Low Reynolds number hydrodynamics of immersed thin and slender bodies
讲座名称：
Low Reynolds number hydrodynamics of immersed thin and slender bodies
讲座时间：
2016-12-23
讲座人：
徐秉睿
形式：
校区：
兴庆校区
实践学分：
讲座内容：
应航天航空学院Marie-Jean Thoraval教授邀请，复旦大学徐秉睿博士将来访我校并作学术报告。
报告题目：Low Reynolds number hydrodynamics of immersed thin and slender bodies
时间：2016年12月23日早上10:00-11:00
地点：航天航空学院教一楼第二会议室
报告人：徐秉睿博士
报告摘要：
The hydrodynamics of thin (sheet-like) and slender (filamentary) bodies of viscous fluid immersed in a second fluid with a different viscosity is studied. Here we focus on two examples: the subduction of oceanic lithosphere and the buckling of viscous threads in diverging micro-channels, both have a characteristic Reynolds number Re<<1.
A hybrid boundary integral & thin sheet method (BITS) is built for the subduction of 2D immersed sheet. After the validation by comparing with the results of full boundary elements method, both instantaneous and time-dependent solutions are done to analyze the subduction with BITS method. The scaling analysis of the normalized sinking speed as a function of the sheet's 'flexural stiffness' is confirmed by our numerical predictions. For moderate viscosity ratios (~100), the sheet thins substantially as it sinks, but not enough to lead to the ‘slab breakoff’ that is observed in several subduction zones on Earth.
Next, the parallel code BLUE for multi-phases flows is used to simulate the 3D viscous folding in diverging micro-channels. We performed a parameter study comprising five simulations in which the flow rate ratio, the viscosity ratio, the Reynolds number, and the shape of the channel were varied relative to a reference model. The thread becomes unstable to a folding instability due to the longitudinal compressive stress. The initial folding axis can be either parallel or perpendicular to the narrow dimension of the chamber. In the former case, the folding slowly transforms via twisting to perpendicular folding, or may disappear totally.
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