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

Rayleigh–Bénard convective flows in rotating cylindrical domain with three value of aspect ratios, ϵ=0.05,0.1, and 0.2 are investigated using large-eddy simulation with dynamic Smagorinsky closure to study the genesis of large scale vortex with poloidal circulation. This vortex is similar to a tropical cyclone in structure, and hence it is called a tropical cyclone-like vortex (TCLV). The Ekman number, which measures rotational influence, and the 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 simulation results identify two characteristic timescales for vortex evolution: intensification time ti∼Ω−1 Ret1/2 and saturation time ts∼Ω−1 Et−1/2, where Ω is the background rotation rate and, Ret and Et are turbulent Reynolds and Ekman numbers, respectively. The TCLV with eye and eyewall is observed to form only when ti<ts, which gives a condition 2 ϵRo≲1, where Ro is the global Rossby number, for the TCLV formation. The effects of moisture, latent heat release, and wind shear are excluded here, so the above condition is a purely hydrodynamic one.