Study of Freckles Formation During Directional Solidification Under the Influence of Single-Phase and Multiphase Convection

2013 ◽  
Vol 5 (2) ◽  
Author(s):  
Prodyut R. Chakraborty ◽  
Pradip Dutta
Keyword(s):  
Numerical Simulation ◽  
Directional Solidification ◽  
Ammonium Chloride ◽  
Solid Fraction ◽  
Single Phase ◽  
Solid Phase ◽  
Single Domain ◽  
Mushy Region ◽  
Convection Model ◽  
Coherency Point

Formation of freckles during directional solidification of hypereutectic aqueous ammonium-chloride in a bottom cooled cavity is studied numerically. The system studied is thermally stable but solutally unstable, which causes plume type convection and formation of channels in the growing solid mush. Solidification of hypereutectic solutions is usually characterized by detached and drifting solid crystals, thus resulting in multiphase convection. The numerical simulation is performed using a fixed grid single domain approach with single-phase and multiphase convection phenomena. For the multiphase convection modeling in the solidifying system under consideration, the mushy region is assumed to consist of an immobile coherent zone containing packed equiaxed crystals and a mobile noncoherent zone where the solid crystals are able to move. The two zones are demarcated by a critical solid fraction criterion, referred to as the coherency point. The overall effects of drifting solid phase on the freckles formation are compared with the results from conventional single-phase convection model.

Rayleigh-Benard Convection During Directional Solidification of a Binary Solution Cooled From the Top

2002 ◽  
Author(s):  
P. Kumar ◽  
S. Chakraborty ◽  
K. Srinivasan ◽  
P. Dutta
Keyword(s):  
Directional Solidification ◽  
Ammonium Chloride ◽  
Binary Solution ◽  
Convective Transport ◽  
Mushy Region ◽  
Two Phase ◽  
Thermal Buoyancy ◽  
Neutrally Buoyant ◽  
Rayleigh Benard ◽  
Double Diffusive

In this paper, we investigate the effects of laminar double-diffusive natural convection on directional solidification of binary fluids when cooled and solidified from the top. The study is performed using aqueous ammonium chloride solution as the model fluid. The experiments are performed with an initial concentration of ammonium chloride is less than the eutectic composition, leading to an aiding double-diffusive convection. In this case, solidification leads to the formation of a diffused matrix of dendritic crystals (mushy region) separating the pure solid and liquid regions. Below the two-phase mushy region, Rayleigh-Benard type of cellular convective motions are observed. The cellular motions, which are caused by thermal buoyancy, die once the thickness of the liquid layer falls below a critical value. The features of convective transport are visualised using a sheet of laser light scattered through neutrally buoyant glass particles seeded in the solution. Numerical simulations are also performed, and the agreement with experimental results is found to be good.

Solid Phase Synthesis and Sintering Properties of Yttrium Iron Garnet

2008 ◽  
Vol 368-372 ◽  
pp. 588-590 ◽  
Author(s):  
Ming Hao Fang ◽  
Jun Tong Huang ◽  
Zhao Hui Huang ◽  
Yan Gai Liu ◽  
Bin Jiang ◽  
...  
Keyword(s):  
Solid State ◽  
Solid State Reaction ◽  
Single Phase ◽  
Solid Phase Synthesis ◽  
Solid Phase ◽  
Volume Density ◽  
Phase Synthesis ◽  
Fe2o3 Content ◽  
Sintering Properties ◽  
Iron Garnet

Single phase YIG powders were synthesized successfully using Fe2O3 and Y2O3 as starting materials by solid state reaction, and YIG ceramics were prepared by pressureless sintering. The influence of synthesizing temperature and Fe2O3 content on the final production were studied The effect of Fe2O3 content on volume density and microstructure of the sintered YIG was also investigated. The results showed that single phase YIG powders were synthesized by solid state reaction at 1400°C for 3h. When Fe2O3 content was excessive 3 wt%, YIG ceramics with a density of 5.294g·cm-3 was fabricated by sintering at 1480°C for 2.5h.

3D Numerical Simulation of Polydisperse Pressurized Gas-Solid Fluidized Bed

2011 ◽  
Author(s):  
P. Fede ◽  
O. Simonin ◽  
I. Ghouila
Keyword(s):  
Numerical Simulation ◽  
Fluidized Bed ◽  
Ethylene Polymerization ◽  
Solid Phase ◽  
Three Dimensional ◽  
Gas Velocity ◽  
Particle Segregation ◽  
3D Numerical Simulation ◽  
Model Predictions ◽  
The Mean

Three dimensional unsteady numerical simulations of dense pressurized polydisperse fluidized bed have been carried out. The geometry is a medium-scale industrial pilot for ethylene polymerization. The numerical simulation have been performed with a polydisperse collision model. The consistency of the polydisperse model predictions with the monodisperse ones is shown. The results show that the pressure distribution and the mean vertical gas velocity are not modified by polydispersion of the solid phase. In contrast, the solid particle species are not identically distributed in the fluidized bed indicating the presence of particle segregation.

scholarly journals Time-dependent interface stability during directional solidification of a single phase alloy(Ⅰ) Theoritical

2004 ◽  
Vol 53 (11) ◽  
pp. 3971
Author(s):  
Lin Xin ◽  
Li Tao ◽  
Wang Lin-Lin ◽  
Su Yun-Peng ◽  
Huang Wei-Dong
Keyword(s):  
Directional Solidification ◽  
Single Phase ◽  
Time Dependent ◽  
Interface Stability ◽  
Single Phase Alloy

scholarly journals Numerical simulation of microstructure evolution during directional solidification of Ti-45at.%Al alloy

2008 ◽  
Vol 57 (5) ◽  
pp. 3048
Author(s):  
Wang Kuang-Fei ◽  
Guo Jing-Jie ◽  
Mi Guo-Fa ◽  
Li Bang-Sheng ◽  
Fu Heng-Zhi
Keyword(s):  
Numerical Simulation ◽  
Directional Solidification ◽  
Microstructure Evolution ◽  
Al Alloy

Numerical simulation of several impacting ceramic droplets with liquid/solid phase change

2015 ◽  
Vol 268 ◽  
pp. 272-277 ◽  
Author(s):  
Cédric Le Bot ◽  
Stéphane Vincent ◽  
Erick Meillot ◽  
Frédéric Sarret ◽  
Jean-Paul Caltagirone ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Phase Change ◽  
Solid Phase
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