564 research outputs found

    Numerical framework for transcritical real-fluid reacting flow simulations using the flamelet progress variable approach

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    An extension to the classical FPV model is developed for transcritical real-fluid combustion simulations in the context of finite volume, fully compressible, explicit solvers. A double-flux model is developed for transcritical flows to eliminate the spurious pressure oscillations. A hybrid scheme with entropy-stable flux correction is formulated to robustly represent large density ratios. The thermodynamics for ideal-gas values is modeled by a linearized specific heat ratio model. Parameters needed for the cubic EoS are pre-tabulated for the evaluation of departure functions and a quadratic expression is used to recover the attraction parameter. The novelty of the proposed approach lies in the ability to account for pressure and temperature variations from the baseline table. Cryogenic LOX/GH2 mixing and reacting cases are performed to demonstrate the capability of the proposed approach in multidimensional simulations. The proposed combustion model and numerical schemes are directly applicable for LES simulations of real applications under transcritical conditions.Comment: 55th AIAA Aerospace Sciences Meeting, Dallas, T

    Amino Acids Were Not All Created Equal

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    The contention that amino acids were not all created equal is based on the simple premise that intestinal uptakes of non-bound (synthetic, crystalline, feed-grade) amino acids are more rapid than their protein-bound counterparts. The post-enteral ramifications of this difference in bioequivalence are amplified in broiler chickens given their express growth rates and just one complication is the post-prandial oxidation of amino acids. The lack of bioequivalence between non-bound and protein-bound amino acids is a real obstacle to the development and adoption of reduced-crude protein diets that have the potential to promote sustainable chicken-meat production Thus, the purpose of this paper is to examine our contention that amino acids were no longer created equal with the introduction of non-bound amino acids

    Amino Acids Were Not All Created Equal

    Get PDF
    The contention that amino acids were not all created equal is based on the simple premise that intestinal uptakes of non-bound (synthetic, crystalline, feed-grade) amino acids are more rapid than their protein-bound counterparts. The post-enteral ramifications of this difference in bioequivalence are amplified in broiler chickens given their express growth rates and just one complication is the post-prandial oxidation of amino acids. The lack of bioequivalence between non-bound and protein-bound amino acids is a real obstacle to the development and adoption of reduced-crude protein diets that have the potential to promote sustainable chicken-meat production Thus, the purpose of this paper is to examine our contention that amino acids were no longer created equal with the introduction of non-bound amino acids

    Heteroepitaxial growth of tetragonal Mn2.7−x_{2.7-x}Fex_{x}Ga1.3_{1.3} (0 ⩽\leqslant x ⩽\leqslant 1.2) Heusler films with perpendicular magnetic anisotropy

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    This work reports on the structural and magnetic properties of Mn2.7−x_{2.7-x}Fex_{x}Ga1.3_{1.3} Heusler films with different Fe content x (0 ⩽\leqslant x ⩽\leqslant 1.2). The films were deposited heteroepitaxially on MgO single crystal substrates, by magnetron sputtering. Mn2.7−x_{2.7-x}Fex_{x}Ga1.3_{1.3} films with the thickness of 35 nm were crystallized in tetragonal D022_{22} structure with (001) preferred orientation. Tunable magnetic properties were achieved by changing the Fe content x. Mn2.7−x_{2.7-x}Fex_{x}Ga1.3_{1.3} thins films exhibit high uniaxial anisotropy Ku ⩾\geqslant 1.4 MJ/m3, coercivity from 0.95 to 0.3 T and saturation magnetization from 290 to 570 kA/m. The film with Mn1.6_{1.6}Fe1.1_{1.1}Ga1.3_{1.3} composition shows high Ku of 1.47 MJ/m3 and energy product (BH)max{(BH)_{max}} of 37 kJ/m3, at room temperature. These findings demonstrate that Mn2.7−x_{2.7-x}Fex_{x}Ga1.3_{1.3} films have promising properties for mid-range permanent magnet and spintronic applications.Comment: 13 pages, 5 figures and 2 table

    Martini coarse-grained models of imidazolium-based ionic liquids:from nanostructural organization to liquid-liquid extraction

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    Ionic liquids (ILs) are remarkable green solvents, which find applications in many areas of nano- and biotechnology including extraction and purification of value-added compounds or fine chemicals. These liquid salts possess versatile solvation properties that can be tuned by modifications in the cation or anion structure. So far, in contrast to the great success of theoretical and computational methodologies applied to other fields, only a few IL models have been able to bring insights towards the rational design of such solvents. In this work, we develop coarse-grained (CG) models for imidazolium-based ILs using a new version of the Martini force field. The model is able to reproduce the main structural properties of pure ILs, including spatial heterogeneity and global densities over a wide range of temperatures. More importantly, given the high intermolecular compatibility of the Martini force field, this new IL CG model opens the possibility of large-scale simulations of liquid-liquid extraction experiments. As examples, we show two applications, namely the extraction of aromatic molecules from a petroleum oil model and the extraction of omega-3 polyunsaturated fatty acids from a fish oil model. In semi-quantitative agreement with the experiments, we show how the extraction capacity and selectivity of the IL could be affected by the cation chain length or addition of co-solvents

    The multidimensional causal factors of ‘wet litter’ in chicken-meat production

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    The problem of ‘wet litter’, which occurs primarily in grow-out sheds for meat chickens (broilers), has been recognised for nearly a century. Nevertheless, it is an increasingly important problem in contemporary chicken-meat production as wet litter and associated conditions, especially footpad dermatitis, have developed into tangible welfare issues. This is only compounded by the market demand for chicken paws and compromised bird performance. This review considers the multidimensional causal factors of wet litter. While many causal factors can be listed it is evident that the critical ones could be described as micro-environmental factors and chief amongst them is proper management of drinking systems and adequate shed ventilation. Thus, this review focuses on these environmental factors and pays less attention to issues stemming from health and nutrition. Clearly, there are times when related avian health issues of coccidiosis and necrotic enteritis cannot be overlooked and the development of efficacious vaccines for the latter disease would be advantageous. Presently, the inclusion of phytate-degrading enzymes in meat chicken diets is routine and, therefore, the implication that exogenous phytases may contribute to wet litter is given consideration. Opinion is somewhat divided as how best to counter the problem of wet litter as some see education and extension as being more beneficial than furthering research efforts. However, it may prove instructive to assess the practice of whole grain feeding in relation to litter quality and the incidence of footpad dermatitis. Additional research could investigate the relationships between dietary concentrations of key minerals and the application of exogenous enzymes with litter quality

    Using LES to Study Reacting Flows and Instabilities in Annular Combustion Chambers

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    Great prominence is put on the design of aeronautical gas turbines due to increasingly stringent regulations and the need to tackle rising fuel prices. This drive towards innovation has resulted sometimes in new concepts being prone to combustion instabilities. In the particular field of annular combustion chambers, these instabilities often take the form of azimuthal modes. To predict these modes, one must compute the full combustion chamber, which remained out of reach until very recently and the development of massively parallel computers. Since one of the most limiting factors in performing Large Eddy Simulation (LES) of real combustors is estimating the adequate grid, the effects of mesh resolution are investigated by computing full annular LES of a realistic helicopter combustion chamber on three grids, respectively made of 38, 93 and 336 million elements. Results are compared in terms of mean and fluctuating fields. LES captures self-established azimuthal modes. The presence and structure of the modes is discussed. This study therefore highlights the potential of LES for studying combustion instabilities in annular gas turbine combustors
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