Characterizing Turbulent Ceiling Jet Dynamics With Salt-water Modeling

Ceiling jet dynamics are quantitatively characterized using the salt-water modeling technique. In this study, salt-water is introduced into fresh water to create an axisymmetric impinging plume and the associated stratified wall jet. This configuration models the canonical ceiling jet flow that results from impinging fire plumes. The saltwater modeling analogy is demonstrated through rigorous scaling of the governing equations and comparison of the resulting fire and salt-water source-based dimensionless quantities. With appropriate scaling, the measured concentrations in the salt-water model can be directly compared with temperatures in the fire configuration. Measurements of the mixing and dispersion in the ceiling jet region are performed using Planar Laser Induced Fluorescence (PLIF). These measurements provide quantitative visualization of the turbulent flow structure in addition to mean concentration profiles. Ceiling layer thicknesses, peak profile values, and profile shapes along the ceiling compare favorably with ceiling jet theory and data from actual fire experiments. Furthermore, turbulent flow details are revealed through the laser sheet visualization providing insight into the flow behavior and providing quantitative data for CFD code validation.