黏弹性效应作用下Taylor-Couette流动转捩的直接模拟研究  

Direct numerical simulation on transition of viscoelastic Taylor-Couette flow

作　　者：王敏妙 刘难生[1] 陆夕云[1] 丁航 WANG MinMiao;LIU NanSheng;LU XiYun;DING Hang(Department of Modern Mechanics,University of Science and Technology of China,Hefei 230027,China)

机构地区：[1]中国科学技术大学近代力学系.合肥230027

出　　处：《中国科学：物理学、力学、天文学》2018年第9期236-243,共8页Scientia Sinica Physica,Mechanica & Astronomica

基　　金：国家自然科学基金(编号：11472268,91752110)和科学挑战专题(编号：TZ2016001)资助项目

摘　　要：本文通过高精度谱方法的直接数值模拟研究了黏弹性Taylor-Couette(TC)流动的转捩问题.通过以下3种方式考察了流体惯性和弹性效应相对强弱的变化对TC流动转捩的影响:(1)增大雷诺数Re(即惯性效应),保持Weissenberg数We(即弹性效应)不变;(2)增大Re,保持弹性数E=We/Re(即弹性和惯性效应比)不变;(3)保持Re不变,增大We.计算重现了黏弹性TC流动的多种典型流态,包括旋转驻波流态、轴对称的振动条带、非轴对称的振动条带和类行波流态.此外,发现了一种间歇孤立波流态,该流态含有明显的间歇性拟序结构,在径向速度u_r的时空图中表现为周期性间歇出现、局部集中的强烈径向内/外流.本文还考察了参数空间中起点和终点相同的3条路径上的转捩过程,对比分析了这些路径终点的流态特征,据此发现了在历经不同路径出现的多态现象.Direct numerical simulation has been performed on transition of viscoelastic Taylor-Couette （TC） flow. Specifically, the transition of viscoelastic TC flow starting from the same initial state （AZI） is examined by varying parameters in the following three ways： （1） increasing the inertia while keeping the elasticity unchanged; （2） keeping the elasticity number （a ratio of inertia to elasticity） unchanged while increasing the inertia; （3） keeping the inertia unchanged while increasing the elasticity. The present calculations succeed in reproducing various typical flow states, including rotating standing waves （RSW）, axisymmetric oscillatory strip （OS）, non-axisymmetric OS and a flow state in form of traveling wave. Interestingly, with the continuously increasing elasticity from OS in Way 3, the OS becomes more turbulent, exhibiting broad PSDs with continuous power-law-decay region. After that, the OS breaks down into a new flow state consisting of intermittent solitary wave （ISW）, which is characterized by solitary coherent structure appearing periodically and intermittently in time and localized axially with intense inflow/outflow spot. The transition sequences have been identified for the aforementioned three ways as： （1） from AZI to RSW to strong-weak RSW, then to RSW; （2） from AZI to OS to non-axisymmetric OS, then to a flow state in form of traveling wave; （3） from AZI to OS, then to ISW. On the other hand, three transition pathways which have the same departure and destination in parameter space are examined. Based on comparing the final states （space-time plots and PSDs） of the three pathways, existence of multiple flow states has been confirmed in viscoelastic TC flows.

关 键 词：黏弹性流体 直接数值模拟 Taylor—Couette流动 转捩 

分 类 号：O35[理学—流体力学]