Experimental study on the flow behavior of a finite dense fluid release at upstream from cubic building face for different Richardson numbers*

The dispersion of heavy polluted gas has become of great interest as an ever-increasing number of individuals live in big cities. Hence, it is important to have a better understanding over heavy gas dispersion in urban areas. To this end, this study illustrates the characteristics behavior of the heavy/dense gas dispersion at the wake of a cubic building for Richardson number (Ri) ranging from 5 to 40. A series of small-scale experiments of the dispersion was carried out in a water flume following the same geometry of the Thorney Island Phase II Trials 26-29. The tracer gas was released instantaneously at different locations upstream from the building face. Light-Induced Fluorescence (LIF) technique was used to visualize the flow in the wake and Acoustic Doppler velocimetry (ADV) was used to measure velocity profile. This study measured the time taken for the heavy gas to reach the building wake, the cloud height formed by the release on the leeward face of the building, and the time taken to flush the gas out of the building wake for the different Ri and release distance. It is observed that a building block significantly impacts the behavior of the dense gas movement at its wake. The results showed that the maximum concentration difference at the wake is low with the high velocity of the ambient fluid and high with the lower velocity. More phenomena of the flow were analyzed and will be discussed in this study.