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An upper bound on the mixing efficiency is derived for a passive scalar under the influence of advection and diffusion with a body source. For a given stirring velocity field, the mixing efficiency is measured in terms of an equivalent…

Fluid Dynamics · Physics 2007-12-12 Jean-Luc Thiffeault , Charles R. Doering , John D. Gibbon

Let $H\in C^1\cap W^{2,p}$ be an autonomous, non-constant Hamiltonian on a compact $2$-dimensional manifold, generating an incompressible velocity field $b=\nabla^\perp H$. We give sharp upper bounds on the enhanced dissipation rate of $b$…

Analysis of PDEs · Mathematics 2022-11-28 Elia Bruè , Michele Coti Zelati , Elio Marconi

The mixing properties of vapor content, temperature and particle fields are of paramount importance in cloud turbulence as they pertain to essential processes, such as cloud water droplet evaporation and entrainment. Our study examines the…

Explicit examples of scalar enhanced diffusion due to resonances between different transport mechanisms are presented. Their signature is provided by the sharp and narrow peaks observed in the effective diffusivity coefficients and, in the…

chao-dyn · Physics 2009-10-31 P. Castiglione , A. Crisanti , A. Mazzino , M. Vergassola , A. Vulpiani

We study the diffusivity of a tagged particle in a binary mixture of Brownian particles with non-reciprocal interactions. Numerical simulations reveal that, for a broad class of interaction potentials, non-reciprocity can significantly…

Diffusion studies of adsorbates moving on a surface are often analyzed using 2D Langevin simulations. These simulations are computationally cheap and offer valuable insight into the dynamics, however, they simplify the complex interactions…

Materials Science · Physics 2015-05-28 Moshe Diamant , Saar Rahav , Riccardo Ferrando , Gil Alexandrowicz

Diffusion of a two component fluid is studied in the framework of differential equations, but where these equations are systematically derived from a well-defined microscopic model. The model has a finite carrying capacity imposed upon it…

Statistical Mechanics · Physics 2015-06-04 D. Fanelli , A. J. McKane , G. Pompili , B. Tiribilli , M. Vassalli , T. Biancalani

Flow and bridge matching are a novel class of processes which encompass diffusion models. One of the main aspect of their increased flexibility is that these models can interpolate between arbitrary data distributions i.e. they generalize…

Machine Learning · Computer Science 2023-11-14 Valentin De Bortoli , Guan-Horng Liu , Tianrong Chen , Evangelos A. Theodorou , Weilie Nie

This work describes three diffuse-interface methods for the simulation of immiscible, compressible multiphase fluid flows and elastic-plastic deformation in solids. The first method is the localized-artificial-diffusivity approach of Cook…

Computational Physics · Physics 2021-09-21 Suhas S. Jain , Michael C. Adler , Jacob R. West , Ali Mani , Parviz Moin , Sanjiva K. Lele

We first established the dynamic equations to describe the noisy circling motion of a single particle and the corresponding probability conservation equation in both two dimensions and three dimensions, and then developed the evolution…

Statistical Mechanics · Physics 2012-06-07 Tieyan Si

Mixing a passive scalar field by stirring can be measured in a variety of ways including tracer particle dispersion, via the flux-gradient relationship, or by suppression of scalar concentration variations in the presence of inhomogeneous…

Fluid Dynamics · Physics 2010-11-08 Zhi Lin , Katarína Bodová , Charles R. Doering

We introduce non-trivial contributions to diffusion constant in generic many-body systems arising from quadratic fluctuations of ballistically propagating, i.e. convective, modes. Our result is obtained by expanding the current operator in…

Statistical Mechanics · Physics 2020-11-25 Marko Medenjak , Jacopo De Nardis , Takato Yoshimura

Diffusion in an evolving environment is studied by continuos-time Monte Carlo simulations. Diffusion is modelled by continuos-time random walkers on a lattice, in a dynamic environment provided by bubbles between two one-dimensional…

Soft Condensed Matter · Physics 2010-11-22 Janne Juntunen , Juha Merikoski

We propose a model for the nonequilibrium enhancement of colloidal self-diffusion in an externally imposed shear flow in charged systems. The enhancement of diffusion is calculated in terms of the electrostatic, two--body interactions…

Soft Condensed Matter · Physics 2007-05-23 Victor Breedveld , Alex J. Levine

We present an extensive direct numerical simulation of statistically steady, homogeneous, isotropic turbulence in two-dimensional, binary-fluid mixtures with air-drag-induced friction by using the Cahn-Hilliard-Navier-Stokes equations. We…

Fluid Dynamics · Physics 2016-11-16 Nairita Pal , Prasad Perlekar , Anupam Gupta , Rahul Pandit

We investigate the dispersion of solutes in active nematic fluids confined in narrow channels based on simulations of nematohydrodynamics. The study focuses on two pre-turbulent regimes: oscillatory flow, with net mass flux, and dancing…

Soft Condensed Matter · Physics 2026-04-13 Tomás Alvim , Margarida M. Telo da Gama , Rodrigo C. V. Coelho

A spherical droplet is given an initial rotation in the streamwise direction and is impulsively accelerated by a uniform free stream. Numerical results for the deformation and dynamics of the droplet are obtained by utilising a finite…

Fluid Dynamics · Physics 2010-10-21 Eric K. W. Poon , Shaoping Quan , Jing Lou , Andrew S. H. Ooi

Particle diffusion in a two dimensional curved surface embedded in $R_3$ is considered. In addition to the usual diffusion flow, we find a new flow with an explicit curvature dependence. New diffusion equation is obtained in $\epsilon$…

Biological Physics · Physics 2015-05-14 Naohisa Ogawa

We study the mixing in the presence of convective flow in a porous medium. Convection is characterized by the formation of vortices and stagnation points, where the fluid interface is stretched and compressed enhancing mixing. We analyze…

Fluid Dynamics · Physics 2018-02-14 Juan J. Hidalgo , Marco Dentz

Condensation is an important aspect of many flow applications due to the universal presence of humidity in the air at ambient conditions. For direct numerical simulations of such flows, simulating the gas phase as a mixture characterized by…

Fluid Dynamics · Physics 2022-06-29 Philipp Bahavar , Claus Wagner