Articles de revues : « Side-Jets »

1

MURAMATSU, Akinori, Kuu Kashino et Seiichi Terahara. « Side jets in strongly-forced round air jets ». Journal of the Visualization Society of Japan 28-1, n^o 2 (2008) : 1009. http://dx.doi.org/10.3154/jvs.28.1009.

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MORIMOTO, Kenta, et Yuichi ITOH. « 20615 Numerical Simulation of Side-jets generated from Round Jets ». Proceedings of Conference of Kanto Branch 2014.20 (2014) : _20615–1_—_20615–2_. http://dx.doi.org/10.1299/jsmekanto.2014.20._20615-1_.

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Monkewitz, Peter A., Bernhard Lehmann, Bernd Barsikow et Dietrich W. Bechert. « The spreading of self‐excited hot jets by side jets ». Physics of Fluids A : Fluid Dynamics 1, n^o 3 (mars 1989) : 446–48. http://dx.doi.org/10.1063/1.857467.

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MURAMATSU, Akinori, Mirko GAMBA et Noel T. CLEMENS. « Flow Visualization of Side Jets in Helium Gas Jets by PLMS ». Journal of the Visualization Society of Japan 27, Supplement2 (2007) : 59–60. http://dx.doi.org/10.3154/jvs.27.supplement2_59.

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Brancher, P., J. M. Chomaz et P. Huerre. « Direct numerical simulations of round jets : Vortex induction and side jets ». Physics of Fluids 6, n^o 5 (mai 1994) : 1768–74. http://dx.doi.org/10.1063/1.868238.

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Monkewitz, Peter A., et Eberhard Pfizenmaier. « Mixing by side jets’’ in strongly forced and self‐excited round jets ». Physics of Fluids A : Fluid Dynamics 3, n^o 5 (mai 1991) : 1356–61. http://dx.doi.org/10.1063/1.858065.

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MIZUSHIMA, J., et Y. KAWAGUCHI. « Transitions of flow past a row of square bars ». Journal of Fluid Mechanics 405 (25 février 2000) : 305–23. http://dx.doi.org/10.1017/s0022112099007399.

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Transitions of flow past a row of square bars placed across a uniform flow are investigated by numerical simulations and the bifurcation analysis of the numerical results. The flow is assumed two-dimensional and incompressible. It is already known that jets coming through gaps between square bars are independent of each other when the pitch-to-side-length ratio of the row is large, whereas the confluence of two or three jets occurs due to a first pitchfork bifurcation from the flow with independent jets when the pitch-to-side-length ratio is small. It is found that confluence of four jets occurs in consequence of the second pitchfork bifurcation from the flow with pairs of jets joined to each other. Bifurcation diagrams of the flow are obtained, which include confluences of double, triple and quadruple jets. Lengths of the twin vortices are evaluated for each flow pattern. The confluences of two, three and four jets are qualitatively confirmed experimentally by flow visualizations.

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YAO, YUFENG. « DIRECT NUMERICAL SIMULATION OF MULTIPLE JETS IN CROSS-FLOW ». Modern Physics Letters B 23, n^o 03 (30 janvier 2009) : 249–52. http://dx.doi.org/10.1142/s0217984909018126.

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Direct numerical simulation has been performed to study flow interactions in multiple jets in cross-flow. Configurations considered are twin jets side-by-side and triple jets in tandem. Computations are carried out at the jet to cross-flow velocity ratio of 2.5 and the Reynolds number 225 based on the free-stream quantities and the jet width D . For twin jets, results show that in the vicinity of jet exits, the merging of two counter rotating vortex pairs (CRVP) is strongly dependent on the gap of two jets. Downstream in the far-field, a large single CRVP dominates. The simulation is in qualitatively good agreement with the experimental findings by other researchers. For triple jets, more complicated flow structures are revealed, in which a total of three vortex pairs has been identified, but none of them is dominating. The observations of complex flow structure could assistant relevant industrial applications.

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BRUNA, ELENA. « DI-JET MEASUREMENTS IN HEAVY-ION COLLISIONS AT STAR ». International Journal of Modern Physics E 20, n^o 07 (juillet 2011) : 1551–55. http://dx.doi.org/10.1142/s0218301311019854.

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Jets are produced from hard scatterings in the early stages of heavy-ion collisions. It is expected that these high-pT partons travel through the hot and dense medium before fragmenting. Therefore they are expected to suffer energy loss in the QGP via gluon radiation and elastic collisions along their path. Measurements of fully reconstructed jets help understand the effect of the energy loss on the jet structure and energy profile. A data-driven characterization of the background in Au + Au is needed in order to compare the results to p + p . The full azimuthal coverage of STAR Time Projection Chamber and Electromagnetic Calorimeter allows measurements of fully reconstructed di-jets, defined by jets that match the online trigger and recoil jets on the away side. A tight selection of the trigger jets allows for a selection of those coming from the surface. Hence, the population of jets on the recoil side is biased towards a maximal energy loss because of the extreme in-medium pathlength. We present measurements of di-jets, exploring their structure and properties in Au + Au and p + p at [Formula: see text] in the STAR experiment.

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KATO, Yushi, et Akinori MURAMATSU. « Effect on Initial Velocity Gradient on Side-Jets Formation in a Round Jets ». Proceedings of the Fluids engineering conference 2018 (2018) : OS5–9. http://dx.doi.org/10.1299/jsmefed.2018.os5-9.

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MURAMATSU, Akinori, Akira SHIBATA et Naoki KUMAZAWA. « 0129 A Criterion for Generation of Side Jets in Pulsed Round Air Jets ». Proceedings of the Fluids engineering conference 2009 (2009) : 59–60. http://dx.doi.org/10.1299/jsmefed.2009.59.

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Sterling, Alphonse C., Ronald L. Moore et Navdeep K. Panesar. « Solar Active Region Coronal Jets. III. Hidden-onset Jets ». Astrophysical Journal 960, n^o 2 (1 janvier 2024) : 109. http://dx.doi.org/10.3847/1538-4357/acff6b.

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Abstract Solar quiet- and coronal-hole region coronal jets frequently clearly originate from erupting minifilaments, but active-region jets often lack an obvious erupting-minifilament source. We observe a coronal-jet-productive active region (AR), AR 12824, over 2021 May 22 0–8 UT, primarily using Solar Dynamics Observatory (SDO) Atmospheric Imaging Array (AIA) EUV images and SDO/Helioseismic and Magnetic Imager magnetograms. Jets were concentrated in two locations in the AR: on the south side and on the northwest side of the AR’s lone large sunspot. The south-location jets are oriented so that we have a clear view of the jets’ origin low in the atmosphere: their source is clearly minifilaments erupting from locations showing magnetic flux changes/cancelations. After erupting a projected distance ≲5″ away from their origin site, the minifilaments erupt outward onto far-reaching field as part of the jet’s spire, quickly losing their minifilament character. In contrast, the northwest-location jets show no clear erupting minifilament, but the source site of those jets are obscured along our line of sight by absorbing chromospheric material. EUV and magnetic data indicate that the likely source sites were ≳15″ from where the we first see the jet spire; thus, an erupting minifilament would likely lose its minifilament character before we first see the spire. We conclude that such AR jets could work like non-AR jets, but the erupting-minifilament jet source is often hidden by obscuring material. Another factor is that magnetic eruptions making some AR jets carry only a harder-to-detect comparatively thin (∼1″–2″) minifilament “strand.”

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Wawrzak, Karol, et Artur Tyliszczak. « Influence of the Mesh Topology on the Accuracy of Modelling Turbulent Natural and Excited Round Jets at Different Initial Turbulence Intensities ». Applied Sciences 12, n^o 21 (6 novembre 2022) : 11244. http://dx.doi.org/10.3390/app122111244.

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The paper is aimed at an assessment of the importance of the coordinate system (Cartesian vs. cylindrical) assumed for simulations of free-round jets. The research is performed by applying the large eddy simulation method with spatial discretisation based on high-order compact difference schemes. The results obtained for natural and excited jets at three different turbulence intensity levels, Ti=0.01%,0.1% and 1.0%, are compared. In the case of the natural jet, it is found that both instantaneous and time-averaged results are significantly dependent on the coordinate system only for the lowest Ti. In this case, in the Cartesian coordinate system, the errors introduced by an azimuthal non-uniformity of the mesh seem to have a larger impact on the solutions than the disturbances generated at the nozzle exit. The azimuthal non-uniformity of the mesh also has a substantial influence on the results of the modelling of the excited jets. In this case, the excitation is introduced as time-varying forcing, with the frequency corresponding to half of the preferred mode frequency and the amplitude equal to 5% of the jet velocity. Such an excitation leads to the formation of the so-called side-jets being revealed as inclined streams of fluid ejected outside the main jet stream. Primary attention is paid to the mechanism of the formation of the side-jets, their number and location. The results obtained on Cartesian meshes show that for very low turbulence intensity levels (Ti=0.01%), the number and direction of the side-jets are dependent on the non-uniform distribution of the mesh nodes along the azimuthal direction of the jet. On the other hand, when the cylindrical coordinate system is used, the number of the side-jets and their locations are random and dependent only on inlet parameters. It has been demonstrated that the mechanism of side-jet formation is the same in both coordinate systems; however, its random nature can only be predicted when the cylindrical coordinate system is used.

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Vuorinen, Laura, Heli Hietala et Ferdinand Plaschke. « Jets in the magnetosheath : IMF control of where they occur ». Annales Geophysicae 37, n^o 4 (6 août 2019) : 689–97. http://dx.doi.org/10.5194/angeo-37-689-2019.

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Abstract. Magnetosheath jets are localized regions of plasma that move faster towards the Earth than the surrounding magnetosheath plasma. Due to their high velocities, they can cause indentations when colliding into the magnetopause and trigger processes such as magnetic reconnection and magnetopause surface waves. We statistically study the occurrence of these jets in the subsolar magnetosheath using measurements from the five Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft and OMNI solar wind data from 2008 to 2011. We present the observations in the BIMF–vSW plane and study the spatial distribution of jets during different interplanetary magnetic field (IMF) orientations. Jets occur downstream of the quasi-parallel bow shock approximately 9 times as often as downstream of the quasi-perpendicular shock, suggesting that foreshock processes are responsible for most jets. For an oblique IMF, with 30–60∘ cone angle, the occurrence increases monotonically from the quasi-perpendicular side to the quasi-parallel side. This study offers predictability for the numbers, locations, and magnetopause impact rates of jets observed during different IMF orientations, allowing us to better forecast the formation of these jets and their impact on the magnetosphere.

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TOI, Takeo, et Akinori MURAMATSU. « Velocity and Vorticity Measurements in Round Jets with Side-Jets Formation Using a PIV ». Proceedings of the Fluids engineering conference 2018 (2018) : OS5–8. http://dx.doi.org/10.1299/jsmefed.2018.os5-8.

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MURAMATSU, Akinori, On Ishikawa et Tomoya SASAKI. « 1904 A region of generation of side jets in round, low-density gas jets ». Proceedings of the JSME annual meeting 2008.2 (2008) : 207–8. http://dx.doi.org/10.1299/jsmemecjo.2008.2.0_207.

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Bario, F., F. Leboeuf, A. Onvani et A. Seddini. « Aerodynamics of Cooling Jets Introduced in the Secondary Flow of a Low-Speed Turbine Cascade ». Journal of Turbomachinery 112, n^o 3 (1 juillet 1990) : 539–46. http://dx.doi.org/10.1115/1.2927692.

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The aerodynamic behavior of cold discrete jets in a cold secondary flow is investigated. Configurations including single jets and rows of jets are studied. These jets are introduced through the side wall of a low-speed nozzle turbine cascade. The experimental setup and the jet behavior are fully described. The effects of location with respect to the blades, mass flow ratio, yaw, and incidence angles on the aerodynamics of single jets are investigated. The influence of neighboring jets is detailed in the case of multiple jet configurations. The interaction with the secondary flow is presented. The local pressure and velocity fields, trajectories, and visualizations are discussed. The measuring apparatus includes a five-hole probe and a hot wire for intermittency measurements.

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SUGAWA, Takafumi, et Akinori MURAMATSU. « Side-jets formation in a rectangular helium gas jet. » Proceedings of the Fluids engineering conference 2016 (2016) : 0209. http://dx.doi.org/10.1299/jsmefed.2016.0209.

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ARAI, Masaaki, Tsuneaki ISHIMA, Mikiya ARAKI, Seiichi SHIGA, Hisao NAKAMURA et Tomio OBOKATA. « Screech Reduction of a Supersonic Jet by Side Jets ». Proceedings of the JSME annual meeting 2003.7 (2003) : 305–6. http://dx.doi.org/10.1299/jsmemecjo.2003.7.0_305.

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Parsons, Lawrence R., Brian S. Combs et D. P. H. Tucker. « Citrus Freeze Protection with Microsprinkler Irrigation during an Advective Freeze ». HortScience 20, n^o 6 (décembre 1985) : 1078–80. http://dx.doi.org/10.21273/hortsci.20.6.1078.

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Abstract Microsprinkler irrigation was used to protect young citrus trees during severe advective freeze conditions in Florida during 24–26 Dec. 1983. Three factors (microsprinkler distance from the tree, compass position, and water volume output) influenced the amount of protection or tree damage. Spray jets that delivered 76 liters/hr (9 mm/hr) and were located 0.7 m or less from the north side of the trees protected the lower scaffold branches and trunk of young trees to temperatures below −6°C. Spray jet irrigation, particularly when jets were more than 1 m away on the east side of the trees resulted in more tree damage than no irrigation. This was due to low dew point temperatures and northwest winds which kept continuously-sprayed water away from the tree. Volume of water per tree needs to be moderately high, and spray jets should be located on the upwind (northwest) side of the tree at a distance no greater than 0.7 m from the tree in order to provide optimum freeze protection with microsprinkler irrigation.

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Aunapu, Nicole V., Ralph J. Volino, Karen A. Flack et Ryan M. Stoddard. « Secondary Flow Measurements in a Turbine Passage With Endwall Flow Modification ». Journal of Turbomachinery 122, n^o 4 (1 février 2000) : 651–58. http://dx.doi.org/10.1115/1.1311286.

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A flow modification technique is introduced in an attempt to allow increased turbine inlet temperatures. A large-scale two half-blade cascade simulator is used to model the secondary flow between two adjacent turbine blades. Various flow visualization techniques and measurements are used to verify that the test section replicates the flow of an actual turbine engine. Two techniques are employed to modify the endwall secondary flow, specifically the path of the passage vortex. Six endwall jets are installed at a location downstream of the saddle point near the leading edge of the pressure side blade. These wall jets are found to be ineffective in diverting the path of the passage vortex. The second technique utilizes a row of 12 endwall jets whose positions along the centerline of the passage are based on results from an optimized boundary layer fence. The row of jets successfully diverts the path of the passage vortex and decreases its effect on the suction side blade. This can be expected to increase the effectiveness of film cooling in that area. The row of jets increases the aerodynamic losses in the passage, however. Secondary flow measurements are presented showing the development of the endwall flow, both with and without modification. [S0889-504X(00)01004-7]

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TOI, Takeo, et Akinori MURAMATSU. « Measurements of velocity and vorticity fields in round jets with side-jets formation using a PIV ». Proceedings of Mechanical Engineering Congress, Japan 2018 (2018) : S0510306. http://dx.doi.org/10.1299/jsmemecj.2018.s0510306.

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RAMAN, GANESH, et RAY TAGHAVI. « Coupling of twin rectangular supersonic jets ». Journal of Fluid Mechanics 354 (10 janvier 1998) : 123–46. http://dx.doi.org/10.1017/s0022112097007441.

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Twin jet plumes on aircraft can couple, producing dynamic pressures significant enough to cause structural fatigue. For closely spaced jets with a moderate aspect ratio (e.g. 5), previous work has established that two coupling modes (antisymmetric and symmetric) are kinematically permissible. However, the dynamics of twin-jet coupling have remained unexplored. In this paper a more fundamental assessment of the steady and unsteady aspects of twin-jet coupling is attempted. While we document and discuss the nozzle spacings and Mach numbers over which phase-locked coupling occurs, our concentration is much more on answering the following questions: (a) What mechanism causes the jets to couple in one mode or the other? (b) Why do the jets switch from one mode to another? (c) Are the two modes mutually exclusive or do they overlap at the transition point? Our results reveal, among many things, the following. (i) For very closely spaced twin jets in the side-by-side configuration phased feedback based on source to nozzle exit distance of adjacent jets does not fully explain the coupling modes. However, the ‘null’ phase regions surrounding the jets where the phase of an acoustic wavefront (arriving from downstream) does not vary appears to correlate well with the existence of the symmetric mode. When the ‘null’ regions of adjacent jets do not overlap antisymmetric coupling occurs and when they do overlap the jets couple symmetrically. We provide a simple correlation using a parameter (α) that can be used as a simple test to determine the mode of coupling. (ii) The switch from the antisymmetric to the symmetric mode of coupling appears to occur because of an abrupt shift in the effective screech source from the third to the fourth shock, which in turn causes the ‘null’ phase region surrounding the jets to grow abruptly and overlap. (iii) The two modes are mutually exclusive. Our results provide considerable insight into the twin-jet coupling problem and offer hope for designing twin-jet configurations that minimize damage to aircraft components.

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Nouali, Nassira, et Amina Mataoui. « Interaction of a hot jet with two cold side jets ». Thermal Science 19, n^o 6 (2015) : 2115–26. http://dx.doi.org/10.2298/tsci140310113n.

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Spreading of the multijet in terms of both the velocity and temperature field depends strongly on the flow type related to the velocity and temperature ratios between the cold side jets to the hot central one. This is the reason why the present work focuses on numerical investigation of non isothermal three parallel non-ventilated turbulent plane jets. As well, it seems natural to pick as reference the available experimental data. The numerical predictions confirm the three types (A, B, C) of flow patterns given by the available flow visualization and reveal a fourth that will be called type D. The purpose of the present study is to explore the effect of the velocity ratio on the decay rates of the velocity and temperature in the fully developed region. It is found that the addition of side jets increase the rate of decrease of the centerline velocity for the flow of type A and decreases in the other cases. The effect of various types of flow on the rate of decrease of the velocity and the temperature in the fully developed flow region are investigated in details: This led to establish several correlations of the rate of decrease that play an important role in the diffusion of momentum and temperature.

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Cutbirth, J. Michael, et David G. Bogard. « Evaluation of Pressure Side Film Cooling With Flow and Thermal Field Measurements—Part I : Showerhead Effects ». Journal of Turbomachinery 124, n^o 4 (1 octobre 2002) : 670–77. http://dx.doi.org/10.1115/1.1504441.

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The goal of this study was to determine how showerhead blowing on a turbine vane leading edge affects of the performance of film cooling jets farther downstream. An emphasis was placed on measurements above the surface, i.e., flow visualization, thermal field, and velocity field measurements. The film cooling performance on the pressure side of a simulated turbine vane, with and without showerhead blowing, was examined. Results presented in this paper are for low mainstream turbulence; high mainstream turbulence effects are presented in the companion paper. At the location of the pressure side row of holes, the showerhead coolant extended a distance of about 3d from the surface (d is the coolant hole diameter). The pressure side was found to be subjected to high turbulence levels caused by the showerhead injection. Results indicate a greater dispersion of the pressure side coolant jets with showerhead flow due to the elevated turbulence levels.

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Kharoua, N., et L. Khezzar. « Flow Asymmetry in Symmetric Multiple Impinging Jets : A Large Eddy Simulation Approach ». Journal of Engineering Research [TJER] 8, n^o 2 (1 décembre 2011) : 40. http://dx.doi.org/10.24200/tjer.vol8iss2pp40-48.

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A numerical study on in-line arrays of multiple turbulent round impinging jets on a flat heated plate was conducted. The Large Eddy Simulation turbulence model was used to capture details of the instantaneous and mean flow fields. The Reynolds number, based on the jets diameter, was equal to 20,000. In addition to flow features known from single jets, the interaction between the neighboring jets was successfully elucidated. Symmetry boundary conditions were imposed to reduce the computational domain to only a quarter. In accordance with previous numerical and experimental works, the asymmetry in the velocity field near to the impingement plate was also found to exist. LES showed oval imprints of the Nusselt number similar to experiments but with some discrepancies on the symmetry boundaries. The asymmetry, observed in previous experimental and numerical results, in the horizontal planes, parallel and close to the impingement wall, was confirmed. The recirculation zone responsible for asymmetry, known to develop due to the wall jets interaction, was seen in only one side of the diagonal formed by the central and the farthest jets.

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TANAKA, Kohei, et Akinori MURAMATSU. « Numerical simulation of a round jet with controlled side jets ». Proceedings of the Fluids engineering conference 2020 (2020) : OS03–29. http://dx.doi.org/10.1299/jsmefed.2020.os03-29.

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Ma, G. L., S. Zhang, Y. G. Ma, X. Z. Cai, J. H. Chen et C. Zhong. « Longitudinal broadening of near-side jets due to parton cascade ». European Physical Journal C 57, n^o 3 (23 août 2008) : 589–93. http://dx.doi.org/10.1140/epjc/s10052-008-0691-6.

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KANEDA, Yasuhiro, et Akinori MURAMATU. « 0110 Conditions for side-jet formation in low-density jets ». Proceedings of the Fluids engineering conference 2010 (2010) : 25–26. http://dx.doi.org/10.1299/jsmefed.2010.25.

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MURAMATSU, Akinori, et Yuta AOKI. « 0604 Issuing conditions for side-jet formation in round jets ». Proceedings of the Fluids engineering conference 2013 (2013) : _0604–01_—_0604–04_. http://dx.doi.org/10.1299/jsmefed.2013._0604-01_.

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PRUNEAU, CLAUDE. « METHODS FOR JET STUDIES WITH THREE-PARTICLE CORRELATIONS ». International Journal of Modern Physics E 16, n^o 07n08 (août 2007) : 1964–70. http://dx.doi.org/10.1142/s0218301307007301.

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We present a method based on three-particle azimuthal correlation cumulants for the study of the interaction of jets with the medium produced in heavy ion collisions at RHIC and LHC where jets cannot be reconstructed on an event-by-event basis with conventional jet finding algorithms. The method is specifically designed to distinguish a range of jet interaction mechanisms such as Mach cone emission, gluon Cerenkov emission, jet scattering, and jet broadening. We discuss how anisotropic flow background conti-butions of second order (e.g. [Formula: see text]) are suppressed in three-particle azimuthal correlation cumulants, and discussed specific model representations of di-jets, away-side scattering, and Mach cone emission.

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Savory, E., et N. Toy. « Real-Time Video Analysis of Twin Jets in a Crossflow ». Journal of Fluids Engineering 113, n^o 1 (1 mars 1991) : 68–72. http://dx.doi.org/10.1115/1.2926499.

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The research presented in this paper is an investigation of the interaction between twin side-by-side circular jets issuing into a crossflow, utilizing a real-time video digitization system to obtain quantitative data from the visualized flow fields. The intermittency field results obtained from experiments with different jet spacings and jet velocity/crossflow velocity ratios are reported.

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Condie, S. A., et P. B. Rhines. « Topographic Hadley cells ». Journal of Fluid Mechanics 280 (10 décembre 1994) : 349–68. http://dx.doi.org/10.1017/s002211209400296x.

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When a rotating fluid over sloping topography is heated from below and/or cooled from above, horizontal temperature gradients develop which drive convection cells aligned with isobaths. We refer to these cells as topographic Hadley cells. Laboratory experiments reveal that sinking occurs in small cyclonic vortices situated in relatively shallow regions. This is balanced by slower upwelling in adjacent deeper regions. The cross-isobath motions which connect the upwelling and downwelling are accelerated by Coriolis forces, resulting in strong jets which follow isobathic contours. For anticlockwise rotation, the surface jets keep the shallows to their left when looking in the direction of flow, which is opposite to both Kelvin and Rossby wave propagation. The width of the jets scales with the Rossby deformation radius and if this is much less than the width of the slope region then a number of parallel jets form. Motions on the deeper side of the jets where the flow is accelerating are adequately described by linear inviscid theory. However, the strong shears generated by this acceleration lead to baroclinic instability. The resulting cross-stream momentum fluxes broaden and flatten the velocity profile, allowing the flow on the shallow side of the jet to decelerate smoothly before sinking. Topographic Hadley cells are dynamically similar to terrestrial atmospheric Hadley cells and may also be relevant to the zonal jet motions observed on Jupiter and Saturn. It is also suggested that in coastal seas they may represent an important mode of heat (or salt) transfer where surface cooling (or evaporation) drives convection.

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Bohn, Dieter E., et Karsten A. Kusterer. « Aerothermal Investigations of Mixing Flow Phenomena in Case of Radially Inclined Ejection Holes at the Leading Edge ». Journal of Turbomachinery 122, n^o 2 (1 février 1999) : 334–39. http://dx.doi.org/10.1115/1.555456.

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A leading edge cooling configuration is investigated numerically by application of a three-dimensional conjugate fluid flow and heat transfer solver, CHT-flow. The code has been developed at the Institute of Steam and Gas Turbines, Aachen University of Technology. It works on the basis of an implicit finite volume method combined with a multiblock technique. The cooling configuration is an axial turbine blade cascade with leading edge ejection through two rows of cooling holes. The rows are located in the vicinity of the stagnation line, one row on the suction side, the other row is on the pressure side. The cooling holes have a radial ejection angle of 45 deg. This configuration has been investigated experimentally by other authors and the results have been documented as a test case for numerical calculations of ejection flow phenomena. The numerical investigations focus on the aerothermal mixing process in the cooling jets and the impact on the temperature distribution on the blade surface. The radial ejection angles lead to a fully three-dimensional and asymmetric jet flow field. Within a secondary flow analysis, the cooling fluid jets are investigated in detail. The secondary flow fields include asymmetric kidney vortex systems with one dominating vortex on the back side of the jets. The numerical and experimental data show a respectable agreement concerning the vortex development. [S0889-504X(00)00102-1]

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Du, Tianrui, Xiefei Zhi, Yuhong Wang, Liqun Zhou, Ling Zhang et Shoupeng Zhu. « The Distinct Spatial Patterns and Physical Mechanisms of Coastal Boundary Layer Jets over the Northern South China Sea ». Monthly Weather Review 152, n^o 12 (décembre 2024) : 2639–60. https://doi.org/10.1175/mwr-d-23-0263.1.

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Abstract Two distinct spatial patterns of coastal boundary layer jets in the northern South China Sea (CBLJ-NSCS) in June 2015–22 are investigated using hourly output data from the Weather Research and Forecasting Model with a horizontal grid spacing of 9 km and ERA5 data. Spatial pattern 1 shows a high-incidence core on the east side of Hainan Island, while pattern 2 features dual high-incidence cores covering both the east side of Hainan Island and the waters south of Guangdong, with the latter being stronger and more extensive. Unique diurnal cycles have been observed in different high-incidence cores of CBLJ-NSCS: the western core, on the east side of Hainan Island, peaks at night and shows a secondary afternoon subpeak, while the eastern core, located south of Guangdong, reaches its maximum intensity at night with a morning subpeak. Inertial oscillations triggered by large-scale perturbation wind circulation and momentum propagation from upstream Indochina Peninsula CBLJs explain the nocturnal enhancement of both cores. The thermal effect exerted by Hainan Island largely contributes to the afternoon enhancement in the western core. The formation of the morning subpeak of the eastern core results from strong convergence and lifting in the northeast region of it. When upstream CBLJs along the Annamite Range intensify, more momentum is propagated to the eastern core instead of the western one due to wind field changes, which promotes the transition from spatial pattern 1 to pattern 2. Significance Statement Two spatial patterns of coastal boundary layer jets in the northern South China Sea have been identified. Spatial pattern 1 shows a high-incidence core on the east side of Hainan Island, while pattern 2 features dual high-incidence cores covering both the east side of Hainan Island and the waters south of Guangdong. The transition between these two spatial patterns is related to low-level westerly winds along the coast of the Annamite Range. This study has uncovered the novel spatial pattern of coastal boundary layer jets in the northern South China Sea and provides new insights into precipitation research in southern China, considering the substantial influence of these jets on coastal weather.

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Palmroth, Minna, Savvas Raptis, Jonas Suni, Tomas Karlsson, Lucile Turc, Andreas Johlander, Urs Ganse et al. « Magnetosheath jet evolution as a function of lifetime : global hybrid-Vlasov simulations compared to MMS observations ». Annales Geophysicae 39, n^o 2 (12 mars 2021) : 289–308. http://dx.doi.org/10.5194/angeo-39-289-2021.

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Abstract. Magnetosheath jets are regions of high dynamic pressure, which can traverse from the bow shock towards the magnetopause. Recent modelling efforts, limited to a single jet and a single set of upstream conditions, have provided the first estimations about how the jet parameters behave as a function of position within the magnetosheath. Here we expand the earlier results by doing the first statistical investigation of the jet dimensions and parameters as a function of their lifetime within the magnetosheath. To verify the simulation behaviour, we first identify jets from Magnetosphere Multiscale (MMS) spacecraft data (6142 in total) and confirm the Vlasiator jet general behaviour using statistics of 924 simulated individual jets. We find that the jets in the simulation are in quantitative agreement with the observations, confirming earlier findings related to jets using Vlasiator. The jet density, dynamic pressure, and magnetic field intensity show a sharp jump at the bow shock, which decreases towards the magnetopause. The jets appear compressive and cooler than the magnetosheath at the bow shock, while during their propagation towards the magnetopause they thermalise. Further, the shape of the jets flatten as they progress through the magnetosheath. They are able to maintain their flow velocity and direction within the magnetosheath flow, and they end up preferentially to the side of the magnetosheath behind the quasi-parallel shock. Finally, we find that Vlasiator jets during low solar wind Alfvén Mach number MA are shorter in duration, smaller in their extent, and weaker in terms of dynamic pressure and magnetic field intensity as compared to the jets during high MA.

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Yuan, Fangyang, Yang Cao, Chengxu Tu et Jianzhong Lin. « Control of vortex shedding from two side-by-side cylinders using a pair of tangential jets ». AIP Advances 10, n^o 10 (1 octobre 2020) : 105129. http://dx.doi.org/10.1063/5.0025544.

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O'Dell, C. R. « Herbig-Haro Objects in the Orion Nebula Region ». Symposium - International Astronomical Union 182 (1997) : 39–46. http://dx.doi.org/10.1017/s0074180900061520.

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The Orion Nebula Region has two different systems of objects classified as HH objects. The North System is associated with the H2 fingers seen in the infrared and is probably the result of Rayleigh-Taylor instabilities in shocked material moving into the near side of the giant molecular cloud OMC-1. The South System is associated with source(s) within the Trapezium cluster, with the shocked HH objects occuring where jets from pre-main sequence stars impinge on the neutral lid of material that lies across the front of the Orion Nebula. Such jets are different from those driving other HH objects in that these are passing through photoionized material and two of the Orion jets may have been detected.

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KATO, Yushi, et Akinori MURAMATSU. « Hysteresis Phenomenon of Side-Jets Formation in a Round Air Jet ». Proceedings of Mechanical Engineering Congress, Japan 2019 (2019) : S05109. http://dx.doi.org/10.1299/jsmemecj.2019.s05109.

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Kovar, A., et E. Schülein. « Comparison of experimental and numerical investigation on a jet in a supersonic cross-flow ». Aeronautical Journal 110, n^o 1108 (juin 2006) : 353–60. http://dx.doi.org/10.1017/s0001924000001263.

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Abstract Flow interaction of three different jet configurations ejecting air from a flat plate into a supersonic cross flow were investigated experimentally and numerically. The test conditions encompassed a jet pressure ratio of Poj, P∞ = 100 at a Mach number of M∞ = 5 and Reynolds number of about Re∞ = 25 × 106 based on the length of the flat plate. The investigated test cases are: a) single jet; b) four jets positioned in-line in main flow direction; c) four jets positioned side-by-side in spanwise direction. The prediction of the overall flow phenomena as occurring within the interaction area was in fair agreement with the experiments, although quantitatively differences occur that will be discussed in the paper. The results of the comparison are presented and the experimental data are used to validate the applied code.

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Aharonian, F., F. Ait Benkhali, J. Aschersleben, H. Ashkar, M. Backes, V. Barbosa Martins, R. Batzofin et al. « Acceleration and transport of relativistic electrons in the jets of the microquasar SS 433 ». Science 383, n^o 6681 (26 janvier 2024) : 402–6. http://dx.doi.org/10.1126/science.adi2048.

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SS 433 is a microquasar, a stellar binary system that launches collimated relativistic jets. We observed SS 433 in gamma rays using the High Energy Stereoscopic System (H.E.S.S.) and found an energy-dependent shift in the apparent position of the gamma-ray emission from the parsec-scale jets. These observations trace the energetic electron population and indicate that inverse Compton scattering is the emission mechanism of the gamma rays. Our modeling of the energy-dependent gamma-ray morphology constrains the location of particle acceleration and requires an abrupt deceleration of the jet flow. We infer the presence of shocks on either side of the binary system, at distances of 25 to 30 parsecs, and that self-collimation of the precessing jets forms the shocks, which then efficiently accelerate electrons.

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Silvers, Levi G., et Wayne H. Schubert. « A Theory of Topographically Bound Balanced Motions and Application to Atmospheric Low-Level Jets ». Journal of the Atmospheric Sciences 69, n^o 9 (1 septembre 2012) : 2878–91. http://dx.doi.org/10.1175/jas-d-11-0309.1.

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Abstract The subject of this study is topographically bound low-level jets, such as the South American summertime low-level jet on the eastern side of the Andes and its companion, the Chilean low-level jet on the western side of the Andes. These jets are interpreted as balanced flows that obey the potential vorticity invertibility principle. This invertibility principle is expressed in isentropic coordinates, and the mathematical issue of isentropes that intersect the topography is treated by the method of a massless layer. In this way, the low-level jets on the western and eastern sides of the Andes can both be attributed to the infinite potential vorticity that lies in the infinitesimally thin massless layer on the topographic feature. To obtain a cyclonic flow centered on the topographic feature, the mountain crest must have been heated enough to draw down the overlying isentropic surfaces; otherwise, isentropic surfaces bend upward at the mountain crest and an anticyclonic flow is produced. Both anticyclonic and cyclonic solutions are obtained here using analytical and numerical methods to solve the invertibility principle. The summertime topographically bound flows discussed here are quite distinct from the wintertime Rossby wave train patterns that occur when strong westerlies impinge on the topography.

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Knost, D. G., et K. A. Thole. « Adiabatic Effectiveness Measurements of Endwall Film-Cooling for a First-Stage Vane ». Journal of Turbomachinery 127, n^o 2 (1 avril 2005) : 297–305. http://dx.doi.org/10.1115/1.1811099.

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In gas turbine development, the direction has been toward higher turbine inlet temperatures to increase the work output and thermal efficiency. This extreme environment can significantly impact component life. One means of preventing component burnout in the turbine is to effectively use film-cooling whereby coolant is extracted from the compressor and injected through component surfaces. One such surface is the endwall of the first-stage nozzle guide vane. This paper presents measurements of two endwall film-cooling hole patterns combined with cooling from a flush slot that simulates leakage flow between the combustor and turbine sections. Adiabatic effectiveness measurements showed the slot flow adequately cooled portions of the endwall. Measurements also showed two very difficult regions to cool, including the leading edge and pressure side-endwall junction. As the momentum flux ratios were increased for the film-cooling jets in the stagnation region, the coolant was shown to impact the vane and wash down onto the endwall surface. Along the pressure side of the vane in the upstream portion of the passage, the jets were shown to separate from the surface rather than penetrate to the pressure surface. In the downstream portion of the passage, the jets along the pressure side of the vane were shown to impact the vane thereby eliminating any uncooled regions at the junction. The measurements were also combined with computations to show the importance of considering the trajectory of the flow in the near-wall region, which can be highly influenced by slot leakage flows.

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O’Dea, Christopher P., et Stefi A. Baum. « Wide-Angle-Tail (WAT) Radio Sources ». Galaxies 11, n^o 3 (12 mai 2023) : 67. http://dx.doi.org/10.3390/galaxies11030067.

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We review the properties of Wide-Angle-Tail (WAT) radio sources. The WAT radio sources are powerful, bent radio sources typically associated with the dominant galaxy in a cluster or group. For the purpose of this review, we define the radio morphology properties of WATs as (1) a sudden jet-tail transition, (2) overall bending of the tails to one side, and (3) non-parallel tails. The mechanism for the rapid jet-tail transition is uncertain but it seems to occur near the transition from the host ISM to ICM. The jet-tail transition may make the jets easier to bend. The narrow range in radio luminosity can be understood if there is a minimum luminosity required to allow the jets to propagate undisturbed for tens of kpc and a maximum luminosity required to allow the jet disruption mechanism to act. WATs are typically hosted by the brightest cluster galaxies in clusters which are currently merging. Thus, WATs can be used as tracers of merging clusters. The merging produces large-scale bulk motions in the ICM which can provide sufficient ram pressure to bend the jets. We suggest that although the Lorentz force may not bend the jets in WATs, it may be relevant in other sources, e.g., protostellar jets.

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López-Cámara, D., et A. C. Raga. « Side-entrainment in a jet embedded in a sidewind ». Proceedings of the International Astronomical Union 6, S275 (septembre 2010) : 400–401. http://dx.doi.org/10.1017/s1743921310016479.

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AbstractIn this study, we present the results from 3D simulations in which a side-streaming motion pushes the post-bow shock into direct contact with the jet beam. This is a possible mechanism for modeling well collimated molecular jets as an atomic/ionic flow which entrains molecules initially present only in the surrounding environment.

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Joshi, Reetika, Ramesh Chandra, Brigitte Schmieder, Fernando Moreno-Insertis, Guillaume Aulanier, Daniel Nóbrega-Siverio et Pooja Devi. « Case study of multi-temperature coronal jets for emerging flux MHD models ». Astronomy & ; Astrophysics 639 (juillet 2020) : A22. http://dx.doi.org/10.1051/0004-6361/202037806.

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Context. Hot coronal jets are a basic observed feature of the solar atmosphere whose physical origin is still actively debated. Aims. We study six recurrent jets that occurred in active region NOAA 12644 on April 4, 2017. They are observed in all the hot filters of AIA as well as cool surges in IRIS slit–jaw high spatial and temporal resolution images. Methods. The AIA filters allow us to study the temperature and the emission measure of the jets using the filter ratio method. We studied the pre-jet phases by analysing the intensity oscillations at the base of the jets with the wavelet technique. Results. A fine co-alignment of the AIA and IRIS data shows that the jets are initiated at the top of a canopy-like double-chambered structure with cool emission on one and hot emission on the other side. The hot jets are collimated in the hot temperature filters, have high velocities (around 250 km s−1) and are accompanied by cool surges and ejected kernels that both move at about 45 km s−1. In the pre-phase of the jets, we find quasi-periodic intensity oscillations at their base that are in phase with small ejections; they have a period of between 2 and 6 min, and are reminiscent of acoustic or magnetohydrodynamic waves. Conclusions. This series of jets and surges provides a good case study for testing the 2D and 3D magnetohydrodynamic emerging flux models. The double-chambered structure that is found in the observations corresponds to the regions with cold and hot loops that are in the models below the current sheet that contains the reconnection site. The cool surge with kernels is comparable with the cool ejection and plasmoids that naturally appears in the models.

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Xiao, Yexiang, Zhengwei Wang, Jidi Zeng, jintai Zheng, Jiayang Lin et Lanjin Zhang. « Prototype and numerical studies of interference characteristics of two ski-jump jets from opening spillway gates ». Engineering Computations 32, n^o 2 (20 avril 2015) : 289–307. http://dx.doi.org/10.1108/ec-04-2013-0104.

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Purpose – The purpose of this paper is to experimentally and numerically investigate the interference characteristics between two ski-jump jets on the flip bucket in a large dam spillway when two floodgates are running. Design/methodology/approach – The volume of fluid (VOF) method together with the Realizable k-ε turbulence model were used to predict the flow in two ski-jump jets and the free surface motion in a large dam spillway. The movements of the two gates were simulated using a dynamic mesh controlled by a User Defined Function (UDF). The simulations were run using the prototype dam as the field test to minimize errors due to scale effects. The simulation results are compared with field test observations. Findings – The transient flow calculations, accurately predict the two gate discharges compared to field data with the predicted ski-jump jet interference flow pattern similar to the observed shapes. The transient simulations indicate that the main reason for the deflected nappe is the larger opening difference between the two gates as the buttress side gate closes. When both gates are running, the two ski-jump jets interfere in the flip bucket and raise the jet nappe to near the buttress to form a secondary flow on this jet nappe surface. As the gate continues to close, the nappe surface continues to rise and the surface secondary flow become stronger, which deflects the nappe over the side buttress. Originality/value – A dynamic mesh is used to simulate the transient flow behavior of two prototype running gates. The transient flow simulation clarifies the hydraulics mechanism for how the two ski-jump jets interfere and deflect the nappe.

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Moran, Rafael, Miguel Ángel Toledo, Javier Peraita et Raffaella Pellegrino. « Energy Dissipation in Stilling Basins with Side Jets from Highly Convergent Chutes ». Water 13, n^o 10 (12 mai 2021) : 1343. http://dx.doi.org/10.3390/w13101343.

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Spillways with Highly Converging Chutes (HCCs) are a non-conventional alternative that can be applied to achieve a higher outflow capacity when the weir length exceeds the width of the valley at the toe of gravity or arch dams. This kind of spillway has been used in the past, but no general studies have yet been published. This article summarizes experimental research work aiming to increase the knowledge of the effect of some design parameters of HCCs on the energy dissipation in the stilling basin at the toe of the dam. As a comparison reference, we use the Type I stilling basins, widely known by the technical dam engineering community. The obtained results show that spillways with HCCs are a promising alternative to traditional designs, combining the ability to increase the weir length with a high capacity to dissipate energy through the impingement effect of the frontal and the side jets inside the stilling basin.

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MURAMATSU, Akinori, et Ikuo HARA. « Side-jets formation in a round jet with an external counter flow ». Proceedings of the Fluids engineering conference 2016 (2016) : 0210. http://dx.doi.org/10.1299/jsmefed.2016.0210.

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CAO, Yuchun, Jinxing WU, Jianchun MI et Yu ZHOU. « Flame Structure of a Jet Flame with Penetration of Side Micro-jets ». Chinese Journal of Chemical Engineering 16, n^o 6 (décembre 2008) : 861–66. http://dx.doi.org/10.1016/s1004-9541(09)60006-9.

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