Article
Mechanics
Priya Sarkar, Krishna Prasad Madasu
Summary: This study investigates the axisymmetric steady flow of a couple stress fluid between two concentric cylinders with a slip effect using the cell model technique. Different boundary conditions are applied on the inner and outer cylindrical surfaces, and both parallel and perpendicular flows are considered. The Kozeny constant is calculated for all cases, and the effects of slip and couple stress parameters on the constant are analyzed graphically.
Article
Mechanics
Zhiwen Cui, Lihao Zhao
Summary: The alignment behavior of particles in different regions of channel flows is investigated, revealing that it is influenced by particle shape and position. The probability distributions of the sign of the discriminant in the Jeffery equation can be used to distinguish weak and strong shape-dependent regions in turbulent channel flows.
Article
Mechanics
Gokul Hariharan, Mihailo R. Jovanovic, Satish Kumar
Summary: In viscoelastic fluids, nonmodal analysis reveals that locally amplified polymer-stress fluctuations may be more pronounced than streamwise-constant polymer-stress fluctuations. The large stress amplification can lead the flow into a regime where nonlinear terms are no longer negligible, triggering a transition to elastic turbulence. This alternate mechanism may help in understanding recent experimental observations of elastic turbulence in microchannel flows of viscoelastic fluids.
JOURNAL OF NON-NEWTONIAN FLUID MECHANICS
(2021)
Article
Physics, Fluids & Plasmas
J. P. Alexander, D. T. Papageorgiou
Summary: This paper investigates the interfacial instabilities in three-layer shear flows by establishing a set of coupled nonlinear evolution equations. The research reveals different dynamic behaviors under different layer thickness, including steady traveling waves and complex spatiotemporal oscillations. Moreover, the kinematic instability is found to be triggered through nonlinear and linear mechanisms in different ways.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Mechanics
Ze Wang, Chun-Xiao Xu, Lihao Zhao
Summary: The study reveals that tiny disk-like particles can significantly influence turbulence modulation and drag reduction, affecting turbulent activities and turbulence anisotropy in the laden flows. The different performances of drag reduction by fibers and disks in the channel flow are explained by analyzing the modulated near-wall turbulence structures and particle shear stress.
Article
Mechanics
P. Brockmann, M. Tvarozek, M. Lausch, J. Hussong
Summary: In this study, previously unreported particle patterns are observed in completely filled rotating drum flows and completely filled co-rotating Taylor-Couette flows for suspensions of initially uniform dispersed non-Brownian particles under the influence of gravity. The experiments include thorough phase mapping for both drum flow and Taylor-Couette flow, and a total of 55 different geometrical combinations are considered. The results show that the pattern formation in drum flow is strongly dependent on the outer cylinder diameter, while in Taylor-Couette flow, the gap height has a strong effect on the pattern formation. Additionally, the wavelength of all band patterns in Taylor-Couette flow is found to be dependent on the cylinder radius and system curvature.
Article
Physics, Fluids & Plasmas
Severine Atis, Matthieu Leclair, Themistoklis P. Sapsis, Thomas Peacock
Summary: Finite-size effects can cause neutrally buoyant particles to exhibit different dynamics and alter their transport properties in fluid flows. Our study investigates the impact of particle shape on dispersion in complex two-dimensional flows, revealing that isotropic and anisotropic particles have distinct dispersion phenomena due to the presence of different Lagrangian coherent structures. Additionally, rod-shaped particles exhibit a focusing effect near vortex cores.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Mechanics
Chuong V. Tran, Xinwei Yu, David G. Dritschel
Summary: Incompressible fluid flows are characterized by high correlations between velocity and pressure, as well as between vorticity and pressure. This correlation plays a significant role in maintaining regularity in Navier-Stokes flows. The study suggests that as long as global pressure minimum (or minima) and velocity maximum (or maxima) are mutually exclusive, regularity is likely to persist.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
B. Hervieu, A. Besq, J. R. Angilella
Summary: The residence time distribution of tiny particles in flows is mainly affected by flow characteristics and can differ significantly from that of fluid particles when particles have a finite response time. This study focuses on shear and extensional flows and investigates their impact on polydisperse suspensions of weakly inertial particles. The theoretical results are validated by numerical simulations.
Article
Mechanics
Chenguang Zhang
Summary: This paper presents a simple idea of incorporating fluid-structure interaction (FSI) into classic rectilinear flow problems by treating solid boundaries as rigid bodies. By extending and solving four examples using Laplace transform, closed-form expressions of solid velocity are obtained, and the impact of solid inertia is discussed. The solutions provide general theoretical interest and can be used to validate numerical methods.
Article
Physics, Fluids & Plasmas
Joost de Graaf, Kim William Torre, Wilson C. K. Poon, Michiel Hermes
Summary: Attractive colloids form gels, which are solidlike particle networks suspended in a fluid. The impact of gravity on the gelation process has been rarely studied. In this study, we used simulations to investigate the effect of gravity on gel formation. We found that gravity-induced flows disrupt gelation at low volume fractions, but above a critical volume fraction, the forming gel network dominates the dynamics. The settling of colloids does not significantly affect the final colloidal gel-like sediment.
Article
Engineering, Chemical
Stefan Heidinger, Simon Unz, Michael Beckmann
Summary: This paper calculates the relaxation behavior of a rigid particle suspended in a one-dimensional oscillating flow according to different drag models and compares the results. Conditions are derived for neglecting relaxation or substituting drag models with simpler ones. The investigation is conducted analytically and graphically using the plane defined by the Reynolds number and amplitude parameter.
Article
Mathematics
The Anh Bui, The Quan Bui, Xuan Thinh Duong
Summary: This study investigates the non-stationary Navier-Stokes equation in the upper half space of Rn and proves the decay estimates of the strong solution and its derivatives in the Besov and Triebel-Lizorkin spaces. It is the first time that such decay estimates have been established on these spaces, extending the known results and providing new estimates.
JOURNAL OF DIFFERENTIAL EQUATIONS
(2022)
Article
Engineering, Chemical
Hongsheng Chen, Wenwei Liu, Zhiwei Chen, Zhong Zheng
Summary: A four-way coupling CFD-DEM model was developed to study the sedimentation of adhesive particles in viscous fluids. Validation of the model was done through three benchmark problems and comparisons between adhesive and non-adhesive particles, revealing differences in settling behavior and the impact of van der Waals adhesion between particles. Agglomeration effect was found to contribute to faster settling of adhesive particles compared to non-adhesive ones.
Article
Engineering, Mechanical
Vladimir V. Shelukhin, Vladimir V. Neverov
Summary: This paper addresses the flows of dense suspensions of particles within the framework of the two-velocity continuum, developing the thermodynamics of such a continuum using the approach suggested by Landau and Khalatnikov. As an application, the authors consider the convective settling problem and capture the Boycott effect, proving that enhanced sedimentation occurs in a tilted vessel due to vortices. Instead of relying on additional interphase forces, they apply a generalized Fick's law for the particle mass concentration flux vector.
JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME
(2022)
