Search results for "Fluid dynamic"
showing 10 items of 1034 documents
Warming of water in a glass
2016
The article focuses on the process of water warming from 0 °C in a glass. An experiment is performed that analyses the temperature in the top and bottom layers of water during warming. The experimental equipment is very simple and can be easily set up using devices available in schools. The temperature curves obtained from the experiment help us to understand the process of convection in the glass and to determine the temperature at which the density of water is maximum. In addition, computational fluid dynamics—CFD modeling is carried out to facilitate better comprehension of the phenomenon observed in the experiment.
Transient solutions for temperature and pressure waves in fluid-saturated porous rocks
1996
SUMMARY In this paper, hot-fluid migration dynamics for a fluid-saturated porous rock is analysed theoretically. We first recall a Bonafede model implemented with a classical scale analysis; this allows us to discuss a fully non-linear formulation related to transient phenomena, which is solved analytically as a solitary shock wave. The resulting time-scales are particularly small, corresponding to intense short-time geothermal phenomena. A novel non-linear migration mechanism, related to Darcy convection, is also discussed.
Interannual variability of circulation under spring ice in a boreal lake
2014
A small range (, 1uC) of under-ice water temperature is shown to result in remarkably different circulation regimes under spring ice in a deep, oligotrophic boreal lake. With the water column at , 4uC, melting of snow led to deepening vertical convection before ice break and a final depth of convection inversely correlated with earlier deep-water temperature. We attribute that to the nonlinear dependence of water density on temperature, albeit further affected by stochastic weather factors. In four of nine study years, convection led to complete under-ice overturn of the lake, indicating that this may not be uncommon in similar lakes with steep topography. River inflow and more intensive wa…
Convective phenomena in large melts including magnetic fields
2007
The set of characteristic parameters which describe modern large industrial CZ silicon single crystal growth systems is introduced. The main melt flow driving mechanisms are considered, and the characteristic density values of various in the melt acting forces are estimated. The analysis is illustrated with examples of numerical simulation and comparisons with experiments.
Magnetic field controlled FZ single crystal growth of intermetallic compounds
2005
Abstract Intermetallic rare-earth-transition-metal compounds with their coexistence of magnetic ordering and superconductivity are still of great scientific interest. The crystal growth of bulk single crystals is very often unsuccessful due to an unfavorable solid–liquid interface geometry enclosing concave fringes. The aim of the work is the contactless control of heat and material transport during floating-zone single crystal growth of intermetallic compounds. This control is provided by a tailored design of the electromagnetic field and the resulting electromagnetically driven convection. Numerical simulations for the determination of the electromagnetic field configuration induced by th…
A study of hydrothermal convection in saturated porous media
1993
Abstract Because of its relevance to many geological and technical problems, hydrothermal convection is investigated here mainly with the aid of numerical models by a systematic analysis of the properties of this type of convection for a range of super-critical Rayleigh numbers. Calculations were performed for two-dimensional models with constant properties in a region of aspect ratio 2. The principal results in the case of temperature fixed at the impermeable top and bottom are the following for the Nusselt number Nu, the cell aspect ratio a, and the boundary layer thickness δ: Nu ≈ 1.7 R0.5, a ≈ 1.3 R−0.4, δc ≈ 0.4 R−0.4 for 2.5 R = R f /R f ∗ and Rf and R f ∗ are the ambient and critical…
Viscous dissipation and thermoconvective instabilities in a horizontal porous channel heated from below
2010
Accepted version of av article from the journal: International Journal of Thermal Sciences. Published version available on Science Direct: http://dx.doi.org/10.1016/j.ijthermalsci.2009.10.010 A linear stability analysis of the basic uniform flow in a horizontal porous channel with a rectangular cross section is carried out. The thermal boundary conditions at the impermeable channel walls are: uniform incoming heat flux at the bottom wall, uniform temperature at the top wall, adiabatic lateral walls. Thermoconvective instabilities are caused by the incoming heat flux at the bottom wall and by the internal viscous heating. Linear stability against transverse or longitudinal roll disturbances …
Onset of convection in a porous rectangular channel with external heat transfer to upper and lower fluid environments
2012
Published version of an article in the journal: Transport in Porous Media. Also available from the publisher at: http://dx.doi.org/10.1007/s11242-012-0018-9 The conditions for the onset of convection in a horizontal rectangular channel filled with a fluid saturated porous medium are studied. The vertical sidewalls are assumed to be impermeable and adiabatic. The horizontal upper and lower boundary walls are considered as impermeable and subject to external heat transfer, modelled through a third-kind boundary condition on the temperature field. The external fluid environments above and below the channel, kept at different temperatures, provide the heating-from-below mechanism which may lead…
The simulation of morphology of dissimilar copper–steel electron beam welds using level set method
2010
Abstract In present work, the simulation of morphology and velocity field in dissimilar electron beam welds formed between the metals with limited solubility is described by the example of copper–stainless steel couple. Finite element software COMSOL Multiphysics 3.5 has been employed due to its flexibility in solving of coupled multiphysical problems. The domination of horizontal flows allows reducing the model to two dimensions. Level set method has been used to determine the position of the interface between immiscible components basing on coupled heat transfer and fluid flow pseudo-stationary solution. The evolution of the shape, fluid flow and mixing pattern in function of operational …
Influence on the macrosegregation of binary metallic alloys by thermoelectromagnetic convection and electromagnetic stirring combination
2014
International audience; Influence of a slowly rotating 0.5 T transverse magnetic field on the directionally solidified metallic alloy has been experimentally studied in this work. Main idea is to study an influence on the melt flow and material structure caused by the simultaneous electromagnetic stirring and thermoelectromagnetic convection with comparable magnitudes. Electromagnetic stirring and thermoelectromagnetic convection intensities have been estimated analytically to find optimal experimental parameters. It is experimentally demonstrated that with such an interaction it is possible to modify component macrosegregation of Sn-10 wt% Pb alloy. Helical macrosegregation within cylindri…