Numerical study of particle suspensions in non-Newtonian fluids
Time: Fri 2026-02-27 10.00
Location: Kollegiesalen, Brinellvägen 8, Stockholm
Language: English
Subject area: Engineering Mechanics
Doctoral student: Shahriar Habibi , SeRC - Swedish e-Science Research Centre, Strömningsmekanik
Opponent: Full Professor Seyed-Mohammad Taghavi, Université Laval
Supervisor: Full professor Outi Tammisola, SeRC - Swedish e-Science Research Centre, Strömningsmekanik
QC 260204
Abstract
Elastoviscoplastic (EVP) fluids are ubiquitous in nature and engineering, appearing in biological systems such as blood flow and the cell cytoskeleton, as well as in geophysical phenomena like avalanches and mudslides. They also play a central role in applications ranging from the transport of waxy crude oil to additive manufacturing and drug delivery in the human body. A defining characteristic of these materials is the presence of a critical yield stress, below which the material behaves as a viscoelastic solid and above which it flows like a liquid. Many EVP fluids also contain additional phases, such as rigid particles, whose interactions significantly influence the flow dynamics. Predicting these flows requires understanding how the non-Newtonian properties of the carrier fluid influence particle distribution, how particles modify the surrounding flow field, and how particle–fluid interactions determine the overall behaviour of the suspension. The aim of this work is therefore to advance the physical understanding of multiphase flow dynamics by developing and employing high-fidelity numerical simulations to study the individual and collective behaviour of finite-size particles in EVP carrier fluids.
The results demonstrate the strong influence of particle shape and fluid rheology on suspension behaviour. For instance, EVP suspensions can exhibit significant drag reduction compared with Newtonian suspensions of the same viscosity. Particles are also shown to migrate across streamlines in ways that depend on both their shape and the non-Newtonian properties of the fluid. The simulations of EVP suspensions are validated against available experimental measurements of finite-size spherical particles in Carbopol duct flows. Additional simulations of droplet-laden EVP turbulent flows reveal that elasticity and yield stress of the carrier fluid strongly influence morphology, size, and spatial distribution of the dispersed droplets. Moreover, numerical simulations and microfluidics experiments show that adjusting channel geometry and fluid elasticity can achieve precise particle focusing at the centre of microchannels. Finally, an efficient immersed boundary method is developed to model viscoelastic flow around static boundaries, improving the accuracy of stress computations near the solid boundaries.