Search results for "Fluid dynamic"
showing 10 items of 1034 documents
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…
Thermal-hydraulic behaviour of the DEMO divertor plasma facing components cooling circuit
2017
Abstract Within the framework of the Work Package DIV 1 – “Divertor Cassette Design and Integration” of the EUROfusion action, a research campaign has been jointly carried out by ENEA and University of Palermo to investigate the thermal-hydraulic performances of the DEMO divertor cassette cooling system. A comparative evaluation study has been performed considering three different options for the cooling circuit layout of the divertor Plasma Facing Components (PFCs). The potential improvement in the thermal-hydraulic performance of the cooling system, to be achieved by modifying cooling circuit layout, has been also assessed and discussed in terms of optimization strategy. The research acti…
Flow Resistance Law in Channels with Flexible Submerged Vegetation
2005
In this paper, experimental data collected in a straight flume having a bed covered by grasslike vegetation have been used to analyze flow resistance for flexible submerged elements. At first, the measurements are used to test the applicability of Kouwen’s method. Then, a calibration of two coefficients appearing in the semilogarithmic flow resistance equation is carried out. Finally, applying the P-theorem and the incomplete self-similarity condition, a flow resistance equation linking the friction factor with the shear Reynolds number, the depth-vegetation height ratio and the inflection degree is deduced.
Breakdown of Burton-Prime-Slichter approach and lateral solute segregation in radially converging flows
2005
A theoretical study is presented of the effect of a radially converging melt flow, which is directed away from the solidification front, on the radial solute segregation in simple solidification models. We show that the classical Burton-Prim-Slichter (BPS) solution describing the effect of a diverging flow on the solute incorporation into the solidifying material breaks down for the flows converging along the solidification front. The breakdown is caused by a divergence of the integral defining the effective boundary layer thickness which is the basic concept of the BPS theory. Although such a divergence can formally be avoided by restricting the axial extension of the melt to a layer of fi…
Simulation of the influence of gas flow on melt convection and phase boundaries in FZ silicon single crystal growth
2015
Abstract Axisymmetric calculations of inert gas flow in a floating zone puller are carried out using an open source software package OpenFOAM. Transient axisymmetric melt flow in liquid silicon and quasi-stationary shape of silicon phase boundaries are calculated using a specialized program FZone. Additional heat losses at silicon surfaces caused by the gas flow are taken into account for argon and helium, while maintaining the height of molten zone by adjusting inductor current. Cooling causes an increase of electromagnetic force, heat sources and more intense melt flow, while crystallization interface deflection decreases. The shear stress of gas flow is found to be an order of magnitude …
Design of a reactor operating in supercritical water conditions using CFD simulations. Examples of synthesized nanomaterials
2011
International audience; Direct information about fluids under supercritical water conditions is unfeasible due to the engineering restrictions at high pressure and high temperature. Numerical investigations based on computational fluid dynamics (CFD) calculations are widely used in order to get extensive information on the fluid behavior, particularly to help the design of a new reactor. This paper presents the numerical investigations performed on an original supercritical water device, especially in the level of the reactor. CFD calculations allow to design and optimize the present reactor described in this study. Currently, this process produces some nanometric oxide powders in continuou…
K-ϵ-L model in turbulent superfluid helium
2020
Abstract We generalize the K − ϵ model of classical turbulence to superfluid helium. In a classical viscous fluid the phenomenological eddy viscosity characterizing the effects of turbulence depends on the turbulent kinetic energy K and the dissipation function ϵ , which are mainly related to the fluctuations of the velocity field and of its gradient. In superfluid helium, instead, we consider the necessary coefficients for describing the effects of classical and quantum turbulence, involving fluctuations of the velocity, the heat flux, and the vortex line density of the quantized vortex lines. By splitting the several fields into a time-average part and a fluctuating part, some expressions…
Phase transitions in a colloidal dispersion flowing through a cylindrical capillary
2008
The flow of a charged-stabilized colloidal dispersion of crystalline equilibrium structure through a cylindrical capillary is investigated. The simultaneous existence of up to three differently ordered states is observed under conditions of stationary flow. The evolution of their concentric arrangement along the capillary is determined by Bragg microscopy. For sufficient low fluxes, stationary phase distributions are obtained. While the apparent viscosity is non-monotonous and non-Newtonian, the corresponding velocity profiles are found to be piecewise parabolic and are compatible to numerical calculations. Furthermore, we test the assumption of a constant yield stress determining the radia…
Heat and mass transfer phenomena in magnetic fluids
2007
In this article the influence of a magnetic field on heat and mass transport phenomena in magnetic fluids (ferrofluids) will be discussed. The first section is dealing with a magnetically driven convection, the so called thermomagnetic convection while in the second section the influence of a temperature gradient on the mass transport, the Soret effect in ferrofluids, is reviewed. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Computational thermofluid-dynamic analysis of DEMO divertor cassette body cooling circuit
2018
Abstract Within the framework of the Work Package Divertor, Subproject: Cassette Design and Integration (WPDIV-Cassette) of the EUROfusion action, a research campaign has been jointly carried out by ENEA and University of Palermo to investigate the thermal-hydraulic performances of the DEMO divertor cassette cooling system. The research activity has been carried out following a theoretical-computational approach based on the finite volume method and adopting a qualified Computational Fluid-Dynamic (CFD) code. Fully-coupled fluid-structure CFD analyses have been carried out for the recently-revised cassette body cooling circuit under nominal steady state conditions, imposing a non-uniform sp…