Relevant bibliographies by topics / Logarithmic jets

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  1. Journal articles
  2. Dissertations / Theses
  3. Book chapters
  4. Conference papers

Academic literature on the topic 'Logarithmic jets'

Author: Grafiati
Published: 4 June 2021
Last updated: 1 February 2022

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Journal articles on the topic "Logarithmic jets"

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Kang, Zhong-Bo. "Recent progress on jet substructure theory." EPJ Web of Conferences 235 (2020): 05001. http://dx.doi.org/10.1051/epjconf/202023505001.

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In these proceedings, we review recent theoretical progress on jet substructure at the colliders. Focusing on two observables – jet mass and groomed jet radius, we perform theoretical computations for jets measured in the single inclusive jet production in proton-proton collisions, pp → jet + X. We consider both standard ungroomed jets as well as soft-drop groomed jets. Within the Soft Collinear Effective Theory (SCET), we establish QCD factorization theorems which allow for the joint resummation of several classes of logarithmic corrections to all orders in the strong coupling constant. We present numerical results and compare with the available data from the LHC.
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Becher, Thomas, Matthias Neubert, Lorena Rothen, and Ding Yu Shao. "Factorization and resummation for jet processes." Journal of High Energy Physics 2016, no. 11 (2016): 1–61. http://dx.doi.org/10.1007/jhep11(2016)019.

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Abstract From a detailed analysis of cone-jet cross sections in effective field theory, we obtain novel factorization theorems which separate the physics associated with different energy scales present in such processes. The relevant low-energy physics is encoded in Wilson lines along the directions of the energetic particles inside the jets. This multi-Wilson-line structure is present even for narrow-cone jets due to the relevance of small-angle soft radiation. We discuss the renormalization-group equations satisfied by these operators. Their solution resums all logarithmically enhanced contributions to such processes, including non-global logarithms. Such logarithms arise in many observables, in particular whenever hard phase-space constraints are imposed, and are not captured with standard resummation techniques. Our formalism provides the basis for higher-order logarithmic resummations of jet and other non-global observables. As a nontrivial consistency check, we use it to obtain explicit two-loop results for all logarithmically enhanced terms in cone-jet cross sections and verify those against numerical fixed-order computations.
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Chien, Yang-Ting. "Resummation of Jet Shapes and Extracting Properties of the Quark-Gluon Plasma." International Journal of Modern Physics: Conference Series 37 (January 2015): 1560047. http://dx.doi.org/10.1142/s2010194515600472.

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Understanding the properties of the quark-gluon plasma (QGP) that is produced in ultra-relativistic nucleus-nucleus collisions has been one of the top priorities of the heavy ion program at the LHC. Energetic jets are produced and subsequently quenched in the collisions. Such jet quenching phenomena provide promising tools to probe the medium properties by studying the modification of jets due to the medium interactions. Significant modifications of jet shapes have been measured. In this talk we focus on the calculation of jet shapes in both proton-proton and lead-lead collisions using soft-collinear effective theory (SCET), with Glauber gluon interactions in the medium. Large logarithms in jet shapes are resummed at next-to-leading logarithmic (NLL) accuracy by the renormalization-group evolution between hierarchical jet scales. The medium interactions contribute as power corrections, and we calculate the modification of jet shapes at leading order in opacity with the static QGP model. Preliminary results are presented with good agreement with the recent CMS jet shape measurements.
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MALAZA, E. D. "ASYMPTOTIC SCALING IN QUARK AND GLUON JET MULTIPLICITY DISTRIBUTIONS IN NEXT-TO-LEADING ORDER QCD." International Journal of Modern Physics A 04, no. 18 (1989): 4909–18. http://dx.doi.org/10.1142/s0217751x89002077.

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Miller, Paul L., and Paul E. Dimotakis. "Measurements of scalar power spectra in high Schmidt number turbulent jets." Journal of Fluid Mechanics 308 (February 10, 1996): 129–46. http://dx.doi.org/10.1017/s0022112096001425.

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We report on an experimental investigation of temporal, scalar power spectra of round, high Schmidt number (Sc ≃ 1.9 × 103), momentum-dominated turbulent jets, for jet Reynolds numbers in the range of 1.25 × 104 ≤ Re ≤ 7.2 × 104. At intermediate scales, we find a spectrum with a slope (logarithmic derivative) that increases in absolute value with Reynolds number, but remains less than 5/3 at the highest Reynolds number in our experiments. At the smallest scales, our spectra exhibit no k−1 power-law behaviour, but, rather, seem to be approximated by a log-normal function, over a range of scales exceeding a factor of 40, in some cases.
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Kato, Kiyoshi, and Tomo Munehisa. "Monte Carlo approach to QCD jets in the next-to-leading-logarithmic approximation." Physical Review D 36, no. 1 (1987): 61–82. http://dx.doi.org/10.1103/physrevd.36.61.

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Tao, Y., W. Adler, and E. Specht. "Numerical analysis of multiple jets discharging into a confined cylindrical crossflow." Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering 216, no. 3 (2002): 173–80. http://dx.doi.org/10.1243/095440802320225383.

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A row of jets discharging normally into a confined cylindrical crossflow is numerically investigated using the control-volume-based finite difference method. Interest is focused on determining the relationship between the temperature trajectory and the upstream flow and geometric variables. Parameter variations studied include nozzle diameter, number of nozzles, duct radius, jet and mainstream volume-flow, temperature ratio, and dynamic pressure ratio. The dynamic pressure ratio, the number of nozzles, and nozzle spacing are found to be significant variables. A logarithmic function describing the relationship between penetration depth and dynamic pressure divided by the square of the number of nozzles is derived by fitting the data of the computation results. The values for penetration depth and nozzle spacing are described for optimum mixing. A suggested design procedure is presented, which can be used as a first approach in configuration design.
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Khoze, Valery A., and Wolfgang Ochs. "Perturbative-QCD Approach to Multiparticle Production." International Journal of Modern Physics A 12, no. 17 (1997): 2949–3120. http://dx.doi.org/10.1142/s0217751x97001638.

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In this review we discuss the analytical perturbative approach, based on perturbative QCD and local parton hadron duality (LPHD), and its application to multiparticle production in jets in the semisoft region. Analytical formulae are presented for various observables within the accuracy of the modified leading logarithmic approximation (MLLA), i.e. with terms of relative order [Formula: see text] taken into account systematically, and in some cases with even higher accuracy. These predictions are confronted with existing experimental data. Many details of the perturbative approach to multiple hadroproduction have been consolidated in recent years, and the overall picture is remarkably healthy. The prospects of future studies of the semisoft jet physics are also discussed.
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Dokshitzer, Yu L., V. A. Khoze, and S. I. Troyan. "Phenomenology of the particle spectra in QCD jets in a modified leading logarithmic approximation." Zeitschrift für Physik C Particles and Fields 55, no. 1 (1992): 107–14. http://dx.doi.org/10.1007/bf01558295.

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Campana, Frédéric, Lionel Darondeau, and Erwan Rousseau. "Orbifold hyperbolicity." Compositio Mathematica 156, no. 8 (2020): 1664–98. http://dx.doi.org/10.1112/s0010437x20007265.

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AbstractWe define and study jet bundles in the geometric orbifold category. We show that the usual arguments from the compact and the logarithmic settings do not all extend to this more general framework. This is illustrated by simple examples of orbifold pairs of general type that do not admit any global jet differential, even if some of these examples satisfy the Green–Griffiths–Lang conjecture. This contrasts with an important result of Demailly (Holomorphic Morse inequalities and the Green-Griffiths-Lang conjecture, Pure Appl. Math. Q. 7 (2011), 1165–1207) proving that compact varieties of general type always admit jet differentials. We illustrate the usefulness of the study of orbifold jets by establishing the hyperbolicity of some orbifold surfaces, that cannot be derived from the current techniques in Nevanlinna theory. We also conjecture that Demailly's theorem should hold for orbifold pairs with smooth boundary divisors under a certain natural multiplicity condition, and provide some evidence towards it.
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Dissertations / Theses on the topic "Logarithmic jets"

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Darondeau, Lionel. "Sur la conjecture de Green-Griffiths logarithmique." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112134/document.

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L'objet d'étude de ce mémoire est la géométrie des courbes holomorphes entières à valeurs dans le complémentaire d'hypersurfaces génériques de l'espace projectif complexe. Les conjectures célèbres de Kobayashi et de Green-Griffiths énoncent que pour de telles hypersurfaces, de grand degré, les images de ces courbes entières doivent satisfaire certaines contraintes algébriques. En adaptant les techniques de jets développées notamment par Bloch, Green-Griffiths, Demailly, Siu, Diverio-Merker-Rousseau, pour les courbes à valeurs dans une hypersurface projective (cas dit compact), nous obtenons la dégénérescence algébrique des courbes entières f : ℂ→Pⁿ∖Xd (cas dit logarithmique), pour les hypersurfaces génériques Xd de Pⁿ de degré d ≥ (5n)² nⁿ. Comme dans le cas compact, notre preuve repose essentiellement sur l'élimination algébrique de toutes les dérivées dans des équations différentielles qui sont vérifiées par toute courbe entière non constante. L'existence de telles équations différentielles est obtenue grâce aux inégalités de Morse holomorphes et à une variante simplifiée d'une formule de résidus originalement élaborée par Bérczi à partir de la formule de localisation équivariante d'Atiyah-Bott. La borne effective d ≥ (5n)² nⁿ est obtenue par réduction radicale d'un calcul de résidus itérés de très grande ampleur. Ensuite, la déformation de ces équations différentielles par dérivation le long de champs de vecteurs obliques, dont l'existence est ici généralisée et clarifiée, nous permet d'engendrer suffisamment de nouvelles équations pour réaliser l'élimination algébrique finale évoquée ci-dessus<br>The topic of this memoir is the geometry of holomorphic entire curves with values in the complement of generic hypersurfaces of the complex projective space. The well-known conjectures of Kobayashi and of Green-Griffiths assert that for such hypersurfaces, having large degree, the images of these curves shall fulfill algebraic constraints. By adapting the jet techniques developed notably by Bloch, Green-Griffiths, Demailly, Siu, Diverio-Merker-Rousseau, in the case of curves with values in projective hypersurfaces (so-called compact case), we obtain the algebraic degeneracy of entire curves f : ℂ→Pⁿ∖Xd (so called logarithmic case), for generic hypersurfaces Xd in Pⁿ of degree d ≥ (5n)² nⁿ. As in the compact case, our proof essentially relies on the algebraic elimination of all derivatives in differential equations that are satisfied by every nonconstant entire curve. The existence of such differential equations is obtained thanks to the holomorphic Morse inequalities and a simplified variant of a residue formula firstly developed by Bérczi from the Atiyah-Bott equivariant localization formula. The effective lower bound d ≥ (5n)² nⁿ is obtained by radically simplifying a huge iterated residue computation. Next, the deformation of these differential equations by derivation along slanted vector fields, the existence of which is here generalized and clarified, allows us to generate sufficiently many new differential equations in order to realize the final algebraic elimination mentioned above
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Staal, Andrew Phillipe. "On the existence of jet schemes logarithmic along families of divisors." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/3327.

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A section of the total tangent space of a scheme X of finite type over a field k, i.e. a vector field on X, corresponds to an X-valued 1-jet on X. In the language of jets the notion of a vector field becomes functorial, and the total tangent space constitutes one of an infinite family of jet schemes Jm(X) for m ≥ 0. We prove that there exist families of “logarithmic” jet schemes JDm(X) for m ≥ 0, in the category of k-schemes of finite type, associated to any given X and its family of divisors D = (D₁, . . . ,Dr). The sections of JD₁(X) correspond to so-called vector fields on X with logarithmic poles along the family of divisors D = (D₁, . . . ,Dr). To prove this, we first introduce the categories of pairs (X,D) where D is as mentioned, an r-tuple of (effective Cartier) divisors on the scheme X. The categories of pairs provide a convenient framework for working with only those jets that pull back families of divisors.
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Staal, Andrew Philippe. "On the existence of jet schemes logarithmic along families of divisors." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/3327.

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A section of the total tangent space of a scheme X of finite type over a field k, i.e. a vector field on X, corresponds to an X-valued 1-jet on X. In the language of jets the notion of a vector field becomes functorial, and the total tangent space constitutes one of an infinite family of jet schemes Jm(X) for m ≥ 0. We prove that there exist families of “logarithmic” jet schemes JDm(X) for m ≥ 0, in the category of k-schemes of finite type, associated to any given X and its family of divisors D = (D₁, . . . ,Dr). The sections of JD₁(X) correspond to so-called vector fields on X with logarithmic poles along the family of divisors D = (D₁, . . . ,Dr). To prove this, we first introduce the categories of pairs (X,D) where D is as mentioned, an r-tuple of (effective Cartier) divisors on the scheme X. The categories of pairs provide a convenient framework for working with only those jets that pull back families of divisors.<br>Science, Faculty of<br>Mathematics, Department of<br>Graduate
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Zumbrägel, Jens Verfasser], Stefan E. [Gutachter] [Schmidt, Gathen Joachim von [Gutachter] Zur, and Elisa [Gutachter] Gorla. "The Discrete Logarithm Problem in Finite Fields of Small Characteristic / Jens Zumbrägel ; Gutachter: Stefan E. Schmidt, Joachim von zur Gathen, Elisa Gorla." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://d-nb.info/1128036649/34.

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Zumbrägel, Jens [Verfasser], Stefan E. [Gutachter] Schmidt, Gathen Joachim von [Gutachter] Zur, and Elisa [Gutachter] Gorla. "The Discrete Logarithm Problem in Finite Fields of Small Characteristic / Jens Zumbrägel ; Gutachter: Stefan E. Schmidt, Joachim von zur Gathen, Elisa Gorla." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://d-nb.info/1128036649/34.

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Sanguinetti, Grégory. "Calcul de la production d'une paire de bosons de jauge faible associée à un jet à l'approximation au-delà des logarithmes dominants." Phd thesis, Chambéry, 2008. http://tel.archives-ouvertes.fr/tel-00331294.

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En 2008, le futur collisionneur du CERN, le Large Hadron Collider (LHC), commencera à récolter les données issues des collisions entre protons à l'échelle du TeV, dans le but de comprendre la brisure de la symétrie électro-faible. Un grand nombre de réactions incluant de nombreuses particules dans l'état final doit être étudié avec précision. Ces possibilités de découverte du LHC ne pourront être pleinement exploitées que si le bruit de fond de la Chromodynamique Quantique est bien maîtrisé. Parmi les réactions comprenant plus de quatre particules, la production associée d'une paire de bosons de jauge faible (W, Z) associée à un jet constitue un des bruits de fond pour la recherche du boson de Higgs au LHC. Il est important de calculer cette réaction à l'approximation dite "au-delà des logarithmes dominants", qui consiste à ajouter à l'ordre dominant le plus bas les deux contributions suivantes : la correction virtuelle (c'est un calcul d'amplitudes à une boucle) et l'émission réelle (c'est un calcul d'amplitudes à l'arbre mais avec un parton de plus dans l'état final). Des expressions analytiques suffisamment compactes pour être évaluées numériquement ont été obtenues et sont en parfait accord avec les résultats de deux autres groupes de recherche indépendants. Quant à l'émission réelle, toutes les contributions ont été évaluées à l'aide de programmes de génération automatique d'amplitudes à l'arbre. Ainsi, nous sommes en mesure de présenter des prédictions précises concernant les corrections à l'ordre supérieur de la section efficace totale de cette réaction au LHC.
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Book chapters on the topic "Logarithmic jets"

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Noguchi, Junjiro. "Logarithmic Jet Spaces and Extensions of de Franchis’ Theorem." In Contributions to Several Complex Variables. Vieweg+Teubner Verlag, 1986. http://dx.doi.org/10.1007/978-3-663-06816-7_11.

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Becher, Thomas. "Soft-Collinear Effective Theory." In Effective Field Theory in Particle Physics and Cosmology. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780198855743.003.0005.

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The lectures that appear within this chapter provide an introduction to soft-collinear effective theory (SCET). It begins by discussing resummation for soft-photon effects in QED, including soft photons in electron–electron scattering and the expansion of loop integrals and the method of regions event-shape variables. It then covers SCET specifically, including the method of regions for the Sudakov form factor, effective Lagrangians, the vector current in SCET, and resummation by renormalization group (RG) evolution. It covers applications of SCET in jet physics, describes the characteristic feature in jet processes of Sudakov logarithms, and discusses factorization for the event-shape variable thrust and factorization and resummation for jet cross sections.
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Conference papers on the topic "Logarithmic jets"

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Arabnejad, H., A. Mansouri, S. A. Shirazi, and B. S. McLaury. "Calculation of Turbulent Boundary Layer for a Slot Jet Impingement on a Flat Surface." In ASME 2014 4th Joint US-European Fluids Engineering Division Summer Meeting collocated with the ASME 2014 12th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/fedsm2014-21677.

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The objective of this study is to characterize flow parameters for two-dimensional turbulent jets impinging on a flat surface. An integral form of the momentum equation has been used to obtain a hydrodynamic solution. The boundary layer was divided into three regions, stagnation zone, developing zone and fully developed zone for free-surface and free shear, and into two regions, stagnation and wall jet zone for submerged jet configurations. A nonlinear ordinary differential equation has been obtained for frictional velocity at each zone using a logarithmic velocity profile with Coles’s law of the wake and solved numerically to predict wall shear stress as well as boundary layer and momentum thicknesses. The proposed method is more straightforward and computationally less expensive in calculating the main flow parameters as compared to turbulent flow models such as RANS and LES. Predicted wall shear stresses for a submerged jet were compared to experimental data for different cases and showed agreement with experimental data.
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Weiland, Chris, and Pavlos Vlachos. "The Effect of Mach Number and Aspect Ratio on the Interfacial Characteristics of a Submerged Rectangular Gas Jet." In ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting collocated with 8th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-31030.

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Gas jets formed by rectangular nozzles submerged in water were studied using a non-invasive photographic technique which allowed simultaneous measurements of the entire interface. Three aspect ratios were considered corresponding to 2, 10, and 20 with all nozzles sharing a common width. As far as the authors know this study represents the first time the effects of aspect ratio and Mach number on a submerged gas jet have been studied. The results indicate aspect ratio and Mach number play a large role in dictating both the unsteadiness of the interface and the penetration of the gas jet into the surrounding liquid medium. The jet pinch-off is shown to have a logarithmic decay with increasing Mach number and when appropriately scaled by the total viewing length and a geometric length scale (LQ) is relatively constant across all aspect ratio nozzles. The location of pinch-off is also a function of aspect ratio, with the subsonic aspect ratio 2 nozzles showing maximum pinch-off at y/LQ ≈ 23–26 while sonic and supersonic Mach numbers have peaks over the range y/LQ ≈ 11–14. The AR 10 and 20 nozzles show no dependence on Mach number with the maximum number of pinch-off events observed over the interval y/LQ ≈ 3–5. Jet spreading which is indicative of liquid entrainment is also shown to increase with Mach number and aspect ratio. The jet penetration also increases with increasing Mach number and aspect ratio. The spatial instability growth rate was deduced from the downstream evolution of the interfacial unsteadiness and it is shown that the nozzle with aspect ratio of 2 follows a different trend than the aspect ratio 10 and 20 nozzles, suggesting a fundamentally different mechanism dominates the stability of large aspect ratio rectangular gas jets.
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Yoon, Churl, Bo Wook Rhee, and Byung-Joo Min. "Validation of a CFD Analysis Model for Predicting CANDU-6 Moderator Temperature Against SPEL Experiments." In 10th International Conference on Nuclear Engineering. ASMEDC, 2002. http://dx.doi.org/10.1115/icone10-22114.

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A validation of a 3D CFD model for predicting local subcooling of the moderator in the vicinity of calandria tubes in a CANDU-6 reactor is performed. The small scale moderator experiments performed at Sheridan Park Experimental Laboratory (SPEL) in Ontario, Canada [1] is used for the validation. Also a comparison is made between previous CFD analyses based on 2DMOTH and PHOENICS, and the current analysis for the same SPEL experiment. For the current model, a set of grid structures for the same geometry as the experimental test section is generated and the momentum, heat and continuity equations are solved by CFX-4.3, a CFD code developed by AEA technology. The matrix of calandria tubes is simplified by the porous media approach. The standard k-ε turbulence model associated with logarithmic wall treatment and SIMPLEC algorithm on the body fitted grid are used. Buoyancy effects are accounted for by the Boussinesq approximation. For the test conditions simulated in this study, the flow pattern identified is the buoyancy-dominated flow, which is generated by the interaction between the dominant buoyancy force by heating and inertial momentum forces by the inlet jets. As a result, the current CFD moderator analysis model predicts the moderator temperature reasonably, and the maximum error against the experimental data is kept at less than 2.0°C over the whole domain. The simulated velocity field matches with the visualization of SPEL experiments quite well.
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Rhee, Bo Wook, Churl Yoon, and Byung-Joo Min. "CFD Simulation of the CANDU-6 Moderator Circulation Under Normal Operating Conditions." In 10th International Conference on Nuclear Engineering. ASMEDC, 2002. http://dx.doi.org/10.1115/icone10-22527.

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A steady-state 3D simulation for predicting the local subcooling of the moderator in the vicinity of the calandria tubes in a CANDU-6 reactor is performed. For the current simulation, a set of grid structures with the same geometry as the CANDU-6 moderator tank, called ‘calandria vessel’, is generated and the momentum, heat and continuity equations are solved by CFX-4.3, a CFD code developed by AEA technology. The standard k-ε turbulence model associated with logarithmic wall treatment is used to model turbulence generation and dissipation within the vessel. The moderator fluid is heavy water. Buoyancy forces are modeled using the Boussinesq approximation in which density is assumed to be a linear function of temperature. The matrix of the calandria tubes in the center region of the calandria vessel is simplified by the porous media approach. The anisotropic hydraulic impedance of the calandria tubes is modeled using the frictional pressure drop correlations suggested by Idelchik and Szymanski. The heat load in this steady-state simulation is conservatively set as 103 MW of 103% full power, consisting of 96.7 MW to the core region and 6.3 MW to the reflector region. The total volumetric flow rate through eight inlet nozzles is 940 L/s and the outlet temperature is constantly 71.0 °C. The thermal boundary condition of the circumferential vessel wall is assumed a little heat flux out. As a result, the velocity field and temperature distribution of a CANDU-6 moderator in the operating condition are presented. The flow pattern identified in this simulation is the weak jet momentum-dominated flow, which is generated by the interaction between the buoyancy force by heating and the dominant momentum forces by inlet jets. The calculated maximum temperature of the moderator is 83.0 °C at the lower center region of the core, which corresponds to the minimum subcooling of 33.0 °C considering the boiling point increase due to the hydrostatic pressure change.
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Dasgupta, Mrinal. "High p_T jet shapes, non-global logarithms and jet algorithms." In XVIII International Workshop on Deep-Inelastic Scattering and Related Subjects. Sissa Medialab, 2010. http://dx.doi.org/10.22323/1.106.0104.

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Hoang, Andre, Mathias Butenschoen, Bahmand Dehnadi, Vicent Mateu, Moritz Preisser, and Iain W. Stewart. "Summing logarithms and factorization for massive quark initiated jets and the Pythia top quark mass." In Loops and Legs in Quantum Field Theory. Sissa Medialab, 2016. http://dx.doi.org/10.22323/1.260.0066.

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Rostamy, Noorallah, Donald J. Bergstrom, David Sumner, and James D. Bugg. "An Experimental Investigation of the Skin Friction in a Plane Turbulent Wall Jet Over Smooth and Rough Surfaces." In ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting collocated with 8th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-30519.

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Estimation of the skin friction in a turbulent wall jet flow over smooth and rough surfaces was studied experimentally. Wall jet flows can be found in many engineering applications in which knowledge of the skin friction behavior is essential for predicting the drag force as well as the heat transfer rate at the wall. Although there are many studies which consider a wall jet on a smooth surface, only a few experiments have examined wall jet flows on a rough surface. This paper reports on an experimental investigation which used a two-component laser Doppler anemometry (LDA) system to measure the mean velocity field in a plane turbulent wall jet on both smooth and transitionally rough surfaces. The Reynolds number based on the slot height and exit velocity of the jet was approximately Re = 7500. A glass plate was used for the smooth surface, while the rough surface consisted of a 36-grit sheet glued to the glass plate. The momentum-viscosity scaling originally introduced by Narasimha et al. (1973) and revisited by Wygnanski et al. (1992) can be used to construct a similarity profile for a wall jet on a smooth surface, which together with the momentum integral equation leads to a convenient expression for the friction velocity and hence skin friction coefficient Cf. This approach has been used to process the experimental results, which gives values of Cf which are consistent with the results of other methods and some existing empirical correlations. However, for rough wall flow, the friction at the wall is not only governed by viscosity, but also by surface roughness. Hogg et al. (1997) suggested that for a fully rough surface, the viscosity be replaced by the roughness parameter Uoke, where Uo and ke are the initial velocity and roughness length, respectively. Here, this approach is applied to our recent velocity measurements in a wall jet on a transitionally rough surface, where both viscous and roughness effects are present. The present results indicate that for an equivalent sand-grain roughness range of 40 &amp;lt; ks+ &amp;lt; 70, the momentum-viscosity scaling is able to capture the skin friction behavior compared to that obtained from the logarithmic and power laws. The results also show that the scalings proposed by Hogg et al. (1997) and Wygnanski et al. (1992) both result in similar values for the friction velocity. However, the values of Cf estimated by both scalings are considerably larger (approximately 47%) than those obtained from the logarithmic and power laws.
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Leclerc, Ce´dric, Euge´nie Levallois, Quentin Gallas, Patrick Gillie´ron, and Azeddine Kourta. "Phase Locked Analysis of a Simplified Car Geometry Wake Flow Control Using Synthetic Jet." In ASME 2006 2nd Joint U.S.-European Fluids Engineering Summer Meeting Collocated With the 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/fedsm2006-98469.

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This paper presents a numerical unsteady analysis of a SJA impact on a car wake flow. First, for the optimal reduced frequency F+, the influence of the Cμ on the mean aerodynamic drag reduction 〈Cd〉 is observed. A spectral analysis of the vortex shedding coming from the upper and the lower part of the car and of the drag coefficient is then presented for different Cμ values. Preliminary results suggest that maximum drag reduction is obtained when most energy in the wake comes from the actuator forcing frequency rather than the natural vortex shedding frequencies of the two contributions. This work is completed by a phase locked analysis of the synthetic jet actuator local effect on the turbulent boundary layer just before the flow separation. For the fixed optimal F+, different Cμ values are compared. The streamwise velocity profiles seem to show that maximal efficiency of the control is obtained when the synthetic jet injected momentum is introduced in the logarithmic sub-layer part of the turbulent boundary layer.
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9

Feng, Xusong, Qingjiang Xiang, Zhengdian Xu, and Tao Sun. "Study on the Methods for Adjusting the Vacuum Degree of Jet Vacuum Device." In ASME 2017 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/fedsm2017-69101.

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Vacuum preloading technique was used to deal with the dredged sludge and the jet vacuum device was adopted. The adjustable vacuum degree device has the advantage for the dredged sludge treatment process. By using the test rig of jet pump, the vacuum adjustable ways and methods were experimentally studied. The results are as follow: when changing the parameter m, which represent the area ratio of throat and nozzle, different gas suction ability and vacuum degree will be obtained. According to vacuum preloading technique construction stage, nozzles with different diameter can be replaced in jet pump to meet different needs. Distance between nozzle outlet and throat inlet L has an optimized value, during the process of adjusting the distance L toward the optimal value, the vacuum degree in jet pump was changed, but the changing range was limited. There is a small influence on the adjustable vacuum degree when changing the length of throat. The highest vacuum value can be achieved with a vertical installation of the jet pump and with long length of throat. The vacuum value appears a logarithmic growth with the nozzle jet intensity, thus changing the working pressure in front of nozzle is a suitable way for vacuum adjustable. There is a good prospect in other applications when the vacuum degree can be adjusted accurately.
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10

Andreini, Antonio, and Riccardo Da Soghe. "Numerical Characterization of Aerodynamic Losses of Jet Arrays for Gas Turbine Applications." In ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-46212.

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Jet array is an arrangement typically used to cool several gas turbine parts. Some examples of such applications can be found in the impingement cooled region of gas turbine airfoils or in the turbine blade tip clearances control of large aero-engines. In order to correctly evaluate the impinging jet mass flow rate, the characterization of holes discharge coefficient is a compulsory activity. In this work an aerodynamic analysis of jet arrays for active clearance control was performed; the aim was the definition of a correlation for the discharge coefficient (Cd) of a generic hole of the array. The data were taken from a set of CFD RANS simulations, in which the behaviour of the cooling system was investigated over a wide range of fluid-dynamics conditions. More in detail, several different holes arrangements were investigated with the aim of evaluating the influence of the hole spacing on the discharge coefficient distribution. Tests were conducted by varying the jet Reynolds number in a wide range of effective engine operative conditions (Re = 2000–12000, Pressure-Ratio = 1.01–1.6). To point out the reliability of the CFD analysis, some comparisons with experimental data, measured at the “Department of Energy Engineering” of the University of Florence, were drawn. An in depth analysis of the numerical data set has underlined the opportunity of an efficient reduction through the mass velocity ratio of hole and feeding pipe: the dependence of the discharge coefficients from this parameter is roughly logarithmic.
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