Search results for "Marangoni effect"
showing 10 items of 13 documents
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 …
Experimental and numerical study of anomalous thermocapillary convection in liquid gallium
1999
Thermocapillary Marangoni convection of liquid gallium was studied experimentally and numerically. A specially designed experimental setup ensured an oxide-free surface of the liquid gallium for a very long time. The convective flow at the free surface was found to be directed opposite to both buoyancy-driven and ordinary thermocapillary convection. The anomalous direction of the thermocapillary flow was explained by the presence of a small amount of a surface-active contaminant—lead adsorbed at the free surface. Two different approaches were used to describe the observed phenomenon. First, the flow was treated as a pure thermocapillary convection with a modified dependence of the surface t…
Influence of growth parameters and melt convection on the solid-liquid interface during RF-floating zone crystal growth of intermetallic compounds
2001
Abstract The influence of growth parameters and melt convection on the solid–liquid interface of the intermetallic compound Ni3Si grown by the RF-floating zone technique was investigated experimentally as well as numerically. Numerical simulations showed that the heat transfer is strongly influenced by the electromagnetically driven and Marangoni convections whereas both the buoyancy and feed rotation have a negligible effect. It was found experimentally that the inductor design, the rod diameter and the length of the molten zone influence the solid–liquid interface shape significantly. The electromagnetically driven convection increases dramatically with increasing zone length due to the r…
Studies on Instabilities and Patterns in Evaporating Liquids at Reduced Pressure and/or Microwave Irradiation
1990
This paper summarizes our recent experimental and theoretical work on the instabilities in liquids and at interfaces which form during evaporation at reduced pressure and/or microwave irradiation. We have observed a variety of patterns (Benard rolls, Marangoni waves, Hickman interface deformations) which depend on the value of the reduced pressure and the power of the incident beam.
Microscale Marangoni actuation: All-optical and all-electrical methods
2006
We present experimental results from an all-optical microfluidic platform that may be complimented by a thin film all-electrical network. Using these configurations we have studied the microfluidic convective flow systems of silicone oil, glycerol, and 1,3,5-trinitrotoluene on open surfaces through the production of surface tension gradients derived from thermal gradients. We show that sufficient localized thermal variation can be created utilizing surface plasmons and/or engaging individually addressable resistive thermal elements. Both studies manipulate fluids via Marangoni forces, each having their unique exploitable advantages. Surface plasmon excitation in metal foils are the driving …
Microwave heating of water in a rectangular waveguide: Validating EOF-Library against COMSOL multiphysics and existing numerical studies
2019
The purpose of this work is two-fold: first, we successfully validate our open-source tool EOF-Library, which efficiently couples Elmer FEM and OpenFOAM, against COMSOL Multiphysics, a commercial simulation package; second, we inform about significant discrepancies between our results and the experimental and simulation data found in a series of research papers. We reproduce the previously published numerical simulations wherein microwaves are supplied to a water domain through a rectangular waveguide, inducing convective flow. This is a conjugate problem with weakly coupled electromagnetics, heat transfer and fluid dynamics. It involves effects such as permittivity dependence on temperatur…
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…
Theoretical study of a Bénard Marangoni problem
2011
[EN] In this paper we prove the existence of strong solutions for the stationary Benard-Marangoni problem in a finite domain flat on the top, bifurcating from the basic heat conductive state. The Benard-Marangoni problem is a physical phenomenon of thermal convection in which the effects of buoyancy and surface tension are taken into account. This problem is modelled with a system of partial differential equations of the type Navier-Stokes and heat equation. The boundary conditions include crossed boundary conditions involving tangential derivatives of the temperature and normal derivatives of the velocity field. To define tangential derivatives at the boundary, intended in the trace sense,…
Microwave heating as a tool for coupling Marangoni and Hickman instabilities
2007
The aim of this paper is the linear stability analysis of an evaporating interface in order to justify hydrodynamic behaviors observed during evaporation of water and ethanol simultaneously under microwave irradiation and reduced pressure. In relation to the local character of the thermal conversion of electromagnetic energy, and of the thermal dependency of the dielectric loss, it seems possible under microwave heating to induce a specific hydrodynamic compared to those induced by conventional heating.
Augmentation of weld penetration by flux assisted TIG welding and its distinct variants for oxygen free copper
2021
Abstract A comparative study to investigate the influences of single component fluxes on the depth-to-width ratio (DWR) of oxygen free copper was carried out with novel variants of tungsten inert gas (TIG) welding namely Activated TIG (A-TIG), Flux Bounded TIG (FB-TIG) and Flux Zoned TIG (FB-TIG) processes. The experiments to identify the fluxes delivering the higher DWRs in A-TIG welding among thirteen distinct fluxes were followed by the trials with FB-TIG and FZ-TIG employing those identified DWR fluxes. The fluxes which outperformed with all the techniques were MoO3 & MgO. Reversed Marangoni and arc constriction mechanisms were perceived to be opt for such an increase in DWR. Metallurgi…