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Zheng JL, Liu YL. Experimental study on the flow structures and dynamics of turbulent Rayleigh-Bénard convection in an annular cell. Phys Rev E 2023; 107:065112. [PMID: 37464695 DOI: 10.1103/physreve.107.065112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2023] [Accepted: 06/04/2023] [Indexed: 07/20/2023]
Abstract
We conduct an experimental study on the flow structures and dynamics of turbulent Rayleigh-Bénard convection in an annular cell with radius ratio η≃0.5 and aspect ratio Γ≃4. The working fluid is water with a Prandtl number of Pr≃5.4, and the Rayleigh number (Ra) ranges from 5.05×10^{7} to 5.05×10^{8}. The multithermal-probe method and the particle image velocimetry technique are employed to measure the temperature profiles and the velocity fields, respectively. Two distinct states with multiroll standing waves are observed, which are the quadrupole state (QS) characterized by a four-roll structure and the sextupole state (SS) by a six-roll structure. The scaling exponents of Reynolds number Re with Ra are different for the two states, which are 0.56 for QS and 0.41 for SS. In addition, the standing waves become unstable upon tilting the cell by 1^{∘} in relation to the horizontal plane, and they evolve into traveling waves. At relatively high Ra, for instance, Ra⩾2.55×10^{8}, it is observed that the traveling wave state SS undergoes a transition to the traveling wave state QS. However, the opposite transition from QS to SS is not observed in our experiments. Our findings provide insights into the flow structures and dynamics in the convection flow with rotation symmetry.
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Affiliation(s)
- Ji-Li Zheng
- Shanghai Institute of Applied Mathematics and Mechanics, School of Mechanics and Engineering Science, Shanghai University, Shanghai 200072, China
| | - Yu-Lu Liu
- Shanghai Institute of Applied Mathematics and Mechanics, School of Mechanics and Engineering Science, Shanghai University, Shanghai 200072, China
- School of Science, Shanghai Institute of Technology, Shanghai 201418, China
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Yuan L, Zou S, Yang Y, Chen S. Boundary-Layer Disruption and Heat-Transfer Enhancement in Convection Turbulence by Oscillating Deformations of Boundary. PHYSICAL REVIEW LETTERS 2023; 130:204001. [PMID: 37267548 DOI: 10.1103/physrevlett.130.204001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Revised: 03/31/2023] [Accepted: 04/20/2023] [Indexed: 06/04/2023]
Abstract
In this Letter, we propose a novel strategy for significantly enhancing the heat transfer in convection turbulence. By introducing a boundary deformation of the standing-wave type, flow modulation can be realized when the amplitude is comparable or larger than the boundary-layer thickness. For a fixed moderate frequency, the entire fluid layer follows the boundary motion at small wave numbers, while only the near-wall regions are affected by the boundary deformation at large wave numbers. The heat-flux enhancement happens for the latter. For a fixed wave number and gradually increasing frequency, the vortical flows inside the wave valleys exhibit nonlinear transition and alter the distribution of boundary heat flux, and the global heat flux increases significantly at large enough frequencies. The current findings suggest that oscillating deformations of boundary can efficiently break the boundary layers, which serves as the bottleneck of global heat transfer, and open a new venue for modulating the convection turbulence.
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Affiliation(s)
- Leiqi Yuan
- State Key Laboratory for Turbulence and Complex Systems, and Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, People's Republic of China
| | - Shufan Zou
- College of Aerospace Science and Engineering, National University of Defense Technology, Changsha 410073, China
| | - Yantao Yang
- State Key Laboratory for Turbulence and Complex Systems, and Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, People's Republic of China
- Joint Laboratory of Marine Hydrodynamics and Ocean Engineering, Laoshan Laboratory, Shandong 266299, People's Republic of China
| | - Shiyi Chen
- State Key Laboratory for Turbulence and Complex Systems, and Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, People's Republic of China
- Eastern Institute for Advanced Study, Eastern Institute of Technology, Ningbo, Zhejiang 315200, People's Republic of China
- Department of Mechanics and Aerospace Engineering, Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
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Garrido PL, Hurtado PI. Molecular hints of two-step transition to convective flow via streamline percolation. Phys Rev E 2022; 106:014144. [PMID: 35974586 DOI: 10.1103/physreve.106.014144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 07/12/2022] [Indexed: 06/15/2023]
Abstract
Convection is a key transport phenomenon important in many different areas, from hydrodynamics and ocean circulation to planetary atmospheres or stellar physics. However, its microscopic understanding still remains challenging. Here we numerically investigate the onset of convective flow in a compressible (non-Oberbeck-Boussinesq) hard disk fluid under a temperature gradient in a gravitational field. We uncover a surprising two-step transition scenario with two different critical temperatures. When the bottom plate temperature reaches a first threshold, convection kicks in (as shown by a structured velocity field) but gravity results in hindered heat transport as compared to the gravity-free case. It is at a second (higher) temperature that a percolation transition of advection zones connecting the hot and cold plates triggers efficient convective heat transport. Interestingly, this picture for the convection instability opens the door to unknown piecewise-continuous solutions to the Navier-Stokes equations.
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Affiliation(s)
- P L Garrido
- Departamento de Electromagnetismo y Física de la Materia, and Institute Carlos I for Theoretical and Computational Physics, Universidad de Granada, Granada 18071, Spain
| | - P I Hurtado
- Departamento de Electromagnetismo y Física de la Materia, and Institute Carlos I for Theoretical and Computational Physics, Universidad de Granada, Granada 18071, Spain
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Zhao CB, Zhang YZ, Wang BF, Wu JZ, Chong KL, Zhou Q. Modulation of turbulent Rayleigh-Bénard convection under spatially harmonic heating. Phys Rev E 2022; 105:055107. [PMID: 35706158 DOI: 10.1103/physreve.105.055107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Accepted: 05/05/2022] [Indexed: 06/15/2023]
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 10^{7}≤Ra≤10^{10} and the wave number range 1≤k≤120 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 δ_{k} above which spatial modulation is negligible, the other is the inversion depth δ_{k2} below which there exists a stable inverse temperature gradient. Based on the relative thickness of the thermal boundary layer (BL) δ_{th} compared with these two length scales, the underlying modulation mechanism is physically explained and three regimes are identified: (1) an unperturbed BL regime (δ_{k}<δ_{th}), in which the modulation effect does not penetrate through the thermal BL and Nu is nearly unchanged; (2) a partially modulated BL regime (δ_{k2}<δ_{th}<δ_{k}), in which hot spots trigger more plume emissions from the thermal BL, resulting in Nu enhancement; and (3) a fully modulated BL regime (δ_{th}<δ_{k2}), in which the stable temperature inversion over the cold phases begins to affect convective flows, which alters the trend of Nu enhancement.
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Affiliation(s)
- Chao-Ben Zhao
- 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
| | - Yi-Zhao Zhang
- 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
| | - Bo-Fu Wang
- 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
| | - Jian-Zhao Wu
- 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
| | - Kai Leong Chong
- 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
| | - 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
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McCormick K. Temperature Oscillation Increases Heat Flow. PHYSICS 2022. [DOI: 10.1103/physics.15.49] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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Urban P, Hanzelka P, Králik T, Musilová V, Skrbek L. Thermal Waves and Heat Transfer Efficiency Enhancement in Harmonically Modulated Turbulent Thermal Convection. PHYSICAL REVIEW LETTERS 2022; 128:134502. [PMID: 35426695 DOI: 10.1103/physrevlett.128.134502] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 12/27/2021] [Accepted: 02/25/2022] [Indexed: 06/14/2023]
Abstract
We study turbulent Rayleigh-Bénard convection over four decades of Rayleigh numbers 4×10^{8}<Ra<2×10^{12}, while harmonically modulating the temperatures of the plates of our cylindrical cell. We probe the flow by temperature sensors placed in the cell interior and embedded in the highly conducting copper plates and detect thermal waves propagating at modulation frequency in the bulk of the convective flow. We confirm the recent numerical prediction [Yang et al., Phys. Rev. Lett. 125, 154502 (2020)PRLTAO0031-900710.1103/PhysRevLett.125.154502] of the significant enhancement of the Nusselt number and report its dependence on the frequency and amplitude of the temperature modulation of plates.
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Affiliation(s)
- P Urban
- The Czech Academy of Sciences, Institute of Scientific Instruments, Královopolská 147, 612 64 Brno, Czech Republic
| | - P Hanzelka
- The Czech Academy of Sciences, Institute of Scientific Instruments, Královopolská 147, 612 64 Brno, Czech Republic
| | - T Králik
- The Czech Academy of Sciences, Institute of Scientific Instruments, Královopolská 147, 612 64 Brno, Czech Republic
| | - V Musilová
- The Czech Academy of Sciences, Institute of Scientific Instruments, Královopolská 147, 612 64 Brno, Czech Republic
| | - L Skrbek
- Charles University, Faculty of Mathematics and Physics, Ke Karlovu 3, 121 16 Prague, Czech Republic
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