CFD analysis of thermal plume behavior under diagonal heat source orientation.

Confined fire environments in marine and industrial compartments present serious safety challenges due to rapid heat accumulation, restricted ventilation, and complex buoyancy-driven flow behavior. Accurate prediction of propagation of heat and development of plume is important for the effective and efficient design of thermal detection and mist-based fire suppression systems. In the present study, a 2D transient Computational Fluid Dynamics analysis has performed to investigate buoyancy-driven heat transfer generated by heat source of 0.5 m diameter maintained at 450 °C inside a closed container of dimensions 2.6 m × 2.6 m. The air was considered as the working fluid, and natural convection was modeled to capture plume rise, entrainment, and thermal stratification effects. The heat source was sequentially positioned at four diagonal locations: D1 (0.65 m, 0.65 m), D2 (1.95 m, 0.65 m), D3 (1.95 m, 1.95 m), and D4 (0.65 m, 1.95 m) to assess the influence of source orientation relative to enclosure (Container) boundaries. The numerical methodology incorporates mesh-independence verification, transient time-step control with Courant numbers maintained below 2, appropriate turbulence modeling, and strict mass conservation to ensure numerical accuracy. The simulation reveals the formation of strong buoyancy-driven thermal plumes with peak velocities in the range of 0.9-1.3 m/s. Lower heat source configurations produce tall vertical plumes, while upper source placements result in early plume impingement and the development of ceiling jets, significantly enhancing lateral heat transport. Temperature and density fields indicate localized high-temperature zones near the heat source, with air density reducing to approximately 0.5-0.7 kg/m3 within plume cores. Turbulent kinetic energy reaches peak values of the order of 10-2 m2/s2 along plume shear layers and ceiling interaction regions, reflecting intense mixing. Pressure and mass imbalance analyses confirm stable transient behavior, with mass imbalance remaining within ± 10-⁷ kg/s. The findings present design trends under idealized enclosed conditions, which may support future development of fire detection and suppression strategies for marine and industrial compartments after further validation under realistic operating conditions.