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Abstract: The sequence of bifurcations leading to the onset of chaotic flow is determined numerically, for the case of a buoyant plume arising from a horizontal cylinder, centred in a square-sectioned, air-filled enclosure. In the frame of the 2D assumption, a specifically-developed high resolution simulation procedure is adopted, with the aim of achieving a detailed description of the transitional dynamics occurring within the system. A large number of simulations are performed, allowing for an accurate estimate of the critical values of the main system parameter, the Rayleigh number Ra, at which bifurcations occur. A single value of the geometric aspect ratio A of the system is considered, for which transition is found to be characterized by an imperfect period-doubling cascade, an uncommon behaviour in thermofluid systems. Peculiarities of the route to chaos are highlighted, such as the existence of a window of quasiperiodic flow, and the detection of high-order period orbits. [Copyright &y& Elsevier]

Abstract: The competition of buoyancy with electromagnetic body forces is examined numerically in terms of flow structure transitions by means of a two-dimensional unsteady, finite volume model. In the present numerical study, we consider a low-Prandtl liquid metal heated by Joule effect in a rectangular cavity with an aspect ratio of 2. The direct current provides heat to the process medium by a pair of plate electrodes, located at the cavity sidewalls. The simulations have been carried out for fixed values of the Prandtl number, Pr = 0.01, and of the Rayleigh number, Ra = 1.5 × 104, while the Hartmann number, Ha, varies from 0 to 104. The variation of Ha is found to have considerable effects on flow patterns and heat transfer inside the cavity. Several hitherto unknown flow structures are revealed, increasing in complexity with increasing Ha. Amongst the oscillatory flows predicted, intermittency and chaos are detected. The effect of Ha on the overall heat transfer performance of the system is also assessed. [Copyright &y& Elsevier]