Experimental Analysis of Unsteady Natural Convection Around a Horizontal Heater in a Water-Filled Enclosure

Particle Image Velocimetry (PIV) measurements are carried out to analyse the buoyancy-induced flows originating from a horizontal heated cylinder enclosed in a square-sectioned cavity, filled with distilled water. A description of the experimental setup is provided, alongside with a discussion of critical issues in the measurement process and thermal conditioning of the system. Repeatability of the tests is assessed in both steady-state and unsteady conditions. Results are provided for four different values of the leading parameter, the modified Rayleigh number Raq, ranging from 1:48 104 to 8:62 104. The system is witnessed to undergo a transition from steady-state, laminar flow to unsteady oscillatory flow. The evolution of the flow throughout the bifurcation is described by velocity profile plots and 2D field visualizations. The suitability of the technique for the analysis of transitional natural convection regimes is confirmed by the quality of the experimental data, and the agreement with comparative numerical computations.