Article
Mechanics
Narges Mohammad Mehdipour, Naveen Reddy, Roman J. Shor, Giovanniantonio Natale
Summary: Small-angle light scattering is used to study the microstructural changes of polydisperse colloidal suspensions under capillary flow. The effects of shape anisotropy are explored by suspending titanium dioxide bundles and kaolinite nanoclay stacks in a Newtonian fluid. The study reveals significant changes in particle orientation angle due to shear rate gradient, but no cross-sectional flow migration was observed. The experiment shows two stages of transition: initial particle alignment and subsequent orientational demixing. These findings provide insights into the flow-microstructure relationship of polydisperse colloidal suspensions for industrial processing optimization.
Article
Polymer Science
Vishal Raju Ahuja, Jasper van der Gucht, Wim Briels
Summary: Large scale simulations of polymer flow through porous media provide an important tool in solving problems in enhanced oil recovery, polymer processing, and biological applications. This study utilizes a coarse-grain particle-based model to simulate the flow of polymers in a background fluid, revealing some phenomena different from that of Newtonian fluids.
Article
Engineering, Multidisciplinary
Shahzad Ahmad, Anique Ahmad, Kashif Ali, Hina Bashir, Muhammad Farooq Iqbal
Summary: This study investigates the convective heat and mass transfer in steady MHD boundary layer flow of an electrically conducting micropolar fluid over an inclined surface. The mathematical modeling reduces partial differential equations to nonlinear ODEs, with a finite difference based scheme used to find numerical solutions. The effects of various factors on flow characteristics are discussed and analyzed through graphs and tables.
ALEXANDRIA ENGINEERING JOURNAL
(2021)
Article
Polymer Science
Cuong Mai Bui, Anh-Ngoc Tran Ho, Xuan Bao Nguyen
Summary: This study numerically investigates the flow behavior of polymers in a lid-driven cavity, inspired by the coating process, over a wide range of Oldroyd numbers (0 <= Od <= 50). The results show that the flow characteristics of polymers, such as velocity, viscosity, and vortex distributions, are significantly influenced by viscoplastic behaviors. Additionally, solid-like regions are observed in the flow patterns, and their size increases and tends to merge together as Od increases. The cavity width/aspect ratio and skewed angle also have significant impacts on the vortex structures and the formation of solid-like regions.
Article
Physics, Fluids & Plasmas
Kristian Stolevik Olsen
Summary: This study investigates the nonequilibrium steady state arising from stochastic resetting to a distribution. It is shown that for a range of processes, the steady-state moments can be expressed as a linear combination of the moments of the resetting position distribution. The coefficients of this series are universal and only dependent on the underlying dynamics, regardless of the resetting distribution. The study focuses on Brownian particles and run-and-tumble particles confined in a harmonic potential, providing explicit closed-form expressions for all moments for any resetting distribution, which are verified through numerical simulations.
Article
Materials Science, Multidisciplinary
Stefano A. Mezzasalma
Summary: A pseudo-velocity concept, based on the extension of a linear body, is defined by a special relativity experiment. It suggests an analogy with the covariance properties of Wiener's process, ultimately implying that the scaling behavior of (Gaussian) polymer solutions can be derived from a Brownian Relativity theory, as it was formerly put forward. An ad-hoc statistical interpretation of the resulting spacetime transforms may be given by the central limit theorem.
RESULTS IN PHYSICS
(2022)
Article
Physics, Mathematical
Mehdi Ouaki, Fraydoun Rezakhanlou
Summary: In this article, we pursue two goals. Firstly, we construct a family M-G of Gibbsian measures on the set of piecewise linear convex functions. Secondly, we study the invariance of M-G with respect to the dynamics of Hamilton-Jacobi PDEs.
COMMUNICATIONS IN MATHEMATICAL PHYSICS
(2022)
Article
Engineering, Electrical & Electronic
Marija Markovic, Bri-Mathias Hodge
Summary: This paper introduces a new model called parameterized linear power flow model for highly accurate distribution voltage solutions. It uses learning-aided parameterization to increase the fidelity of voltage solutions over a wide range of operating points. The parameter is system-specific and controls the accuracy of the proposed power flow equations according to loading conditions.
IEEE TRANSACTIONS ON POWER SYSTEMS
(2023)
Article
Mechanics
Meisam Pourali, Martin Kroger, Jan Vermant, Patrick D. Anderson, Nick O. Jaensson
Summary: This study investigates the flow of viscous interfaces carrying an insoluble surface active material, exploring the complex interplay between Marangoni stresses, compressibility, and surface shear and dilatational viscosities. By conducting numerical simulations on particle probes, the relationship between drag and interfacial properties necessary for microrheology is quantified. The research reveals the intimate coupling between bulk and interfacial flows, demonstrating the effects of different physical factors on the velocity field and drag coefficient.
Article
Mechanics
Shuang Liu, Yanjie Zhang, Zhijie Zhang, Quan Chen
Summary: This study examines the nonlinear rheology properties of telechelic ionomers with connecting ions at the chain ends. The research reveals the influence of connecting ion groups on relaxation time and strains. The experiments demonstrate that the peak strain plays a critical role in inducing dissociation. Surprisingly, a phenomenon of time-strain separability is observed.
JOURNAL OF RHEOLOGY
(2022)
Article
Chemistry, Multidisciplinary
Anuva Pal, Rajinder Pal
Summary: The rheology of oil-in-water emulsions thickened by starch nanoparticles was investigated in this study. It was found that at a given nanoparticle concentration, the emulsions behave as a Newtonian fluid at low oil concentrations and exhibit shear-thinning behavior at high oil concentrations. Furthermore, increasing the nanoparticle and oil concentrations increases the consistency of the emulsion and enhances its shear-thinning behavior.
Article
Mechanics
S. J. Coombs, M. A. Kanso, K. El Haddad, A. J. Giacomin
Summary: The complex viscosity of planar star-branched polymers was derived from general rigid bead-rod theory, with the analysis revealing that a slightly irregular center-beaded tetrahedron is required to describe the behavior of quadrafunctional polybutadiene.
Article
Mechanics
Mary A. A. Joens, Patrick S. S. Doyle, Gareth H. H. McKinley, James W. W. Swan
Summary: This study investigates the motion of a small rotating spherical particle in a two-dimensional trajectory through a viscoelastic fluid using the Giesekus model. The study analyzes both steady-state and time-dependent flows, quantifying the relative unsteadiness and nonlinearity of the flows. The impact of changing dimensionless parameters on the flow characteristics is discussed.
Article
Physics, Multidisciplinary
Giovanni Savorana, Steffen Geisel, Tianyu Cen, Yuya Ling, Roman Stocker, Roberto Rusconi, Eleonora Secchi
Summary: This article investigates the effect of polymer solutions on bacterial transport in fluid flow. Microfluidic experiments and numerical modeling show that an increase in viscosity reduces bacterial depletion in low-shear regions of Newtonian solutions, while non-Newtonian solutions exhibit depletion similar to buffer solutions despite having higher viscosity.
FRONTIERS IN PHYSICS
(2022)
Article
Chemistry, Physical
Anh Vu Nguyen Le, Adrien Izzet, Guillaume Ovarlez, Annie Colin
Summary: This study investigates the non-Newtonian behaviors of hard sphere suspensions in Newtonian fluids, and reveals different macroscopic and microscopic behaviors of the suspensions when immersed in different solvents. The study demonstrates the impact of interparticle contact forces on the macroscopic behavior and proposes several particle-scale mechanisms. It provides new quantitative data for micromechanical models and simulations, challenges the interpretation of previous experiments, and emphasizes the systematic characterization of interparticle normal and tangential forces in studying hard sphere suspensions in Newtonian fluids.
JOURNAL OF COLLOID AND INTERFACE SCIENCE
(2023)
Article
Chemistry, Multidisciplinary
Valerie Garcia-Negron, Stephen C. Chmely, Jan Ilavsky, David J. Keffer, David P. Harper
Summary: This study investigated the thermochemical conversion of lignin powders from different feedstocks using X-ray scattering techniques. The results showed that the carbonization temperature affects the crystallinity and morphological features of the carbon. Softwoods and switchgrass were found to be viable substitutes for graphite and can be used to produce application-specific materials.
ACS SUSTAINABLE CHEMISTRY & ENGINEERING
(2022)
Article
Chemistry, Multidisciplinary
Dayton G. Kizzire, Valerie Garcia-Negron, David P. Harper, David J. Keffer
Summary: This study investigates the radial distribution functions (RDFs) of lignin-based carbon composites (LBCCs) using synchrotron X-ray and neutron scattering, and proposes a Hierarchical Decomposition of the Radial Distribution Function (HDRDF) modeling method to characterize the local atomic environment and develop quantitative Process-Structure-Property-Performance (PSPP) relationships. The PSPP relationships for LBCCs defined in this work include the dependence of crystallite size on lignin feedstock and the increase of crystalline volume fraction, nanoscale composite density, and crystallite size with increasing reduction temperature.
Article
Physics, Multidisciplinary
Clifton C. Sluss, Jace Pittman, Donald M. Nicholson, David J. Keffer
Summary: Evaluation of entropy from molecular dynamics simulation remains challenging. A recent study demonstrated a functional based on pair correlation function that can accurately determine excess entropy. This research explores the general applicability of this method and applies it to three different materials.
Article
Energy & Fuels
Lu Yu, Kendhl Seabright, Ishan Bajaj, David J. Keffer, David M. Alonso, Chien-Te Hsieh, Mi Li, Hao Chen, Sheng Dai, Yasser Ashraf Gandomi, Christos T. Maravelias, David P. Harper
Summary: In this study, lignins extracted from yellow pine and switchgrass were converted into porous activated carbon electrodes for high energy-density supercapacitors. The research explores the impact of lignin composition on the structure and electrochemical properties of activated carbons. The resulting electrodes exhibited excellent stability and efficiency.
FRONTIERS IN ENERGY RESEARCH
(2022)
Article
Materials Science, Multidisciplinary
Leo Zella, Jaeyun Moon, David Keffer, Takeshi Egami
Summary: Metallic glasses exhibit fast mechanical relaxations known as nearly constant loss (NCL) at temperatures below the glass transition. Through molecular dynamics simulations, it is found that NCL relaxation is due to transient groups of atoms that revert to typical atomic-level viscoelastic behavior. These groups of atoms are homogeneously distributed throughout the glass, without any outstanding features.
Article
Engineering, Chemical
Lu Yu, David J. Keffer, Chien-Te Hsieh, Jakob R. Scroggins, Hao Chen, Sheng Dai, David P. Harper
Summary: This study develops a recyclable adsorbent for the large-scale environmental remediation of polluted water. The adsorbent is produced from an abundant, low-cost, and renewable feedstock via a simple processing procedure. The experimental results demonstrate that the adsorbent has high adsorption performance, high regeneration efficiency, economic and environmental viability, single-step processing, and large-scale production.
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
(2022)
Review
Multidisciplinary Sciences
Jiaxing Song, Yabiao Zhu, Fenghui Lin, Nansheng Liu, Bamin Khomami
Summary: This retrospective aims to present a coherent history of important findings in direct numerical simulations and experiments in turbulent Taylor-Couette flow of dilute polymeric solutions in the last decade. Specifically, the article discusses the sequence of flow transitions due to an increase in fluid elasticity, including drag modification, flow structures, statistics, and mechanisms of turbulence, as well as a comparison with curvilinear and rectilinear shear flows. This article is part of a theme issue on Taylor-Couette and related flows.
PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES
(2023)
Article
Chemistry, Physical
Mahdi Boudaghi, Brian J. J. Edwards, Bamin Khomami
Summary: The evolution of shear banding under startup of shear flow was simulated for different molecular weight polyethylene melts. It was found that shear stress was dominated by segmental orientation at low shear rates, but flow-induced disentanglement resulted in the onset of chain tumbling and reduced shear stress at a critical shear rate. During shear flow startup, distinct fast and slow bands formed, consisting of more disentangled and extended chains and relatively entangled and coiled molecules, respectively. The simulation results showed temporary reverse flow, consistent with earlier experiments and theoretical results. The phenomenon of shear banding appeared to arise from flow-induced disentanglement and differential stretching of individual chains, resulting in the formation of slow and fast bands.
Article
Physics, Fluids & Plasmas
Jiaxing Song, Fenghui Lin, Yabiao Zhu, Zhen-Hua Wan, Nansheng Liu, Xi-Yun Lu, Bamin Khomami
Summary: Direct numerical simulation is used to identify the dominant flow structures in the Taylor-Couette flow of dilute polymer solutions. It is found that unsteady diwhirls and elastic waves play important roles in the formation of elastic turbulence. The interaction between these elements leads to stochastic or chaotic cycles that sustain the turbulent dynamics.
PHYSICAL REVIEW FLUIDS
(2023)
Article
Mechanics
Yabiao Zhu, Zhenhua Wan, Fenghui Lin, Nansheng Liu, Xiyun Lu, Bamin Khomami
Summary: The existence of a maximum drag enhancement (MDE) asymptote at high rotation (Ro) and Weissenberg (Wi) numbers in turbulent viscoelastic spanwise-rotating plane Couette flow has been demonstrated. Above a critical Wi, drag enhancement plateaus and the MDE asymptote is realized in a broad range of Ro. The mean velocity profiles at MDE closely follow a log-law profile that has a nearly identical slope but different intercepts as a function of Ro. Moreover, the intriguing finding is that MDE occurs in the elasto-inertial turbulence (EIT) flow state and is mainly sustained by elastic forces like the MDR flow state. Hence, a universal picture of elastically induced drag modification asymptotes is emerging, where these asymptotic states are inherent to the elastically sustained EIT flow state.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Polymer Science
Mohammad Hadi Nafar Sefiddashti, Brian J. Edwards, Bamin Khomami
Summary: Atomistic simulations were performed on linear, entangled polyethylene melt under uniaxial elongational flow conditions. Flow-induced phase separation and crystallization were observed at intermediate and high flow strengths, respectively. The flow-induced crystallization occurred at a temperature higher than the quiescent melting point and remained stable after flow cessation. The results were consistent with experimental measurements of thermodynamic properties.
Article
Chemistry, Physical
Michael T. T. Broud, Mohsen Samandari, Lu Yu, David P. P. Harper, David J. J. Keffer
Summary: Mitigating the extreme effects of climate change caused by fossil fuel burning requires global carbon sequestration. Carbon quantum dots (CQD) are evaluated as materials for selective carbon dioxide adsorption. CQDs can selectively adsorb CO2 from gas mixtures and the selectivity depends on their size, composition, and modification. This preliminary computational study provides a framework for optimizing CQD atomic architecture on a CQD/AC adsorbent.
JOURNAL OF PHYSICAL CHEMISTRY C
(2023)
Article
Polymer Science
Mahdi Boudaghi, Brian J. J. Edwards, Bamin Khomami
Summary: The temporal and spatial evolution of shear banding in polyethylene solutions was studied during startup and steady-state shear flow. A high-fidelity method was developed to simulate and evaluate this phenomenon. The study observed transient shear banding during startup flow, with inhomogeneous concentration distribution within the system.