Experimental Investigation of Particle-Flow Interaction in Turbulent Channel Flows

• Author / Creator

  Ahmadi Jokani, Farzad

• The transportation of mixtures of particles and liquids using slurry pipelines plays a crucial role in the petroleum and mining industries. Slurry pipeline flows are typically turbulent and the presence of the particulate phase results in pipe wear and increased pumping cost. As a result, slurry pipeline design and operation relies on analysis and modeling of turbulent two-phase flows. The main objective of this research is to study the transport and dispersion mechanism of particles in particle-laden turbulent flows. To achieve this goal, a series of experimental studies were performed in a horizontal turbulent channel flow. The research started by investigating the effect of the flow Reynolds number (Re), particle size, and volumetric concentration of the solid phase on the turbulence statistics of the particles and the liquid carrier phase. A combined two-dimensional particle tracking velocimetry (PTV) and particle image velocimetry (PIV) was used to obtain the instantaneous velocity of the glass beads and liquid phase. The PTV results indicated that the turbulence intensity of the particulates decreases with increase of Stokes number (St). It was also observed that the turbulence modulation of the liquid phase depends on the particle Reynolds number (Rep). The turbulence intensity of the liquid phase augmented when Rep was large enough to produce vortex shedding.
  To study the interaction between the particles and turbulent events, an experiment was conducted to simultaneously measure the velocity of particles and the carrier liquid phase. Time-resolved three-dimensional PTV (3D-PTV) method based on shake-the-box algorithm was employed in this study. A conditional sampling of the beads and their surrounding fluid, based on the bead wall-normal motion, showed that the beads ascending from the bottom wall were mostly located within ejection motions of the fluid. However, the beads descending to the bottom wall did not indicate any correlation with the streamwise fluid velocity.
  Distribution of the glass beads in the near-wall region of a horizontal turbulent channel flow was studied to investigate the effect of different particle transport mechanisms. In addition to the gravitational settling and turbulence dispersion, it was identified that shear-induced lift, particle-wall lubrication, and inter-particle collisions affect the distribution of the beads. The shear-induced lift force was effective at larger Re and smaller concentrations, and tended to create a core-peaking profile of particle concentration. The number of interparticle collisions became larger for the denser suspensions, which confined the beads to a region of high concentration near the wall.
  The simultaneous velocity of the beads and their surrounding fluid was used to calculate the quasi-steady and viscous-unsteady forces in turbulent channel flow. It was observed that the viscous-unsteady force is significant in turbulent solid-liquid flows. This force is negatively correlated to the net force on the beads. It tends to reduce the magnitude of the acceleration. Investigation of the quasi-steady force showed that this is the main source of acceleration in the streamwise direction. The importance of this force reduced in the transverse directions.

• Subjects / Keywords

  • Slurry Flow
  • Particle-Laden
  • Turbulent Flow
  • Particle Image Velocimetry
  • Particle Tracking Velocimetry

• Graduation date

  Fall 2020

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-ycwr-xa13

• License

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