arXiv subjects

Vedad Dzanic

Publications and source records attributed to Vedad Dzanic.

4 recordsLinked to original sources

arXiv2026

Lattice Boltzmann methods for simulating non-Newtonian fluids: A comprehensive review

Non-Newtonian fluids encompass a large family of fluids with additional nonlinear material properties, contributing to non-trivial flow behaviour that cannot be captured through a single constant viscosity term. Common non-Newtonian characteristics include shear-thinning, shear-thickening, viscoplasticity, and viscoelasticity, commonly encountered in everyday fluids, such as ketchup, blood, toothpaste, mud, etc., as well as practical applications involving porous media, cosmetics, food processing, and pharmaceuticals. Due to the complex nature of these fluids, accurate computational fluid dynamics simulations are essential for predicting their behaviour under various flow conditions. Recent advancements have highlighted the growing trend of using the lattice Boltzmann method to solve such complex flows, owing to its ability to handle intricate boundary conditions, ease of including additional multiphysics, and providing computationally efficient parallel simulations. Since the initial review over a decade ago [Phillips & Roberts, IMA J. Appl. Math. 76, 790-816 (2011)], significant advancements have been made to the lattice Boltzmann method to simulate non-Newtonian fluids. Here, we present a comprehensive review of different lattice Boltzmann techniques used to solve non-Newtonian fluid systems, specifically dealing with shear-dependent viscosity, viscoplasticity, and viscoelasticity. In addition, we discuss various benchmark cases that validate these approaches and highlight their growing application to realistic and challenging complex flow problems. We further address outstanding issues in current lattice Boltzmann models, as well as future directions for numerical advancement and application.

physics.flu-dyn↗

arXiv2026

Bridging Elastic and Active Turbulence

Remarkably, even under negligible inertia, the addition of microstructural agents can generate chaotic flow fields. Such behavior can arise in polymer solutions, leading to elastic turbulence, or from active, self-driven particles, which generate active turbulence. Here, we demonstrate a close and hitherto unrecognized connection between these two classes of turbulence. Specifically, we reveal that their continuum descriptions are analogous at the macroscopic level, such that polymeric fluids can be interpreted as a deformable analogue of contractile active matter. Moreover, our numerical results for Kolmogorov flow demonstrate that the transition into the well-known traveling arrowhead structures in elastic turbulence is marked by the emergence of $\pm 1/2$ topological defects, long recognized as a defining feature of active turbulence, in the polymer director field. Importantly, these coherent structures originate from a transverse instability driven by activity-like gradients generated by anisotropically stretched, contractile polymers. At sufficiently strong activity, the system undergoes a transition into a flow-suppressed state characterized by weak polymer stretching and ordering, a behavior that can be explained by analogy with the spontaneous-flow transition observed in channel-confined active nematics.

physics.flu-dyn↗

arXiv2025

Jamming of Elastoviscoplastic fluids in Elastic Turbulence

Elastoviscoplastic (EVP) fluid flows are driven by a non-trivial interplay between the elastic, viscous, and plastic properties, which under certain conditions can transition the otherwise laminar flow into complex flow instabilities with rich space-time-dependent dynamics. We discover that under elastic turbulence regimes, EVP fluids undergo dynamic jamming triggered by localised polymer stress deformations that facilitate the formation of solid regions trapped in local low-stress energy wells. Below the jamming transition $ϕ<ϕ_J$, the solid volume fraction $ϕ$ scales with $\sqrt{Bi}$, where $Bi$ is the Bingham number characterizing the ratio of yield to viscous stresses, in direct agreement with theoretical approximations based on the laminar solution. The onset of this new dynamic jamming transition $ϕ\geqϕ_J$ is marked by a clear deviation from the scaling $ϕ\sim \sqrt{Bi}$, scaling as $ϕ\sim \exp{Bi}$. We show that this instability-induced jamming transition -- analogous to that in dense suspensions -- leads to slow, minimally diffusive, and rigid-like flows with finite deformability, highlighting a novel phase-change in elastic turbulence regimes of complex fluids.

cond-mat.soft↗

arXiv2022

Conserving elastic turbulence numerically using artificial diffusivity

To simulate elastic turbulence, where viscoelasticity dominates, numerical solvers introduce an artificial stress diffusivity term to handle the steep polymer stress gradients that ensue. This has recently been shown [Gupta & Vincenzi, J. Fluid Mech. 870, 405-418 (2019); Dzanic, From & Sauret, J. Fluid Mech. 937, A31 (2022)] to introduce unphysical artifacts with a detrimental impact on simulations. In this Letter, we propose that artificial diffusion is limited to regions where stress gradients are steep instead of seeking the zero-diffusivity limit. Through the cellular forcing and four-roll mill problem, we demonstrate that this modified artificial diffusivity is devoid of unphysical artifacts, allowing all features of elastic turbulence to be retained. Results are found to conform with direct simulations, reducing the impact of artificial diffusivity from a qualitative scale to a quantitative scale while only requiring a fraction of the numerical resolution.

physics.flu-dyn↗