Mean velocity and temperature profiles in turbulent Rayleigh-Benard convection at low Prandtl numbers

Xu, Wei1; Wang, Yin2; He, Xiaozhou3; Wang, Xiaoping4; Schumacher, Joerg5; Huang, Shi-Di6,7; Tong, Penger2

2021-05-05

10.1017/jfm.2021.255

JOURNAL OF FLUID MECHANICS   影响因子和分区

0022-1120

1469-7645

We report a direct numerical simulation (DNS) study of the mean velocity and temperature profiles in turbulent Rayleigh-Benard convection (RBC) at low Prandtl numbers (Pr). The numerical study is conducted in a vertical thin disk with Pr varied in the range 0.17 <= Pr <= 4.4 and the Rayleigh number (Ra) varied in the range 5 x 10(8) <= Ra <= 1 x 10(10). By varying Pr from 4.4 to 0.17, we find a sharp change of flow patterns for the large-scale circulation (LSC) from a rigid-body rotation to a near-wall turbulent jet. We numerically examine the mean velocity equation in the bulk region and find that the mean horizontal velocity profile u(z) can be determined by a balance equation between the mean convection and turbulent diffusion with a constant turbulent viscosity.t. This balance equation admits a self-similarity jet solution, which fits the DNS data well. In the boundary-layer region, we find that both the mean temperature profile T(z) and u(z) can be determined by a balance equation between the molecular diffusion and turbulent diffusion. Within the viscous boundary layer, both u(z) and T(z) can be solved analytically and the analytical results agree well with the DNS data. Our careful characterisation of the mean velocity and temperature profiles in low-Pr RBC provides a further understanding of the intricate interplay between the LSC, plume emission and boundary-layer dynamics, and pinpoints the physical mechanism for the emergence of a pronounced LSC in low-Pr RBC.

Benard convection buoyant boundary layers turbulent convection

SCI ; EI

英语

其他

Hong Kong Research Grants Council[16301719,"N_HKUST604/19",16305819] ; National Natural Science Foundation of China[11772111,91952101,11702128,11961160719,91752201] ; Deutsche Forschungsgemeinschaft[DFG-SPP 1881]

Mechanics ; Physics

Mechanics ; Physics, Fluids & Plasmas

WOS:000647147400001

CAMBRIDGE UNIV PRESS

20211910328448

Atmospheric turbulence ; Boundary layers ; Diffusion ; Natural convection ; Prandtl number ; Temperature control ; Velocity

Atmospheric Properties:443.1 ; Thermodynamics:641.1 ; Heat Transfer:641.2 ; Specific Variables Control:731.3

ENGINEERING

Web of Science

1.Hong Kong Univ Sci & Technol, Nano Sci & Technol Program, Kowloon, Clear Water Bay, Hong Kong, Peoples R China
2.Hong Kong Univ Sci & Technol, Dept Phys, Kowloon, Clear Water Bay, Hong Kong, Peoples R China
3.Harbin Inst Technol, Sch Mech Engn & Automat, Shenzhen, Peoples R China
4.Hong Kong Univ Sci & Technol, Dept Math, Kowloon, Clear Water Bay, Hong Kong, Peoples R China
5.Tech Univ Ilmenau, Inst Thermo & Fluiddynam, Postfach 100565, D-98684 Ilmenau, Germany
6.Southern Univ Sci & Technol, Ctr Complex Flows & Soft Matter Res, Shenzhen 518055, Peoples R China
7.Southern Univ Sci & Technol, Dept Mech & Aerosp Engn, Shenzhen 518055, Peoples R China

Xu, Wei,Wang, Yin,He, Xiaozhou,et al. Mean velocity and temperature profiles in turbulent Rayleigh-Benard convection at low Prandtl numbers[J]. JOURNAL OF FLUID MECHANICS,2021,918.

Xu, Wei.,Wang, Yin.,He, Xiaozhou.,Wang, Xiaoping.,Schumacher, Joerg.,...&Tong, Penger.(2021).Mean velocity and temperature profiles in turbulent Rayleigh-Benard convection at low Prandtl numbers.JOURNAL OF FLUID MECHANICS,918.

Xu, Wei,et al."Mean velocity and temperature profiles in turbulent Rayleigh-Benard convection at low Prandtl numbers".JOURNAL OF FLUID MECHANICS 918(2021).