Development of two-phase PIV and its applications to sedimentation within a particle-laden turbulent channel flow

This thesis presents a fundamental study of two-way coupling particle/wall turbulence interaction in a horizontal turbulent channel. The experiments were carried out by particle image velocimetry (PIV) for single-phase water flow, as well as particle-laden two-phase flow. A two-phase PIV technique, which based on phase separation during image processing, has been developed for dilute solid-liquid flows to provide detailed quantitative measurement for both carrier and discrete phases, and particle/fluid statistics. The objective of the work is to advance the understanding of the physics and dynamics underlying particle/wall turbulence interaction, which can he used to aid the development of two-fluid closure models.; The results show that particles significantly modified wall turbulence not only in the wall region, but also in the outer region. The presence of particles changes the mean streamwise velocity of the carrier phase, suppressed turbulent intensity close to the wall, while enhanced it further away from the wall in both streamwise and cross-stream locations. Particles also modified the Reynolds stress profiles by shifting the profile further from the wall when plotted using an inner scaling.; Particles were entrained by turbulence wall structure. Particle velocities exhibit a lag in the streamwise direction, while the local streamwise slip velocity is very small. A strong particle preferential concentration was observed, with large numbers of particles occupying the low-speed streaks region. The particle mean concentration profile is in a good agreement with a power law of the form, CCa= ay^b . The study provides quantitative instantaneous information about particle/wall turbulence interaction, as well as particle/fluid statistics. The significant effects of particles on the turbulence modification and particle dispersion by turbulence in both wall and outer region indicate a strong particle/wall interaction, which must be accounted in closure terms in numerical modeling.