Investigation of the transition of natural convective flow of water in a differentially heated cubic enclosure

Abstract

ABSTRACT The present study aims at the investigation of the transition of the natural convective flow in a water-filled differentially heated cubic enclosure. The schlieren-particle image velocimetry (PIV) system has been developed and employed for simultaneous measurement of ray-averaged velocity and temperature fields from transient schlieren images for distinct Rayleigh number (Ra) (1 × 107 ≤ Ra ≤ 5 × 108). The experimentally obtained results have been compared with three-dimensional computational results. The three-dimensional incompressible simulations are carried out for a wide range of Ra (1 × 105 ≤ Ra ≤ 5 × 108), treating the density difference using Boussinesq approximation. The results from present simulations show that the flow is found steady in the range of Ra (1 × 105 ≤ Ra ≤ 1 × 108) while the critical Ra, at which the steady flow becomes unsteady, lies between 1 × 108 and 5 × 108. The critical Ra from the experiments is found to lie between 4 × 108 and 5 × 108. Also, the three-dimensionality effect on large-scale temperature field is found to decrease as Ra increases.