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Natural convection is happening due to the temperature field variations in the river. Owing to the presence of various plants the river bottom becomes hot, the plume arises owing to the buoyancy effect and transports vertically. In this paper, transition to chaos in a V-shaped cavity is numerically studied by considering a large range of Rayleigh numbers (Ra = 100 – 106) with the Prandtl number, Pr = 7.0 and the aspect ratio, A = 0.5. A set of bifurcations can happened with the increase of Ra, where a Pitchfork bifurcation from symmetric to asymmetric state and a Hopf bifurcation from steady to unsteady state are included. The critical Rayleigh numbers for all the bifurcations have been confirmed by a great number of numerical tests.The spectral analysis with fundamental frequency has been investigated. [ABSTRACT FROM AUTHOR]

Transient natural convection is common in nature such as in a valley. In this paper, transient flows in a valley shaped triangular cavity initially filled with stratified water are investigated using scaling analysis and numerical simulations. The development of the flow on the inclined thermal wall from start-up to a steady-state has been described and discussed. The scaling relations are derived for the thickness, velocity, transitional time and Nusselt number of the thermal boundary layer dependent on the Rayleigh number and the stratified parameter. Moreover, corresponding numerical results are consistent with the scaling results. [ABSTRACT FROM AUTHOR]