Large-eddy simulation of tropical cyclone-like vortex in confined-rotating convection

Abstract

Rayleigh-B´enard convective (RBC) flows in rotating cylindrical domain with three value of aspect ratios, ϵ = 0.05,0.1 and 0.2 are investigated using large-eddy simu- lation (LES) with dynamic Smagorinsky closure to study the genesis of large scale vortex with poloidal circulation. This vortex is similar to a tropical cyclone in struc- ture and hence it is called as tropical-cyclone-like vortex (TCLV). The Ekman number measuring rotational influence and Rayleigh number related to thermal forcing are varied systematically over six and sixteen orders of magnitude respectively. Three values of Prandtl number, 0.025, 0.1 and 0.7, are considered. The analyses of simula- tion results identify two characteristic timescales for vortex evolution: intensification time ti ∼Ω−1 Re1/2 t and saturation time ts ∼Ω−1 E−1/2 t , where Ω is the background rotation rate and, Ret and Et are turbulent Reynolds and Ekman numbers respec- tively. The TCLV with eye and eyewall is observed to form only when ti