SCALE MODEL VISUALIZATION OF SMOKE WAVE INSTABILITY THROUGH CEILING SMOKE AND HEAT VENTS

摘要

The aim of this study is to illustrate the usefulness of physical models in reduced scale in order tornexamine the smokeflow field due to a fire induced scenario inside an enclosed space having ceilingrnvents. The possible occurrence of smoke wave instability through ceiling smoke and heat naturalrnvents is investigated and visualized. Starting from the “hot” fire scenario in the real scale enclosure,rnby applying the Italian national standard UNI 9494 dealing with the design of smoke and heat naturalrnvents, this study moves to an experimental set-up in which the “hot” fire and smoke currents in thernenclosure are replicated by reduced scaled models. The dynamic similitude between the prototype andrnthe model has been one of the primary concerns of this study, so to guarantee as best as possible thernresemblance and the development of the same type of smokeflow dynamics through the enclosedrnspace ceiling vents in real and in reduced scale. Two space configurations were investigated, byrnmaintaining the same overall enclosure topology but varying the number, dimension and positioningrnof the natural ceiling horizontal vents and the area for fresh air vertical inlets on two end sides.rnDepending on the interactions among the fire source and the vents and inlets available for ventingrnheat and smoke out while sucking air in, a smoke wave appeared traveling along the ceiling in thernenclosure and developing an instability that periodically puffed smoke out of some of the ceilingrnvents. Furthermore, a CFD study was conducted to highlight this smokewave instability pattern with arnholistic approach in order to maximize benefits available from engineered physical scaling coupledrnwith computer modeling.