Study Of Oscillation Flow In Confined Space With Openings

Enclosure fires are always considered as a key point for the science of fires. Many workshad been done on theoretical and experimental studies of fires by scholars, when the confiendenclosure exists a small vent, it will appear oscillation phenomenon through the openings.Oscillation is a regular gas reciprocating motion, which is also a common phenomenon in fire,and it is significant for fire research. Only when thermal expansion pressure is equal tobuoyancy, which is the critical state, the opening will occur obvious oscillation, at present,domestic and international research on the oscillation mostly concentrat in a small enclosurewith horizontal openings, but few for vertical openings. This thesis mainly studies when theoscillation happened and when the oscillation phenomenons come obviously duing ISO9705ROOM with vertical openings. Finally, we will fand the oscillation frequency.This thesis described the present researches about the fire with openings, summarized thekey factors affecting oscillation and associated calculations. Accoording to the theoreticalanalysis, this thesis finally selected ten different opening sizes to simulate which had differentopening positions. The simulation software is FDS(Fire Dynamics Simulator). A, B, C, Dmodels were selected in four different vertical opening height, opening size uniform as0.8m×0.5m, simulation results show that: the bottom-opening model (D model) most prone to thephenomenon of oscillation and the oscillation frequency is about0.45Hz. The last six kinds ofmodels all had the bottom openings, by changing the opening sizes, do further research onoscillation phenomenons, draw the appropriate conclusions: not all bottom-opening modelscan occur oscillation phenomenons, the size of the openings is directly linked with theoscillation, what’s more, the oscillation intensity are different when the model have the sameopen area but different aspect ratio.According to simulation results, we do experiments for A, B, C models which conductedin the ISO9705standard room. Compared with the simulation, the experiments have the sameexperimental conditions. Experimental results and simulation results are basically the same, A,B no-oscillation phenomenon, C model occur oscillations which are unstable.The obtained results can provide a reference for the study of enclosure fire with verticalopenings. It has practical significance for understanding the oscillation phenomenon.