Three‐Dimensional CFD Simulation of Stratified Two‐Fluid Taylor‐Couette Flow

Two‐fluid Taylor‐Couette flow, with either one or both of the co‐axial cylinders rotating, has potential advantages over the conventional process equipment in chemical and bio‐process industries. This flow has been investigated using three‐dimensional CFD simulations. The occurrence of radial stratification, the subsequent onset of centrifugal instability in each phase, the cell formation and the dependency on various parameters have been analyzed and discussed. The criteria for the stratification, Taylor cell formation in each phase have been established. It can be stated that the analysis of single‐phase flow acts as the base state for the understanding of radial stratification of the two‐fluid flows. The extent of interface deformation also has been discussed. A complete energy balance has been established and a very good agreement was found between dissipation rate by CFD predictions and the energy input rate through the cylinder/s rotation.     

Three‐Dimensional Simulation of Bubble Formation Through a Microchannel T‐Junction

Three‐dimensional simulations of bubble formation in Newtonian and non‐Newtonian fluids through a microchannel T‐junction are conducted by the volume‐of‐fluid method. For Newtonian fluids, the critical capillary number Ca for the transition of the bubble breakup mechanism is dependent on the velocity ratio between the two phases and the microchannel dimension. For the power law fluid, the bubble diameter decreases and the generation frequency increases with higher viscosity parameter K and power law index n. For a Bingham fluid, the viscous force plays a more important role in microbubble formation. Due to the yield stress τ_y, a high‐viscous region is developed in the central area of the channel and bubbles deform to a flat ellipsoid shape in this region. The bubble diameter and generation frequency are almost independent of K.     

Three‐Dimensional Stereolithography of Alumina Photonic Crystals for Terahertz Wave Localization

Using stereolithography as an additive manufacturing (AM) process, photonic crystals, with a diamond‐like structure composed of alumina microlattices, were fabricated and their electromagnetic band gap profiles, in terahertz frequency ranges, were investigated. Acrylic resins with dispersed alumina particles were fabricated by stereolithography with micrometer‐order accuracy. After dewaxing and sintering processes, alumina lattices were obtained with high relative densities that reflected the terahertz waves, through Bragg diffraction, perfectly in all directions. Twinned crystal structures with mirror symmetric diamond lattices were designed to introduce defect interfaces. Double‐cavity defects consisting of unit cells hollowed from the diamond lattices formed the coupled resonation modes.     

Geometrical Models for Tortuosity of Streamlines in Three‐Dimensional Porous Media

Based on the assumption that some particles in porous media are unrestrictedly overlapped and hence of different configurations, this paper presents three three‐dimensional geometry models for tortuosity of streamlines in porous media with spherical, cubic and plate‐like particles, respectively. The proposed models are expressed as a function of porosity with no empirical constant, and they are helpful for understanding the physical mechanism for tortuosity of flow paths in three‐dimensional porous media. The model predictions are compared with those from the available correlations obtained by experimental data, and good agreement is found between them.     

Ag Nanoparticles‐Enhanced Photoluminescence in LaPO4: Eu Three‐Dimensional Ordered Macroporous Films

The three‐dimensional ordered macroporous (3DOM) LaPO₄:Eu³⁺ films and Ag nanoparticles (NPs) were prepared via a template‐assisted process and sodium citrate reduction method, respectively. Composite systems consisting of 3DOM LaPO₄:Eu³⁺ films and Ag NPs were obtained by adding the Ag NPs into voids of 3DOM LaPO₄:Eu³⁺ films. The influence of Ag NPs on photoluminescence of 3DOM LaPO₄:Eu³⁺ was investigated. The results show that photoluminescence properties of 3DOM LaPO₄:Eu³⁺ films were enhanced after addition of Ag NPs, which was attributed to the local surface plasmons resonance effect of Ag NPs.     

Three‐Dimensional Observation of Single Air Bubble Breakup in a Stirred Tank

A fully automated three‐dimensional observation of single bubble breakup trajectories in a stirred tank is demonstrated to gain unbiased and statistically relevant information about the breakup process. The mother bubble size is kept constant, independently of the stirring rate. The investigated parameter in this work is the power input. Three‐dimensional bubble breakup trajectories and heat maps for the initial breakup location probability for the bottom and side views are provided. The influence of the stirrer blade angle position, at the moment of bubble detachment from the capillary, on the breakup probability is analyzed. The breakup positions are linked to the current flow field, related to the stirrer blade angle, within the tank.     

Near‐Net‐Shape Fabrication of Ti3SiC2‐based Ceramics by Three‐Dimensional Printing

This paper focuses on the preparation of near‐net‐shaped dense Ti₃SiC₂‐based materials via an indirect three‐dimensional printing (3D printing) and postreactive melt infiltration (RMI) processes. TiC preforms with bimodal pore size distribution were fabricated through 3D printing, followed by the infiltration of Si melt and Al–Si alloy (Al₄₀Si₆₀ and Al₇₀Si₃₀). Dense composites with density of ~4.1 g/cm³ were obtained after the infiltration. No volume shrinkage was obtained after the reactive infiltration with Al–Si alloy. The participation of Al during the infiltration process promoted the formation of Ti₃SiC₂. The as‐fabricated Ti₃SiC₂‐based materials showed enhanced mechanical and electromagnetic interference shielding properties.     

Three‐Dimensional Database Mining Identifies a Unique Chemotype that Unites Structurally Diverse Botulinum Neurotoxin Serotype A Inhibitors in a Three‐Zone Pharmacophore

A search query consisting of two aromatic centers and two cationic centers was defined based on previously identified small molecule inhibitors of the botulinum neurotoxin serotype A light chain (BoNT/A LC) and used to mine the National Cancer Institute Open Repository. Ten small molecule hits were identified, and upon testing, three demonstrated inhibitory activity. Of these, one was structurally unique, possessing a rigid diazachrysene scaffold. The steric limitations of the diazachrysene imposed a separation between the overlaps of previously identified inhibitors, revealing an extended binding mode. As a result, the pharmacophore for BoNT/A LC inhibition has been modified to encompass three zones. To demonstrate the utility of this model, a novel three‐zone inhibitor was mined and its activity was confirmed.     

Calculation of Crystallization with Injection Moulding Simulation Software based on Three‐Dimensional Approaches

Injection moulding is the most popular process for manufacturing technical plastics parts. The computer simulation of the process is an essential tool to fulfil requirements with respect to part quality and efficiency. Up to now, the entire simulation has been based on two‐dimensional software. Presently, the three‐dimensional software offers new applications to improve the quality of the simulation. As in other groups, research at the IKV deals with the three‐dimensional calculation of crystallization. In a first step, the calculation of thermally induced crystallization based on a three‐dimensional temperature calculation is now available. First results show a good qualitative agreement with experimental studies. For the improvement of the quantitative quality of the simulation results further developments have to be performed.     

Three‐Dimensional Computational Fluid Dynamics Modeling of a Planar Solid Oxide Fuel Cell

A three‐dimensional computational fluid dynamics model was developed to study the performance of a planar solid oxide fuel cell (SOFC). The governing equations were solved with the finite volume method. The model was validated by comparing the simulation results with data from literature. Parametric simulations were performed to investigate the coupled heat/mass transfer and electrochemical reactions in a planar SOFC. Different from previous two‐dimensional studies the present three‐dimensional analyses revealed that the current density was higher at the center along the flow channel while lower under the interconnect ribs, due to slower diffusion of gas species under the ribs. The effects of inlet gas flow rate and electrode porosity on SOFC performance were examined as well. The analyses provide a better understanding of the working mechanisms of SOFCs. The model can serve as a useful tool for SOFC design optimization.     

Benzo[c]isothiazole 2‐Oxides: Three‐Dimensional Heterocycles with Cross‐Coupling and Functionalization Potential

A robust method for the synthesis of benzo[c]isothiazole 2‐oxides has been developed providing a range of functionalized derivatives starting from anilines and DMSO. The reaction sequence can be performed on a gram scale and leads to products that can easily be modified by standard cross‐coupling reactions.

     

Three‐arm poly (ε‐caprolactone) by extrusion polymerization

Three‐arm poly (ε‐caprolactone, reactive extruded) (REX‐PCL) polymer was continuously produced using a twin‐screw extruder with aluminum tri‐sec butoxide (ATSB) initiator in residence times of less than five minutes. Monomer conversions in excess of 95% were achieved, and high molecular weight PCL was produced. The number average molecular weight of each arm of REX‐PCL ranged from 30,000 to 200,000 g/mol. A screw configuration comprising entirely of conveying elements was most effective in the extrusion polymerization process. The REX‐PCL polymer was characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and intrinsic viscosity measurements. POLYM. ENG. SCI. 46:235–240, 2006. © 2006 Society of Plastics Engineers     

Three‐dimensional solubility parameters of poly(ε‐caprolactone)

The three‐dimensional solubility parameter model was applied to analyze solution thermodynamic data of 27 solutes in poly(ε‐caprolactone) (PCL) between 70 and 110 °C. A linear regression method was compared with a nonlinear least square regression method, which searches solubility parameter components by minimization of the sum of error squares. The parameters of polymers were the same by both methods. When compared with the error in predicting χRT/V, the data showed a different slope from the simple three‐dimensional model. These deviations were reduced by a different model using a smaller weight on the polar and hydrogen bonding components. In the new model, the solubility parameter components were closer to the value of a structure analogue of PCL. The confidence intervals for the parameters were estimated from a linearized equation based on the sum of error squares. The solubility parameter components obtained were different from the average values of the five solutes with the smallest χ. The inclusion of solutes with high hydrogen bonding components contributed to the increase of the component in the nonlinear regression method. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2002–2009, 2006