Convective Transport Phenomena and Macrosegregation During Solidification of a Binary Metal Alloy: I—Numerical Predictions

1994 ◽  
Vol 116 (3) ◽  
pp. 735-741 ◽  
Author(s):  
P. J. Prescott ◽  
F. P. Incropera
Keyword(s):  
Continuum Model ◽  
Transport Phenomena ◽  
Vertical Wall ◽  
Convective Transport ◽  
Interior Region ◽  
Numerical Predictions ◽  
Outer Periphery ◽  
Diffusive Convection ◽  
Macrosegregation Pattern ◽  
Double Diffusive

A continuum model is used to simulate transient convective transport phenomena numerically during solidification of a Pb-19 percent Sn alloy in an experimental test cell. Solidification occurs in an axisymmetric, annular mold of stainless steel, cooled along its outer vertical wall. Results show that, during early stages of solidification, double-diffusive convection and liquid exchange between melted and mushy zones are responsible for the formation of channels in the outer periphery of the ingot, which ultimately lead to a form of macrosegregation known as A-segregates. During intermediate stages of solidification, solutally driven natural convection spawns a cone segregate in the interior region of the ingot. The final macrosegregation pattern is characterized, in general, by increasing Sn concentration with increasing height throughout the ingot and by increasing Sn concentration with decreasing radius in the upper portion of the ingot.

Numerical Study of the Onset of Double-Diffusive Cellular Convection Due to a Uniform Lateral Heat Flux

1982 ◽  
Vol 104 (4) ◽  
pp. 649-655 ◽  
Author(s):  
S. Takao ◽  
M. Tsuchiya ◽  
U. Narusawa
Keyword(s):  
Heat Flux ◽  
Numerical Study ◽  
Vertical Wall ◽  
Lewis Number ◽  
Double Diffusive Convection ◽  
Physical Experiments ◽  
Diffusive Convection ◽  
The Stability ◽  
Double Diffusive ◽  
Lateral Heat

When a fluid with a vertical solute gradient of (−dS/dy)0 is heated laterally, roll cells start to form at the boundary, developing into a series of convective layers. Numerical experiments were performed to investigate the onset of the abovementioned double-diffusive convection under the application of a uniform lateral heat flux. The paper reports the results and discussion of the following aspects of the stability of double-diffusive convection; (i) the relationship between the critical value, (Ra/Rs)c, above which convection cells form along the vertical wall and the nondimensional slot width, (d/L), (ii) the effect of the Lewis number on (Ra/Rs)c. It was also confirmed that values of (Ra/Rs)c as well as H/L (the nondimensional vertical size of incipient cells) obtained in this numerical experiment for wide slot widths (d/L>∼30), agreed well with those obtained previously by physical experiments.

Numerical Study of Double Diffusive Convection within the Annular Region of Two Concentric Vertical Cylinders

2017 ◽  
Vol 374 ◽  
pp. 1-17 ◽  
Author(s):  
Mohamed Amine Medebber ◽  
Nourddine Retiel
Keyword(s):  
Numerical Study ◽  
Vertical Wall ◽  
Annular Region ◽  
Geometrical Parameters ◽  
Double Diffusive Convection ◽  
Uniform Temperature ◽  
Simpler Algorithm ◽  
Diffusive Convection ◽  
Vertical Cylinders ◽  
Double Diffusive

This article reports a numerical study of double-diffusive convection within the annular region of two concentric vertical cylinders. The outer vertical wall is maintained at lower uniform temperature and concentration, while the inner vertical wall is maintained at higher uniform temperature and concentration. The top and bottom horizontal walls are adiabatic and impermeable to mass transfer. The resulting governing equations are solved using a finite volume method. The coupling between the continuity and momentum equations is solved using the SIMPLER algorithm. The compilations have been obtained for Prandtl numbers (Pr) equal to 7.0, and Lewis number (Le) equal to 100. The thermal Rayleigh number (RaT) and height ratio (X) are, respectively, varied in the range 103≤RaT≤106 and 0.0≤X≤1.0. The influence of physical and geometrical parameters on the streamlines, isotherms, isoconcentrations, average Nusselt and Sherwood numbers has been numerically investigated in detail.

Liquid-Liquid Mixing Due to G-Jitter in Microgravity

2002 ◽  
Author(s):  
C. Benjapiyaporn ◽  
V. Timchenko ◽  
S. S. Leong ◽  
G. de Vahl Davis ◽  
E. Leonardi
Keyword(s):  
Numerical Simulation ◽  
Vertical Wall ◽  
Double Diffusive Convection ◽  
Low Gravity ◽  
Diffusive Convection ◽  
Higher Temperature ◽  
Miscible Liquids ◽  
Range Of Values ◽  
Buoyancy Ratio ◽  
Double Diffusive

This paper describes a study of double diffusive convection inside a rectangular cavity in low gravity; it arose out of a much broader study of solidification of a binary alloy in microgravity. The cavity initially contained two different but miscible liquids meeting at a sharp vertical interface at the middle of a cavity. One vertical wall was kept at a uniform low temperature, while the opposite wall was at a uniform higher temperature. The top and bottom walls were adiabatic. All walls were impermeable. A numerical simulation was made of the induced convection and mixing for a range of values of buoyancy ratio and gravity characteristics, including both steady g and g-jitter.

DOUBLE-DIFFUSIVE CONVECTION IN LIQUID FREON

1998 ◽  
Author(s):  
Pierre Dupont ◽  
O. Gorieu ◽  
Hassan Peerhossaini ◽  
M. Kestoras
Keyword(s):  
Double Diffusive Convection ◽  
Diffusive Convection ◽  
Double Diffusive
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