Heat transfer in a quasi-one-dimensional Rayleigh-Benard convection cell

Zhang, Lu1,2; Xia, Ke-Qing1,2,3

2023-10-23

10.1017/jfm.2023.600

JOURNAL OF FLUID MECHANICS   影响因子和分区

0022-1120

1469-7645

We report an experimental and numerical study on Rayleigh-Benard convection in a slender rectangular geometry with the aspect ratio Gamma varying from 0.05 to 0.3 and a Rayleigh number range of 10(5) <= Ra <= 3 x 10(9). The Prandtl number is fixed at Pr = 4.38. It is found that the onset of convection is postponed when the convection domain approaches the quasi-one-dimensional limit. The onset Rayleigh number shows a Ra-c = 328 Gamma(-4.18) scaling for the experiment and a Ra-c = 810 Gamma(-3.95) scaling for the simulation, both consistent with a theoretical prediction of Ra-c similar to Gamma(-4). Moreover, the effective Nusselt-Rayleigh scaling exponent beta = partial derivative(log Nu)/partial derivative(log Ra) near the onset of convection also shows a rapid increase with decreasing Gamma. Power-law fits to the experimental and numerical data yield beta = 0.290 Gamma(-0.90) and beta = 0.564 Gamma(-0.92), respectively. Near onset, the flow shows a stretched cell structure. In this regime, the velocity and temperature variations in a horizontal cross-section are found to be almost invariant with height in the core region of a slender domain. As the Rayleigh number increases, the system evolves from the viscous dominant regime to a plume-controlled one, a feature of which is enhancement in the heat transport efficiency. Upon further increase of Ra, the flow comes back to the classical boundary-layer-controlled regime, in which the quasi-one-dimensional geometry has no apparent effect on the global heat transfer.

Benard convection buoyancy-driven instability

SCI ; EI

英语

第一 ; 通讯

Mechanics ; Physics

Mechanics ; Physics, Fluids & Plasmas

WOS:001087648100001

CAMBRIDGE UNIV PRESS

20234515023620

Aspect ratio ; Boundary layers ; Natural convection

Heat Transfer:641.2 ; Physical Properties of Gases, Liquids and Solids:931.2

ENGINEERING

Web of Science

1.Southern Univ Sci & Technol, Ctr Complex Flows & Soft Matter Res, Shenzhen 518055, Peoples R China
2.Southern Univ Sci & Technol, Dept Mech & Aerosp Engn, Shenzhen 518055, Peoples R China
3.Southern Univ Sci & Technol, Dept Phys, Shenzhen, Peoples R China

Zhang, Lu,Xia, Ke-Qing. Heat transfer in a quasi-one-dimensional Rayleigh-Benard convection cell[J]. JOURNAL OF FLUID MECHANICS,2023,973.

Zhang, Lu,&Xia, Ke-Qing.(2023).Heat transfer in a quasi-one-dimensional Rayleigh-Benard convection cell.JOURNAL OF FLUID MECHANICS,973.

Zhang, Lu,et al."Heat transfer in a quasi-one-dimensional Rayleigh-Benard convection cell".JOURNAL OF FLUID MECHANICS 973(2023).