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By taking into account photon absorption, we investigate the vertical structure of accretion flows with comparable radiation and gas pressures. We consider two separate energy equations for matter and radiation in the diffusion limit. In…

High Energy Astrophysical Phenomena · Physics 2019-08-10 Maryam Samadi , Shahram Abbassi , Wei-Min Gu

We investigate spherical, isothermal and polytropic steady accretion models in the presence of the cosmological constant. Exact solutions are found for three classes of isothermal fluids, assuming the test gas approximation. The…

General Relativity and Quantum Cosmology · Physics 2013-11-13 Patryk Mach , Edward Malec , Janusz Karkowski

Cylindrical coordinates are often used in computational fluid dynamics, in particular, when one considers gas flow accreting onto a central object. Although the cylindrical coordinates have several advantages in describing rotation, they…

Instrumentation and Methods for Astrophysics · Physics 2021-03-17 Tomoyuki Hanawa , Yosuke Matsumoto

A numerical framework for rigorous linear stability analysis of two-phase stratified flows of two immiscible fluids in horizontal circular pipes is presented. For the first time, three-dimensional disturbances, including those at the…

Fluid Dynamics · Physics 2023-07-17 Ilya Barmak , Alexander Gelfgat , Neima Brauner

Line integration of stream-, streak-, and pathlines is widely used and popular for visualizing single-phase flow. In multiphase flow, i.e., where the fluid consists, e.g., of a liquid and a gaseous phase, these techniques could also provide…

Fluid Dynamics · Physics 2022-12-20 Alexander Straub , Sebastian Boblest , Grzegorz K. Karch , Filip Sadlo , Thomas Ertl

This article presents a new finite element method for convection-diffusion equations by enhancing the continuous finite element space with a flux space for flux approximations that preserve the important mass conservation locally on each…

Numerical Analysis · Mathematics 2017-10-24 Yujie Liu , Junping Wang , Qingsong Zou

We show that when the gravitational force is correctly calculated in dealing with the vertical hydrostatic equilibrium of black hole accretion disks, the relationship that is valid for geometrically thin disks, i.e., $c_s/\Omega_K H =$…

Astrophysics · Physics 2010-11-05 Wei-Min Gu , Ju-Fu Lu

An evolving surface finite element discretisation is analysed for the evolution of a closed two-dimensional surface governed by a system coupling a generalised forced mean curvature flow and a reaction--diffusion process on the surface,…

Numerical Analysis · Mathematics 2022-06-06 Charles M. Elliott , Harald Garcke , Balázs Kovács

In the present chapter we focus on the fundamentals of non-grid-conforming numerical approaches to simulating particulate flows, implementation issues and grid convergence vs. available reference data. The main idea is to avoid adapting the…

Fluid Dynamics · Physics 2024-12-11 Markus Uhlmann , Jos Derksen , Anthony Wachs , Lian-Ping Wang , Manuel Moriche

We have performed a systematic, large-scale simulation study of granular media in two- and three-dimensions, investigating the rheology of cohesionless granular particles in inclined plane geometries, i.e., chute flows. We find that over a…

Statistical Mechanics · Physics 2009-11-07 L. E. Silbert , D. Ertas , G. S. Grest , T. C. Halsey , D. Levine , S. J. Plimpton

An analytic solution is presented to the three-dimensional problem of steady axisymmetric fluid flow through an accretion disk. The solution has been obtained through a systematic expansion in the small parameter epsilon =H/R (the ratio of…

Astrophysics · Physics 2007-05-23 W. Kluzniak , D. Kita

When one considers a shock wave in the frame where the shock is at rest, on either side one has a steady flow which converges to equilibrium away from the shock. However, hydrodynamics is unable to describe this flow if the asymptotic…

Nuclear Theory · Physics 2022-03-14 Esteban Calzetta

In this technical note, we demonstrate the robustness of our numerical scheme of vorticity iteration in dealing with the dipole-wall interaction at small viscosity, with emphasis on mesh convergence, boundary vorticity as well as wall…

Fluid Dynamics · Physics 2019-03-15 F. Lam

We study the effects of impurity scattering on the low energy edge state dynamic s for a broad class of quantum Hall fluids at filling factor $\nu =n/(np+1)$, for integer $n$ and even integer $p$. When $p$ is positive all $n$ of the edge…

Condensed Matter · Physics 2009-10-22 C. L. Kane , M. P. A. Fisher

We consider a model of a binary mixture of two immiscible compressible fluids. We propose a numerical scheme and discuss its basic properties: Stability, consistency, convergence. The convergence is established via the method of generalized…

Analysis of PDEs · Mathematics 2022-02-02 Eduard Feireisl , Madalina Petcu , Bangwei She

We consider dry granular flow down an inclined chute with a localised contraction theoretically and numerically. The flow regimes are predicted through a novel extended one-dimensional hydraulic theory. A discrete particle method validated…

Geophysics · Physics 2015-04-20 D. R. Tunuguntla , T. Weinhart , A. R. Thornton , O. Bokhove

This paper presents numerical and analytical investigation of gas flow in gas-dynamic filter - a device for cleaning gas from solid particles with counter flow of large water particles in order to prevent their release to the atmosphere.…

Numerical Analysis · Mathematics 2025-10-20 Ulyan G. Pirumov

We numerically investigate, through discrete element simulations, the steady flow of identical, frictionless spheres sheared between two parallel, bumpy planes in the absence of gravity and under a fixed normal load. We measure the spatial…

Soft Condensed Matter · Physics 2024-07-25 Dalila Vescovi , Astrid S. de Wijn , Graham L. W. Cross , Diego Berzi

In this paper, we study the linear stability properties of perturbations around the homogeneous Couette flow for a 2D isentropic compressible fluid in the domain $\mathbb{T}\times \mathbb{R}$. In the inviscid case there is a generic…

Analysis of PDEs · Mathematics 2021-08-24 Paolo Antonelli , Michele Dolce , Pierangelo Marcati

During the last few years, a number of works in computer simulation have focused on the clustering and percolation properties of simple fluids based in an energetic connectivity criterion proposed long ago by T.L. Hill [J. Chem. Phys. 23,…

Soft Condensed Matter · Physics 2009-11-07 Luis A. Pugnaloni , Ileana F. Marquez , Fernando Vericat