Search results for "hydrodynamic"
showing 10 items of 530 documents
On the convexity of relativistic ideal magnetohydrodynamics
2015
We analyze the influence of the magnetic field in the convexity properties of the relativistic magnetohydrodynamics system of equations. To this purpose we use the approach of Lax, based on the analysis of the linearly degenerate/genuinely non-linear nature of the characteristic fields. Degenerate and non-degenerate states are discussed separately and the non-relativistic, unmagnetized limits are properly recovered. The characteristic fields corresponding to the material and Alfv\'en waves are linearly degenerate and, then, not affected by the convexity issue. The analysis of the characteristic fields associated with the magnetosonic waves reveals, however, a dependence of the convexity con…
MHD evolution of a fragment of a CME core in the outer solar corona
2007
Detailed hydrodynamic modeling explained several features of a fragment of the core of a Coronal Mass Ejection observed with SoHO/UVCS at 1.7 Ro on 12 December 1997, but some questions remained unsolved. We investigate the role of the magnetic fields in the thermal insulation and the expansion of an ejected fragment (cloud) traveling upwards in the outer corona. We perform MHD simulations including the effects of thermal conduction and radiative losses of a dense spherical or cylindrical cloud launched upwards in the outer corona, with various assumptions on the strength and topology of the ambient magnetic field; we also consider the case of a cylindrical cloud with an internal magnetic fi…
Magnetized relativistic jets and helical magnetic fields: II. Radiation
2021
This is the second of a series of two papers that deepen our understanding of the transversal structure and the properties of recollimation shocks of axisymmetric, relativistic, superfast magnetosonic, overpressured jets. They extend previous work that characterized these properties in connection with the dominant type of energy (internal, kinetic, or magnetic) in the jet to models with helical magnetic fields with larger magnetic pitch angles and force-free magnetic fields. In the first paper of this series, the magnetohydrodynamical models were computed following an approach that allows studying the structure of steady, axisymmetric, relativistic (magnetized) flows using one-dimensional t…
Coupled fluid-flow and magnetic-field simulation of the Riga dynamo experiment
2006
Magnetic fields of planets, stars, and galaxies result from self-excitation in moving electroconducting fluids, also known as the dynamo effect. This phenomenon was recently experimentally confirmed in the Riga dynamo experiment [ A. Gailitis et al., Phys. Rev. Lett. 84, 4365 (2000) ; A. Gailitis et al., Physics of Plasmas 11, 2838 (2004) ], consisting of a helical motion of sodium in a long pipe followed by a straight backflow in a surrounding annular passage, which provided adequate conditions for magnetic-field self-excitation. In this paper, a first attempt to simulate computationally the Riga experiment is reported. The velocity and turbulence fields are modeled by a finite-volume Navi…
Effects of non-uniform interstellar magnetic field on synchrotron X-ray and inverse-Compton γ-ray morphology of supernova remnants
2011
Context. Observations of SuperNova Remnants (SNRs) in X-ray and γ-ray bands promise to contribute important information to our understanding of the kinematics of charged particles and magnetic fields in the vicinity of strong non-relativistic shocks and, therefore, the nature of Galactic cosmic rays. The accurate analysis of SNR images collected in different energy bands requires theoretical modeling of synchrotron and inverse Compton emission from SNRs. Aims. We develop a numerical code (remlight) to synthesize, from MHD simulations, the synchrotron radio, X-ray, and inverse Compton γ-ray emission originating in SNRs expanding in a non-uniform interstellar medium (ISM) and/or non-uniform i…
VORTEX LAYERS IN THE SMALL VISCOSITY LIMIT
2006
In this paper we suppose that the initial datum for the 2D Navier–Stokes equations are of the vortex layer type, in the sense that there is a rapid variation in the tangential component across a curve. The variation occurs through a distance which is of the same order of the square root of the viscosity. Assuming the initial as well the matching (with the outer flow) data analytic, we show that our model equations are well posed. Another necessary assumption is that the radius of curvature of the curve is much larger than the thickness of the layer.
Upwind Relativistic MHD Code for Astrophysical Applications
2003
We describe the status of devolpment of a 2.5D numerical code to solve the equations of ideal relativistic magnetohydrodynamics. The numerical code, based on high-resolution shock-capturing techniques, solves the equations written in conservation form and computes the numerical fluxes using a linearized Riemann solver. A special procedure is used to force the conservation of magnetic flux along the evolution.
A Divergence-Free High-Resolution Code for MHD
2001
We describe a 2.5D numerical code to solve the equations of ideal magnetohydrodynamics (MHD). The numerical code, based on high-resolution shock-capturing (HRSC) techniques, solves the equations written in conservation form and computes the numerical fluxes using a linearized Riemann solver. A special procedure is used to force the conservation of magnetic flux along the time.
Numerical Study of Forced MHD Convection Flow and Temperature Around Periodically Placed Cylinders
2016
In this paper we consider 2D stationary boundary value problems for the system of magnetohydrodynamic (MHD) equations and the heat transfer equation. The viscous electrically conducting incompressible liquid moves between infinite cylinders with square or round sections placed periodically. We also consider similar 2D MHD channel flow with periodically placed obstacles on the channel walls. We analyse the 2D forced and free MHD convection flow and temperature around cylinders and obstacles in homogeneous external magnetic field. The cylinders, obstacles and walls of the channel with constant temperature are heated. The distributions of electromagnetic fields, forces, velocity and temperatur…
Field and numerical study of river confluence flow structures
2010
River hydrodynamics Turbulent open channel flow and transport phenomena