Experimental Analysis of Suspension Flow over Permeable Surfaces
Creators: name: Bagheri, Maryam
Publisher: name: University of Illinois at Chicago
Year: 2023

description: The behavior of Newtonian fluids and suspensions is of particular interest in a wide range of industries including ceramics, food, detergents, cosmetics, magnetic disks, batteries, and energetics. In particular, it is important to examine their behavior in applications which involves porous media as the substrates such as construction, oil mining, as well as in the movement of various biological flows through the body. On the other hand, the extensive real-world applications of modified surfaces to enhance and control the flow such as periodically grooved channels necessitate the understanding and characterizing the flow behavior in different regimes such as transitional regions. This study can also perform a framework for the future studies of different flows including Brownian suspension flow and flow of particles in non-Newtonian suspending fluids in the applications where porous media are present. In the first part of this thesis, we focus on an experimental investigation of the flow of non-colloidal, non-Brownian suspensions via rheological tests over and through well-designed porous media models. We performed a series of simple shear flow experiments using a rheometer with the parallel-plate geometry where different porous structures placed on the lower plate. The impact of various bulk particle volume fractions of suspensions ϕ_b, ranging from 0 to 0.4 has been studied by considering four different porous microstructures with porosities of 0.7 and 0.9. We designed and built porous media models with known permeability and porosity where the particles are either allowed or obstructed to move inside the porous structures. We found when particles move inside the porous layer the slip velocity at the fluid-porous interface increases and varies with the porosity compared to when they are not flowing into the porous layer. Also, with the increase in volume fraction of suspensions, slip velocity decreases at a constant stress while the slip length rises. We then compared these data with the volume-averaged Navier Stokes (VANS) equations for flow in the porous medium coupled with the Stokes equations in the free-flow region to further examine the slip velocity. In the second project, we experimentally investigate pressure-driven flow of a pure Newtonian Fluid through three-dimensional (3D) porous media models. We employed a time resolved three-dimensional Particle Tracking Velocimetry (3D Shake-the-Box) technique for a range of Reynolds numbers 111≤Re≤890, to observe the flow structures and vortex formation between the cylinders with different porosities of ε=0.7,0.8 ,and 0.9 which corresponds to spacing ratio of L/D=1.75,2,and 3. For all the examined cases, we further analyzed the effect of Re number and the spacing ratio on the instantaneous and averaged patterns of velocity, vorticity, and the other flow parameters after obtaining the two-dimensional velocity fields using bin-averaging method. Increasing Re number reduced the symmetrical patterns of flow structures with respect to the centerline of the gap region while spacing ratio was randomly affecting the symmetry degree. Vortex shedding was considerable for the two examined high Re numbers of Re= 444, and Re=890 behind the upstream cylinder as the porosity increased. The backward movement of the reattachment point has been observed by increasing Re number. In the third part, we focus on the motion of a dilute, non-Brownian, neutrally-buoyant suspension of rigid spherical particles passing over and through a periodic two-dimensional groove geometries transverse to the mean flow. We performed particle image velocimetry and particle tracking velocimetry (PIV/PTV) techniques to examine the velocity, vorticity, and particle concentrations along the stream wise and span wise directions and also to analyze in detail the flow and particle dynamics. We also performed pressure drop measurements towards the determination of transition regions.