Article
Mechanics
Changwoo Kang, Harunori N. Yoshikawa, Parisa Mirbod
Summary: This study investigates thermal convection in neutrally buoyant, non-colloidal suspensions confined between horizontal plates using a constitutive diffusion equation coupled with flow equations. The model proposed by Metzger et al. for effective thermal diffusivity of suspensions is employed. Results show that the critical Rayleigh number gradually increases with bulk particle volume fraction, enhancing heat transfer, and the heat transfer is affected by shear-induced particle migration.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Andreas D. Demou, Mehdi Niazi Ardekani, Parisa Mirbod, Luca Brandt
Summary: This study presents direct numerical simulations of turbulent Rayleigh-Benard convection in non-colloidal suspensions, with special focus on the heat transfer modifications in the flow. The research found that the Nusselt number weakly but steadily increases when the particle volume fraction is below 25%, mainly due to increased thermal agitation. However, when the particle volume fraction exceeds 30%, the Nusselt number exhibits a substantial drop, attributed to the dense particle layering in the near-wall region, which reduces convection and inhibits the formation of coherent structures near the wall.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Peifeng Lin, Rui Wang, Xiao Hu, Zuchao Zhu, Chenlin Zhu
Summary: Experimental research was conducted to investigate the shear-thinning and strain-stiffening behavior of a bidisperse non-colloidal suspension under steady-state shear and oscillatory shear. The results showed the presence of a second shear-thinning behavior when the volume fraction of the particle suspension was between medium and high. The viscosity exhibited a significant particle size dependence at low shear rates, while the dependence became almost nonexistent at high shear rates. Furthermore, the addition of a surfactant of specific concentration confirmed the influence of microstructural changes on the rheological properties of the suspension.
Article
Physics, Fluids & Plasmas
J. Schwarz, P. Leiderer, T. Palberg
Summary: The study investigated bulk crystal nucleation rates in aqueous suspensions of charged spheres at low metastability, showing a correlation between crystal size distributions and electrolyte concentration. Parameterization of the results in terms of classical nucleation theory revealed unusually low interfacial free energies of the nucleus surfaces and nucleation barriers well below thermal energy. The presence of doublets introduced by the conditioning technique may be responsible for the observed phenomena of nucleation induced by small seeds.
Article
Mechanics
Yuan Lin, Ying Wang, Zixin Weng, Dingyi Pan, Jiawang Chen
Summary: The presence of bubbles in non-colloidal suspensions significantly affects the shear thinning behavior, with large bubbles enhancing shear thinning and nano-bubbles suppressing it. Additionally, nano-bubbles influence the particle organization behavior, leading to a larger critical strain for the finish of the organization process. Therefore, a degassing process is essential to obtain reliable rheological properties of the two-phase suspension system.
Article
Mechanics
Thomas Russell, Pavel Bedrikovetsky
Summary: This study focuses on mathematical modeling of suspension-colloidal-nano transport in porous media at different scales, discussing the homogenization of equations and the relationship between the filtration function and carrier fluid velocity. The developed model provides explicit formulas for large-scale transport coefficients in terms of micro-scale parameters for various velocity-dependent filtration functions, showing typical dependencies on velocity and micro-scale parameters. Treatment of laboratory tests reveals close match with modeling-based predictions.
Article
Mechanics
D. A. Bratsun, V. O. Oschepkov, E. A. Mosheva, R. R. Siraev
Summary: The article investigates the stability of a two-layer miscible system to the double-diffusive instability by considering the effect of a concentration-dependent diffusion coefficient. A closed-form analytical expression for the time-dependent density profile is derived and validated by direct numerical simulation. The experiments confirm the theoretical predictions and show opposite results for different solute pairs.
Article
Chemistry, Physical
Yawei Liu, Asaph Widmer-Cooper
Summary: A dissipative particle dynamics (DPD) model is developed to study dynamics in colloidal rod suspensions, where the interaction between solvent particles and rigid linear chains representing individual rods is controlled using a hard repulsive potential. The model accurately predicts diffusion coefficients of single colloids in the DPD solvent, showing good agreement with theoretical calculations based on rod size and including correct Navier-Stokes hydrodynamic interactions. Comparison with experimental measurements of gold nanorod diffusion coefficients validates the model's ability to describe dynamics in real nanorod suspensions and suggests potential for further extension to study colloid dynamics in more complex situations or particle types.
JOURNAL OF CHEMICAL PHYSICS
(2021)
Article
Engineering, Chemical
J. W. S. McCullough, L. Laniewski-Wollk, S. M. Aminossadati, C. R. Leonardi
Summary: This paper proposes a numerical coupling method for resolving particle suspensions exposed to thermal influences, and validates the model through the study of suspensions' relative viscosity. Results show significant impact of temperature on suspension flow behavior, and future work will focus on modifying particle properties for industrial improvements.
Article
Multidisciplinary Sciences
Florian Katzmeier, Friedrich C. Simmel
Summary: This study investigates the second-order electrokinetic flow caused by concentration polarization electro-osmosis (CPEO) around colloidal particle dimers. The researchers demonstrate the controllable manipulation and assembly of charged dielectric particles by controlling the orientation of the AC electric field. The experimental results provide parameter ranges for the operation of microrobots and indicate that CPEP is a generic phenomenon.
NATURE COMMUNICATIONS
(2023)
Article
Physics, Fluids & Plasmas
R. More, A. M. Ardekani
Summary: This study successfully unifies and quantitatively reproduces the various state transitions of a dense non-Brownian particulate suspension at different shear rates or stresses using discrete particle dynamics simulations. The transitions are found to be a result of changes in interparticle interactions of hydrodynamic and nonhydrodynamic origins due to increasing shear rate or stress.
Article
Mechanics
C. Jain, V. S. Solomatov
Summary: We investigate the onset of convection in internally heated fluids with strongly temperature-dependent viscosity. As the viscosity contrast increases, a high-viscosity stagnant lid develops at the upper surface and convection occurs in a sublayer beneath it. The results of this study can help improve our understanding of the conditions under which convection occurs in planetary interiors.
Article
Mechanics
Roger Tanner, Shaocong Dai
Summary: An inelastic model of non-Brownian suspension behavior based on the persistence of straining concept of Thompson and Souza Mendes (TSM model) is proposed and compared with experiments and computations in various flow conditions. The model shows good agreement in general and highlights the significant influence of interparticle friction, which has been incorporated via a bootstrap concept.
Article
Mechanics
Enzo D'Ambrosio, Frederic Blanc, Elisabeth Lemaire
Summary: This study investigates the viscous resuspension in non-Brownian suspensions through local measurements of both velocity and particle volume fraction. The radial profiles of velocity and particle volume fraction are found to be inconsistent within the framework of local rheology of a Newtonian material, but discrepancies disappear for neutrally buoyant suspensions. The third particle normal stress is derived from vertical concentration profiles, showing a power law relationship with shear rate and an exponent close to 0.7, consistent with recent research.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Chemistry, Physical
Ian Williams, Erdal C. Oguz, Hartmut Loewen, Wilson C. K. Poon, C. Patrick Royall
Summary: Colloids can be considered as big atoms and provide good models for atomic and molecular systems. Colloidal hard disks, serving as good models for 2D materials, have received relatively little attention in rheology despite being well-characterized in phase behavior. This study measures the shear rheology of quasi-hard-disk colloids in extreme confinement using a novel experimental setup and computer simulations. The results show that the rheological behavior of the confined system is similar to unconfined 2D and 3D hard particle systems, with the occurrence of dynamic yield stress and shear thinning.
JOURNAL OF CHEMICAL PHYSICS
(2022)
