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1
Chen, Fengyang, Ping Lu, Dongqin Li, Yadong Li, Yanqing Hou, Gang Xie, Ni Yang, and Lin Tian. "The Mixing Character within Oxidation Reactor in Titanium Dioxide Production by Chloride Process." Advances in Engineering Technology Research 1, no. 2 (September 22, 2022): 48. http://dx.doi.org/10.56028/aetr.1.2.48.
Повний текст джерелаАнотація:
Chloride process is cost effective and environmental benefit, and the TiCl4 oxidation is the most important stage in this process. The structure of the jet ring has an obviously effect on the mixing of TiCl4 and O2 in the oxidation reactor, which is the key equipment in the production of titanium pigment. In this paper, the gas mixing condition with five jet rings of different structure was simulated and analyzed by computational fluid dynamics (CFD) simulation. The radial concentration distribution of TiCl4 and the non-uniformity of the mixture with different jet rings were obtained. The results showed the structure of the jet ring has great effect on the gas mixing. The mixing condition of the jet ring with combined opening orifice is better than that of the jet ring with uniform opening orifice， which is more effective in realizing fast and uniform mixing condition of TiCl4 and O2.
2
Chen, Fengyang, Ping Lu, Dongqin Li, Yadong Li, Yanqing Hou, Gang Xie, Ni Yang, and Lin Tian. "The Mixing Character within Oxidation Reactor in Titanium Dioxide Production by Chloride Process." Advances in Engineering Technology Research 2, no. 1 (September 22, 2022): 48. http://dx.doi.org/10.56028/aetr.2.1.48.
Повний текст джерелаАнотація:
Chloride process is cost effective and environmental benefit, and the TiCl4 oxidation is the most important stage in this process. The structure of the jet ring has an obviously effect on the mixing of TiCl4 and O2 in the oxidation reactor, which is the key equipment in the production of titanium pigment. In this paper, the gas mixing condition with five jet rings of different structure was simulated and analyzed by computational fluid dynamics (CFD) simulation. The radial concentration distribution of TiCl4 and the non-uniformity of the mixture with different jet rings were obtained. The results showed the structure of the jet ring has great effect on the gas mixing. The mixing condition of the jet ring with combined opening orifice is better than that of the jet ring with uniform opening orifice， which is more effective in realizing fast and uniform mixing condition of TiCl4 and O2.
3
ŠAJN GORJANC and DOMINIKA GLAŽAR. "The influence of air-jet and vortex yarn on functionality of woven fabric." Industria Textila 69, no. 02 (May 1, 2018): 87–95. http://dx.doi.org/10.35530/it.069.02.1412.
Повний текст джерелаАнотація:
The basic intention of the research is to analyse the influence of air-jet and vortex yarn structure on woven fabric functionality. With the research, the air-jet and vortex yarn from the mixture of 65 % PES / 35 % CO fibres and fineness 20 tex were analysed. For comparison, the conventional ring-spun yarn was chosen from the mixture of 65 % PES/35 % CO fibres and fineness 20 tex. The woven fabric in the twill weave T1/3Z was produced from the air-jet, vortex and ring-spun yarn in the weft direction with two different weft densities (20 and 30 yarns per cm). In the first part of the study, the structure, physical and mechanical properties of the air-jet, vortex and ring-spun yarn were analysed, while in the second part of the research, the influence of used yarn in the weft direction on the functionality of woven fabric was studied. The research was focused mainly on physical, mechanical properties as well as permeability properties of woven fabric with air-jet and vortex yarn in the weft direction in comparison with woven fabric with conventional ring-spun yarn in the weft direction, with equal chemical composition and fineness of yarn. The research results was shown which yarn structure in the weft direction of woven fabric (air-jet or vortex) the most closely approximates the characteristics of the ring-spun yarn, which has because of ring-traveller-spindle mechanism ideal and the most even structure, mainly because of the insertion of the true twist.
4
Lu, Ru-Sen, Keiichi Asada, Thomas P. Krichbaum, Jongho Park, Fumie Tazaki, Hung-Yi Pu, Masanori Nakamura, et al. "A ring-like accretion structure in M87 connecting its black hole and jet." Nature 616, no. 7958 (April 26, 2023): 686–90. http://dx.doi.org/10.1038/s41586-023-05843-w.
Повний текст джерелаАнотація:
AbstractThe nearby radio galaxy M87 is a prime target for studying black hole accretion and jet formation1,2. Event Horizon Telescope observations of M87 in 2017, at a wavelength of 1.3 mm, revealed a ring-like structure, which was interpreted as gravitationally lensed emission around a central black hole3. Here we report images of M87 obtained in 2018, at a wavelength of 3.5 mm, showing that the compact radio core is spatially resolved. High-resolution imaging shows a ring-like structure of $${8.4}_{-1.1}^{+0.5}$$ 8.4 − 1.1 + 0.5 Schwarzschild radii in diameter, approximately 50% larger than that seen at 1.3 mm. The outer edge at 3.5 mm is also larger than that at 1.3 mm. This larger and thicker ring indicates a substantial contribution from the accretion flow with absorption effects, in addition to the gravitationally lensed ring-like emission. The images show that the edge-brightened jet connects to the accretion flow of the black hole. Close to the black hole, the emission profile of the jet-launching region is wider than the expected profile of a black-hole-driven jet, suggesting the possible presence of a wind associated with the accretion flow.
5
HÜSEYİN GAZ, TÜRKSOY, AKKAYA TUĞBA, VURUŞKAN DENİZ, and ÜSTÜNTAĞ SÜMEYYE. "A comparative analysis of air-jet yarn properties with the properties of ring spun yarns." Industria Textila 69, no. 01 (March 1, 2018): 11–16. http://dx.doi.org/10.35530/it.069.01.1419.
Повний текст джерелаАнотація:
Ring spinning is the most common method used among the short staple fibers spinning methods. Due to limitations of the production speed in the ring spinning, new spinning methods become more popular with each passing day. Air-jet spinning systems gathered attention with their market share in the new spinning methods. In this study, the properties of the air-jet yarns were comparatively analyzed with the properties of the equivalent Ring yarns, for both single and ply-twisted forms. It was found that the Rieter and Murata air-jet yarns do not show significant differences in terms of physical properties of yarns. Due to their special structure, air-jet yarns show lower hairiness and tenacity values when compared to the equivalent Ring yarns.
6
NOUMI, Yuhei, and Hiroaki HASEGAWA. "Visualization of vortex ring structure in a synthetic jet." Proceedings of the Fluids engineering conference 2018 (2018): OS5–25. http://dx.doi.org/10.1299/jsmefed.2018.os5-25.
Повний текст джерела
7
Longmire, Ellen K., and John K. Eaton. "Structure of a particle-laden round jet." Journal of Fluid Mechanics 236 (March 1992): 217–57. http://dx.doi.org/10.1017/s002211209200140x.
Повний текст джерелаАнотація:
The interaction of solid particles with the temporal features of a turbulent flow has direct relevance to problems in particle and spray combustion and the processing of particulate solids. The object of the present study was to examine the behaviour of particles in a jet dominated by vortex ring structures. An axisymmetric air jet laden with 55 μm glass particles was forced axially with an acoustic speaker to organize the vortex ring structures rolling up in the free shear layer downstream of the nozzle exit. Visualization studies of forced and unforced flow with Reynolds number of the order of 20000 were completed using a pulsed copper vapour laser. Instantaneous photographs and videotapes of strobed forced flow show that particles become clustered in the saddle regions downstream of the vortex rings and are propelled away from the jet axis by the outwardly moving flow in these regions. Phase-averaged spatial distribution of particle number density computed from digitized photographs and phase-averaged particle velocity measurements yield further evidence that local particle dispersion and concentration are governed by convection due to large-scale turbulence structures. The large-scale structures and convection mechanisms were shown to persist for particle-to-air mass loading ratios up to 0.65.
8
VERNET, A., G. A. KOPP, J. A. FERRÉ, and FRANCESC GIRALT. "Three-dimensional structure and momentum transfer in a turbulent cylinder wake." Journal of Fluid Mechanics 394 (September 10, 1999): 303–37. http://dx.doi.org/10.1017/s0022112099005807.
Повний текст джерелаАнотація:
Simultaneous velocity and temperature measurements were made with rakes of sensors that sliced a slightly heated turbulent wake in the spanwise direction, at different lateral positions 150 diameters downstream of the cylinder. A pattern recognition analysis of hotter-to-colder transitions was performed on temperature data measured at the mean velocity half-width. The velocity data from the different ‘slices’ was then conditionally averaged based on the identified temperature events. This procedure yielded the topology of the average three-dimensional large-scale structure which was visualized with iso-surfaces of negative values of the second eigenvector of [S2+Ω2]. The results indicate that the average structure of the velocity fluctuations (using a triple decomposition of the velocity field) is found to be a shear-aligned ring-shaped vortex. This vortex ring has strong outward lateral velocities in its symmetry plane which are like Grant's mixing jets. The mixing jet region extends outside the ring-like vortex and is bounded by two foci separated in the spanwise direction and an upstream saddle point. The two foci correspond to what has been previously identified in the literature as the double rollers.The ring vortex extracts energy from the mean flow by stretching in the mixing jet region just upstream of the ring boundary. The production of the small-scale (incoherent) turbulence by the coherent field and one-component energy dissipation rate occur just downstream of the saddle point within the mixing jet region. Incoherent turbulence energy is extracted from the mean flow just outside the mixing jet region, but within the core of the structure. These processes are highly three-dimensional with a spanwise extent equal to the mean velocity half-width.When a double decomposition is used, the coherent structure is found to be a tube-shaped vortex with a spanwise extent of about 2.5l0. The double roller motions are integral to this vortex in spite of its shape. Spatial averages of the coherent velocity field indicate that the mixing jet region causes a deficit of mean streamwise momentum, while the region outside the foci of the double rollers has a relatively small excess of streamwise momentum.
9
Miyoshi, Makoto, Yoshiaki Kato, and Junichiro Makino. "The Jet and Resolved Features of the Central Supermassive Black Hole of M87 Observed with the Event Horizon Telescope (EHT)." Astrophysical Journal 933, no. 1 (June 30, 2022): 36. http://dx.doi.org/10.3847/1538-4357/ac6ddb.
Повний текст джерелаАнотація:
Abstract We report the result of our independent image reconstruction of the M87 from the public data of the Event Horizon Telescope Collaborators (EHTC). Our result is different from the image published by the EHTC. Our analysis shows that (a) the structure at 230 GHz is consistent with those of lower-frequency very long baseline interferometry observations, (b) the jet structure is evident at 230 GHz extending from the core to a few milliarcsecond, although the intensity rapidly decreases along the axis, and (c) the “unresolved core” is resolved into three bright features presumably showing an initial jet with a wide opening angle of ∼70°. The ring-like structures of the EHTC can be created not only from the public data but also from the simulated data of a point image. Also, the rings are very sensitive to the field-of-view (FOV) size. The u−v coverage of the Event Horizon Telescope (EHT) lacks ∼ 40 μas fringe spacings. Combining with a very narrow FOV, it created the ∼40 μas ring structure. We conclude that the absence of the jet and the presence of the ring in the EHTC result are both artifacts owing to the narrow FOV setting and the u−v data sampling bias effect of the EHT array. Because the EHTC's simulations only take into account the reproduction of the input image models, and not those of the input noise models, their optimal parameters can enhance the effects of sampling bias and produce artifacts such as the ∼40 μas ring structure, rather than reproducing the correct image.
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Miyoshi, Makoto, Yoshiaki Kato, Junichiro Makino, and Masato Tsuboi. "The Jet and Resolved Features of the Central Supermassive Black Hole of M87 Observed with EHT in 2017—Comparison with the GMVA 86 GHz Results." Astrophysical Journal Letters 963, no. 1 (February 22, 2024): L18. http://dx.doi.org/10.3847/2041-8213/ad250e.
Повний текст джерелаАнотація:
Abstract M87 is the best target for studying black hole accretion and jet formation. Reanalysis of the Event Horizon Telescope (EHT) public data at 230 GHz shows a core–knots structure at the center and jet features. We here compare this with the new results of GMVA at 86 GHz showing a spatially resolved central core. There are similarities and differences between the two. At 86 GHz, “two bright regions” are seen on the ring in the core. The “core–knot–west knot” triple structure in the 230 GHz image shows apparent appearance of two peaks similar to the “two bright regions” when convolved with the GMVA beam. This similarity suggests that both frequencies reveal the same objects in the core area. Protrusions are observed on both the south and north sides of the core at both frequencies, becoming prominent and winglike at 230 GHz. The 86 GHz image shows a triple ridge jet structure, while the 230 GHz image shows only a bright central ridge with two roots. Both frequencies show a shade between the core and the central ridge. To detect the faint features from the EHT2017 data, we found that the use of all baseline data is essential. Using all baseline data, including the ultrashort data, revealed the jet and faint structures. Without the ultrashort baselines, these structures were not detectable. The lack of detection of any faint structures other than the ring in the M87 data by the EHTC is presumably due to the exclusion of ultrashort baselines from their analysis.
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Forsting, Thomas, Hannes C. Gottschalk, Beppo Hartwig, Michel Mons, and Martin A. Suhm. "Correcting the record: the dimers and trimers of trans-N-methylacetamide." Physical Chemistry Chemical Physics 19, no. 17 (2017): 10727–37. http://dx.doi.org/10.1039/c6cp07989j.
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Alston, Peter V. "Effect of Yarn Spinning System on Pill Resistance of Polyester/Cotton Knit Fabrics." Textile Research Journal 62, no. 2 (February 1992): 105–8. http://dx.doi.org/10.1177/004051759206200208.
Повний текст джерелаАнотація:
We have determined the effect of ring, rotor, and air-jet spinning on the pill resistance of jersey and interlock fabrics. The jersey fabrics contained the same polyester type, while the interlock fabrics contained the preferred polyester for each spinning system. In each of the constructions, the air-jet spun fabrics were significantly more pill resistant than ring and rotor spun fabrics. Kinetic studies of the rates of pill formation and wear-off indicate that this difference is due to the much slower formation rate of the air-jet spun fabric. Analysis of pill character suggests that the tightly wrapped structure of the air-jet yarn inhibits the formation of free ends of polyester, which are the primary cause of the pills. Pill resistance for the ring spun fabric was only slightly better than for the rotor spun fabric when the same polyester type was used.
13
Tsai, Feng Chin, and Rong Fung Huang. "Topological Flow Structures of Annular Swirling Jets." Journal of Mechanics 17, no. 3 (September 2001): 131–38. http://dx.doi.org/10.1017/s1727719100004494.
Повний текст джерелаАнотація:
AbstractThe effects of blockage and swirl on the macro flow structures of the annular jet past a circular disc are experimentally studied through the time-averaged streamline patterns. In the blockage-effect regime, the flows present multiple modes, single bubble, dual rings, vortex breakdown, and triple rings, in different regimes of blockage ratio and swirl number. The topological models of the flow structures are proposed and discussed according to the measured flow fields to manifest the complex flow structures. The single bubble is a closed recirculation bubble with a stagnation point on the central axis. The dual-ring flow is an open-top recirculsation zone, in which a pair of counter-rotating vortex rings exists in the near wake. The fluids in the dual rings are expelled downstream through a central jet-like swirling flow. A vortex breakdown may occur in the central jet-like swirling flow if the exit swirl number exceeds critical values. When the vortex breakdown interacts with the dual rings, a complex triple-ring flow structure forms. Axial distributions of the local swirl number are presented and discussed. The local swirl number increases with the increase of the exit swirl number and attains the maximum in the dual-ring mode. At large exit swirl numbers where the vortex breakdown occurs, the local swirl number decreases drastically to a low value.
14
Prasetya, Rubby, Akira Sou, Junichi Oki, Akira Nakashima, Keiya Nishida, Yoshitaka Wada, Yoshiharu Ueki, and Hideaki Yokohata. "Three-dimensional flow structure and string cavitation in a fuel injector and their effects on discharged liquid jet." International Journal of Engine Research 22, no. 1 (March 14, 2019): 243–56. http://dx.doi.org/10.1177/1468087419835697.
Повний текст джерелаАнотація:
Two kinds of cavitation may occur in mini-sac type diesel injectors. The first is geometrical cavitation, which can usually be seen as a film-like structure in the nozzle. The second is the filament-like string cavitation. Both types of cavitation are known to affect fuel spray characteristics, although the effects of geometrical cavitation and that of string cavitation have not been individually clarified. Moreover, the mechanism behind string cavitation occurrence is still unclear. String cavitation usually occurs at low needle lift, which might indicate the existence of a vortex ring flow in the sac. However, because of the difficulty in precise flow measurement of the three-dimensional flow structure in the sac, the link between vortex ring flow and string cavitation occurrence in the sac has not been proven. In this study, high-speed imaging of string cavitation, geometrical cavitation, and discharged liquid jet of an enlarged three-hole mini-sac diesel fuel injector was conducted to individually clarify the effects of string cavitation and geometrical cavitation on the discharged liquid jet angle. Furthermore, tomographic–stereo particle image velocimetry was carried out on the sac. The experiments were conducted at two different needle lifts, to clarify the link between needle lifts and flow structure in the sac, as well as how it affects string cavitation occurrence and liquid jet angle. The results confirmed that at low needle lift, vortex ring flow forms in the sac, which may induce helical flow in the nozzle, resulting in a large jet angle. Vortex strength varies with time, and string cavitation occurs when the vortex is particularly strong. As a result, the magnitude of the jet angle increase at low needle lift is enhanced when string cavitation occurs. At high needle lift, flow pattern in the sac becomes relatively uniform, which makes it harder for string cavitation to form.
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Britzen, S., M. Zajaček, L. Č. Popović, C. Fendt, A. Tramacere, I. N. Pashchenko, F. Jaron, et al. "A ring accelerator? Unusual jet dynamics in the IceCube candidate PKS 1502+106." Monthly Notices of the Royal Astronomical Society 503, no. 3 (March 17, 2021): 3145–78. http://dx.doi.org/10.1093/mnras/stab589.
Повний текст джерелаАнотація:
ABSTRACT On 2019/07/30.86853 ut, IceCube detected a high-energy astrophysical neutrino candidate. The Flat Spectrum Radio Quasar PKS 1502+106 is located within the 50 per cent uncertainty region of the event. Our analysis of 15 GHz Very Long Baseline Array (VLBA) and astrometric 8 GHz VLBA data, in a time span prior and after the IceCube event, reveals evidence for a radio ring structure that develops with time. Several arc-structures evolve perpendicular to the jet ridge line. We find evidence for precession of a curved jet based on kinematic modelling and a periodicity analysis. An outflowing broad line region (BLR) based on the C iv line emission (Sloan Digital Sky Survey) is found. We attribute the atypical ring to an interaction of the precessing jet with the outflowing material. We discuss our findings in the context of a spine-sheath scenario where the ring reveals the sheath and its interaction with the surroundings (narrow line region, NLR, clouds). We find that the radio emission is correlated with the γ-ray emission, with radio lagging the γ-rays. Based on the γ-ray variability time-scale, we constrain the γ-ray emission zone to the BLR (30–200 rg) and within the jet launching region. We discuss that the outflowing BLR provides the external radiation field for γ-ray production via external Compton scattering. The neutrino is most likely produced by proton–proton interaction in the blazar zone (beyond the BLR), enabled by episodic encounters of the jet with dense clouds, i.e. some molecular cloud in the NLR.
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YAMADA, Naomi, Fujio AKAGI, Youichi ANDO, and Sumio YAMAGUCHI. "Vortex Ring Structure induced by Pulsatile Jet flow in a Pipe." Proceedings of Conference of Kyushu Branch 2004.57 (2004): 225–26. http://dx.doi.org/10.1299/jsmekyushu.2004.57.225.
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Zhou, Jianhan. "Research on the interaction mechanism of multiple vortices in biological wake flow field." Journal of Physics: Conference Series 2634, no. 1 (November 1, 2023): 012026. http://dx.doi.org/10.1088/1742-6596/2634/1/012026.
Повний текст джерелаАнотація:
Abstract The vortex-ring interaction of synchronous jets has been paid more attention by predecessors, while the research of asynchronous jets (i.e. there is a time difference between the start of jets) of parallel dual nozzles has been studied less. Therefore, the interaction between vortex rings and the vortex structure evolution of the dual-nozzle asynchronous jets with different time differences (Δt) is studied in this paper. Numerical results obtained can be divided into four intervals: 1. Synchronous jets (Δt = 0); 2. Critical interval (Δt < 0.1t, where t is the jet time), having similar vortex structure evolution modes and dynamic characteristics as the synchronous jet; 3. Strong interaction interval (0.2t ≤ Δt ≤ 0.4t), in which the main vortex ring shows obvious acceleration, and the streamwise vortex structure is found in the wake; 4. weak interaction interval (Δt ≥ 0.6t), in which the interaction between vortex rings is much less strong and the streamwise vortex structure also appears in the wake. In addition, it is found that pressure on the nozzle outlet plane increases and the vortex dissipation in the downstream flow field slows down significantly due to the vortex-ring interaction on the condition of asynchronous jets.
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PARK, CHEOL WOO. "INVESTIGATION ON FLOW STRUCTURE BEHIND A RING BY IMPLEMENTING OPTICAL PARTICLE CHARACTERIZATIONS." International Journal of Modern Physics B 20, no. 25n27 (October 30, 2006): 4511–16. http://dx.doi.org/10.1142/s0217979206041604.
Повний текст джерелаАнотація:
The flow structure behind circular and elliptical type rings embedded in a cross-flow was investigated experimentally using a particle image velocimetry (PIV), implementing optical particle characterizations. The experiments were performed in a circulating water channel with a test section of 0.2m height × 0.3m width × 1.2m length. The Reynolds number based on the ring hoop cord length is about Re =1200. The velocity fields near the ring hoop were measured using the two-frame cross-correlation PIV method. As a result, the flow near the sharp-edged end of ring hoop ascends fast and showed a conventional vortical structure appeared in a bluff body wake. In the mean velocity field behind a circular ring, there were two large vortices rotating in different directions from each other in the near wake regime caused by the interaction between the central jet flow and the entrained ambient fluids from outer side of ring hoop.
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Srinivasan, J., A. K. Sengupta, and V. K. Kothari. "Air-Jet Texturing of Spun Cotton Yarns for Improved Comfort." Textile Research Journal 62, no. 1 (January 1992): 40–43. http://dx.doi.org/10.1177/004051759206200106.
Повний текст джерелаАнотація:
We have studied air-jet texturing of spun yarns with different structural configurations. After texturing, the yarns have improved bulk and reduced modulus and flexural rigidity, rendering them more suitable for improved comfort applications. Increased bulk after texturing is accompanied by reduced strength. We have observed that after air-jet texturing, certain structures such as carded ring spun yarns and Siro spun yarns possess a higher level of bulk compared to other structures. Rotor spun yarns have lower bulk after texturing because of their tripartite structure, twist angle variations, and the alternating Z and S helices in their fiber belts. Yarns with reinforced structures like composite spun, wrap spun, and rotor spun are able to withstand higher overfeed and air pressure during texturing.
20
Gizani, N. A. B., and J. P. Leahy. "The Environment of Hercules A." Symposium - International Astronomical Union 175 (1996): 351–52. http://dx.doi.org/10.1017/s0074180900081079.
Повний текст джерелаАнотація:
The bright radio galaxy Hercules A (z = 0.154), has power P178MHz = 8 × 1026 W Hz–1sr–1 and although this puts it well above the FR break, its structure is intermediate between Fanaroff and Riley classes I and II. With a linear size of 334 kpc (for H0 = 100 kms–1Mpc–1), Hercules A possesses an unusual jet-dominated morphology and no compact hotspots. The western jet shows partial or full ring-like features that form a linear sequence heading from the core to the lobes and follow an inner jet.
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Ni, Yongyan, Zhongyong Pan, Zhenjie Huang, and Weimin Liu. "Vortex characteristics downstream a fan and its effect on the heat transfer of the temperature inversion under late spring coldness." Advances in Mechanical Engineering 9, no. 7 (July 2017): 168781401770435. http://dx.doi.org/10.1177/1687814017704353.
Повний текст джерелаАнотація:
Tea plant in East China usually suffers from frost damage due to sudden low temperature under late spring coldness. A fan is a frost protection device that can blow the warmer air aloft to the tea canopy level under radiative frost meteorological event with temperature inversions. In this study, the flow fields and the temperature distribution downstream a fan were numerically simulated. It is found that the flow structure downstream the fan is divided into two flow regimes: one is the jet flow that blows the warmer air aloft downward and the other one is vortex ring that enhances turbulence at the tea canopy level. The jet and the vortex characteristics are nearly independent on the shaft rotation speed. However, the heat transfer process is obviously related to the flow structures, and the temperature distribution on the tea canopy plane coincides with the vortex characteristics. The temperature peak is near the core of the flow vortex, and the high-temperature zone coincides with the vortex ring regime.
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Weclas, M., and J. Cypris. "Characterization of the distribution-nozzle operation for mixture homogenization by a late-diesel-injection strategy." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 226, no. 4 (October 3, 2011): 529–46. http://dx.doi.org/10.1177/0954407011420499.
Повний текст джерелаАнотація:
In order to realize a homogeneous combustion process it is necessary to decouple this combustion process from fuel injection. This homogeneous combustion process requires the charge to be homogeneous prior to simultaneous volumetric ignition. This kind of ignition is a self-ignition process requiring control of the ignition timing. A late-injection strategy as used in a conventional diesel engine permits control of the ignition timing; however, the time available for mixture formation and the homogenization process is very limited. The present paper deals with a distribution-nozzle concept which combines both strategies: a late-injection strategy for controlling the ignition timing with significantly accelerated fuel distribution in space and corresponding mixture homogenization. The distribution-nozzle concept combines a conventional diesel nozzle with a porous element (ring) positioned in proximity to the nozzle outlet. Because of multi-jet splitting as a result of the diesel-jet interaction with a porous structure, the fuel leaving the porous ring spreads widely in space. Additionally, a very effective fuel vaporization process occurs within the porous structure, supporting quick mixture formation. The paper describes both the fuel distribution in space and its vaporization for different configurations of the distribution elements, the injection pressure, and the porous ring temperature. In comparison with a free diesel injection, the distribution nozzle results in a significantly increased fuel surface area, a reduced jet penetration length, a reduced jet velocity, and very quick fuel vaporization. This process is three dimensional in nature. Depending on the distribution-element structure, the geometry, and its temperature, as well as the injection pressure, the contributions of multi-jet splitting, and fuel vaporization, are different with respect to the surface area, penetration length, and exit velocity, as well as intensity distribution. Generally, at higher injection pressures these parameters are less temperature dependent, except for the fact that the intensity distribution is a function of the fuel vapour’s concentration.
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Crawley, Michael, Lior Gefen, Ching-Wen Kuo, Mo Samimy, and Roberto Camussi. "Vortex dynamics and sound emission in excited high-speed jets." Journal of Fluid Mechanics 839 (January 29, 2018): 313–47. http://dx.doi.org/10.1017/jfm.2017.906.
Повний текст джерелаАнотація:
This work aims to study the dynamics of and noise generated by large-scale structures in a Mach 0.9 turbulent jet of Reynolds number $6.2\times 10^{5}$ using plasma-based excitation of shear layer instabilities. The excitation frequency is varied to produce individual or periodic coherent ring vortices in the shear layer. First, two-point cross-correlations are used between the acoustic near field and far field in order to identify the dominant noise source region. The large-scale structure interactions are then investigated by stochastically estimating time-resolved velocity fields using time-resolved near-field pressure traces and non-time-resolved planar velocity snapshots (obtained by particle image velocimetry) by means of an artificial neural network. The estimated time-resolved velocity fields show multiple mergings of large-scale structures in the shear layer, and indicate that disintegration of coherent ring vortices is the dominant aeroacoustic source mechanism for the jet studied here. However, the merging of vortices in the initial shear layer is also identified as a non-trivial noise source mechanism.
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HASHIMOTO, Yuta, Tsutomu ISHIDO, and Hiroaki HASEGAWA. "Effect of Pitch Angle of a Synthetic Jet on Vortex Ring Structure." Proceedings of Conference of Kanto Branch 2017.23 (2017): 318. http://dx.doi.org/10.1299/jsmekanto.2017.23.318.
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ISHII, R., H. FUJIMOTO, N. HATTA, and Y. UMEDA. "Experimental and numerical analysis of circular pulse jets." Journal of Fluid Mechanics 392 (August 10, 1999): 129–53. http://dx.doi.org/10.1017/s0022112099005303.
Повний текст джерелаАнотація:
Unsteady circular jets are treated experimentally and numerically. The time evolution of circular pulse jets is investigated systematically for a wide range of jet strength, with the focus on the jet evolution, in particular the formation processes of Mach disks in the middle stage and of shock-cell structures in the later stage. It is shown that unsteady second shocks are realized for all sonic underexpanded jets and they either breed conical shocks for lower pressure ratios or truncated cones (Mach disk and reflected shock) for higher pressure ratios. The vortex ring produced near the nozzle lip plays an important role in the formation of the shock-cell structure. In particular, interactions between the vortex ring and the Mach disk connected with a strong second shock affect remarkably the formation process of the first shock cell. Different formation processes of the first cell structure are found. It is also made clear that the Kelvin–Helmholtz instability along slip surfaces originating from the triple point at the outer edge of the Mach disk is responsible for the generation of large second vortices which entrain the first vortex. This results in strong mixing between the primary jet and surrounding gas for higher pressure ratios. Numerical simulations with a TVD-scheme for the Euler equations are also performed and the numerical results are compared with the experimental ones to understand and predict the flow characteristics of the pulse jets.
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York, Carly A., Ian K. Bartol, Paul S. Krueger, and Joseph T. Thompson. "Squids use multiple escape jet patterns throughout ontogeny." Biology Open 9, no. 11 (September 24, 2020): bio054585. http://dx.doi.org/10.1242/bio.054585.
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ABSTRACTThroughout their lives, squids are both predators and prey for a multitude of animals, many of which are at the top of ocean food webs, making them an integral component of the trophic structure of marine ecosystems. The escape jet, which is produced by the rapid expulsion of water from the mantle cavity through a funnel, is central to a cephalopod's ability to avoid predation throughout its life. Although squid undergo morphological and behavioral changes and experience remarkably different Reynolds number regimes throughout their development, little is known about the dynamics and propulsive efficiency of escape jets throughout ontogeny. We examine the hydrodynamics and kinematics of escape jets in squid throughout ontogeny using 2D/3D velocimetry and high-speed videography. All life stages of squid produced two escape jet patterns: (1) ‘escape jet I’ characterized by short rapid pulses resulting in vortex ring formation and (2) ‘escape jet II’ characterized by long high-volume jets, often with a leading-edge vortex ring. Paralarvae exhibited higher propulsive efficiency than adult squid during escape jet ejection, and propulsive efficiency was higher for escape jet I than escape jet II in juveniles and adults. These results indicate that although squid undergo major ecological transitions and morphology changes from paralarvae to adults, all life stages demonstrate flexibility in escape jet responses and produce escape jets of surprisingly high propulsive efficiency.This article has an associated First Person interview with the first author of the paper.
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Li, Chun Qi, Li Jun Yan, Yang Wang, and Jing Tang. "Simulation on the Effects of Misaligned Coupling on the Output Intensity Distribution in Water-Jet Guided Laser." Advanced Materials Research 211-212 (February 2011): 400–405. http://dx.doi.org/10.4028/www.scientific.net/amr.211-212.400.
Повний текст джерелаАнотація:
Water-jet guided laser machining is a kind of material processing technology using water optical waveguide which is formed by coupling a high energy laser beam into variable-length water jet. In order to design the coupling unit and form the effective energy-jet, the research on the distribution of output intensity is beneficial to understand the structure of the coupling unit and improve the coupling efficiency of laser energy. This paper lists the different coupling misalignments in the coupling unit when laser couplings into water-jet. In this paper, the distribution of energy output intensity in water-jet guided laser is simulated with the ray trace theory under several different types of coupling misalignments with ZEMAX software, the results show that misaligned coupling provide various morphology of energy output intensity distribution: center peak morphology, ring peak morphology, and uniform peak morphology, which provides a method to optimize the energy output intensity distribution of water-jet guided laser.
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NAKAGAWA, Hiroyuki, Yamato OKADA, Masato AKIMOTO, and Motoaki KIMURA. "Investigation of Vortex Ring Structure in Jet Diffusion Using Active and Passive Control." Proceedings of the Fluids engineering conference 2020 (2020): OS03–24. http://dx.doi.org/10.1299/jsmefed.2020.os03-24.
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NOUMI, Yuhei, Yuya YAMASHITA, and Hiroaki HASEGAWA. "Effect of orifice depth on vortex ring structure generated by a synthetic jet." Proceedings of Conference of Kanto Branch 2019.25 (2019): 19B05. http://dx.doi.org/10.1299/jsmekanto.2019.25.19b05.
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Hsiao, Chao-Tsung, A. Jayaprakash, A. Kapahi, J. K. Choi, and Georges L. Chahine. "Modelling of material pitting from cavitation bubble collapse." Journal of Fluid Mechanics 755 (August 14, 2014): 142–75. http://dx.doi.org/10.1017/jfm.2014.394.
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AbstractMaterial pitting from cavitation bubble collapse is investigated numerically including two-way fluid–structure interaction (FSI). A hybrid numerical approach which links an incompressible boundary element method (BEM) solver and a compressible finite difference flow solver is applied to capture non-spherical bubble dynamics efficiently and accurately. The flow codes solve the fluid dynamics while intimately coupling the solution with a finite element structure code to enable simulation of the full FSI. During bubble collapse high impulsive pressures result from the impact of the bubble re-entrant jet on the material surface and from the collapse of the remaining bubble ring. A pit forms on the material surface when the impulsive pressure is large enough to result in high equivalent stresses exceeding the material yield stress. The results depend on bubble dynamics parameters such as the size of the bubble at its maximum volume, the bubble standoff distance from the material wall, and the pressure driving the bubble collapse. The effects of these parameters on the re-entrant jet, the following bubble ring collapse pressure, and the generated material pit characteristics are investigated.
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Volodin, L. Y. "Three-color pyrometry study of radiation and gas dynamic processes in a heterogeneous plasma-vortex ring." Journal of Physics: Conference Series 2270, no. 1 (May 1, 2022): 012058. http://dx.doi.org/10.1088/1742-6596/2270/1/012058.
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Abstract The paper presents the results of a study of a heterogeneous plasma vortex ring using the three-color image pyrometry technique. The vortex ring is formed during deceleration of a supersonic pulsed aluminum plasma jet in atmospheric air. A technique for calibrating a digital camera and a post-processing process for images are proposed that makes it possible to visualize the internal structure of the vortex. As a result of the study, the effect of vortex separation of condensed and gas flow components was experimentally demonstrated.
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Schubert, Andreas, Philipp Steinert, Torsten Schmidt, and Matthias Hackert-Oschätzchen. "Manufacturing of Tribologically Optimized Surfaces for Powertrain Applications." Key Engineering Materials 523-524 (November 2012): 799–804. http://dx.doi.org/10.4028/www.scientific.net/kem.523-524.799.
Повний текст джерелаАнотація:
Among the major interests in powertrain development are the reduction of frictional losses and service life extension from improved wear resistance. Surface finishing and deterministic microstructuring have been shown to be effective methods in improving the tribological properties of sliding contacts such as bearings and cylinder liners. This is due to their acting as micro pressure-chambers and as wear debris traps. In this work, tribometric ring-on-disc tests were performed in order to evaluate the influence of surface structure − namely, the microstructure geometry and layout − on the frictional behavior of lubricated surfaces. The material combination bronze against steel as typically used in powertrain applications was investigated. The surface structures where machined using electrochemical machining by closed electrolytic free jet (Jet-ECM). It was determined that microstructuring reduced the friction coefficient by up to 45 % in the hydrodynamic regime under loads and speeds found in automotive components. The friction measurements showed that microstructures with low aspect ratios result in the least friction. In addition to the tribological investigations, the process capabilities and implementability in serial production of two surface microstructure fabrication processes: Jet-ECM and a newly developed, hybrid roller micro-embossing and burnishing process were evaluated and contrasted. It was shown that both fabrication methods can attain high structure quality.
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Grover, Ronald O., Xiaofeng Yang, Scott Parrish, Lorenzo Nocivelli, Katherine J. Asztalos, Sibendu Som, Yanheng Li, et al. "CFD simulations of electric motor end ring cooling for improved thermal management." Science and Technology for Energy Transition 77 (2022): 17. http://dx.doi.org/10.2516/stet/2022015.
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Proper thermal management of an electric motor for vehicle applications extends its operating range. One cooling approach is to impinge Automatic Transmission Fluid (ATF) onto the rotor end ring. Increased ATF coverage correlates to enhanced heat transfer. Computational Fluid Dynamics (CFD) analytical tools provide a mechanism to assess motor thermal management prior to hardware fabrication. The complexity of the fluid flow (e.g., jet atomization, interface tracking, wall impingement) and heat transfer makes these simulations challenging. Computational costs are high when solving these flows on high-speed rotating meshes. Typically, a Volume-of Fluid (VOF) technique (i.e., two-fluid system) is used to resolve ATF dynamics within this rotating framework. Suitable numerical resolution of the relevant physics for thin films under strong inertial forces at high rotor speeds is computationally expensive, further increasing the run times. In this work, a numerical study of rotor-ring cooling by ATF is presented using a patent automated Cartesian cut-cell based method coupled with Automatic Mesh Refinement (AMR). This approach automatically creates the Cartesian mesh on-the-fly and can effectively handle complex rotating geometries by adaptively refining the mesh based on local gradients in the flow field which results in better resolution of the air-ATF interface. A Single non-inertial Reference Frame (SRF) approach is used to account for the rotating geometry and to further improve the overall computational efficiency. Quasi-steady state conditions are targeted in the analysis of the results. Important physics such as ATF jet structure, velocity detail near the air-jet interface, ATF coverage/accumulation on the ring surface, and cooling capacity are presented for a low-resolution Reynolds averaged Navier-Stokes (RANS), high-resolution RANS, and high-resolution Large-Eddy Simulation (LES) models. Computations are scaled over hundreds of cores on a supercomputer to maximize turnaround time. Each numerical approach is shown to capture the general trajectory of the oil jet prior to surface impingement. The high-resolution LES simulation, however, is superior in capturing small scale details and heat transfer between the free jet and surrounding air.
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Zhong, Ya Hong, Jian Hui Ma, and Ming Jie Xing. "Fiber Configuration of Air Jet Vortex Spinning Yarns." Advanced Materials Research 834-836 (October 2013): 1784–88. http://dx.doi.org/10.4028/www.scientific.net/amr.834-836.1784.
Повний текст джерелаАнотація:
In this paper, the spinning process of air jet vortex spinning was described. The structure of air jet vortex spun yarn was studied by means of blending tracer fibers in spinning. Then the yarns were viewed with the optical microscope and SEM etc. The result shows that air jet vortex spun yarn comprises two parts. The outer layer, composed of twisted fibers, presents helical form. And the inner layer contains about 30% fibers untwisted or slackly twisted. The distance between twisted fiber groups is very short, so the borderline isnt obvious. There is a certain angle between core fibers in parallel and the axes of the yarn. The coefficient of fiber migration of the yarn was calculated, and it is lower than that of ring spun yarn and compact spun yarn.
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PENG, GAOZHU, NORMAN J. ZABUSKY, and SHUANG ZHANG. "Jet and vortex flows in a shock/ hemispherical-bubble-on-wall configuration." Laser and Particle Beams 21, no. 3 (July 2003): 449–53. http://dx.doi.org/10.1017/s0263034603213252.
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We suggest an easily obtained laboratory configuration to observe jet and vortex flows for the Richtmyer–Meshkov (accelerated inhomogeneous flow) environment. A hemispherical bubble in air with density ratio of 5 is placed against an ideally reflecting wall and struck by a planar shock. This also models a spherical bubble struck symmetrically by two identical approaching shocks, that is, a “reshock” configuration. For all Mach numbers (M = 1.2, 1.5, and 2.0), our axisymmetric simulations show that the heavy hemispherical bubble expands axially away from the wall as a jet, and a weaker vortex ring moves radially along the wall. In addition, when M = 1.5, a ringlike vortex projectile (VP) of small diameter follows closely behind the reflected shock and is associated with its moving triple point. This VP contains an entrained shocklet and quadrupole structure of dilatation. Various methods are applied to quantify the emerging coherent structures.
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Zhang, Zhenyu, Yehui Hou, Zezhou Hu, Minyong Guo, and Bin Chen. "Polarized images of charged particles in vortical motions around a magnetized Kerr black hole." Journal of Cosmology and Astroparticle Physics 2024, no. 03 (March 1, 2024): 013. http://dx.doi.org/10.1088/1475-7516/2024/03/013.
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Abstract In this work, we study the images of a Kerr black hole (BH) immersed in uniform magnetic fields, illuminated by the synchrotron radiation of charged particles in the jet. We particularly focus on the spontaneously vortical motions (SVMs) of charged particles in the jet region and investigate the polarized images of electromagnetic radiations from the trajectories along SVMs. We notice that there is a critical value ω_c for charged particle released at a given initial position and subjected an outward force, and once |qB_0/m|=|ω_B|>|ω_c| charged particles can move along SVMs in the jet region. We obtain the polarized images of the electromagnetic radiations from the trajectories along SVMs. Our simplified model suggests that the SVM radiations can act as the light source to illuminate the BH and form a photon ring structure.
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López, Juan Carlos, Alberto Macario, Andrés Verde, Alfonso Pérez-Encabo, and Susana Blanco. "Decoding the Structure of Non-Proteinogenic Amino Acids: The Rotational Spectrum of Jet-Cooled Laser-Ablated Thioproline." Molecules 26, no. 24 (December 14, 2021): 7585. http://dx.doi.org/10.3390/molecules26247585.
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The broadband rotational spectrum of jet-cooled laser-ablated thioproline was recorded. Two conformers of this system were observed and identified with the help of DFT and ab initio computations by comparison of the observed and calculated rotational constants and 14N quadrupole coupling constants as well as the predicted energies compared to the observed relative populations. These conformers showed a mixed bent/twisted arrangement of the five-membered ring similar to that of the related compound thiazolidine with the N–H bond in axial configuration. The most stable form had the COOH group in an equatorial position on the same side of the ring as N-H. The arrangement of the C=O group close to the N-H bond led to a weak interaction between them (classified as type I) characterized by a noncovalent interaction analysis. The second form had a trans-COOH arrangement showing a type II O–H···N hydrogen bond. In thioproline, the stability of conformers of type I and type II was reversed with respect to proline. We show how the conformation of the ring depends on the function associated with the endocyclic N atom when comparing the structures of isolated thioproline with its zwitterion observed in condensed phases and with peptide forms.
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Yang, H., and Y. Zhou. "Axisymmetric jet manipulated using two unsteady minijets." Journal of Fluid Mechanics 808 (November 2, 2016): 362–96. http://dx.doi.org/10.1017/jfm.2016.634.
Повний текст джерелаАнотація:
The manipulation of a turbulent axisymmetric jet is experimentally investigated based on two unsteady radial minijets. The Reynolds number is 8000. The mass flow rate ratio$C_{m}$of the two minijets to that of the main jet and the ratio$f_{e}/f_{0}^{\prime }$of the excitation frequency$f_{e}$to the preferred-mode frequency$f_{0}^{\prime }$in the natural jet are examined. The decay rate$K$of the jet centreline mean velocity exhibits a strong dependence on$C_{m}$and$f_{e}/f_{0}^{\prime }$and is classified into three distinct categories in terms of required$C_{m}$, achievable enhancement in$K$and flow physics involved. Great effort is made to understand the flow physics associated with the first category of the manipulated jet, under which$K$can be immensely improved with a very small$C_{m}$. Detailed measurements are conducted upstream and downstream of the nozzle exit using hot-wire, flow visualization and particle imaging velocimetry techniques. Whilst strong entrainment is predominant in the injection plane of the minijets, rapid spread occurs in the orthogonal non-injection plane. Three types of coherent structures are identified, i.e. the contorted ring vortex, two pairs of streamwise vortices and mushroom-like counter-rotating structures sequentially ‘tossed’ out radially in the non-injection plane. Their interactions account for the large rise in$K$. The unsteady disturbance of the minijets is found to play a key role in the formation and interaction of these vortices, which are distinct from those formed under the manipulation of steady minijets and other techniques. A conceptual model of the flow structure under manipulation is proposed.
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CITRINITI, J. H., and W. K. GEORGE. "Reconstruction of the global velocity field in the axisymmetric mixing layer utilizing the proper orthogonal decomposition." Journal of Fluid Mechanics 418 (September 10, 2000): 137–66. http://dx.doi.org/10.1017/s0022112000001087.
Повний текст джерелаАнотація:
Experimental data are presented from 138 synchronized channels of hot-wire anemometry in an investigation of the large-scale, or coherent, structures in a high Reynolds number fully developed, turbulent axisymmetric shear layer. The dynamics of the structures are obtained from instantaneous realizations of the streamwise velocity field in a single plane, x/D = 3, downstream of a round jet nozzle. The Proper Orthogonal Decomposition (POD) technique is applied to an ensemble of these realizations to determine optimal representations of the velocity field, in a mean-square sense, in terms of an orthogonal basis. The coefficients of the orthogonal functions, which describe the temporal evolution of the POD eigenfunctions, are determined by projecting instantaneous realizations of the velocity field onto the basis.Evidence is presented to show that with a partial reconstruction of the velocity field, using only the first radial POD mode, the large-scale structure is objectively educed from the turbulent field. Further, it is shown that only five azimuthal Fourier modes (0,3,4,5,6) are necessary to represent the evolution of the large-scale structure. The results of the velocity reconstruction using the POD provide evidence for azimuthally coherent structures that exist near the potential core. In addition to the azimuthal structures near the potential core, evidence is also found for the presence of counter-rotating, streamwise vortex pairs (or ribs) in the region between successive azimuthally coherent structures as well as coexisting for short periods with them. The large-scale structure cycle, which includes the appearance of the ring structure, the advection of fluid by the ribs in the braid region and their advection toward the outside of the layer by a following ring structure, repeats approximately every one integral time scale. One surprising result was that the most spatially correlated structure in the flow, the coherent ring near the potential core which ejects fluid in the streamwise direction in a volcano-like eruption, is also the one with the shortest time scale.
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YOSHIDA, Fumiya, Taichi USUZAWA, and Takahiro KIWATA. "S0510402 LES of a Flow Structure for Round Jet with Divergent and Convergent Deflecting Ring." Proceedings of Mechanical Engineering Congress, Japan 2014 (2014): _S0510402——_S0510402—. http://dx.doi.org/10.1299/jsmemecj.2014._s0510402-.
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KOJIMA, Tadatomo, Mari SHIMAZUE, Yoshihiro MATSUOKA, and Jun KUSUI. "Jet Noise Containing Discrete Frequency. 2nd Report. Effect of Structure and Behavior of Vortex Ring." Transactions of the Japan Society of Mechanical Engineers Series B 62, no. 594 (1996): 637–44. http://dx.doi.org/10.1299/kikaib.62.637.
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CHOUTAPALLI, I., A. KROTHAPALLI, and J. H. ARAKERI. "An experimental study of an axisymmetric turbulent pulsed air jet." Journal of Fluid Mechanics 631 (July 17, 2009): 23–63. http://dx.doi.org/10.1017/s0022112009007009.
Повний текст джерелаАнотація:
An experimental study is carried out to elucidate the structure of a high Reynolds number (~105) turbulent pulsed jet. Particle image velocimetry measurements showed that the near flow field is dominated by a series of vortex rings with jet-like flows in between. The data show that the vortex rings convect at nearly constant speed of 0.6Uj(Uj: mean jet exit velocity) and the spacing between the rings assumes a value of about 0.6/St(St: Strouhal number=fd/Uj, wherefis the pulsing frequency anddis the nozzle exit diameter). With increasing Strouhal number, the rings are closely spaced and the flow tends to assume a steady jet character at five diameters downstream of the nozzle exit. At lower Strouhal numbers there is a distinct region of jet flow in between the rings. Many of the global characteristics, entrainment, mass and momentum flux are essentially determined by the strength and spacing of the rings which, in turn, depend onSt. We show that the increase in momentum is due to both increased momentum flux and overpressure at the exit in accordance with Krueger & Gharib (AIAA J., vol. 43 (4), 2005, p. 792). This increase in momentum comes at the expense of higher energy required to produce the jet. We also present results of organized and random components of the fluctuations and production of the random turbulence in a pulsed jet. The two regions of dominant turbulence production are identified with the ring and the trailing jet shear layers.
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Zhao, Peng, and Rongxun Piao. "Lattice Boltzmann Method Modeling of the Evolution of Coherent Vortices and Periodic Flow in a Continuous Casting Mold." Metals 12, no. 4 (March 28, 2022): 572. http://dx.doi.org/10.3390/met12040572.
Повний текст джерелаАнотація:
Transient phenomena and vortex structures throughout the mold are simulated using a lattice Boltzmann method (LBM) coupled with large eddy simulation (LES) using a free surface model under steady operating conditions. The accuracy of the LBM-LES model has been verified by comparing the simulated velocities with published experimental values. The current work focuses on the evolution of the vortex structure in internal flow inside the submerged entry nozzle (SEN) jet flow and the turbulent flow near the wall of the mold. The results show various types of vortex structures with different directions are presented during the jet impingement, including the “ring, rib, and horseshoe”-like shaped vortices in the simulation, resulting in complex turbulent flow near the wall of the mold. Vortices structures are then identified and compared by different vorticial criteria, including vortex methods (ω), Q method, λ2 method (Lambda-2), Δ method (Delta), and Ω method (Omega). The formation, development, and dissipation of the vortex structures and their effects on turbulence are investigated. The results indicate that the turbulent flow (viscosity) can reflect changes in asymmetric vortices structures and flow patterns (via crossflow), which can reflect the periodical flow in the mold. Flow oscillation frequencies are mainly concentrated in the range of 0.3 Hz in this simulation. The oscillations are not a simple combination of frequency modes of crossflow in the mold. These new studies can elucidate the mechanism of vortex structure distributions in representative flow regions of the continuous casting mold.
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Rogina-Car, Beti, Zenun Skenderi, and Zlatko Vrljičak. "Thermophysiological wear comfort of viscose and tencel socks." Koža & obuća 68, no. 4 (2020): 22–29. http://dx.doi.org/10.34187/ko.68.4.3.
Повний текст джерелаАнотація:
Men’s socks were designed and manufactured in multiple plated single jersey structure using 20 tex viscose and Tencel yarn, 156 and 220 dtex multifilament PA 6.6 yarn and 25 tex cotton yarn. Sock mass and sock thickness were determined, the height of the sock leg, the length of the sock foot and half of the leg circumference and half of the foot circumference were measured. Thermophysiological sock wear comfort was determined by measuring thermal resistance on the thermal foot manikin. The results revealed that the sock samples containing the ring spun yarn in the structure had higher thermal resistance than the socks containing rotor and air-jet spun yarns. The obtained difference of thermal resistance of the sock samples per type of the basic yarn was significant. The viscose socks made of ring spun yarns with an added coarser cotton yarn and PA 6.6 yarn had the highest thermal resistance, while the lowest thermal resistance was recorded for the Tencel rotor spun yarns
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Sardanashvily, G., and W. Wachowski. "Differential Calculus onN-Graded Manifolds." Journal of Mathematics 2017 (2017): 1–19. http://dx.doi.org/10.1155/2017/8271562.
Повний текст джерелаАнотація:
The differential calculus, including formalism of linear differential operators and the Chevalley–Eilenberg differential calculus, overN-graded commutative rings and onN-graded manifolds is developed. This is a straightforward generalization of the conventional differential calculus over commutative rings and also is the case of the differential calculus over Grassmann algebras and onZ2-graded manifolds. We follow the notion of anN-graded manifold as a local-ringed space whose body is a smooth manifoldZ. A key point is that the graded derivation module of the structure ring of graded functions on anN-graded manifold is the structure ring of global sections of a certain smooth vector bundle over its bodyZ. Accordingly, the Chevalley–Eilenberg differential calculus on anN-graded manifold provides it with the de Rham complex of graded differential forms. This fact enables us to extend the differential calculus onN-graded manifolds to formalism of nonlinear differential operators, by analogy with that on smooth manifolds, in terms of graded jet manifolds ofN-graded bundles.
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Birkinshaw, Mark, Josie Rawes, and Diana Worrall. "Extreme jet distortions in low-z radio galaxies." Proceedings of the International Astronomical Union 14, A30 (August 2018): 61–65. http://dx.doi.org/10.1017/s1743921319003466.
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AbstractJets often display bends and knots at which the flows change character. Extreme distortions have implications for the nature of jet flows and their interactions. We present the results of three radio mapping campaigns. The distortion of 3CRR radio galaxy NGC 7385 is caused by a collision with a foreground magnetised gas cloud which causes Faraday rotation and free-free absorption, and is triggered into star formation. For NGC 6109 the distortion is more extreme, creating a ring-shaped structure, but no deflector can be identified in cold or hot gas. Similar distortions in NGC 7016 are apparently associated with an X-ray gas cavity, and the adjacent NGC 7018 shows filaments drawn out beyond 100 kpc. Encounters with substructures in low-density, magnetised, intergalactic gas are likely causes of many of these features.
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Cheng, Chin-Hsiang, Yi-Shen Chen, Hsin-Yu Tsai, Yu-Ling Liang, David T. W. Lin, and Yitung Chen. "Development of a Flexible Metamaterial Film with High EM Wave Absorptivity by Numerical and Experimental Methods." Materials 15, no. 12 (June 10, 2022): 4133. http://dx.doi.org/10.3390/ma15124133.
Повний текст джерелаАнотація:
The present study is intended to develop and test a cost-effective and efficient printing method for fabricating flexible metamaterial film with high electromagnetic wave absorptivity. The film can be easily applied to the surfaces with curved aspects. Firstly, numerical parametric study of the absorption characteristics of the film is performed for the range of frequency varying from 2.0 to 9.0 GHz based on commercial software package. Secondly, the flexible metamaterial films are fabricated, and experiments are conducted. The flexible metamaterial film consists of a flexible dielectric film made of polyimide (PI) and an array of split-ring resonators. The split-ring resonators of different geometric dimensions are fabricated on the PI film surface by using a silver nanoparticles ink jet printer. The performance of the flexible structure is then measured and dependence of operation frequency with higher absorptivity on the dimensions of the split-ring resonators is investigated. A comparison between the numerical and experimental data shows that the numerical predictions of the operation frequency with higher absorptivity closely agree with the experimental data.
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Blanco, Mónica W., Martín A. Guerrero, Luis F. Miranda, Eric Lagadec, and Olga Suárez. "VISIR-VLT images of the water maser: Emitting planetary nebula K3-35." Proceedings of the International Astronomical Union 7, S283 (July 2011): 312–13. http://dx.doi.org/10.1017/s1743921312011180.
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AbstractK3-35 is an extremely young bipolar planetary nebula that contains a precessing bipolar jet and a small (radius 80 AU) water maser equatorial ring. We have obtained VISIR-VLT images of K3-35 in the PAH1 (λ=8.6 μm), [S iv] (λ=10.6 μm), and SiC (λ=11.85 μm) filters to analize the mid-IR morphology and the temperature structure of its dust emission. The images show the innermost nebular regions undetected at optical wavelegths and the precessing bipolar jets. The temperature map shows variations in the temperature in the equatorial zone and in regions associated to its jets.
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Nair, K. P. Rajappan, Sven Herbers, Daniel A. Obenchain, and Jens-Uwe Grabow. "Internal methyl rotation and molecular structure of trifluorotoluenes: microwave rotational spectra of 2,3,4- and 2,4,5-trifluorotoluene." Canadian Journal of Physics 98, no. 6 (June 2020): 543–50. http://dx.doi.org/10.1139/cjp-2019-0477.
Повний текст джерелаАнотація:
The microwave rotational spectra of 2,3,4- and 2,4,5-trifluorotoluenes, along with all 13C isotopic species in natural abundance, have been recorded in the frequency range 8–27 GHz employing pulsed-jet Fourier transform microwave spectroscopy. The analysis of the spectra in the lowest torsional state has yielded the rotational constants, centrifugal distortion constants, three-fold barrier to methyl rotation, and the direction of the internal rotation axis in the moment of inertia principal axes systems of these trifluorotoluenes. For both molecules, the molecular constants of their eight isotopologues have been used to obtain the substitution rs structures of the ring and the methyl-carbon. The potential barriers hindering the internal rotation of the methyl top in 2,3,4- and 2,4,5-trifluorotluene are 2.5878(80) and 2.2809(23) kJ/mol, respectively.
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HADŽIABDIĆ, M., and K. HANJALIĆ. "Vortical structures and heat transfer in a round impinging jet." Journal of Fluid Mechanics 596 (January 17, 2008): 221–60. http://dx.doi.org/10.1017/s002211200700955x.
Повний текст джерелаАнотація:
In order to gain a better insight into flow, vortical and turbulence structure and their correlation with the local heat transfer in impinging flows, we performed large-eddy simulations (LES) of a round normally impinging jet issuing from a long pipe at Reynolds number Re = 20000 at the orifice-to-plate distance H = 2D, where D is the jet-nozzle diameter. This configuration was chosen to match previous experiments in which several phenomena have been detected, but the underlying physics remained obscure because of limitations in the measuring techniques applied. The instantaneous velocity and temperature fields, generated by the LES, revealed interesting time and spatial dynamics of the vorticity and eddy structures and their imprints on the target wall, characterized by tilting and breaking of the edge ring vortices before impingement, flapping, precessing, splitting and pairing of the stagnation point/line, local unsteady separation and flow reversal at the onset of radial jet spreading, streaks pairing and branching in the near-wall region of the radial jets, and others. The LES data provided also a basis for plausible explanations of some of the experimentally detected statistically-averaged flow features such as double peaks in the Nusselt number and the negative production of turbulence energy in the stagnation region. The simulations, performed with an in-house unstructured finite-volume code T-FlowS, using second-order-accuracy discretization schemes for space and time and the dynamic subgrid-scale stress/flux model for unresolved motion, showed large sensitivity of the results to the grid resolution especially in the wall vicinity, suggesting care must be taken in interpreting LES results in impinging flows.