Numerical investigation of turbulent natural convection heat transfer and air flow in vaulted and domed roofed buildings

This numerical study investigates turbulent natural convection air flow (Pr = 0.71) and heat transfer in structures with vaulted and domed roofs for a wide Rayleigh number range (10^8–10^13) and two arch/dome aspect ratios (h/H = 0.25 and 0.5) in order to better understand the effects of two heating scenarios (wall heating-S1 and floor heating-S2). The governing equations are solved by ANSYS-Fluent 2020 R1 software. The RNG k-ε turbulence model with the Boussinesq approximation is adopted to model the buoyancy-driven flow. For vaulted structures, the isotherms and streamlines are produced for h/H ratio and Ra numbers to visualize and interpret the flow and heat transport. Similarly, to help visualize the fluid and heat transport in domed structures, the visual aids such as stream traces, and isosurfaces of the dimensionless temperature, turbulent kinetic energy, and dissipation rates were obtained and presented for h/H ratio and Ra number ranges covered. Besides the vaulted and domed structures, the mean Nusselt numbers for square and cubic boxes were also computed to enable comparisons. For the vaulted and domed structures, the Nusselt number correlations were developed as functions of Ra number and h/H for both heating scenarios. In vaulted structures, compared to flat-roof enclosures, the mean Nusselt numbers for Ra = 10^13 depict increases up to 85% and 67% in S1 and 8.5% and 21% in S2 for h/H = 0.25 and 0.5, respectively. In domed structures, the mean Nusselt numbers similarly depict increases up to 9.9% and 5.4% in S1 and 10% and 8.4% in S2 for h/H = 0.25 and 0.5, respectively.