Simultaneous measurements of temperature and velocity fluctuations in a double stream-twin jet air curtain for heat confinement in case of tunnel fire

Abstract

This paper briefly describes laboratory experiments performed to investigate the ability of air curtain arrangements to prevent heat propagation in case of fire in a corridor-like geometry. The arrangement considered in this study is a system based on two twin plane jets. Simultaneous measurements of temperature and velocity were performed with fine thermocouples and a Laser Doppler Anemometer (LDA), respectively. The jet Reynolds number based on the average discharge velocity U 0 and the total width 2 e of the investigated twin-jet was about 1000. Information about the spatial distributions of the one-point correlations u θ ¯ and v θ ¯ is provided. Results show that it is the longitudinal turbulent heat flux that predominantly contributes to turbulent transfers. Transfer rates increase on approaching the impingement region. The jet can be split into three regions: for x/2 e < 5 one can still distinguish the separate influence of the two initial jets composing the curtain: for 5 < x/2 e < 8.5, a transition zone exists where the two initial jets merge. In this region, transfers are not necessarily much higher. They are expected to intensify closer to the wall due to strong mixing in the impingement region.