Boundary Effects of Vertical Buoyant Jets in a Stagnant Fluid in a Crossflow

Abstract

This study includes an experimental study of a buoyant jet in an open channel. For this reason experiments to measure the mean axial velocity at the centreline of a buoyant jet which is discharged vertically upwards from a source, into a denser fluid (water) contained in an open channel a) without flow and b) into flowing environment, were performed. The presence of a buoyant jet is studied experimentally using 2D Particle Image Velocimetrer (PIV). For the flow visualization of the buoyant jet, the water, was dyed with either rhodamin (red color) or fluorescein (green color), aiming to the best appearance of the buoyant jet field. The velocity fields of the buoyant jet were determined with the analysis of a lot of pairs of photographs in each experiment. These fields were used to quantify the behaviour of the buoyant jet in the surrounding fluid (salt water) with several densities and flow depths. Also were used to quantify the different behaviour of the buoyant jet into flowing environment in comparison to the behaviour of the buoyant jet without flow. Results show that the depth and density of salt water can affect the flow dynamics. Flow velocity is reduced with the increase of the depth of salt water, due to the proximity to the free surface, while an increase in the salt density increase the buoyant forces and hence the velocity rate. Also the presence of salt water can affect the flow dynamics of the buoyant jet in different way into flowing environment in comparison to the buoyant jet without flow. © 2019, The Society for Experimental Mechanics, Inc.