剪切流动亚临界转捩中的时空间歇性和相变研究进展  

Spatio-temporal intermittency and phase transition in the subcritical transition of shear flows:Current status and open problems

作　　者：宋保方 SONG BaoFang(State Key Laboratory for Turbulence and Complex Systems,Department of Aeronautics and Astronautics,College of Engineering,Peking University,Beijing 100871,China)

机构地区：[1]北京大学工学院航空航天工程系,湍流与复杂系统国家重点实验室,北京100871

出　　处：《中国科学:物理学、力学、天文学》2025年第1期141-151,共11页Scientia Sinica Physica,Mechanica & Astronomica

基　　金：国家自然科学基金(编号:12272264,12322209,91852105)资助项目。

摘　　要：剪切流动中层流向湍流的转捩是流体力学中的一个经典难题.近些年在亚临界转捩方面取得了若干重要进展,特别是在转捩的时空特征方面.研究发现,亚临界转捩中湍流以局地湍流形式存在,且表现出复杂的时空间歇性.对局地湍流结构及其时空复杂性的研究逐步揭示了转捩现象和统计物理中的连续型相变之间的关系:流动转捩可能属于一个可描述广泛临界现象的相变普适类,即导向逾渗相变普适类.目前学界仍在试图证明这种相变比拟适用于所有壁面剪切流动中的亚临界转捩.近期在泰勒-库埃特流动实验中给出了相变的直接证据,但对于管道和槽道流动,由于转捩临界点附近系统演化的巨大时间和空间尺度,实验和计算都难以足够靠近临界点进行直接验证,而且槽道流转捩临界点附近湍流的时空特征与导向逾渗相变之间的关系仍不明晰.因而,该比拟的普适性还有待进一步的确认.Transition to turbulence in shear flows has been a long-standing problem of fluid mechanics.In recent decades,great advancements have been made in this area,especially in the spatio-temporal intermittency of the subcritical transition.Even in simple shear flows,localized turbulence exhibits spatio-temporal complexity on large scales.Studies of this complexity have gradually revealed the relationship between the subcritical transition and non-equilibrium phase transition,i.e.,transition probably belongs to the directed-percolation universality class that embraces a broad range of critical phenomenon.Although it has been long believed that the subcritical transition in all shear flows belongs to this universality class,only until very recently has the evidence been obtained in Taylor-Couette experiments.However,in pipe and channel flows,the vast spatial and temporal scales involved hinder experimental and numerical measurements to reach sufficiently close to the critical point.Besides,the spatio-temporal characteristics of localized turbulence in channel flow at low Reynolds numbers seem more complicated than the simple dynamics of directed percolation.Therefore,the generality of the phase-transition analogy of shear-flow transition remains to be clarified.

关 键 词：剪切流动 亚临界转捩 局地湍流 时空间歇性 相变 

分 类 号：O35[理学—流体力学]