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We present the optimal hydrodynamic model for rarefied gas flows relative to a given kinetic model by combining the recent theory of slow spectral closure with machine learning techniques. We learn generalized transport coefficients from…

Fluid Dynamics · Physics 2025-09-09 Florian Kogelbauer , Candi Zheng , Ilya Karlin

We present a method to impose linear shear flow in discrete-velocity kinetic models of hydrodynamics through the use of sliding periodic boundary conditions. Our method is derived by an explicit coarse-graining of the Lees-Edwards boundary…

Soft Condensed Matter · Physics 2007-05-23 R. Adhikari , J. -C. Desplat , K. Stratford

An overview of recent results pertaining to the hydrodynamic description (both Newtonian and non-Newtonian) of granular gases described by the Boltzmann equation for inelastic Maxwell models is presented. The use of this mathematical model…

Soft Condensed Matter · Physics 2011-08-30 V. Garzó , A. Santos

A model kinetic equation is solved exactly for a special stationary state describing nonlinear Couette flow in a low density system of inelastic spheres. The hydrodynamic fields, heat and momentum fluxes, and the phase space distribution…

Statistical Mechanics · Physics 2016-08-15 M. Tij , E. E. Tahiri , J. M. Montanero , V. Garzó , A. Santos , J. W. Dufty

We investigate the nonlinear dynamics of turbulent shear flows, with and without rotation, in the context of a simple but physically motivated closure of the equation governing the evolution of the Reynolds stress tensor. We show that the…

Astrophysics · Physics 2009-11-10 Pascale Garaud , Gordon I. Ogilvie

We prove an explicit, non-local hydrodynamic closure for the linear one-dimensional kinetic equation independent on the size of the relaxation time. We compare this dynamical equation to the local approximations obtained from the…

Mathematical Physics · Physics 2020-08-26 Florian Kogelbauer

A closed-form analytical solution is found for the nonlinear dynamics of isolated, near-threshold waves in the presence of strong scattering. The proposed solution can be useful in verifying codes across several disciplines, including…

Plasma Physics · Physics 2020-01-17 Vinicius Duarte , Nikolai Gorelenkov

An exact closure for hydrodynamic variables is rigorously derived from the linear Boltzmann kinetic equation. Our approach, based on spectral theory, structural properties of eigenvectors and the theory of slow manifolds, allows us to…

Fluid Dynamics · Physics 2024-11-11 Florian Kogelbauer , Ilya Karlin

We present a hybrid lattice Boltzmann algorithm for the simulation of flow glass-forming fluids, characterized by slow structural relaxation, at the level of the Navier-Stokes equation. The fluid is described in terms of a nonlinear…

Soft Condensed Matter · Physics 2015-04-24 S. Papenkort , Th. Voigtmann

We describe a special class of steady Couette flows in dilute granular gases admitting a non-Newtonian hydrodynamic description for strong dissipation. The class occurs when viscous heating exactly balances inelastic cooling, resulting in a…

Soft Condensed Matter · Physics 2010-01-13 Francisco Vega Reyes , Andrés Santos , Vicente Garzó

We consider the problem of short-term prediction of rare, extreme water waves in unidirectional fields, a critical topic for ocean structures and naval operations. One possible mechanism for the occurrence of such rare, unusually-intense…

Pattern Formation and Solitons · Physics 2015-01-22 Will Cousins , Themistoklis P. Sapsis

We show that a Galilean invariant version of fluid dynamics can be derived by the methods of statistical dynamics using Maxwell's balance equations. The basic equation is non-local, and might replace Boltzmann's equation if the latter turns…

Mathematical Physics · Physics 2007-05-23 R. F. Streater

Collisionless regime kinetic models for coherent nonlinear Alfven wave dynamics are studied using fluid moment equations with an approximate closure anzatz. Resonant particle effects are modelled by incorporating an additional term…

Plasma Physics · Physics 2009-10-30 M. V. Medvedev , P. H. Diamond

We consider two scalar conservation laws with non-local flux functions, describing traffic flow on roads with rough conditions. In the first model, the velocity of the car depends on an averaged downstream density, while in the second model…

Analysis of PDEs · Mathematics 2018-09-11 Wen Shen

We formulate a data-driven, physics-constrained closure method for coarse-scale numerical simulations of turbulent fluid flows. Our approach involves a closure scheme that is non-local both in space and time, i.e. the closure terms are…

Fluid Dynamics · Physics 2021-02-16 Alexis-Tzianni G. Charalampopoulos , Themistoklis P. Sapsis

This study investigates the role of thermal boundary conditions on natural convection and entropy generation in non-Newtonian power-law fluids confined within a square cavity and a concentric cylindrical annulus. Steady, two-dimensional…

Fluid Dynamics · Physics 2026-05-14 Lambert Theisen , Satyvir Singh

We investigate a system of nonlinear partial differential equations modeling the unsteady flow of a shear-thinning non-Newtonian fluid with a concentration-dependent power-law index. The system consists of the generalized Navier-Stokes…

Analysis of PDEs · Mathematics 2025-05-09 Kyueon Choi , Kyungkeun Kang , Seungchan Ko

We derive equations for fluid dynamics from a non-extensive Boltzmann transport equation consistent with Tsallis' non-extensive entropy formula. We evaluate transport coefficients employing the relaxation time approximation and investigate…

Nuclear Theory · Physics 2015-05-30 T. S. Biro , E. Molnar

In the paper, we study the plane Couette flow of a rarefied gas between two parallel infinite plates at $y=\pm L$ moving relative to each other with opposite velocities $(\pm \alpha L,0,0)$ along the $x$-direction. Assuming that the…

Analysis of PDEs · Mathematics 2021-07-07 Renjun Duan , Shuangqian Liu , Tong Yang

Non-local closures allow kinetic effects on parallel transport to be included in fluid simulations. This is especially important in the scrape-off layer, but to be useful there the non-local model requires consistent kinetic boundary…

Plasma Physics · Physics 2015-12-09 J. T. Omotani , B. D. Dudson , E. Havlickova , M. Umansky
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