Transition to fully developed turbulence in liquid-metal convection facilitated by spatial confinement

Ren, Lei1; Tao, Xin1; Xia, Ke-Qing2,3; Xie, Yi-Chao1

2024-02-23

10.1017/jfm.2024.86

JOURNAL OF FLUID MECHANICS   影响因子和分区

0022-1120

1469-7645

Using thermal convection in liquid metal, we show that strong spatial confinement not only delays the onset Rayleigh number Ra-c of Rayleigh-B & eacute;nard instability but also postpones the various flow-state transitions. The Ra-c and the transition to fully developed turbulence Rayleigh number Ra(f )depend on the aspect ratio Gamma with Ra-c similar to Gamma-4.05 and Ra-f similar to Gamma-3.01, implying that the stabilization effects caused by the strong spatial confinement are weaker on the transition to fully developed turbulence when compared with that on the onset. When the flow state is characterized by the supercritical Rayleigh number Ra/Ra-c (Ra is the Rayleigh number), our study shows that the transition to fully developed turbulence in strongly confined geometries is advanced. For example, while the flow becomes fully developed turbulence at Ra approximate to 200Ra(c) in a Gamma = 1 cell, the same transition in a Gamma = 1/20 cell only requires Ra approximate to 3Ra(c). Direct numerical simulation and linear stability analysis show that in the strongly confined regime, multiple vertically stacked roll structures appear just above the onset of convection. With an increase of the driving strength, the flow switches between different -roll states stochastically, resulting in no well-defined large-scale coherent flow. Owing to this new mechanism that only exists in systems with Gamma < 1, the flow becomes turbulent in a much earlier stage. These findings shed new light on how turbulence is generated in strongly confined geometries.

Benard convection turbulent convection

SCI

英语

其他

NSFC["92152104","12232010","12072144"]

Mechanics ; Physics

Mechanics ; Physics, Fluids & Plasmas

WOS:001169868000001

CAMBRIDGE UNIV PRESS

ENGINEERING

Web of Science

1.Xi An Jiao Tong Univ, State Key Lab Strength & Vibrat Mech Struct, Xian 710049, Peoples R China
2.Southern Univ Sci & Technol, Ctr Complex Flows & Soft Matter Res, Dept Mech & Aerosp Engn, Shenzhen 518055, Peoples R China
3.Southern Univ Sci & Technol, Dept Phys, Shenzhen 518055, Peoples R China

Ren, Lei,Tao, Xin,Xia, Ke-Qing,et al. Transition to fully developed turbulence in liquid-metal convection facilitated by spatial confinement[J]. JOURNAL OF FLUID MECHANICS,2024,981.

Ren, Lei,Tao, Xin,Xia, Ke-Qing,&Xie, Yi-Chao.(2024).Transition to fully developed turbulence in liquid-metal convection facilitated by spatial confinement.JOURNAL OF FLUID MECHANICS,981.

Ren, Lei,et al."Transition to fully developed turbulence in liquid-metal convection facilitated by spatial confinement".JOURNAL OF FLUID MECHANICS 981(2024).