Measurements of spray-plume interactions for model validation

Abstract

Fire suppression using automatic fire sprinklers is tremendously successful in reducing loss of life and property in the event of a fire. With the increasing computing power available, as well as the spread of performance-based design methods, the ability to accurately model spray dispersion and suppression is desirable. In this study, experiments were conducted to quantify spray dispersion and spray-plume interactions for model validation. Numerical simulations of these spray interactions were performed using FireFOAM. These simulations were distinguished by the use of comprehensive highly-resolved initial spray measurements to generate the numerical spray. The experimental Sprinkler Array Facility (SAF) used in this study consisted of a centrally located, well-characterized, forced air jet (simulating the updraft from a real fire plume) providing a challenge to the spray. Reliable model boundary conditions were established from detailed measurements of the air jet injection velocities and detailed measurements of the initial spray using the Spatially-resolved Spray Scanning System (4S). Measurements of volume flux as well as optical measurements of drop size and velocity were obtained at various locations within the air jet. Four flow conditions were investigated with the intent of providing model validation data; close and far sprinkler spacing, each with quiescent air and strong jet conditions. The strong jet was capable of overwhelming the smallest drops within the spray, reversing their direction, and reducing the volume flux at the floor. Computational simulations (informed by detailed initial spray measurements) demonstrated good agreement with the spray dispersion and plume penetration experiments.