Numerical Simulations of Strong-Plume Driven Ceiling Flows

Large eddy simulations (LES) of ceiling flow driven by strong-plumes of rack-storage fires have been simulated for a range of convective heat release rates (HRR) and ceiling heights. An actual delivered density (ADD) apparatus plume generator burner setup has been modeled using buoyant diffusion flames and with the inclusion of an upstream airflow vent producing the higher plume velocities observed in rack-storage fires. Computed results for plume centerline excess temperature and velocity have been compared against experimental data. In addition to the modeled burner setup, an alternate volumetric HRR source has also been applied in the simulations. Flows under ceilings located at different heights above the ADD apparatus have been simulated. Various convective HRR plumes have been used and the resulting ceiling flow radial distributions of computed excess temperature and velocity have been compared against experimental measurements. Predicted temperature and radial velocity profiles have also been shown to agree favorably with experimental data at two depths below the ceiling heights. Comparison of ceiling layer depths have also shown good comparison with an empirical correlation.