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Bifurcation of thermocapillary convection in a shallow annular pool of silicon melt

Acta Mechanica Sinica 2007年第1期23卷 43-48页

作者： Yourong Li Lan Peng Shuangying Wu Nobuyuki Imaishi College of Power Engineering Chongqing University Chongqing 400044 China Institute for Materials Chemistry and Engineering Kyushu University Fukuoka 816-8580 Japan

In order to understand the nature of surface patterns on silicon melts in industrial Czochralski furnaces, we conducted a series of unsteady threedimensional numerical simulations of thermocapillary convections in thin silicon melt pools in an annular container. The pool is heated from the outer cylindrical wall and cooled at the inner wall. Bottom and top surfaces are adiabatic. The results show that the flow is steady and axisymmetric at small temperature difference in the radial direction. When the temperature difference exceeds a certain threshold value, hydrothermal waves appear and bifurcation occurs. In this case, the flow is unsteady and there are two possible groups of hydrothermal waves with different number of waves, which are characterized by spoke patterns traveling in the clockwise and counter-clockwise directions. Details of the flow and temperature disturbances are discussed and number of waves and traveling velocity of the hydro- thermal wave are determined.

关键词： Computer simulation thermocapillary convection Semiconducting silicon Bifurcation

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EXPERIMENTAL STUDY ON thermocapillary convection

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Acta Mechanica Sinica 2003年第2期19卷 127-133页

作者：束继祖 NationalMicrogravityLaboratory InstituteofMechanicsCASBeijing100080China

In the present paper, the experimental studies on thermocapillary convection are reviewed. The author's interest is mainly focused on the onset of oscillatory thermocapillary convection,the features of oscillatory flow pattern, and the critical Marangoni number related with temperature and free surface oscillation. The coordinated measurement in a microgravity environment of a drop shaft is also addressed.

关键词： microgravity fluid dynamics thermocapillary convection liquid bridge floating zone oscillatory process free surface wave experiment in drop shaft

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Control of Oscillatory thermocapillary convection in a Half-Zone Liquid Bridge by Circumference Round Heating

Control of Oscillatory Thermocapillary Convection in a Half-...

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第六届中日微重力科学专题研讨会

作者： Masaki KUDO Hiroshi KAWAMURA Tokyo University of Science Chiba Japan Tokyo University of Science Chiba Japan

＜正＞1. INTRODUCTION Thermocapaillarity is of fundamental importance in material processing under microgravity condition. The floating-zone method （FZ） is a material process technique for producing and purifying single crystals of metals and oxides. It is widely known that, using this method, a transition to three-dimensional oscillatory thermocapillary convection takes place in the melt. The oscillatory state of the convection causes detrimental striations in the crystal structure, even under the microgravity condition . A half-zone model （HZ） has been employed to simplify the thermocapillary convection in FZ （fig.1）. In this model, two co-axial cylindrical rods hold a

关键词： thermocapillary convection Half-zone liquid bridge Oscillation Control

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TWO BIFURCATION TRANSITION PROCESSES IN FLOATING HALF ZONE convection OF LARGER PRANDTL NUMBER FLUID

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Acta Mechanica Sinica 2002年第4期18卷 328-341页

作者：唐泽眉阿燕曹重华胡文瑞 National Microgravity Laboratory CASInstitute of MechanicsCASBeijing 100080China

Processes of the onset oscillation in the thermocapillary convection under the Earth's gravity are investigated by the numerical simulation and exper- iments in a floating half zone of large Prandtl number with different volume ratio. Both computational and experimental results show that the steady and axisymmetric convection turns to the oscillatory convection of m=l for the slender liquid bridge, and to the oscillatory convection before a steady and 3D asymmetric state for the case of a fat liquid bridge.It implies that,there are two critical Marangoni numbers related,respectively,to these two bifurcation transitions for the fat liquid bridge.The computational results agree with the results of ground-based experiments.

关键词： thermocapillary convection microgravity fluid numerical simulation experiment

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Bifurcation Diversity in an Annular Pool Heated from Below:Prandtl and Biot Numbers Effects

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Communications in Computational Physics 2013年第2期13卷 428-441页

作者： A.J.Torregrosa S.Hoyas M.J.Pérez-Quiles J.M.Mompò-Laborda CMT-Motores Térmicos Universitat Politécnica de ValénciaValencia 46022Spain Instituto Universitario de Matemática Pura y Aplicada Universitat Politécnica de ValénciaValencia 46022Spain

In this article the instabilities appearing in a liquid layer are studied numerically by means of the linear stability method.The fluid is confined in an annular pool and is heated from below with a linear decreasing temperature profile from the inner to the outer wall.The top surface is open to the atmosphere and both lateral walls are adiabatic.Using the Rayleigh number as the only control parameter,many kind of bifurcations appear at moderately low Prandtl numbers and depending on the Biot number.Several regions on the Prandtl-Biot plane are identified,their boundaries being formed from competing solutions at codimension-two bifurcation points.

关键词： thermocapillary convection Prandtl number Biot number linear stability

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EFFECTS OF CONVECTIVE FLUID MOTION UPON OXIDE CRYSTAL GROWTH IN HIGH TEMPERATURE SOLUTION

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空间科学学报 2002年第Z1期22卷 159-159页

作者： JIN Weiqing CAI Lixia LIANG Xinan PAN Zhilei Shanghai Institute of Ceramics The Chinese Academy of Sciences Shanghai 200050 P.R. China Shanghai Institute of Ceramics The Chinese Academy of Sciences Shanghai 200050 P.R. China Shanghai Institute of Ceramics The Chinese Academy of Sciences Shanghai 200050 P.R. China Shanghai Institute of Ceramics The Chinese Academy of Sciences Shanghai 200050 P.R. China

　　For understanding of the influence of convective flow on crystal growth, space high temperature in situ observation instrument (SHITISOI) is dedicated to visualize and record the whole growth process of oxide crystals in high temperature up to 1000°C. Model experiments using transparent liquids such as KNbO3 and a mix ture of Li2B4O7+KNbO3 were chosen to investigate effects on ground and in space.On the earth, an investigation of growth kinetics of KNbO3 crystal related to two different states of convection: diffusive-advective flow and diffusive-convective flow,has been performed. The per unit length of a step e is calculated from the exper imental data for two different states of convection. Analyses of these data show the effect of buoyancy convection is to enhance the sharpness of the interface. The growth of KNbO3 crystals from solution of KNbO3+Li2B4O7 was investigated in space. The streamlines of the steady thermocapillary convection in Li2B4O7 solvent was observed. Due to thermocapillary convection, KNbO3 crystal grains grew and filled the whole solution homogeneously. Earth-based quenching experiments are de signed in order to study polyhedral instability of KNbO3 crystal, which is controlled by diffusion mechanism limitation. In all cases, when the crystal was nucleated near air/solution surface, it lost its polyhedral stability and varied from polyhedrons to dedrites. The thickness of diffusion mechanism limitation layer is about 60μm.……

关键词： HIGH TEMPERATURE thermocapillary convection diffusion mechanism high temperature polyhedral instability in situ observation growth kinetics oxide crystals crystal growth the earth in order

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