We study statistical properties of two-dimensional turbulent flows. Three systems are considered: the Navier-Stokes equation, surface quasigeostrophic flow, and a model equation for thermal convection in the Earth's mantle. Direct numerical simulations are used to determine one-point fluctuation properties. Comparative study shows universality of probability density functions (PDFs) across diff...

Abstract

A compressible finite volume formulation for large eddy simulation (LES) of turbulent channel flows was extended to solve the turbulent flows in pipes and annular passages. A general finite volume scheme was developed based on conservation equations in Cartesian coordinates with non-Cartesian control volumes. A dual-time stepping approach with time derivative preconditioning was employed and ti...

We present three-dimensional numerical magnetohydrodynamic simulations of radiatively inefficient spherical accretion onto a black hole. The simulations are initialized with a Bondi flow, and with a weak, dynamically unimportant, large-scale magnetic field. The magnetic field is amplified as the gas flows in. When the magnetic pressure approaches equipartition with the gas pressure, the field b...

Context. Oscillations of stellar p modes, excited by turbulent convection, are investigated. In the uppermost part of the solar convection zone, radiative cooling is responsible for the formation of turbulent plumes, hence the medium is modelled with downdrafts and updrafts. Aims. We take into account the asymmetry of the upand downflows created by turbulent plumes through an adapted closure mo...

The principles underlying a proposed class of black hole accretion models are examined. The flows are generally referred to as “convection-dominated,” and are characterized by inward transport of angular momentum by thermal convection and outward viscous transport, vanishing mass accretion, and vanishing local energy dissipation. In this paper we examine the viability of these ideas by explicit...

In this paper we investigate the role of convection in clusters of galaxies. A number of studies have shown that the convective stability criterion for the intracluster medium (ICM) is very different from the Schwarzchild criterion due to the effects of anisotropic thermal conduction and cosmic rays. Building on these studies, we present a model in which a central active galactic nucleus (AGN) ...