要約

A numerical study is made of the self-sustained oscillations and bifurcations of mixed convection in a two-dimensional multiple ventilated enclosure. These two mechanisms of buoyancy [Richardson number (Ri) is a measure] and forcing by the inlet flow [Reynolds number (Re) is a measure] lead to complex interaction. The results are obtained for a range of the Richardson number from 0 to 20 at Pr = 0.701, and the Reynolds number is given in a range of 1000-2500. The results show that depending on the values of Re and Ri, the flow inside the enclosure may be steady, periodic, nonperiodic, or turbulent; and the velocity and temperature fields may show an asymmetric structure for certain combinations of the control parameters, even though the boundary conditions are steady and symmetric. Further, certain features of nonlinear dynamical systems such as bifurcation, self-sustained oscillations are also seen. The simulation results also show that when the inlet flow angle θ (θ) equals 70° (proved to be the most unstable among four given values of θ) the enclosure loses its stability at Re = 1500, Ri = 0, and Re = 1000, Ri = 0.5; transforms into periodic oscillatory flow via the steady symmetry breaking Hopf bifurcation; and becomes nonperiodic-unstable at Re = 2000