Modulation of turbulent Rayleigh-Bénard convection under spatially harmonic heating

Chao-Ben Zhao, Yi-Zhao Zhang, Bo-Fu Wang, Jian-Zhao Wu, Kai Leong Chong, and Quan Zhou
Phys. Rev. E 105, 055107 – Published 23 May 2022

Abstract

We numerically study turbulent Rayleigh-Bénard (RB) convection under spatial temperature modulation, where the bottom temperature varies sinusoidally around a mean value in space. Both two- and three-dimensional simulations are performed over the Rayleigh number range 107Ra1010 and the wave number range 1k120 at fixed Prandtl number Pr=0.7. It is demonstrated that spatial temperature modulation with small wave numbers can enhance the global heat transfer (characterized by the Nusselt number Nu) in the turbulent regime, while Nu is close to that in standard RB convection in the case of large wave numbers. Further, we propose two characteristic modulation length scales: one is the penetration depth δk above which spatial modulation is negligible, the other is the inversion depth δk2 below which there exists a stable inverse temperature gradient. Based on the relative thickness of the thermal boundary layer (BL) δth compared with these two length scales, the underlying modulation mechanism is physically explained and three regimes are identified: (1) an unperturbed BL regime (δk<δth), in which the modulation effect does not penetrate through the thermal BL and Nu is nearly unchanged; (2) a partially modulated BL regime (δk2<δth<δk), in which hot spots trigger more plume emissions from the thermal BL, resulting in Nu enhancement; and (3) a fully modulated BL regime (δth<δk2), in which the stable temperature inversion over the cold phases begins to affect convective flows, which alters the trend of Nu enhancement.

  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
5 More
  • Received 3 December 2021
  • Accepted 5 May 2022

DOI:https://doi.org/10.1103/PhysRevE.105.055107

©2022 American Physical Society

Physics Subject Headings (PhySH)

Fluid Dynamics

Authors & Affiliations

Chao-Ben Zhao, Yi-Zhao Zhang, Bo-Fu Wang, Jian-Zhao Wu*, Kai Leong Chong, and Quan Zhou

  • Shanghai Institute of Applied Mathematics and Mechanics, Shanghai Key Laboratory of Mechanics in Energy Engineering, School of Mechanics and Engineering Science, Shanghai University, Shanghai, 200444, China

  • *jianzhao_wu@shu.edu.cn
  • klchong@shu.edu.cn
  • qzhou@shu.edu.cn

Article Text (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand
Issue

Vol. 105, Iss. 5 — May 2022

Reuse & Permissions
Access Options
Author publication services for translation and copyediting assistance advertisement

Authorization Required


×
×

Images

×

Sign up to receive regular email alerts from Physical Review E

Log In

Cancel
×

Search


Article Lookup

Paste a citation or DOI

Enter a citation
×