Periodicity and chaos of thermal convective flows in annular cylindrical domains using the method of isolation by spectral expansions.

The dynamical and chaotic behaviors of natural convection flow in the semi-annular and full-annular cylindrical domains are studied using the method of isolation by spectral expansion. For each of the flow cases, spectral models with different orders are obtained and dynamical characteristics of the flow are investigated using numerical simulations. For the semi-annular case of study, results reveal that in all the generated spectral models, chaotic solution appears, but the onset of chaos between each system requires different set of control parameters. Bifurcation diagrams are provided for all the systems which show the ranges of periodic and chaotic behavior of the flow. Strange attractors are captured for all the systems with different orders. For the lowest-order model, a Lorenz-like attractor is produced, which has two distinguishable scrolls similar to Lorenz's famous attractor and for the other high-order models, the shape of strange attractor gets different. For the full-annular case of study, the physical characteristics of the flow are obtained. The results show that the produced thermal plume on the top of annulus gets higher fluctuations as the flow Rayleigh number gets higher. At a specific Rayleigh number, the flow behavior gets completely unstable, which shows a transitional regime change. At this state of flow, the domain is dominated by several vortices. [Display omitted] • The dynamical behavior of natural convection in a cylindrical annulus is studied. • Spectral models with different orders are obtained for the fluid flow system. • Numerical simulations are made in order to capture the flow field of study. • Bifurcation diagrams are provided for the high-order spectral models of flow system. • The flow transition from a stable steady to an unstable point is discussed. [ABSTRACT FROM AUTHOR]