Search results for " Convection"

Three-Dimensional Flow and Temperature Distribution in Rayleigh-Bènard Convection Using Thermochromic Liquid Crystals and Digital Image Processing

2000

Improved Tomographic Particle Image Velocimetry and Thermography in Rayleigh-Bènard Convection

2001

Parallel Schwarz methods for convection-dominated semilinear diffusion problems

2002

AbstractParallel two-level Schwarz methods are proposed for the numerical solution of convection-diffusion problems, with the emphasis on convection-dominated problems. Two variants of the methodology are investigated. They differ from each other by the type of boundary conditions (Dirichlet- or Neumann-type) posed on a part of the second-level subdomain interfaces. Convergence properties of the two-level Schwarz methods are experimentally compared with those of a variant of the standard multi-domain Schwarz alternating method. Numerical experiments performed on a distributed memory multiprocessor computer illustrate parallel efficiency of the methods.

Melt evolution beneath a rifted craton edge: 40Ar/39Ar geochronology and Sr-Nd-Hf-Pb isotope systematics of primitive alkaline basalts and lamprophyr…

2016

A new high-precision Ar-40/Ar-39 anorthoclase feldspar age of 176.7 +/- 0.5 Ma (2-sigma) reveals that small-volume alkaline basaltic magmatism occurred at the rifted SW margin of the Baltic Shield in Scania (southern Sweden), at a time of global plate reorganization associated with the inception of Pangea supercontinent break-up. Our combined elemental and Sr-Nd-Hf-Pb isotope dataset for representative basanite and nephelinite samples (>8 wt.% MgO) from 16 subvolcanic necks of the 30 by 40 km large Jurassic volcanic field suggests magma derivation from a moderately depleted mantle source (Sr-87/(86)Sri = 0.7034-0.7048; epsilon Nd-i = +4.4 to +5.2; epsilon Hf-i = +4.7 to +8.1; Pb-206/(204)Pb…

Traces of ancient mafic layers in the Tethys oceanic mantle

2014

Abstract Oceanic basalts are formed by melting of a chemically and isotopically heterogeneous mantle source. The oceanic mantle probably resembles a marble cake containing layers of mafic rock – perhaps recycled ocean crust – stored in the mantle for >1 billion years. Many questions about the nature and distribution of these mantle heterogeneities remain. Here we show that lithological and isotopic traces of ancient mafic layers can still be seen in mantle rocks that have melted to form oceanic crust at a spreading centre in the Tethys Ocean. We have found centimetre-scale heterogeneity in initial osmium isotope ratios in mantle rocks from the Pindos Ophiolite. Deformed pyroxenite layers ha…

Refrigeration of an Array of Cylindrical Nanosystems by Flowing Superfluid Helium

2016

We consider the refrigeration of an array of heat-dissipating cylindrical nanosystems as a simplified model of computer refrigeration. We explore the use of He II as cooling fluid, taking into account forced convection and heat conduction. The main conceptual and practical difficulties arise in the calculation of the effective thermal conductivity. Since He II does not follow Fourier’s law, the effective geometry-dependent conductivity must be extracted from a more general equation for heat transfer. Furthermore, we impose the restrictions that the maximum temperature along the array should be less than (Formula presented.) transition temperature and that quantum turbulence is avoided, in o…

Heat and mass transfer phenomena

2002

This section deals with main problems of the heat and mass transfer in magnetic colloids. The analysis is mainly based on the general model given in the Chapter written by R. E. Rosensweig. Hydrodynamic and thermal problems are simplified considering incompressible liquids and neglecting the effects of polarization and electric conductivity as well as ignoring some other secondary effects that usually can be neglected in ferrofluid experiments. Contrarily, the analysis of mass transfer accounts for new sedimentation phenomena and cross effects of interrelated heat and mass transfer. Since the description given by Rosensweig is of general theoretical nature, while the present work mainly foc…

A study of free convection in air around horizontal cylinders of different diameters based on holographic interferometry. Temperature field equations…

2002

Abstract Holographic interferometry is used to study free convection in air around horizontal cylinders of different diameters and equal length, involving different surface temperatures, with the aim of defining the corresponding temperature fields. Interferograms were obtained to determine the temperature (T) of each point as well as its distance (x) from the surface of the cylinder. These values in turn made it possible to define functions (of an exponential nature in our case), T=f(x), that satisfactorily reproduced the temperature fields. Posteriorly, these functions were used to calculate the local convection coefficients, determining their dependency upon temperature and the direction…

Fully Developed Mixed Magnetohydrodynamic Convection in a Vertical Square Duct

2008

The fully developed flow of an electrically conducting, internally heated fluid in a vertical square duct under the influence of buoyancy and magnetohydrodynamic forces is studied. The flow being parallel, the governing equations are two-dimensional and linear; an analytical solution exists for temperature, while velocity and electric potential are computed by a finite difference technique under different electric boundary conditions, forced to natural convection intensity ratios and values of the magnetic induction. Limiting values of pressure gradient and mean velocity are determined for the flow to be unidirectional throughout the duct's section; recirculation occurs for intermediate val…

Influence of a Magnetic Field on Liquid Metal Free Convection in an Internally Heated Cubic Enclosure

2002

The buoyancy‐driven magnetohydrodynamic flow in a cubic enclosure was investigated by three‐dimensional numerical simulation. The enclosure was volumetrically heated by a uniform power density and cooled along two opposite vertical walls, all remaining walls being adiabatic. A uniform magnetic field was applied orthogonally to the gravity vector and to the temperature gradient. The Prandtl number was 0.0321 (characteristic of Pb–17Li at 300°C), the Rayleigh number was 104, and the Hartmann number was made to vary between 0 and 2×103. The steady‐state Navier–Stokes equations, in conjunction with a scalar transport equation for the fluid's enthalpy and with the Poisson equation for the electr…