Effect of Release Height on the Motion of Particle Cloud in Stagnant Water

A series of laboratory experiments were conducted in the Multiphase Flow Research Laboratory (MFRL) at Lakehead University to investigate the effect of release height on the motion of particle clouds produced from relatively large mass of sand particles. Sand particles with median diameters of D50 = 0.507 mm and an initial volumetric sand concentration of co = 60% were released through a 6-mm nozzle. Different release heights were tested in this study providing non-dimensional release heights ranged from η = 1 to 21. A wide range of sand masses was tested and the effect of sand mass and nozzle diameter was represented by an aspect ratio ranged between 46 and 93. The velocity fluctuations and turbulent intensity of sand particles in the cloud were calculated from the time-series data. It was found that particle velocity fluctuations increase with increasing the mass of sand particles and reducing nozzle diameter. The variations of penetration length and width of particle clouds with time were measured and the frontal velocity of particle clouds were calculated from the measurements. The characteristics of particle cloud released above the water surface were compared with that of sand particles released from the water surface as a benchmark test. For sand particles with high sand mass and small nozzle size (i.e., large aspect ratio), cloud’s width increased dramatically when sand particles were released above the water surface (i.e., η > 1). In addition, the horizontal dispersion of sand particles began earlier when sand particles were released above the water surface, and particle clouds reached the cloud’s deeper penetration length and width.