On the effective horizontal buoyancy in turbulent thermal convection generated by cell tilting

Zhang, Lu1,2,3; Ding, Guang-Yu1,2,3; Xia, Ke-Qing1,2,3

2021-03-05

10.1017/jfm.2020.825

JOURNAL OF FLUID MECHANICS   影响因子和分区

0022-1120

1469-7645

We consider the situation of a misalignment between the global temperature gradient and gravity in thermal convection. In such a case an effective horizontal buoyancy arises that will significantly influence the transport properties of heat, mass and momentum. It may also change the flow morphology in turbulent convection. In this paper, we present an experimental and numerical study, using Rayleigh-Benard convection as a platform, to explore systematically the effect of horizontal buoyancy on heat transport in turbulent thermal convection. Experimentally, a condition of increasing horizontal Rayleigh number (RaH, which is the non-dimensional horizontal thermal driving strength) under fixed vertical Rayleigh number (RaV, the non-dimensional vertical driving strength) is achieved by tilting the convection cell and simultaneously increasing the imposed temperature difference. We find that, with increasing horizontal to vertical buoyancy ratio (Lambda = RaH/RaV), the overall heat transport manifests a monotonic increase in vertical heat transport (NuV) as well as a monotonic increase in its horizontal component (NuH). However, the horizontal Nusselt number is found to be approximately one order of magnitude smaller than the vertical Nusselt for the parameter range explored. We also show that the non-zero NuH results from the broken azimuthal symmetry of the system induced by the horizontal buoyancy. We find that the enhancement of vertical heat transport comes from the increased shear generated by the horizontal buoyancy at the boundary layer. The effect of Prandtl number (Pr) is also studied numerically. Finally, we extend the Grossmann-Lohse theory to the case with an effective horizontal buoyancy, the result of which is successful in predicting NuV(RaV, Lambda, Pr).

Benard convection turbulent convection

SCI ; EI

英语

第一 ; 通讯

Research Grants Council of Hong Kong SAR[CUHK14302317]

Mechanics ; Physics

Mechanics ; Physics, Fluids & Plasmas

WOS:000625455500001

CAMBRIDGE UNIV PRESS

20211110067843

Atmospheric thermodynamics ; Boundary layers ; Buoyancy ; Natural convection ; Prandtl number

Oil Fields:512.1.1 ; Thermodynamics:641.1 ; 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, PR, Peoples R China
2.Southern Univ Sci & Technol, Dept Mech & Aerosp Engn, Shenzhen 518055, Peoples R China
3.Chinese Univ Hong Kong, Dept Phys, Shatin, Hong Kong, Peoples R China

Zhang, Lu,Ding, Guang-Yu,Xia, Ke-Qing. On the effective horizontal buoyancy in turbulent thermal convection generated by cell tilting[J]. JOURNAL OF FLUID MECHANICS,2021,914.

Zhang, Lu,Ding, Guang-Yu,&Xia, Ke-Qing.(2021).On the effective horizontal buoyancy in turbulent thermal convection generated by cell tilting.JOURNAL OF FLUID MECHANICS,914.

Zhang, Lu,et al."On the effective horizontal buoyancy in turbulent thermal convection generated by cell tilting".JOURNAL OF FLUID MECHANICS 914(2021).