by Storming Media .
Written in English
|The Physical Object|
This work develops a boundary-layer model for the thermocapillary feedback mechanism that can occur at the edge of weld pools and other materials processes, in the limit where convection dominates the heat transport but the Prandtl number is small. Previously, Canright [Phys. Fluids 6, ()] showed that in this regime the dynamics of this "cold corner" region is locally Cited by: 1. Thermocapillary flow near a “cold corner” A distinct Prandtl boundary layer on the solid boundary and a Marangoni boundary layer on the free boundary and high gradients of the longitudinal velocity along the free boundary in the immediate vicinity of the “cold corner” are observed. It is found for the first time that with distance Author: I. B. Semenova. A complete structural analogy is observed between flow in a cavity driven by a moving lid and thermocapillary flow in the boundary layer limit, and it is found that all the solutions, spanning a Author: David Canright. Thermocapillary and buoyant flows induced by nonuniform heating of the free surface of a horizontally unbounded liquid layer over a cold solid bottom are studied numerically and by order of magnitude analyses for large Marangoni and Rayleigh numbers. The Prandtl number of the liquid is assumed to be of order unity or large, which are the cases of most interest in combustion.
The thermocapillary feedback mechanism important at the edge of weld pools and other materials processes is examined through a model problem. A pool of liquid with a flat horizontal free surface is bounded on one side by a vertical solid wall, which is maintained at a cold temperature to unit depth, and at a warmer temperature below; far away the fluid is at the warmer temperature. The Stokes flow in differentially heated cylindrical liquid bridges is calculated revealing the fundamental flow structures when the thermocapillary surface stresses are low. As general characteristics of thermocapillary flows the boundary layer scalings for certain limits of the Marangoni and Prandtl numbers are derived. Scale Analysis of Thermocapillary Weld Pool Shape With High Prandtl Number P. S. Wei, P. S. Wei whereas high Prandtl number represents the thermal boundary layer thickness to be less than that of momentum. Since Marangoni number is usually very high, the scaling of transport processes is divided into the hot, intermediate and cold corner. This banner text can have markup.. web; books; video; audio; software; images; Toggle navigation.
A transient heat transfer model was utilized to simulate the heat flow and fluid flow in the weld pool. In this paper, the results of the heat flow and fluid flow analysis are presented. View. The thermocapillary convection (Marangoni flow) is driven by temperature-induced surface tension variations along the surface of a thin liquid layer as shown in Figure When the temperature gradient along the liquid surface is relatively small, a two-dimensional surface flow directs from the hot side to the cold side, and a return flow appears at the bottom of the layer. A turbulent boundary layer is very unsteady and the streamlines do not remain parallel. The boundary layer shape represents an average of the velocity at any height. There is a region between the laminar and turbulent section where transition takes place The turbulent boundary layer exists on top of a thin laminar layer called the LAMINAR SUB. Formation of the boundary layer. Previously we noted that the boundary layer grows from zero when a fluid starts to flow over a solid surface. As is passes over a greater length more fluid is slowed by friction between the fluid layers close to the boundary. Hence the thickness of the slower layer increases.