Particle dynamics within Newtonian and viscoelastic shear thinning flows were investigated with a self-confined cloud of particles around an obstacle. Water and three aqueous Poly-Anionic Cellulose (PAC) solutions were test fluids. An experimental study of an upward vertical pipe was carried out using particle image velocimetry (PIV) techniques to measure the particle and liquid velocity profiles. The fluidized cloud height was measured for better assessing rheological and particle loading effects on particle interactions within liquid flows. It was observed that the dynamics of particles were closely associated with local shear rate, fluid rheology and particle loading. Additionally, it was noted that the slip velocity of particles was relative to the surrounding liquid and was high in regions with a high shear rate and depended significantly on the liquid rheological parameters. The experimental findings were compared against three-dimensional numerical CFD simulations. In the case of particle dynamics in the water sample, it was noted that the simulation results were comparable to the experimental observations. However, for PAC solutions, particles were completely flushed out from the computational domain. This was considered a consequence of inadequate drag and settling velocity formulation within the CFD model. These shortcomings of the drag model were rendered, as Newtonian drag laws were applied to a non-Newtonian fluid, and only used background shear rates of the fluid flow field in estimating the local viscosity experienced by these particles.

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