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Chemical-mechanical polishing (CMP) is commonly used in semiconductor fabrication for flattening wafer surfaces. The study uses 3-D computational fluid dynamics (CFD) to investigate slurry flow dynamics during CMP in a wafer-to-pad zone. Three fluids, used slurry, tracer and fresh incoming slurry, are marked in a wafer-to-pad zone to reveal the fluid dynamics influenced by the operational parameters including pad speed of 30–120 RPM, wafer speed of 30–120 RPM, pad to wafer center-to-center distance of 100–200 mm and wafer size of 100–200 mm and pad size of 610 mm. After validation, the computational model is applied to investigate slurry flow fields with comprehensive operational conditions that were not previously studied but are of significant concern in energy saving and CMP process yields. • Computational approach is proposed to analyze the slurry flow dynamics in CMP. • Tracer is used to examine the residence time of slurry flow. • Pad and wafer spinning speeds influence the CMP performance dramatically. • Recirculation zone is found to trap used slurry. • Large wafer size and short pad to wafer center-to-center distance hinder the slurry replacement. [ABSTRACT FROM AUTHOR]

The study aims at proposing a skeletal mechanism of propane oxidation that describes low-temperature combustion and predicts major hydrocarbon product formation in nonpremixed flames. Utilizing a combination of a sensitivity analysis and path flux analysis, we refine and minimize a recently proposed detailed mechanism of UC San Diego (Prince et al., 2017) without empirical adjustments of rate constants for elementary reactions. The skeletal mechanism with 33 species and 122 reactions improves accuracy for autoignition calculations in the negative temperature coefficient region and its size is commensurate to numerical grids used in solutions of computational fluid dynamics with detailed kinetics. For the first time, the previously measured temperature, major products and non-fuel hydrocarbons in diffusion flames of propane associated with counterflow and coflow configurations are, respectively, verified by means of 1-D kinetic modeling and 2-D computational fluid dynamics. A comprehensive analysis of decomposition pathways connected with preserved and removed reactions provides a clear foundation for mechanism developers to build mechanisms of other alkane fuel oxidation. The rate of production analysis interprets how the experimentally measured propene and 1-butene are formed earlier than acetylene and propyne in the coflow flame. Moreover, the present skeletal mechanism, compared with published detailed mechanisms, features a significant reduction in computational cost. [ABSTRACT FROM AUTHOR]

Branched-chain fatty acid methyl esters (FAME), known for cold flow improvers for biodiesel, have received less attention to their chemical kinetics in flames. This study proposes a detailed mechanism reduced to be a compact form to predict the formation of non-fuel small hydrocarbons and light-weight polycyclic aromatic hydrocarbons (PAH) from the oxidation of methyl isobutanoate [MIB, (CH 3) 2 CHC(=O)OCH 3 ], a C5-branched methyl ester. Using the path flux analysis, the newly constructed MIB oxidation mechanism with 344 species and 2147 reactions is shrunk and refined to 63 species and 288 reactions, a minimum size for its application to computational fluid dynamics. The minimized MIB mechanism incorporated into a 2D axisymmetric coflow model is used to validate mass-spectrometric data obtained from a laminar coflow diffusion flame of methane doped with MIB. For the first time, ten experimentally measured centerline profiles in the flame are computationally interpreted by nine C3–C6 unsaturated hydrocarbons, three carbonyls and four aromatics. Furthermore, we analyze the spatial distribution of the investigated intermediates and reveal their corresponding reaction pathways linked to the MIB decomposition. • Compact kinetic mechanism for methyl isobutanote oxidation is proposed. • CFD coupled with the kinetic mechanism describes chemistry in a nonpremixed flame. • Non-fuel hydrocarbons measured by mass-spectrometry are modeled for the first time. • Reaction pathway analyses elucidate abundant formation of aromatics correlated with the fuel. [ABSTRACT FROM AUTHOR]

Transport of aerosol particles is a fundamental phenomenon in many environmental and industrial applications. Among the several computational fluid dynamical schemes used to study this problem, the lattice Boltzmann methods (LBMs) have shown great promise. Using a 2-D LBM model coupled with a Lagrangian formalism, this study investigates an early stage of particle–surface collisions in a free-stream flow over a semi-infinite array of staggered obstructions at operating conditions of woven-wire screens. After an initial validation of the model, the particle–surface collision efficiency with different diameters is then examined as functions of the number of staggered obstructions, obstruction morphology, and separation distance between two center points of obstructions. Particle motion mechanisms include drag, lift, and Brownian forces. Enhanced collision efficiency of particles to obstructions due to the presence of multiple staggered cylindrical obstructions is identified and highlighted. Based on these insights, our work also explores the possibility that collision efficiency of particles to obstructions can be enhanced by a change of obstruction morphology. Finally, the results highlight the range where particle–surface collision efficiency is sensitive to the longitudinal spacing between two cylindrical obstructions. Copyright 2014 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

Since existing reduced mechanisms of ethylene oxidation are either too large or lack of sufficient chemical reactions to describe aromatics formation, the study aims at developing a skeletal mechanism with extended predictive capability and lowered computational cost in computational fluid dynamics modeling of ethylene combustion. The newly assembled and refined kinetic mechanism composed of 664 species and 3582 reactions is minimized to 79 species and 538 reactions without empirically adjusting kinetic parameters. In the 1-D simulation for a premixed flame of ethylene, the ethylene-PAH mechanism generally well predicts experimental profiles of five hydrocarbons and nine aromatics. Integrated into a 2-D axisymmetric laminar finite-rate model, the ethylene-PAH mechanism reproduces experimental data of seven C2–C5 hydrocarbons, five aromatic hydrocarbons and soot in a diffusion flame of ethylene. In comparison with the 158-species (Narayanaswamy) mechanism, the newly proposed ethylene mechanism leads to a speedup of approximately 5.5 times in the 2-D laminar diffusion flame simulation and improved accuracy for predicting species formation in both premixed and nonpremixed flames. Moreover, we unveil the correlation between reaction pathways and intermediate formation from ethylene oxidation at the low temperature regime. • Skeletal kinetic mechanism for ethylene oxidation is proposed. • CFD coupled with the kinetic mechanism describes chemistry in a nonpremixed flame. • Prediction accuracy for non-fuel hydrocarbons formation is improved. • Reaction pathway analyses elucidate abundant formation of aromatics correlated with the fuel. [ABSTRACT FROM AUTHOR]

• Investigating the effect of pulsating blood flow on oxygen transfer in oxygenators. • Using CFD to elucidate in-vitro studies that reported divergent outcomes. • Identifying operational parameters of blood flows that influence the oxygen transport. • Quantitative and qualitative comparisons of the predicted results with experiments. While previous in vitro studies showed divergent results concerning the influence of pulsatile blood flow on oxygen advection in oxygenators, no study was done to investigate the uncertainty affected by blood flow dynamics. The aim of this study is to utilize a computational fluid dynamics model to clarify the debate concerning the influence of pulsatile blood flow on the oxygen transport. The computer model is based on a validated 2D finite volume approach that predicts oxygen transfer in pulsatile blood flow passing through a 300-micron hollow-fiber membrane bundle with a length of 254 mm, a building block for an artificial lung device. In this study, the flow parameters include the steady Reynolds number (Re = 2, 5, 10 and 20), Womersley parameter (Wo = 0.29, 0.38 and 0.53) and sinusoidal amplitude (A = 0.25, 0.5 and 0.75). Specifically, the computer model is extended to verify, for the first time, the previously measured O 2 transport that was observed to be hindered by pulsating flow in the Biolung, developed by Michigan Critical Care Consultants. A comprehensive analysis is carried out on computed profiles and fields of oxygen partial pressure (P O2) and oxygen saturation (S O2) as a function of Re, Wo and A. Based on the present results, we observe the positive and negative effects of pulsatile flow on P O2 at different blood flow rates. Besides, the S O2 variation is not much influenced by the pulsatile flow conditions investigated. While being consistent with a recent experimental study, the computed O 2 volume flow rate is found to be increased at high blood flow rates operated with low frequency and high amplitude. Furthermore, the present study qualitatively explains that divergent outcomes reported in previous in vitro experimental studies could be owing to the different blood flow rates adopted. Finally, the contour analysis reveals how the spatial distributions of P O2 and S O2 vary over time. [ABSTRACT FROM AUTHOR]