Author(s): Fardin Sharif; Amir Azimi

Linked Author(s):

Keywords: Swirling jets; Slurry jets; Aspect ratio; SPOD; Sand concentration

Abstract: A series of laboratory experiments was conducted to investigate the effects of swirling number on the flow properties of vertically discharged sand-water swirling jets in stagnant water. The effects of swirling motion on the evolution of particles, mixing properties, and the coherent structure of sand-water swirling jets were studied. A swirling cylinder was designed with an inner diameter of 32 mm surrounded by six inner spiral channels with 4 mm inner diameters. Sand particles with a median diameter of 0.507 mm and initial volumetric concentration of 60% were added to water and the mixture was released through a 6 mm nozzle. Different mixture discharges were tested to provide a swirling number ranging between 0.45 and 0.60. The instantaneous velocity and concentration of sand particles were measured by employing an advanced optical fiber probe (PV6). In addition, image analysis was performed to study the flow characteristic of swirling jets. The frequency histogram of sand concentration indicated that the instantaneous volumetric concentration of particles increased by increasing swirling intensity. In the Processing Vortex Core (PVC) region, velocity fluctuations increased by increasing the swirling number. The Power Spectral Density (PSD) analysis of sand concentration for sand-water swirling jets indicated that increasing the swirling motion increased the frequency of dominant coherent structure in the PVC region. The Spectral Proper Orthogonal Decomposition method (SPOD) was used to characterize the evolution of unsteady inter-scale coherent structures and extract the energy spectra in sand-water swirling jets. The SPOD spectra analysis revealed that the first two modes of the low-frequency range had a considerable portion of the turbulent kinetic energy and an adverse correlation was found between the strength of vortex shedding and swirling number.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022694

Year: 2022