Search results for "Buoyancy"

Analytical Study of the Thermal Induced Oscillations Known as Heartbeats

1998

Abstract A laser beam traveling horizontally at a short distance below the free surface of an absorbing solution exhibits various oscillatory states (periodic, quasiperiodic, and chaotic) which depend on both the buoyancy (Archimedes force) and the thermal coefficient of the surface tension (Marangoni effect). The beam oscillations have been called “heartbeats.” In this work, the heartbeats were produced by pumping 1-(2-pyridylazo)-2-naphthol (PAN) solutions in silicone oil with an Ar+continuous-wave laser beam. The relationships between PAN concentration and the other parameters that control the oscillatory behavior were studied. The frequency of the oscillations sensitively varied with sm…

Effect of pseudo-gravitational acceleration on the dissolution rate of miscible drops

2017

The effect of pseudo-gravitational acceleration on the dissolution process of two phase miscible systems has been investigated at high acceleration values using a spinning drop tensiometer with three systems: 1-butanol/water, isobutyric acid/water, and triethylamine/water. We concluded that the dissolution process involves at least three different transport phenomena: diffusion, barodiffusion, and gravitational (buoyancy-driven) convection. The last two phenomena are significantly affected by the centrifugal acceleration acting at the interface between the two fluids, and the coupling with the geometry of the dissolving drop leads to a change of the mass flux during the course of the dissol…

Separation of Ferrocolloids in Thermodiffusion Columns: the Effect of Solute Buoyancy

2002

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…

Direct numerical simulation of MR suspension: The role of viscous and magnetic interactions between particles

2009

A numerical method is developed with aim to simulate the magnetorheological (MR) suspension taking into account realistic magnetic forces. The MR suspension is described by spherical particles with nonlinear magnetic properties suspended in a shear flow. Inertia effects, Brownian motion and buoyancy forces are neglected. The hydrodynamic interaction between close particles is taken into account approximately. Results of some test simulations are presented.

Statistical analysis of the influence of forces on particles in EM driven recirculated turbulent flows

2011

The present paper contains an analysis of the statistical distribution of forces affecting non-conducting particles dispersed in an EM induced recirculated flow in induction furnaces. The simulation is conducted adopting the LES-based Euler-Lagrange approach in the limit of dilute conditions (one-way coupling). It is done by means of a development of OpenFOAM software code. The used Lagrange equation for particle tracking includes drag, EM, buoyancy, lift, acceleration and added mass forces. The relevant approximations for the forces are chosen on the basis of the statistical analysis of the non-dimensional parameters (particle Reynolds number, shear stress and acceleration parameter). The …

Adiabatic eigenflows in a vertical porous channel

2014

AbstractThe existence of an infinite class of buoyant flows in a vertical porous channel with adiabatic and impermeable boundary walls, called adiabatic eigenflows, is discussed. A uniform heat source within the saturated medium is assumed, so that a stationary state is possible with a net vertical through-flow convecting away the excess heat. The simple isothermal flow with uniform velocity profile is a special adiabatic eigenflow if the power supplied by the heat source is zero. The linear stability analysis of the adiabatic eigenflows is carried out analytically. It is shown that these basic flows are unstable. The only exception, when the power supplied by the heat source is zero, is th…

Explicit cloud-top entrainment parameterization in the global climate model ECHAM5-HAM

2011

New developments in the turbulence parameterization in the general circulation model ECHAM5-HAM are presented. They consist mainly of an explicit entrainment closure at the top of stratocumulus-capped boundary layers and the addition of an explicit contribution of the radiative divergence in the buoyancy production term. The impact of the new implementations on a single column model study and on the global scale is presented here. The parameterization has a "smoothing" effect: the abnormally high values of turbulence kinetic energy are reduced, both in the single column and in the Californian stratocumulus region. A sensitivity study with prescribed droplet concentration shows a reduction i…

Magnetic Control of Convection in Liquid Metal Heated from Above

1999

We investigated experimentally the buoyancy driven convection induced by localized central heating from above in cylindrical tanks filled with liquid metal eutectic alloy (low-Prandtl-number liquid). The experiments were carried out for two aspect ratios A = (radius/height) = 4.125 and 0.333. Time-averaged local temperature distributions and radial and azimuthal velocity components in the liquid at different distances from heater axis were measured. It is shown that maximum temperature gradient is centered in vicinity heater. Temperature difference in radial direction creates pressure gradient between heater and cold wall regions. This gradient leads to upraising of liquid nearly heater and…

Applied multi-pulsed laser in surface treatment and numerical–experimental analysis

2011

International audience; This paper presents a comparison between simulation and experimental results of the melting process of metallic material by a pulsed laser source Nd–YAG. The simulations of temperature and velocity fields of melted material were done by solving the transient heat transfer and fluid-flow equations. Variations of the thermophysical properties were considered. Furthermore, the model included the effects of the surface-tension gradient on the fluid surface and the buoyancy force. The simulation was useful in improving our understanding of the phenomena occurring in the treated material. Using a laser triangulation sensor, an experimental study was also conducted on the s…