| dc.description.abstract | Turbulent natural convection in cylindrical enclosures is a significant phenomenon in most engineering and industrial
applications, such as thermal insulation, electronics cooling, and building climate control. An explicit understanding of the
transition of flow from laminar to turbulent and its influence on heat transfer is essential in terms of optimizing system
performance. The study solves two major objectives: Model the governing equations of turbulent natural convection in a
cylindrical enclosure using K-Omega turbulence model, and compute the effective thermal conductivity, turbulence intensity,
and streamline distribution as functions of Rayleigh number. The enclosure that has been considered is an insulated vertical
sidewall enclosure with a top wall at 298 K and a bottom wall at 320 K. The mathematical formulation consists of the
Reynolds-Averaged Navier–Stokes (RANS) equations, the energy equation, and transport equations for turbulence, subject to
the Boussinesq approximation to model buoyancy. A low-Reynolds-number two-equation model is used to model turbulence
close to the walls, and the Prandtl number is set to 0.71 to model air as the working fluid. Numerical solutions are achieved by
the use of the finite difference technique and verified by simulations done in ANSYS Fluent. The simulation identifies how
structures flow and mechanisms of heat transfer change with increasing Rayleigh numbers. At small Rayleigh numbers, the
flow is steady, conduction-dominated, with smooth streamlines and little or no turbulence. It is noted that as the Rayleigh
number increases, buoyancy-driven convection becomes more significant, leading to the formation of vortices, intensified
turbulence, and enhanced mixing, which collectively improve the effective thermal conductivity. The streamline distribution
becomes increasingly complex and disordered, reflecting the transition to chaotic flow. These results demonstrate that the
Rayleigh number is a key parameter influencing thermal and flow characteristics in cylindrical enclosures. The study provides
practical insights in designing and optimizing systems involving buoyancy-induced turbulent heat transfer. | en_US |
