Abstract
The purpose of this numerical study is to analyze the characteristics of transition from laminar to chaotic natural convection in a fluid-filled two-dimensional, unity aspect ratio rectangular cavity with mixed thermal boundary conditions. For a medium Prandtl number fluid ( Pr ) the numerical solution of the two-dimensional Navier-Stokes momentum and energy equation with Bousinessq approximation, it is found that there are finite Rayleigh numbers Ral Ra2, and Ra3 for the onset of single-, double-, and multiple-frequency oscillatory motion at different spatial locations in the enclosure. As Ra increases, the flow exhibits a change from steady convection to periodic to quasi-periodic flow, while no period doubting is observed. The onset of strong chaos appears when Ra = 57,000 Rac. This system does not revert to steady state convection for Rac as high as 285,000. As Ra increases, various measures of chaos, such as power spectrum, Poincare sections, phase portrait, and time series of various dynamical variable signals, all show an increasing degree of characteristics of chaos,
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