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  • Interface Deformation and Convective Transport in Horizontal Differentially Heated Air-Oil Layers
  • Abstract Convection in a differentially heated cavity partly filled with silicone oil has been experimentally studied. The air-oil layers are subjected to a temperature difference in the vertical direction, with the lower wall being heated with respect to the top. The overall geometry is that of an enclosed cavity that is octagonal in plan. Heights of oil layers considered for experiments correspond to 30, 50, and 70% of the vertical cavity dimension. Measurements have been carried out using a shadowgraph technique. A limited number of interferograms have also been recorded. The shadowgraph technique has been validated against interferograms under identical experimental…
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  • Modeling a Discontinuous CVD Coating Process: II. Detailed Simulation Results
  • Abstract The atmospheric chemical vapor deposition process on continuous glass sheets is a well developed one and the parameters that affect it are relatively well understood. When this process is converted to coat discrete glass plates it introduces a new variable, the gap between the glass plates, which can significantly impact the quality of the coatings. In this study a 2D pseudo steady state model of the process was developed to study the effect of the gap, and the ratio of outlet to inlet gas flow rates (called the bias), on the coating quality. The model was solved with the commercially…
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  • Modeling a Discontinuous CVD Coating Process: I. Model Development and Validation
  • Abstract A simplified 2D pseudo steady state model was developed for an atmospheric chemical vapor deposition (CVD) process on glass. This is used to study the feasibility of converting a continuous coating process to one with discrete glass plates with a gap between them. A preliminary estimate employing mass transfer correlations suggested that there would be significant concentration variations due to the gap between the plates. More detailed studies were done by solving the model numerically employing a finite difference scheme with a vorticity-stream function formulation, and employing the commercial computational fluid dynamics program FIDAP which employs a finite element scheme.…
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  • A Comparative Study of G-jitter Effect on Thermal Diffusion aboard the International Space Station
  • Abstract Fluid science research including thermal diffusion in fluids benefits from the quiescent low-gravity environment provided by the International Space Station (ISS). However, residual gravities (or g-jitters) aboard the ISS impact the overall environment in which experiments are being performed. The impact of these residual gravities needs to be assessed to ensure that they are appropriately accounted for when results are being reported for experiments performed onboard the ISS. In this paper we study the thermal diffusion process in a ternary mixture of n-butane, dodecane and methane. Measured data from the Space Acceleration Measurement System (SAMS) acceleration system onboard the ISS…
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  • Oxygen Transport in Tissue Engineering Systems: Cartilage and Myocardium
  • Abstract Efficient transport of oxygen is one of the main requirements in tissue engineering systems in order to avoid cell death in the inner tissue regions and support uniform tissue regeneration. In this paper, we review approaches to design of tissue engineering systems with adequate oxygen delivery for cultivation of cartilage and myocardium, two distinctly different tissue types with respect to the tissue structure and oxygen requirements. Mathematical modeling was used to support experimental results and predict oxygen transport within the cultivated tissues and correlate it to the cell response and tissue properties.
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  • Solid/Liquid Phase Change: Recent Studies and Models
  • Abstract Some problems related to solid/liquid phase change are presented. Attention is focused on interface modeling for numerical analysis and one-dimensional directional growing and melting. Microgravity relevance of some situations is emphasized. It is shown, in particular, that in some circumstances melting is not the simple reversal of crystal growth due to some (still poorly known) phenomena (nucleation and growth of liquid droplets in the bulk, solid and liquid dendrites due to a morphological instability of the phase boundary). Relevant mathematical models are discussed and described (to a certain extent) for analysis and/or characterization of these phenomena when they are disjoint…
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  • Recent Developments in Oscillatory Marangoni Convection
  • Abstract A Marangoni Convection Modeling Research group was formed in Japan in order to investigate oscillatory thermocapillary flow systematically over a wide range of Prandtl number (Pr). The research by the group represents the current status of the subject. The present article reports the work done by the group members. The work is divided into three Pr ranges (low, medium and high) because the cause of oscillations is different in each range. For the low-Pr case, the transition to oscillatory flow is preceded by a steady bifurcation to three-dimensional convection. For the first time an experimental proof of this first transition…
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  • Flow Features and Industrial Applications of TSE Rheoextrusion Process
  • Abstract This paper presents an overview of diverse extrusion techniques and, in particular, a focused discussion about the rheoextrusion process for semi-solid casting (a novel casting process for the fabrication of high quality metals). The review reveals a wealth of interesting rheological and microstructural features, illustrating qualitative and quantitative data. The analysis is supported by relevant numerical results and examples. It is shown how numerical studies can lead to significant insights into these processes by providing more detailed information on the fundamental mechanisms of morphology development (during phase change) and profile forming. The die filling and solidification behaviours within extrusion dies…
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  • Modeling the Flow of Molten Steel in a Tundish Containing an Inclusion Filtering Trap
  • Abstract A novel physical chemical filtration process in a tundish for removal of inclusion particles from molten steel is proposed and analyzed. The considered inclusion particles are mainly composed of the minerals alumina (Al2O3 and spinel (MgAl2O4, which have an affinity to adhere (on contact) to an inclusion trap. An industrial tundish is considered and modified with a zigzag channel block insert installed across the molten steel flow so that when the molten steel flows through the zigzag channels, the inclusion particles are driven into contact with the channel surfaces by increased recirculation and turbulence. The inclusions will bond with the…
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