Experimental characterization of the entrained droplet velocities into a submerged gaseous jet

Abstract

The study of submerged gaseous jets injected into stagnant water pools began in the 70s caused by the fact that they are commonly found in many industrial processes and engineering applications, such as underwater propulsion, metallurgical and chemical processes or nuclear reactors. Consequently it is important to be able to characterize these processes. The low air-water density ratio and the aggressiveness of the pool discharge process result in very complicated flow structures, which are inherently unsteady and turbulent. This poses a major challenge for the measurement of the various parameters involved in the discharge of gaseous submerged jets. Experimental studies of round turbulent air jets submerged in stagnant water are described in this paper. In particular, the entrained droplet velocity, which is crucial for the characterization of the jet, was determined. The experiments were performed using a water tank equipped with an air injector. A high speed camera in conjunction with Particle Image Velocimetry (PIV) techniques was used to measure the velocity of the entrained droplets during jet spreading. Results indicate that the droplet velocity distribution follows a decreasing exponential function. Moreover, the Reynolds number at the injector nozzle was used to develop a correlation linking the initial jet properties and the mean velocity of the entrained droplets. This work represents a new step towards a better understanding of the behavior of submerged gas jets injected into aqueous mediums. The velocity of the entrained droplets was determined, both its mean and distribution function. The extension of the present work to different nozzle diameters and aqueous mediums properties will be addressed in an upcoming paper.