Experimental study on natural convection in a cylindrical envelope with an internal concentric cylinder with slots

Detailed experimental analysis is presented for natural convection in a cylindrical envelope with an internal concentric cylinder with slots. For the case of φ = 90°, where φ is the angle of slot opening from the vertical axis, and two types of temperature fields were obtained at the same Rayleigh number of 5.49 × 104. It is demonstrated that the steady state solution was not unique and was dependent on the initial conditions, which is related to static bifurcation. For the two cases of φ = 0° and φ = 45°, the natural convection turned to unsteady, although the boundary conditions were not time-dependent. The most obvious oscillation regions were above the inner cylinder, and the amplitude increased with increasing Rayleigh numbers. The nonlinear characteristic of these problems led to the multiplicity of convections and self-sustained oscillation.