We are pleased to announce that Wim-Paul Breugem from the TU Delft (The Netherlands), will give the SFB 1313 "Pretty Porous Science Lecture" #34. His talk will be on "Sedimentation characteristics and rheology of non-colloidal suspensions".
Date: Wednesday, 22 March 2023
Time: 4:00 pm CET
Speaker: Dr. Wim-Paul Breugem from the TU Delft (The Netherlands)
Lecture title: "Sedimentation characteristics and rheology of non-colloidal suspensions"
Place: Department of Hydromechanics and Modelling of Hydrosystems, Pfaffenwaldring 61, 70569 Stuttgart, Campus Vaihingen, Room: MML
The talk will be a hybrid event. If you are interested in participating in the lecture online, please contact melanie.lipp@iws.uni-stuttgart.de
Abstract
The study of suspension flows is relevant to many processes in nature and a wide variety of industrial applications. Examples are sediment transport in rivers, excavation and slurry transport in dredging, sedimentation in settling basins, fluidized beds in chemical industry, and 3D printing of, e.g., food, paper pulp and cement slurries. In this talk I will present results from particle-resolved Direct Numerical Simulations (DNS) of non-colloidal particle suspensions for which Brownian motion and molecular forces such as Van der Waals and electrostatic forces can be neglected (i.e., particle diameters >> 1 micron). The first part of the presentation will be devoted to sedimentation in the inertial regime, while in the second part I will discuss the rheological behavior of neutrally-buoyant particle suspensions in a simple shear flow.
The collective settling of particles in a large settling tank is characterized by three dimensionless numbers: the Galileo number (i.e., the particle Reynolds number based on the inertio-gravitational velocity), the particle-to-fluid density ratio and the bulk solid volume concentration. Sedimentation is characterized by hindered settling for concentrations larger than 1%, whereas for dilute concentrations (< 1%) and in the inertial regime (Galileo number > O(150)) the formation of elongated vertical particle clusters may result in an enhanced settling speed with respect to a single settling particle. A thorough understanding of such behavior is important for accurate modelling of (the tendency of) sedimentation in the aforementioned examples. I will present DNS results on the suspension microstructure by means of particle-conditioned averages and particle and fluid statistics for Galileo numbers equal to 144, 178 and 210, and concentrations varying from 0.5-30% at a fixed density ratio of 1.5.
In the second part of my talk, I will present DNS results on neutrally-buoyant suspensions in plane Couette flow (Fig. 1a) with a focus on the effect of interparticle friction on the suspension rheology. We fixed the particle Reynolds number based on the imposed shear rate to 0.1 (Stokes regime) and the channel-to-particle height ratio to 13.5, while we varied the concentration from 10-60% and considered two different Coulomb coefficients of sliding friction (𝜇𝜇𝐶𝐶=0 and 0.39). The rheology is analyzed in terms of velocity and concentration profiles (Fig. 1b), momentum balances, particle stress (differences), relative and normal viscosities, pair distribution functions to assess the suspension microstructure, and 𝜇𝜇(𝐼𝐼𝑣𝑣) rheology (where 𝜇𝜇 is a macroscopic friction coefficient and 𝐼𝐼𝑣𝑣 the so-called viscous number).
About Wim-Paul Breugem
Wim-Paul Breugem is specialized in fluid mechanics. He does fundamental research on turbulence, multiphase flows, flows in porous media, rheology, and computational fluid dynamics, with applications in process, energy, environmental and maritime engineering and often in close collaboration with industrial partners.
More specifically, Breugem’s expertise covers: wall-bounded turbulent flows, turbulent drag reduction, atmospheric flows, suspension flows, bubbly flows, break-up of liquid jets, droplet coalescence, continuum modelling for porous-media and multiphase flows, slender-jet modelling, linear hydrodynamic stability analysis, Direct Numerical Simulation, Immersed Boundary Methods for particle-laden flows, Level-Set and Volume-of-Fluid methods for flows laden with deformable bubbles or drops, high-performance computing.
Applications Breugem has been working on, relate to: prilling for production of fertilizer pellets, rheology of dense suspensions used for 3D (extrusion-based) printing, sedimentation and fluidization processes, turbulent sediment transport through pipelines related to dredging applications, turbulent bed erosion near hydraulic structures or in dredging applications, turbulent flows over porous/permeable walls, shark-skin riblet textures or compliant (visco-elastic) coatings in maritime applications, ship air lubriction, by-pass pigging in pipelines, micro-fluidic flows driven by artificial cilia, and interannual climate variability in the tropical Atlantic region.