Numerical Investigation of the Influence of the Initial Momentum and Buoyancy at the Plume Source on the Ceiling-Jet Properties

摘要

Large-eddy simulation results are presented for ceiling-jets. The CFD (Computational Fluid Dynamics) results have been obtained with FireFOAM 2.2.x [1]. A range of simulations have been carried out, keeping the 'heat release rate' of the issued hot air constant, but varying the mass flow rate and inlet temperature. The maximum velocity observed beneath the ceiling is illustrated to scale linearly with the maximum velocity on the centerline in case of a momentum-driven jet, while it scales with the buoyancy flux at the inlet in buoyancy-driven flows. This explains why correlations, based on buoyancy driven flows (i.e., natural fires), do not match the velocity evolution, obtained from experiments that are not purely buoyancy driven.