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

• Published in: Experimental heat transfer 2023-04, Vol.36 (3), p.376-403
• Main Authors: Bharti, Omprakash S., Saha, Arun K., Das, Malay K.
• Format: Article
• Language: English
• Subjects: Boussinesq approximation; Convective flow; critical Rayleigh number; Enclosures; Free convection; numerical simulation; Particle image velocimetry; schlieren-PIV method; Steady flow; Temperature distribution; unsteady flow
• ISSN: 0891-6152; 1521-0480
• DOI: 10.1080/08916152.2022.2039329

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 × 10 7 ≤ Ra ≤ 5 × 10 8 ). 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 × 10 5 ≤ Ra ≤ 5 × 10 8 ), 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 × 10 5 ≤ Ra ≤ 1 × 10 8 ) while the critical Ra, at which the steady flow becomes unsteady, lies between 1 × 10 8 and 5 × 10 8 . The critical Ra from the experiments is found to lie between 4 × 10 8 and 5 × 10 8 . Also, the three-dimensionality effect on large-scale temperature field is found to decrease as Ra increases.