2020/05/05 by Qi Wang, Kai Leong Chong, Wang, Qi +7 · 1 citation
Engineering · Environmental Science · #Fluid Dynamics and Turbulent Flows #Plant Water Relations and Carbon Dynamics #Fluid Dynamics and Vibration Analysis
paper · pdf · doi:10.48550/arxiv.2005.02084
Rayleigh-Bénard (RB) convection with free-slip plates and horizontally periodic boundary conditions is investigated using direct numerical simulations. Two configurations are considered, one is two-dimension (2D) RB convection and the other one three-dimension (3D) RB convection with a rotating axis parallel to the plate. We explore the parameter range of Rayleigh numbers Ra from 107 to 109 and Prandtl numbers Pr from 1 to 100. We show that zonal flow, which was observed, for example, by Goluskin et al. J. Fluid. Mech. 759, 360-385 (2014) for Γ=2, is only stable when Γ is smaller than a critical value, which depends on Ra and Pr. With increasing Γ, we find a second regime in which both zonal flow and different convection roll states can be statistically stable. For even larger Γ, in a third regime, only convection roll states are statistically stable and zonal flow is not sustained. For the 3D simulations, we fix Ra=107 and Pr=0.71, and compare the flow for Γ=8 and Γ= 16. We demonstrate that with increasing aspect ratio Γ, zonal flow, which was observed for small Γ=2π by von Hardenberg et al. Phys. Rev. Lett. 15, 134501 (2015), completely disappears for Γ=16. For such large Γ only convection roll states are statistically stable. In between, here for medium aspect ratio Γ= 8, the convection roll state and the zonal flow state are both statistically stable. What state is taken depends on the initial conditions, similarly as we found for the 2D case.