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Auswahl der wissenschaftlichen Literatur zum Thema „Ring-jet structure“
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Zeitschriftenartikel zum Thema "Ring-jet structure"
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Chen, Fengyang, Ping Lu, Dongqin Li, Yadong Li, Yanqing Hou, Gang Xie, Ni Yang und Lin Tian. „The Mixing Character within Oxidation Reactor in Titanium Dioxide Production by Chloride Process“. Advances in Engineering Technology Research 1, Nr. 2 (22.09.2022): 48. http://dx.doi.org/10.56028/aetr.1.2.48.
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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.
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Chen, Fengyang, Ping Lu, Dongqin Li, Yadong Li, Yanqing Hou, Gang Xie, Ni Yang und Lin Tian. „The Mixing Character within Oxidation Reactor in Titanium Dioxide Production by Chloride Process“. Advances in Engineering Technology Research 2, Nr. 1 (22.09.2022): 48. http://dx.doi.org/10.56028/aetr.2.1.48.
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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 und DOMINIKA GLAŽAR. „The influence of air-jet and vortex yarn on functionality of woven fabric“. Industria Textila 69, Nr. 02 (01.05.2018): 87–95. http://dx.doi.org/10.35530/it.069.02.1412.
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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.
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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, Nr. 7958 (26.04.2023): 686–90. http://dx.doi.org/10.1038/s41586-023-05843-w.
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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.
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HÜSEYİN GAZ, TÜRKSOY, AKKAYA TUĞBA, VURUŞKAN DENİZ und ÜSTÜNTAĞ SÜMEYYE. „A comparative analysis of air-jet yarn properties with the properties of ring spun yarns“. Industria Textila 69, Nr. 01 (01.03.2018): 11–16. http://dx.doi.org/10.35530/it.069.01.1419.
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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.
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NOUMI, Yuhei, und 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.
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Longmire, Ellen K., und John K. Eaton. „Structure of a particle-laden round jet“. Journal of Fluid Mechanics 236 (März 1992): 217–57. http://dx.doi.org/10.1017/s002211209200140x.
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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.
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VERNET, A., G. A. KOPP, J. A. FERRÉ und FRANCESC GIRALT. „Three-dimensional structure and momentum transfer in a turbulent cylinder wake“. Journal of Fluid Mechanics 394 (10.09.1999): 303–37. http://dx.doi.org/10.1017/s0022112099005807.
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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.
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Miyoshi, Makoto, Yoshiaki Kato und 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, Nr. 1 (30.06.2022): 36. http://dx.doi.org/10.3847/1538-4357/ac6ddb.
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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 und 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, Nr. 1 (22.02.2024): L18. http://dx.doi.org/10.3847/2041-8213/ad250e.
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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.
Dissertationen zum Thema "Ring-jet structure"
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Manna, Sanjib Kumar. „Non-statistical fluctuation of singly charged particles produced in 16O-Ag/Br interaction at 200A Ge V/c“. Thesis, University of North Bengal, 2021. http://ir.nbu.ac.in/handle/123456789/4761.
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Han, Kewen, Zhe Zhang, Steven T. Wereley und Je Hoon Oh. „Study of Factors in Coffee-Ring Structure Formation Using PIV Methods“. In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-63231.
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The evaporating liquid droplet with suspended particles on a solid substrate may leave a ring-like structure along the droplet circumference under certain conditions, which is commonly known as the coffee ring phenomenon. This phenomenon has many interesting applications related to microfluidic problem such as self-assembly of colloidal particle, particle and biomolecule separation and concentration and ink-jet printing. Although much work has been done on this topic, not very much work focused on the fluid flow inside a droplet. In order to investigate the inner flow inside of the droplet, water solutions with the fluorescing or non-fluorescing particles as the solute are dropped on surfaces with different hydrophilicity. The whole process are recorded using high dynamic CCD camera system and analyzed using Particle Image Velocimetry (PIV) methods. It is found that in all the droplets that form coffee ring, a central symmetric outward radial flow is observed. The velocity of the flow is zero at the center of the droplet. Along with radius outside, the flow velocity increases. For the same droplet, the flow velocity increases as the evaporation goes on and the velocity reaches its maximum at the end the evaporation. For different droplets, with the higher concentration, smaller droplet size and more hydrophilic surface, the flow velocity is larger. Comparisons between the experimental data and the published convection models show that the flow can be considered as part of the flow caused by the maximum evaporation rate at the pinned wetting line.
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Lawandy, N. M. „Bichromatic emission in a homogeneously broadened ring dye laser: evidence of a new mode structure hierarchy“. In International Laser Science Conference. Washington, D.C.: Optica Publishing Group, 1986. http://dx.doi.org/10.1364/ils.1986.tuf3.
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We present experimental measurements on a high-Q rhodamine 6G ring dye laser which was found to exhibit bichromatic emission with splittings of the order of 15–80 Å while operating in the range of 2–6 times above threshold in the bidirectional mode. Experiments were performed with the insertion of a low loss Faraday isolator (loss < 1%) in order to examine the effects of saturation gratings on the bichromatic emission. The results showed that even though the intracavity power went up, owing to the elimination of spatial hole burning, the bichromatic emission was completely eliminated in the operating range between 1 and 10 times above threshold. In addition the sidelight fluorescence of the jet was spectrally examined in order to search for sideband splittings similar to those found in Na atoms in a strong resonant field. No evidence of splittings or fluorescence shape change was found when the laser was 1–10 times above threshold. When a weak reflection from an intracavity element was allowed to make a single pass through the active part of the jet in a direction opposite to that allowed by the Faraday rotator, bichromatic emission was recovered at high pump powers (2–5 W). This is believed to be a consequence of a Bragg grating which appears when the weak beam is sent through the active medium. We describe the experiments and the results which we obtained, as well as offer a theory which consistently explains our observations and perhaps those of others.
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Wang, Hai-bo, Joon-wan Kim, Shinichi Yokota und Kazuya Edamura. „Performance Evaluation of a Triangular-Prism-Slit Electrode Pair as an Electro-Conjugate Fluid Jet Generator“. In ASME 2011 Dynamic Systems and Control Conference and Bath/ASME Symposium on Fluid Power and Motion Control. ASMEDC, 2011. http://dx.doi.org/10.1115/dscc2011-6077.
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Electro-conjugate fluid (ECF) is a dielectric and functional fluid, which generates a powerful jet when electrodes inserted into it are subjected to a constant voltage of less than one thousand volts. As one essential research field on ECF, researchers have been conducting the study on electrodes. Several structures, e.g. planar parallel rod-like electrode array, ring-needle electrode pair and triangular-prism-slit (TPS) electrode pair, were proposed. Among them, the TPS electrode structure is often thought as the most promising candidate for future ECF applications thanks to its great merits of combining easy fabrication and relatively high performance. In this paper, in order to evaluate performance of the TPS electrode pair, a novel modular ECF-jet generator capable of independently adjusting alignment and gap of each electrode is designed. By utilizing it, the relationship between output pressure and parameters of the TPS electrode pair, including thickness, slit width, tip angle, electrode gap and alignment, are obtained.
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Yang, Jinxin, Dongchan Kim, Sanghoon Kook, Kenneth S. Kim und Chol-Bum Kweon. „Evaluation of swirl ratio effects on the flow fields using Particle Image Velocimetry and Flame image Velocimetry in a small-bore optical compression-ignition engine“. In 2023 JSAE/SAE Powertrains, Energy and Lubricants International Meeting. 10-2 Gobancho, Chiyoda-ku, Tokyo, Japan: Society of Automotive Engineers of Japan, 2023. http://dx.doi.org/10.4271/2023-32-0061.
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<div class="section abstract"><div class="htmlview paragraph">This study applies high-speed particle image velocimetry (HS-PIV) and flame image velocimetry (HS-FIV) to show flow fields under the effect of varied swirl ratios in a small-bore optical compression-ignition engine. The base swirl ratio and maximum swirl ratio conditions were applied to investigate structures, magnitude and turbulence distribution of the in-cylinder flow as well as the flow within the flame. For each swirl ratio, 100 individual cycles were measured for PIV analysis at motoring conditions and then another 100 cycles for FIV analysis at firing conditions. The derived flow fields were ensemble averaged to show flow structure evolution while the spatial filtering method was applied to extract high-frequency flow component for the analysis of turbulence distributions. The results showed that the intake air flow generates undefined, chaotic flow fields, which are followed by a gradual production of an asymmetric swirl flow. This is due to uneven intake port shape with one spiraling passage and the other straight passage. Upon the formation of a clearly defined swirl flow structure, its centre position rotates in the counter-clockwise direction within the measurement field of view, which impacts the reacting jet flame development with the down-swirl side of the wall-interacting jet penetrating faster. At the maximum swirl ratio realised by blocking the straight port, the intake air flow vectors become more chaotic and stronger, resulting in increased bulk flow magnitude and turbulence. Also, a ring vortex of the flame head on the up-swirl side appears closer to the jet axis while the vectors travelling faster on the down-swirl side than that of the base swirl ratio. Notably, the cyclic variation of in-flame vector magnitude is observed to decrease for the higher swirl ratio, which is attributed to faster mixing to eliminate the high cyclic variation zone formed within the jet-jet interaction region.</div></div>
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Miller, Terry A. „Ultrahigh resolution spectroscopy of free radicals“. In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1988. http://dx.doi.org/10.1364/oam.1988.thr2.
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Rotationally resolved electronic spectra of moderately large free radicals such as CH3O, C2H5O, C5H5, and C6 F6+ have been obtained by using a pulsed amplified tunable ring dye laser system. This system is capable of producing laser radiation of moderately high energy, 5–10 mJ/pulse throughout the visible spectral region, and may be doubled into the UV. The radicals are produced by excimer laser photolysis of suitable precursors in a supersonic free jet expansion. Spectra of radicals with internal temperatures in the range of ~0.5–20 K have been recorded. The analyses of these spectra to obtain information about the radicals' geometries and electronic structure are discussed.
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O’Connor, Jacqueline, und Tim Lieuwen. „Influence of Transverse Acoustic Modal Structure on the Forced Response of a Swirling Nozzle Flow“. In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-70053.
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This study describes continued investigations of the response of a swirling flow to transverse acoustic excitation. This work is motivated by transverse combustion instabilities in annular gas turbine engine architectures. This instability provides a spatially varying acoustic velocity disturbance field around the annulus, so that different nozzles encounter different acoustic disturbance fields. In this study, we simulate this effect by looking at a standing wave acoustic field where the nozzle is located at either a velocity anti-node, referred to as out-of-phase forcing, and a velocity node, referred to as in-phase forcing. The out-of-phase forcing condition provides an asymmetric forcing field about the center plane of the flow and excites an asymmetric response in the flow field; the in-phase forcing provides a symmetric forcing condition and results in symmetric flow response near the nozzzle. The symmetric versus asymmetric flow response was measured in two ways. First, in the r-x plane where axial and radial components of velocity are measured using high-speed particle image velocimetry (PIV), a helical and ring vortex rollup of the shear layers is evident in the asymmetric and symmetric forcing condition, respectively. Additionally, the swirling motion of the jet is measured in the r-θ plane at two downstream locations and a spatial decomposition is used to calculate the strength of azimuthal modes in radial velocity fluctuations. At the forcing frequency, the m = 0 mode is strongly excited at the nozzle exit with symmetric forcing, while asymmetric forcing results in a strong peak in the m = 1 mode, or the first helical mode. The results in this plane of view are congruent with those in the r-x plane. Further downstream, however, the mode strengths change as the vorticity is religned and natural asymmetries of the swirling jet set in. Finally, the low frequency self-excited motion of the vortex core was measured and characterized in the unforced flow. It is composed of an m = −1 and m = −2 mode, and the physical interpretation of these mode numbers is highlighted. High amplitude acoustic forcing decreases the amplitude of oscillation of this structure in both the in-phase and out-of-phase forcing, but to varying degrees.
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Pokhmurskii, V., M. Student, V. Dovhunyk, I. Sydorak und H. Pokhmurska. „Wear Resistance of Arc-Sprayed Coatings from Powder Wires“. In ITSC2002, herausgegeben von C. C. Berndt und E. Lugscheider. Verlag für Schweißen und verwandte Verfahren DVS-Verlag GmbH, 2002. http://dx.doi.org/10.31399/asm.cp.itsc2002p0559.
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Abstract This paper presents the results of a study on arc-sprayed coatings made from powder-cored wire. The wires used consist of a ferrochromium core with additions of boron, aluminum, and carbon compacted in a steel sheath. The coatings are sprayed using a modified burner operated at 34 V and 140 A with an air jet pressure of 0.6 MPa. During spraying, specimens are rotated at a speed of 60 rpm. XRD analysis is used to examine the initial phase composition of the layers as well as friction-induced changes in the subsurface resulting from block-on-ring wear tests. Cross-sectional examination shows that the coatings have low porosity (∼10%) and small grain size (50 to 150 µm). Based on these findings, it is concluded that the wear resistance of wire arc sprayed coatings is largely determined by powder wire composition, initial coating structure, and the structural stability of the subsurface layer. Paper includes a German-language abstract.
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Li, Bangming, Qi Xiao, Yong Li, Xu Hu und Wei Wang. „Numerical Study on Streamwise Vorticity and Entrainment Enhancement of a Round Jet“. In 2018 26th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/icone26-81794.
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The jet pump has many outstanding advantages such as simple structure, high reliability, and low operation and maintenance costs and so on. Therefore, it has been widely used in nuclear industry fields. The entrainment ability of the jet pump is the core performance. It is generally recognized that, although the vorticity value of streamwise vortex is smaller than that of spanwise, it plays an important role in the entrainment process. Thus, a numerical simulation of streamwise vortex influence on the entrainment ability of a round jet is carried out. To enhance the entrainment of the round jet, tabs (streamwise vortex generator) and vibrator (perturbation) are set at the exit of nozzle. Tabs are set of number as 0, 2, 4 and 6, and the frequency of vibrator is set as natural frequency and its half. Based on the above configuration, numerical simulations of different nozzle types were carried out. Based on above results, firstly the influence of tabs on the entrainment ability was analyzed. The vortex intensity of the jet flow is obviously enhanced under introducing tabs. Similarly, the intensity of streamwise vortex downstream also increase significantly, thus enhance the entrainment ability. From the figure of local entrainment flow rate, the jet of nozzle with 6 tabs has the strongest entrainment ability; its local entrainment flow rate is 1.5 times of the round jet. Then, the influence of perturbation on the entrainment ability is analyzed. After introducing velocity perturbation, the evolution of the mixing layer evidently accelerated. Under natural frequency perturbation, mixing layer evolution is the most rapid. The mixing layer roll into a vortex ring in less than one diameter distance downstream allowing to 1.75 times the amount of fluid entrained in comparison with the round jet. Finally, integrating the influence of tabs and perturbation, the variation of the jet entrainment ability is analyzed. Due to the combined effect of tabs enhancing vortex intensity and natural frequency accelerating the evolution process, local entrainment ability of the jet is further improved which is more than three times that of the round jet. Taking the nozzle with 6 tabs and perturbation of natural frequency as an example, the streamwise vorticity increases rapidly to a maximum. Local entrainment flow rate also has a corresponding maximum value, which is one-to-one correspondence with the intensity distribution of streamwise vortex, indicating that streamwise vortex plays a predominant role in the entrainment ability of the jet.
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Fuchiwaki, Masaki, und Kazuhiro Tanaka. „Characteristics of Dynamic Forces Generated by a Flapping Butterfly and its Wake Structure“. In ASME 2017 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/fedsm2017-69285.
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A typical example of the flow field around a moving elastic body is that around butterfly wings. Butterflies fly by skillfully controlling this flow field, and vortices are generated around their bodies. The motion of their elastic wings produces dynamic fluid forces by manipulating the flow field. For this reason, there has been increased academic interest in the flow field and dynamic fluid forces produced by butterfly wings. A number of recent studies have qualitatively and quantitatively examined the flow field around insect wings. In some such previous studies, the vortex ring or vortex loop formed on the wing was visualized. However, the characteristics of dynamic forces generated by the flapping insect wing are not yet sufficiently understood. The purpose of the present study is to investigate the characteristics of dynamic lift and thrust produced by the flapping butterfly wing and the relationship between the dynamic lift and thrust and the flow field around the butterfly. We conducted the dynamic lift and thrust measurements of a fixed flapping butterfly, Idea leuconoe, using a six-axes sensor. Moreover, two-dimensional PIV measurement was conducted in the wake of the butterfly. The butterfly produced dynamic lift in downward flapping which became maximum at a flapping angle of approximately 0.0 deg. At the same time, the butterfly produced negative dynamic thrust during downward flapping. The negative dynamic thrust was not produced hydrodynamically by a flapping butterfly wing because a jet was not formed in front of the butterfly. The negative dynamic thrust was the kicking force for jumping and the maximum of this kicking force was about 6.0 times as large as the weight. On the other hand, the butterfly produced dynamic thrust in upward flapping which was approximately 6.0 times as large as the weight of the butterfly. However, the attacking force by the abdomen of the butterfly was included in the dynamic thrust and we have not yet clarified quantitatively the dynamic thrust produced by the butterfly wing.
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Kim, Seon Ho, Kyeong Hwan Ahn, Jun Su Park, Eui Yeop Jung, Ki-Young Hwang und Hyung Hee Cho. „Local Heat and Mass Transfer Characteristics for Multi-Layered Impingement/Effusion Cooling“. In ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-43831.
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Multi-layered impingement/effusion cooling is an advanced cooling configuration that combines impingement jet cooling, pin cooling, and effusion cooling. The arrangement of the pins is a critical design factor because of the complex heat transfer in the internal structure. Therefore, it is important to measure the local heat transfer at all internal surfaces as a function of the pin spacing. In this study, a naphthalene sublimation method was employed to measure the details of the heat/mass transfer at the internal surfaces, including the injection plate, effusion plates, and the pins. An staggered array of holes was formed at the injection plate and effusion plates where the ratio of the height to the diameter of the pins, h/d, was fixed at 0.25. The ratio of the pin spacing to the diameter, sp/d, was varied in the range 1.5≤sp/d≤6, and the Reynolds number based on the hole diameter was 3000. As a result, a vortex ring formed near the pin, leading to re-impingement flows in the narrow channel. The jet flow impinged strongly on the pin, resulting in a large heat transfer region at each surface. The total average Sherwood number with sp/d=1.5 was larger than that with sp/d=6 by a factor of 1.5.