow is categorized into 4 different regimes, namely no-shedding regime, primary shedding regime, secondary shedding regime and tertiary shedding regime. Before the transitions between flow regimes happen, shear layer re-attachment or extended shear layers are formed. For large gap to diameter ratios, the three vortex shedding regimes can co-exist and each regime dominates a region around the group of cylinders. The effect of the flow regime transition on vortex shedding frequency and force coefficients of each cylinder are quantified and explained. When the number of cylinders is increased further, the vortex shedding processes of the downstream cylinders become chaotic after transition to tertiary wake.
Professor Tongming Zhou has been in the area of fluid dynamics for more than 20 years. He obtained his PhD in 1999 in the area of Fluid Mechanics from The University of Newcastle (Australia). After completing his PhD, he worked as a post-doc fellow for about 2 years and then joined Nanyang Technological University, Singapore, as an assistant/associate professor. Since July 2007, he has been working in School of Civil, Environmental and Mining Engineering, The University of Western Australia. His main research interests include manipulation of vortex shedding and vortex-induced vibrations of cylindrical structures, resonance of waves in the gap between a floating LNG facility and a LNG carrier and liquid sloshing in a partially-filled tank by conducting experiments on the hexapod.