Synchronized PIV-PLIF experiments on mixing in confined space by a decelerating, turbulent, buoyant jet

Abstract

Turbulent jets of miscible uids of di erent densities are commonly observed in natural and industrial ows. In these type of ows, the di erence in densities causes a buoyancy driven convection along with the momentum driven ow. In the case of miscible uids, the mixing causes variations in density and a ects the properties of the jet. Understanding the behaviour of buoyant jet ows and mixing in con ned space would help in the design of buildings in improving natural ventilation, especially during re or gas leakage. Understanding the ow and mixing patterns and enhancing the natural ventilation would help in cases like re or gas leakage as power shut-down during emergencies would stop forced ventilation. The present work aims at studying the patterns of ow and mixing through experiments in a con ned space with a jet source of unsteady buoyancy ux. The experiments were conducted in simple con nements that replicate a wall or roof opening. Approximately 50 ow visualization experiments were conducted on scaled models of a room with a jet source of buoyancy and ow outlets that resemble windows or roof openings. The air-smoke pair was replaced by water-salt solution pair to scale down the dimensions of the experiment set up. The con nement is located at the near- eld of the jet. The results from the project may be used in optimizing the ventilation design to maintain su cient oxygen levels inside buildings for safe evacuation and prevent su ocation from smoke caused by re. The experiments were conducted using synchronized Particle Image Velocimetry (PIV) and Planar Laser Induced Fluorescence (PLIF) techniques to get the high resolution, simultaneous, velocity and concentration elds. The design of the experiment set up, instrumentation, experiment techniques and analysis methods are discussed in the report. Di erent sets of experiments by varying the ow rate and the position of outlet have been conducted using simultaneous PIV-PLIF technique. A detailed description of velocity and density pro les along the ow are presented.