Analysis of periodic non-rotational W striations in Mo single crystals due to nonsteady thermocapillary convection

Jurisch, M.; Löser, W.

doi:10.1016/0022-0248(90)90904-y

Cited by 48 publications

(18 citation statements)

References 23 publications

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“…The frequency obtained in this experiment is higher than that given in Refs. [8][9][10][11]. An estimation of the main frequency was given by dimension analyses as [4] …”

Section: Resultsmentioning

confidence: 99%

“…Difficulties in experiments of liquids with Pr < 1 include flow visualization due to non-transparency and sensitivity of their surface to impurities. Only a few experiments of 0022-0248/96/$15.00 Copyright © 1996 Elsevier Science B.V. All rights reserved thermocapillary convection with low Pr can be found in the literature [6][7][8][9][10][11][12][13]. Jurisch used an electron beam heating facility to study the surface temperature oscillations of oscillatory thermocapillary convection in a floating Mo full zone (Pr = 0.025) and found that the critical Marangoni number for the onset of oscillations is 1200 and the frequency is around 1 Hz [10,11].…”

Section: Introductionmentioning

confidence: 99%

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Experiment on the thermocapillary convection of a mercury liquid bridge in a floating half zone

Han

Sun

Dai

et al. 1996

Journal of Crystal Growth

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A liquid bridge of a floating half zone consisting of liquid mercury sealed in a glass tube with nitrogen atmosphere was used for the experiment of thermocapillary convection with a low Prandtl number liquid. A non-contacted diagnostic method was developed to monitor the surface flow and the surface oscillation. A growing surface film (or skin) is a crucial source to suppress thermocapillary convection, and is discussed in this paper. For the case of a mercury liquid bridge, the critical Marangoni number was obtained as 900, and the oscillatory frequency was around 5 Hz.

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“…The frequency obtained in this experiment is higher than that given in Refs. [8][9][10][11]. An estimation of the main frequency was given by dimension analyses as [4] …”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Experiment on the thermocapillary convection of a mercury liquid bridge in a floating half zone

Han

Sun

Dai

et al. 1996

Journal of Crystal Growth

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“…Jurisch et al [9,10] employed an electron beam equipment with a circular W-electron gun to heat the Mo and Nb rod at the center in a dynamical vacuum chamber to investigate the thermocapillary convection and its instability of floating full-zone liquid bridge. Since there is no need to apply the temperature difference by using different materials (like copper rods in our experiment), the possibility of reaction of different materials leading to surface film is eliminated and the dynamical vacuum can greatly reduce the interaction of the rod material with surrounding gases.…”

Section: Discussionmentioning

confidence: 99%

Experimental study of thermocapillary convection on a liquid bridge consisting of fluid with low Prandtl number in a floating half-zone

Sun

Han

Dai

et al. 1997

Sci. China Ser. E-Technol. Sci.

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A device of mercury liquid bridge of floating half-zone is designed to experimentally explore thermocapillary convection and its instability of a low Prandtl number liquid. Noncontacted diagnostic techniques were developed to monitor surface flow and surface deformation. The surface flow and the influence of a growing surface film (or skin) on the flow were observed. It is shown that the film is a key factor in changing the behavior associated with the thermocapiUary convection. The experiment indicates that the critical Marangoni number should be much higher than that expected by the numerical simulation. The condition and process of surface film growth are disc~. The surface oscillation of the mercury bridge wrapped with "dirt-film" was observed, and the characteristics and the frequency associated with this oscillation are given. Keywords: liquid bridge, low Prandtl fluid, microgravity, thermocapillary convection.Marangoni convection is driven by non-uniformity of surface tension due to a temperature (or concentration) gradient along the free surface of a liquid. The liquid bridge of the floating half zone is a typical model for simulating the surface tension driven flow of crystal growth processes performed in a floating zone configuration. The steady and oscillatory convection of molten materials during the materials processing is considered one of the main causes for crystal defects and inhomogeneities. The convection driven by buoyancy is inevitable on the ground but is greatly reduced in a microgravity environment. Therefore space material science has become a new research field. In maerogravity the convection driven by surface tension gradient, or thermocapiUary convection, becomes dominant. A great number of publications are devoted to the thermocapillary convection and its instability in the past two decades. However, most experimental work on this area is limited to transparent liquids with Prandtl (Pr) number around 1 or larger [1-51 . On the other hand, from the view of applications, melts of semiconductors, metals or alloys are related to the behavior of liquids having low Prandtl numbers. ;l'hese liquids are basically opaque, so the ex-

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“…14 was an amplitude equation for the complex amplitude of the excited capillary wave, which is standing. In addition, the mean flow produced by the wave was calculated in order to elucidate its ability to counterbalance the undesirable thermocapillary flow, 16 which is always present in nonisothermal conditions; this counterbalancing effect has been analyzed both experimentally 17 and theoretically. 1819 The mean flow produced by the capillary waves was the well known streaming flow 20 (also called steady streaming, or acoustic streaming 21 ), chiven by nonzero time averaged Reynolds stresses in the Stokes boundary layer attached to the disks supporting the bridge.…”

Section: Introduction and Formulationmentioning

confidence: 99%

Weakly nonlinear nonaxisymmetric oscillations of capillary bridges at small viscosity

2002

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Weakly nonlinear nonaxisymmetric oscillations of a capillary bridge are considered in the limit of small viscosity. The supporting disks of the liquid bridge are subjected to small amplitude mechanical vibrations with a frequency that is cióse to a natural frequency. A set of equations is derived for accounting the slow dynamics of the capillary bridge. These equations describe the coupled evolution of two counter-rotating capillary waves and an associated streaming flow. Our derivation shows that the effect of the streaming flow on the capillary waves cannot be a priori ignored because it arises at the same order as the leading (cubic) nonlinearity. The system obtained is simplified, then analyzed both analytically and numerically to provide qualitative predictions of both the relevant large time dynamics and the role of the streaming flow. The case of parametric forcing at a frequency near twice a natural frequency is also considered.

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Analysis of periodic non-rotational W striations in Mo single crystals due to nonsteady thermocapillary convection

Cited by 48 publications

References 23 publications

Experiment on the thermocapillary convection of a mercury liquid bridge in a floating half zone

Experiment on the thermocapillary convection of a mercury liquid bridge in a floating half zone

Experimental study of thermocapillary convection on a liquid bridge consisting of fluid with low Prandtl number in a floating half-zone

Weakly nonlinear nonaxisymmetric oscillations of capillary bridges at small viscosity

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