Article
Mechanics
S. S. Gopalakrishnan, B. Knaepen, A. De Wit
Summary: The study investigates the convective finger structures formed by two solutions of different solutes in the gravity field, and analyses the nonlinear dynamics of these buoyancy-driven instabilities. Numerical simulations reveal the evolution of mixing length and the linear relationship between mixing velocity and dynamic density difference.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Yun Chang, Alberto Scotti
Summary: This paper examines the early stage of radiatively driven convection and finds that perturbations grow exponentially over time, with the system characteristics determined by the Reynolds number.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Carlo Cossu
Summary: In this study, the genesis of large-scale coherent rolls in turbulent wall-bounded flows was investigated through linear stability analysis, revealing the importance of modeling turbulent Reynolds stresses for consistent predictions. The onset of large-scale convection was found to be associated with a critical friction Richardson number.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
E. Villermaux
Summary: The composition of the Earth's mantle, which is formed by the collisions of planetesimal fragments, depends on the equilibrium between metal and silicate resulting from the settling of these fragments. This study analyzes the intermingled phenomena occurring when a drop impacts a substrate of a different liquid, providing insight into the primary instability that determines the penetration depth and wavelength between the impactor and the mantle. The research sheds light on the relative importance of fragmentation and mixing in determining the overall chemical composition of planets.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Multidisciplinary Sciences
Andrei Ermolaev, Anastasiia Sheveleva, Goery Genty, Christophe Finot, John M. Dudley
Summary: Using sparse regression, we successfully recovered the governing differential equation model of ideal four-wave mixing in a nonlinear Schrodinger equation optical fiber system from dynamical data. Analysis of ensemble data allowed us to reliably identify the governing model in the presence of noise.
SCIENTIFIC REPORTS
(2022)
Article
Mechanics
S. F. Lewin, C. P. Caulfield
Summary: Motivated by the variation of local shear produced by internal waves in the ocean, this study investigates the effect of a time-dependent shear forcing on the evolution and mixing of turbulence produced by Kelvin-Helmholtz instability (KHI) through direct numerical simulations. The results demonstrate that turbulence produced by KHI with a decelerating shear mixes in a distinctly different way from the flow with constant background shear, with characteristics more in common with convectively driven flows.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Everest G. Sewell, Kevin J. Ferguson, Vitaliy V. Krivets, Jeffrey W. Jacobs
Summary: Experiments were conducted on Richtmyer-Meshkov instability with a three-dimensional, multi-mode initial perturbation, investigating the effect of perturbation amplitude on measured quantities and observing the development of the mixing region. However, the results did not fully meet the more stringent requirements proposed by previous researchers.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Meng-Juan Xiao, Ze-Xi Hu, Zi-Huan Dai, You-Sheng Zhang
Summary: Re-shocked Richtmyer-Meshkov (RM) mixing is a fundamental physical process involving multiple instabilities, and accurate prediction of its mixing width (MW) has not been achieved with pure large-eddy simulation (LES). By using velocity perturbation and a new LES model, a consistent prediction of MW with experiments is achieved for the first time.
Article
Chemistry, Analytical
Keyi Nan, Yanxia Shi, Tianyun Zhao, Xiaowei Tang, Yueqiang Zhu, Kaige Wang, Jintao Bai, Wei Zhao
Summary: This study investigated the effects of electric field intensity, AC frequency, electric conductivity ratio, and channel width at the entrance on the mixing effect of a Y-type electrokinetic turbulent micromixer. It was found that the optimal mixing can be achieved in a 350 μm wide micromixer under specific conditions.
ANALYTICAL CHEMISTRY
(2022)
Article
Engineering, Mechanical
Hansong Xie, Yaomin Zhao, Yousheng Zhang
Summary: In this study, a data-driven nonlinear K-L mixing model is developed via the gene expression programming (GEP) method to address the shortcomings of traditional Boussinesq-type RANS mixing models in resolving turbulence anisotropy. The model trains the undetermined coefficients as functions of the Galilean invariants and considers the realizability principle to ensure physics of the flow field. The results show that the new model is robust with different mixing problems and improves predictive accuracy while capturing physics of turbulence at a higher level. This is the first study to investigate turbulent mixing problems using machine learning methods.
ACTA MECHANICA SINICA
(2023)
Article
Mechanics
Fernando F. Grinstein, Juan A. Saenz, Massimo Germano
Summary: The study revisits coarse-grained simulation strategies for turbulent material mixing involving shock-driven turbulence, using newly available LMC-xRAGE hydrodynamics. Improved simulated mixing and turbulence levels on coarser grids were achieved, with the more accurate models requiring less resolution and resulting in grid-coarsening savings for mixing prediction.
Article
Mechanics
E. Parente, J-Ch Robinet, P. De Palma, S. Cherubini
Summary: Recently, the origin and growth of turbulent bands in shear flows have been investigated. Streaks and their inflectional instability play a significant role in the process. Linear and nonlinear energy optimisations reveal the mechanisms allowing the creation of a turbulent band in a tilted domain. Linear optimal perturbation generates oblique streaks, inducing turbulence in the whole domain. Spatially localised perturbations lead to the generation of a localised turbulent band.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Environmental Sciences
Mehdi Cherif, Russell N. N. Arnott, Danielle J. J. Wain, Lee D. D. Bryant, Henrik Larsson, Emily I. I. Slavin
Summary: A mesocosm experiment was conducted to investigate the response of a natural phytoplankton community to climate change-induced changes in water column stability and mixing. Results showed that the biological response of phytoplankton groups to different turbulence scenarios did not conform to the usual expectations.
FRONTIERS IN MARINE SCIENCE
(2023)
Article
Mechanics
Yohei Onuki, Sylvain Joubaud, Thierry Dauxois
Summary: A new technique was developed to assess internal wave-driven mixing in the ocean through direct numerical simulations of stratified turbulence. The study found that the external wave can directly supply energy for turbulence and mixing, and the mixing coefficient tends to increase with the Fr number of the external wave. Disturbances in the model go through two stages, converting wave energy into turbulence energy and eventually dissipating it.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
A. Mizev, E. A. Mosheva, D. A. Bratsun
Summary: In the experimental study, buoyancy-driven instabilities triggered by neutralization reactions were investigated, and a dimensionless parameter called reaction-induced buoyancy number was introduced to classify experimental observations and predict the development of two global scenarios based on the value of this parameter.
One scenario is mainly controlled by diffusion, resulting in weak convective motion, while the other leads to vigorous convection in the upper layer, causing the reaction front to move downwards quickly. A new parameter was shown to plot stability maps for predicting reaction-diffusion-convection processes in similar systems before experiments.
JOURNAL OF FLUID MECHANICS
(2021)