Numerical Prediction of Multicellular Melt Flow During Natural Convection-Dominated Melting

2003 ◽  
Vol 17 (1) ◽  
pp. 62-68 ◽  
Author(s):  
Sin Kim ◽  
Samim Anghaie ◽  
Gary Chen
Keyword(s):  
Natural Convection ◽  
Numerical Prediction ◽  
Melt Flow ◽  
Convection Dominated

Mechanisms of Thermo-Solutal Transport and Segregation in High-Pressure Liquid-Encapsulated Czochralski Crystal Growth

1999 ◽  
Vol 121 (1) ◽  
pp. 148-159 ◽  
Author(s):  
Y. F. Zou ◽  
G.-X. Wang ◽  
H. Zhang ◽  
V. Prasad
Keyword(s):  
Boundary Layer ◽  
High Pressure ◽  
Natural Convection ◽  
Driving Forces ◽  
Axisymmetric Flow ◽  
Melt Flow ◽  
Pure Crystal ◽  
Radial Segregation ◽  
Crystal Rotation ◽  
Crucible Rotation

The mechanism of dopant transport and segregation in high-pressure liquid-encapsulated Czochralski (HPLEC) grown III-V compound crystals (e.g., GaAs, InP) has been numerically studied using an integrated model, MASTRAPP. The model approximates the melt flow in the crucible as a quasi-steady-state, laminar, and axisymmetric flow, but the gas flow is considered as turbulent. Based on the physics of the growth process, a two-time-level scheme has been implemented where the dopant transport and growth are simulated at a smaller time scale while flow and temperature solutions are obtained from quasi-static calculations. Detailed numerical analyses are performed for the conditions of pure crystal rotation, pure thermally driven natural convection, and pure crucible rotation as well as for mixed flow with all of these forces present simultaneously. The dopant transport and segregation in these cases are well correlated to the corresponding melt flow pattern. Very weak radial segregation is predicted for pure crystal rotation because the resulting melt flow leads to a fairly flat solute boundary layer. The natural convection, on the other hand, produces a nonuniform boundary layer along the melt/crystal interface. This leads to a strong radial segregation with a high concentration along the central axis of the crystal. The crucible rotation has a similar effect. The combined effect of all of these flow mechanisms produces a strong radial segregation, whose extent depends on the relative strength of the driving forces. In all of these cases, strong melt flows lead to thin boundary layers that result in decreased longitudinal segregation. The predictions agree well with the experimental observations reported in the literature.

A Study on the Importance of Natural Convection During Solidification in Rectangular Geometry

2011 ◽  
Vol 133 (10) ◽  
Author(s):  
Mehmet Akif Ezan ◽  
Aytunc Erek ◽  
Ibrahim Dincer
Keyword(s):  
Natural Convection ◽  
Solidification Process ◽  
Rectangular Cavity ◽  
Change Processes ◽  
Test Cases ◽  
One Dimensional ◽  
Critical Effect ◽  
Numerical Predictions ◽  
The Mathematical Model ◽  
Convection Dominated

In this study, solidification process inside a water filled rectangular cavity is numerically investigated. The mathematical model is validated by comparing the current numerical predictions with the available analytical, numerical, and experimental results for three different test cases: one-dimensional conduction dominated solidification, natural convection in rectangular cavity, and natural convection dominated solidification in rectangular cavity. For all three cases, some good agreements are achieved in terms of isotherms, interface positions, and streamlines. After validation, time-wise ice formations are represented, and comparisons are made between bare and finned wall cases. In addition to these, further analyses are carried out by neglecting the buoyancy forces to introduce the differences between natural convection dominated and conduction dominated models. The results emphasize that natural convection has a critical effect in actual phase change processes.

scholarly journals Unsteady near-shore natural convection induced by surface cooling

2009 ◽  
Vol 642 ◽  
pp. 213-233 ◽  
Author(s):  
YADAN MAO ◽  
CHENGWANG LEI ◽  
JOHN C. PATTERSON
Keyword(s):  
Natural Convection ◽  
Scaling Analysis ◽  
Mean Flow ◽  
Flow Properties ◽  
Surface Cooling ◽  
Environmental Implications ◽  
Near Shore ◽  
Radiation Induced ◽  
The Stability ◽  
Convection Dominated

Natural convection in calm near-shore waters induced by daytime heating or nighttime cooling plays a significant role in cross-shore exchanges with significant biological and environmental implications. Having previously reported an improved scaling analysis on the daytime radiation-induced natural convection, the authors present in this paper a detailed scaling analysis quantifying the flow properties at varying offshore distances induced by nighttime surface cooling. Two critical functions of offshore distance have been derived to identify the distinctness and the stability of the thermal boundary layer. Two flow scenarios are possible depending on the bottom slope. For the relatively large slope scenario, three flow regimes are possible, which are discussed in detail. For each flow regime, all the possible distinctive subregions are identified. Two different sets of scaling incorporating the offshore-distance dependency have been derived for the conduction-dominated region and stable-convection-dominated region respectively. It is found that the scaling for flow in the stable-convection-dominated region also applies to the time-averaged mean flow in the unstable region. The present scaling results are verified by numerical simulations.

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