Effect of Free-slip Boundaries on Flow and Heat Transport Characteristics in Two-dimensional Rayleigh-Bénard Convection

doi:10.19596/j.cnki.1001-246x.7923

Abstract

Abstract: Temperature fields in two-dimensional (2D) Rayleigh-Bénard (RB) convection with no-slip and free-slip walls were simulated with parallel direct method of direct numerical simulation (PDM-DNS) at different Rayleigh numbers (Ra) and aspect ratio numbers (Γ). Different from no-slip boundary thermal convection with random plume, free-slip boundary thermal convection eventually forms a large-scale circulation without turbulent features and temperature distributes only on four walls. Temperature distribution characteristics of time-average field near floor changes gradually for no-slip boundary but overshoot occurs for free-slip boundary. Dependences of Nusselt numbers (Nu) with Ra at Γ=1 have same scale index Nu~Ra^0.3. Free-slip boundary thermal convection enhances heat transfer. Changes of Nu with Γ are obvious in free-slip boundary thermal convection. They are in two stages. At Γ=0.5, Nu_max≈250, it is five times of Nu in no-slip boundary thermal convection.

Key words: Rayleigh-Bénard convection, free-slip boundary, large-scale circulation, enhancement of heat transport, PDM-DNS

CLC Number:

O358

HE Peng, BAO Yun. Effect of Free-slip Boundaries on Flow and Heat Transport Characteristics in Two-dimensional Rayleigh-Bénard Convection[J]. CHINESE JOURNAL OF COMPUTATIONAL PHYSICS, 2019, 36(5): 542-550.

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