scholarly journals Existence and static stability of a capillary free surface appearing in a dewetted Bridgman process. Part II.

2019 ◽  
Vol 11 (4) ◽  
pp. 37-48
Author(s):  
Agneta M. BALINT ◽  
Stefan BALINT
Keyword(s):  
Free Surface ◽  
Pressure Difference ◽  
Thermal Conditions ◽  
Static Stability ◽  
Surface Shape ◽  
Growth Technique ◽  
Free Surface Shape ◽  
Bridgman Crystal Growth ◽  
The Right ◽  
Theoretical Results

This paper presents six theoretical results concerning the existence and static stability of a capillary free surface appearing in a dewetted Bridgman crystal growth technique. The results are obtained in an axis-symmetric 2D model for semiconductors for which 𝜃𝜃𝑐𝑐+𝛼𝛼𝑒𝑒>𝜋𝜋 (where:𝜃𝜃𝑐𝑐- wetting angle and 𝛼𝛼𝑒𝑒- growth angle). Numerical results are presented in case of GaSb semiconductor growth. The reported results can help, the practical crystal growers, in better understanding the dependence of the free surface shape and size on the pressure difference across the free surface and the right choice of crystal size, pressure difference and thermal conditions for the growth process.

scholarly journals Existence and static stability of a capillary free surface appearing in a dewetted Bridgman process. Part I.

2019 ◽  
Vol 11 (3) ◽  
pp. 29-40
Author(s):  
Agneta M. BALINT ◽  
Stefan BALINT
Keyword(s):  
Free Surface ◽  
Growth Process ◽  
Thermal Conditions ◽  
Static Stability ◽  
Surface Shape ◽  
Growth Technique ◽  
Free Surface Shape ◽  
Bridgman Crystal Growth ◽  
Theoretical Results ◽  
2D Model

This paper presents six theoretical results concerning the existence and static stability of a capillary free surface appearing in a dewetted Bridgman crystal growth technique. The results are obtained in an axis-symmetric 2D model for semiconductors for which 𝜃𝜃𝑐𝑐+𝛼𝛼𝑒𝑒<𝜋𝜋 (where:𝜃𝜃𝑐𝑐- wetting angle and 𝛼𝛼𝑒𝑒- growth angle). Numerical results are presented in case of InSb semiconductor growth. The reported results can help, the practical crystal growers, in better understanding the dependence of the free surface shape and size on the pressure difference across the free surface and prepare the appropriate seed size, and thermal conditions before seeding the growth process.

Investigation of Steady-State Drawing Force and Heat Transfer in Polymer Optical Fiber Manufacturing

2004 ◽  
Vol 126 (2) ◽  
pp. 236-243 ◽  
Author(s):  
Hayden M. Reeve ◽  
Ann M. Mescher ◽  
Ashley F. Emery
Keyword(s):  
Heat Transfer ◽  
Free Surface ◽  
Optical Fiber ◽  
Conjugate Problem ◽  
Surface Shape ◽  
Polymer Optical Fiber ◽  
Draw Force ◽  
Free Surface Shape ◽  
Cylindrical Furnace ◽  
Fiber Manufacturing

The force required to draw a polymer preform into optical fiber is predicted and measured, along with the resultant free surface shape of the polymer, as it is heated in an enclosed cylindrical furnace. The draw force is a function of the highly temperature dependent polymer viscosity. Therefore accurate prediction of the draw force relies critically on the predicted heat transfer within the furnace. In this investigation, FIDAP was used to solve the full axi-symmetric conjugate problem, including natural convection, thermal radiation, and prediction of the polymer free surface. Measured and predicted shapes of the polymer free surface compared well for a range of preform diameters, draw speeds, and furnace temperatures. The predicted draw forces were typically within 20% of the experimentally measured values, with the draw force being very sensitive to both the furnace wall temperature and to the feed rate of the polymer.

scholarly journals Dynamics of flow structures and surface shapes in the surface switching of rotating fluid

2016 ◽  
Vol 789 ◽  
pp. 402-424 ◽  
Author(s):  
M. Iima ◽  
Y. Tasaka
Keyword(s):  
Free Surface ◽  
Vortex Structure ◽  
Surface Deformation ◽  
Surface Shape ◽  
Flow Structures ◽  
Rotating Fluid ◽  
Turbulent Transition ◽  
Structure Changes ◽  
Before And After ◽  
Free Surface Shape

We present a study of the dynamics of the free-surface shape of a flow in a cylinder driven by a rotating bottom. Near the critical Reynolds number of the laminar–turbulent transition of the boundary layer, the free surface exhibits irregular surface switching between axisymmetric and non-axisymmetric shapes, and the switching often occurs with a significant change in the free-surface height. Although such surface deformation is known to be caused by the flow structures, the detailed flow structures of a rotating fluid with a large surface deformation have yet to be analysed. We thus investigate the velocity distribution and surface shape dynamics and show that the flow field during the loss of its axisymmetry is similar to that predicted by the theory of Tophøj et al. (Phys. Rev. Lett., vol. 110, 2013, 194502). The slight difference observed by quantitative comparison is caused by the fact that the basic flow of our study contains a weak rigid-body rotation in addition to the potential flow assumed by the theory. Furthermore, the observed non-axisymmetric surface shape, which has an elliptic horizontal cross-section, is generally associated with a quadrupole vortex structure. It is also found that the relative position between the free surface and the flow structure changes before and after the detachment of the free surface from the bottom. The change just after the detachment is drastic and occurs via a transient dipole-like vortex structure.

Free Surface Effects on Normal Stress Measurements in Cone and Plate Flow

2007 ◽  
Vol 17 (3) ◽  
pp. 36494-1-36494-6 ◽  
Author(s):  
David C. Venerus
Keyword(s):  
Free Surface ◽  
Stress Field ◽  
Normal Stress ◽  
Spherical Shape ◽  
Normal Stress Difference ◽  
Surface Shape ◽  
Stress Difference ◽  
Stress Measurements ◽  
Free Surface Shape ◽  
Normal Stress Differences

Abstract The effects of free surface shape on normal stress difference measurements in cone and plate flow are investigated. The analysis shows that the stress field is significantly altered by deviations of the free surface from an ideal (spherical) shape. For the cone and partitioned plate technique, it is shown how modest deviation from a spherical free surface shape can lead to errors of roughly 10% in the measured normal stress differences.

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