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 dense polluted gas has become of great interest as an ever-increasing number of individuals live in big cities. Hence, it is important to understand dense gas dispersion in urban areas better. To this end, this study illustrates the characteristics behavior of the dense gas dispersion at the wake of a cubic building for Richardson number (Ri) ranging from 1 to 33. A series of small-scale experiments were carried out in a water channel following the same geometry of the Thorney Island Phase II Trials 26-29. Salt water was used as the dense gas and it 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 the 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 distances. It is observed that a building block significantly impacts the behavior of the dense gas movement in its wake. Initially, the dense fluid did not enter the building wake and flowed over and around the block. The dense fluid, however, later entered the wake; it was drawn upstream to the leeward face of the block and pushed up towards the top of the building.