Experience with turbulence interaction and turbulence-chemistry models at Fluent Inc.

This viewgraph presentation discusses (1) turbulence modeling: challenges in turbulence modeling, desirable attributes of turbulence models, turbulence models in FLUENT, and examples using FLUENT; and (2) combustion modeling: turbulence-chemistry interaction and FLUENT equilibrium model. As of now, three turbulence models are provided: the conventional k-epsilon model, the renormalization group model, and the Reynolds-stress model. The renormalization group k-epsilon model has broadened the range of applicability of two-equation turbulence models. The Reynolds-stress model has proved useful for strongly anisotropic flows such as those encountered in cyclones, swirlers, and combustors. Issues remain, such as near-wall closure, with all classes of models

Proteomic Analysis of Saliva from Patients with Oral Chronic Graft-Versus-Host Disease

AbstractChronic graft-versus-host disease (cGVHD) is an immune-mediated disorder and is the major long-term complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT). The oral mucosa, including the salivary glands, is affected in the majority of patients with cGVHD; however, at present there is only a limited understanding of disease pathobiology. In this study, we performed a quantitative proteomic analysis of saliva pooled from patients with and without oral cGVHD—cGVHD(+) and cGVHD(−), respectively—using isobaric tags for relative and absolute quantification labeling, followed by tandem mass spectrometry. Among 249 salivary proteins identified by tandem mass spectrometry, 82 exhibited altered expression in the oral cGVHD(+) group compared with the cGVHD(−) group. Many of the identified proteins function in innate or acquired immunity, or are associated with tissue maintenance functions, such as proteolysis or the cytoskeleton. Using ELISA immunoassays, we further confirmed that 2 of these proteins, IL-1 receptor antagonist and cystatin B, showed decreased expression in patients with active oral cGVHD (P < .003). Receiver operating curve characteristic analysis revealed that these 2 markers were able to distinguish oral cGVHD with a sensitivity of 85% and specificity of 60%, and showed slightly better discrimination in newly diagnosed patients evaluated within 12 months of allo-HSCT (sensitivity, 92%; specificity 73%). In addition to identifying novel potential salivary cGVHD biomarkers, our study demonstrates that there is coordinated regulation of protein families involved in inflammation, antimicrobial defense, and tissue protection in oral cGVHD that also may reflect changes in salivary gland function and damage to the oral mucosa

Use of ward closure to control outbreaks among hospitalized patients in acute care settings: a systematic review

MEDLINE Search Strategy. (DOCX 23 kb

Design of experiments to study the impact of process parameters on droplet size and development of non-invasive imaging techniques in tablet coating

Atomisation of an aqueous solution for tablet film coating is a complex process with multiple factors determining droplet formation and properties. The importance of droplet size for an efficient process and a high quality final product has been noted in the literature, with smaller droplets reported to produce smoother, more homogenous coatings whilst simultaneously avoiding the risk of damage through over-wetting of the tablet core. In this work the effect of droplet size on tablet film coat characteristics was investigated using X-ray microcomputed tomography (XμCT) and confocal laser scanning microscopy (CLSM). A quality by design approach utilising design of experiments (DOE) was used to optimise the conditions necessary for production of droplets at a small (20 μm) and large (70 μm) droplet size. Droplet size distribution was measured using real-time laser diffraction and the volume median diameter taken as a response. DOE yielded information on the relationship three critical process parameters: pump rate, atomisation pressure and coating-polymer concentration, had upon droplet size. The model generated was robust, scoring highly for model fit (R2 = 0.977), predictability (Q2 = 0.837), validity and reproducibility. Modelling confirmed that all parameters had either a linear or quadratic effect on droplet size and revealed an interaction between pump rate and atomisation pressure. Fluidised bed coating of tablet cores was performed with either small or large droplets followed by CLSM and XμCT imaging. Addition of commonly used contrast materials to the coating solution improved visualisation of the coating by XμCT, showing the coat as a discrete section of the overall tablet. Imaging provided qualitative and quantitative evidence revealing that smaller droplets formed thinner, more uniform and less porous film coats

Prediction of NOx Emissions from Oxygen-Enriched Burners

Nitrogen oxides are important air pollutants, believed to play a central role in the formation of photo-chemical smog and acid rain. The' nitrogen oxides are generated in high-temperature combustion processes and thus are released by stationary combustion sources, motor vehicles, as well as a wide range of domestic fossil fuel fired appliances. Recently, the emissions from these sources are legislated. Meeting the ever evolving standards continues to challenge available combustion technology. As a result, the interest in predicting the formation of nitrogen oxides in practical combustion systems has become large. Unfortunately, the formulation of reliable, accurate models has been severely hampered by the absence of proper descriptions of, amongst others, turbulence-chemistry interactions, radical super equilibria, prompt, and fuel-NO chemistry

The Prediction of No Emissions from an Industrial Burner

A recently developed 3-D post-processing package was linked to the output from commercial combustion computer code to predict the NOx emission in a regenerative burner used in the steel industry. To evaluate the effect of turbulence/chemistry interaction on the rate of formation of thermal and prompt-NO two essential physical phenomena, not properly described in previous models, were included in the post-processing code. First, the influence of turbulent fluctuations in temperature on NO formation rate is evaluated using a two-variable formalism for the treatment of chemical reactions leading to NO emissions and, second, the effects of radical superequilibrirum formed in turbulent flames on thermal NO formation is quantified. In addition, the influence of oxygen enrichment in the primary or secondary air on combustion performance especially on the level of NO emission was examined. The validity of the post-processing code was compared with measured values of NOx obtained at industrial laboratories. The predictions showed that NO emissions are in good qualitative agreement with experimentally observed values when the effects of superequilibrium radical formation and turbulence/chemistry interaction are considered. Virtually all the prompt-NO in the flame occurred in the mixing area of primary air and fuel, and the rate of formation of thermal NO reaches its maximum value far downstream of the burner just after secondary air injection. By adding oxygen (in the range of 2-8%) to the primary air, the temperature distribution was more uniform with maximum temperatures not exceeding the preheated air/fuel case. Here the NO emissions did not change significantly. In conclusion our findings indicate that the postprocessing package described here could provide detailed and accurate information on the NO emission in all types of industrial burners

An Unusual Case of Abdominal Pain

Peer Reviewe