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Full-Text Articles in Physical Sciences and Mathematics
Convectively Driven Shear And Decreased Heat Flux, David Goluskin, Hans Johnston, Glenn R. Flierl, Edward A. Spiegel
Convectively Driven Shear And Decreased Heat Flux, David Goluskin, Hans Johnston, Glenn R. Flierl, Edward A. Spiegel
Hans Johnston
We report on direct numerical simulations of two-dimensional, horizontally periodic Rayleigh–Bénard convection between free-slip boundaries. We focus on the ability of the convection to drive large-scale horizontal flow that is vertically sheared. For the Prandtl numbers (Pr) between 1 and 10 simulated here, this large-scale shear can be induced by raising the Rayleigh number (Ra) sufficiently, and we explore the resulting convection for Ra up to 1010. When present in our simulations, the sheared mean flow accounts for a large fraction of the total kinetic energy, and this fraction tends towards unity as Ra→∞. The shear helps disperse convective structures, …
A Comparison Of Turbulent Thermal Convection Between Conditions Of Constant Temperature And Constant Flux, Hans Johnston, Charles R. Doering
A Comparison Of Turbulent Thermal Convection Between Conditions Of Constant Temperature And Constant Flux, Hans Johnston, Charles R. Doering
Hans Johnston
We report the results of high-resolution direct numerical simulations of two-dimensional Rayleigh-Bénard convection for Rayleigh numbers up to Ra=1010 in order to study the influence of temperature boundary conditions on turbulent heat transport. Specifically, we considered the extreme cases of fixed heat flux (where the top and bottom boundaries are poor thermal conductors) and fixed temperature (perfectly conducting boundaries). Both cases display identical heat transport at high Rayleigh numbers fitting a power law Nu≈0.138×Ra0.285 with a scaling exponent indistinguishable from 2/7=0.2857… above Ra=107. The overall flow dynamics for both scenarios, in particular, the time averaged temperature profiles, are also indistinguishable …