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1
Zhao, Wanqi, Xin Ren, Bin Liu, Yao Xiao, and Dawei Liu. "Formation of Lunar Swirls: Implication from Derived Nanophase Iron Abundance." Remote Sensing 17, no. 8 (2025): 1324. https://doi.org/10.3390/rs17081324.
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Lunar swirls are enigmatic features on the Moon’s surface, and their formation remains debated. Previous studies suggest that the distinctive spectral characteristics of lunar swirls result from the asymmetric space weathering between their bright markings (on-swirl) and dark surrounding background (off-swirl) regions. Nanophase iron (npFe0), as the product of space weathering, directly reflects this varying degree of space weathering. In this study, we investigated the formation of lunar swirls from the perspective of the npFe0 distribution across five lunar swirls using Chang’e-1 (CE-1) Interference Imaging Spectrometer (IIM) data. Our results show that (1) on-swirl regions exhibit an obvious lower npFe0 abundance compared to their backgrounds; (2) the relationship between the npFe0 abundance in swirl dark lanes and the off-swirl regions is associated with different stages of space weathering; (3) the difference in the npFe0 abundance between on-swirl regions and off-swirl fresh craters could be due to their different weathering processes; and (4) there is a correlation between npFe0, water content, and the strength of magnetic anomalies related to lunar swirls. These findings support the view that the process of solar wind deflection leads to the preservation of swirl surfaces with reduced space weathering and provide a new perspective for comparing different swirl formation models.
2
Elkersh, A. M., A. H. Elgammal, and N. R. L. Maccallum. "An Experimental Investigation of the Performance of Equiangular Annular Diffusers with Swirled Flow." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 199, no. 4 (1985): 293–97. http://dx.doi.org/10.1243/pime_proc_1985_199_126_02.
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An experimental study of the influence of geometrical parameters and swirl on the performance of equiangular diffusers is presented. Three diffusers were tested over a range of inlet swirls up to 45°, the swirls being of free vortex distribution. The data presented indicate similar flow patterns for different cant angles, and show that the centrifugal forces due to swirl stabilize the flow on the outer wall, while increasing the tendency towards separation at the inner wall. Diffuser performance improves as the inlet swirl increases up to 30°, the improvement being influenced by area ratio and cant angle. A further increase of swirl causes a deterioration of performance.
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Kinczyk, Mallory J., Brett W. Denevi, Hiroyuki Sato, et al. "Photometry of Lunar Swirls in Comparison to Fresh Crater Ejecta." Planetary Science Journal 6, no. 3 (2025): 57. https://doi.org/10.3847/psj/adafa6.
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Abstract Swirls are sinuous high-reflectance lunar surface features collocated with crustal magnetic anomalies. These bright features and their geographical relationship to magnetic anomalies have been studied for decades, although their cause remains unclear. Several mechanisms for swirl formation have been proposed, including altered space weathering due to solar wind shielding, scouring of the surface by cometary impacts, and sorting of regolith materials. We use an empirical phase curve analysis and Hapke radiative transfer modeling of single-scattering albedo, bidirectional reflectance, and the angular width of the shadow hiding opposition effect to investigate regolith and crater ejecta properties at three prominent swirl sites: Reiner Gamma, Firsov, and Mare Ingenii. We assess the photometric differences between swirls, nearby background regolith, and fresh impact crater ejecta, and discuss implications for swirl formation. Our results suggest that both swirl and background regolith are consistently less backscattering than fresh crater ejecta, although swirl regolith and crater ejecta within swirls maintain higher single-scattering albedo values than the corresponding background materials. Physical processing via micrometeoroid impacts may explain the similar backscattering characteristics of swirl and background regolith, while additional space weathering of background regolith by solar wind causes differences in single-scattering albedo. In contrast, fresh crater ejecta is more backscattering than both swirl and background regolith, likely due to the impact process that exposes blocky material and alters the nearby surface. As a result, an anomalous space weathering environment caused by solar wind shielding remains a compelling hypothesis for the high-reflectance nature of lunar swirls.
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Chuang, Frank C., Matthew D. Richardson, John R. Weirich, Amanda A. Sickafoose, and Deborah L. Domingue. "Mapping Lunar Swirls with Machine Learning: The Application of Unsupervised and Supervised Image Classification Algorithms in Reiner Gamma and Mare Ingenii." Planetary Science Journal 3, no. 10 (2022): 231. http://dx.doi.org/10.3847/psj/ac8f43.
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Abstract Lunar swirls are recognized as broad, bright albedo features in various regions of the Moon. These features are often separated by dark off-swirl lanes or terminate against the dark background, such as lunar maria. Prior mapping of swirls has been done primarily by albedo contrast, which is prone to subjectivity. Closer examination of on-swirl areas shows that they are not uniform, making the boundary between on- and off-swirl difficult to map with certainty. We have applied machine learning techniques to address these issues by identifying the number of swirl units and then mapping them based on actual reflectance, or I/F data. Using LROC NAC paired stereo images that are converted to I/F reflectance at a range of incidence angles, we applied both unsupervised K-means clustering and supervised Maximum Likelihood Classification algorithms to classify and map portions of lunar swirls in Reiner Gamma and Mare Ingenii. Results show that the classification maps are a reasonable match to the representative albedos for the two study regions. A third transitionary swirl unit, termed diffuse-swirl, is present in both the maps and the cumulative distribution plots of the reflectance values. Overall, we find that the use of both algorithms provides independent confirmation of both the number and location of these units and their interrelation. More importantly, the algorithms remove mapping subjectivity by using quantitative information. The data and the statistics generated from the maps also have value in future studies by placing limits for categorizing swirl units in different regions on the Moon.
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Hess, M., C. Wöhler, M. Bhatt, et al. "Processes governing the VIS/NIR spectral reflectance behavior of lunar swirls." Astronomy & Astrophysics 639 (July 2020): A12. http://dx.doi.org/10.1051/0004-6361/201937299.
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We investigated six bright swirls associated with magnetic anomalies of variable strength using Chandrayaan-1 Moon Mineralogy Mapper (M3) hyperspectral image data. We examined the 3 μm absorption band generally ascribed to solar wind-induced OH/H2O and spectral trends in the near-infrared wavelength range at on-swirl and off-swirl locations. We found that the 3 μm absorption band is weaker at on-swirl than at off-swirl locations and shows only weak variations with time-of-day. This result is consistent with magnetic anomaly shielding that reduces solar wind interaction with the surface. For a small swirl structure in Mare Moscoviense, we found the 3 μm absorption band to be similar to that of its surroundings due to the absence of strong magnetic shielding. Our spectral analysis results at on-swirl and off-swirl locations suggest that the spectral trends at on-swirl and off-swirl locations cannot always be explained by reduced space-weathering alone. We propose that a combination of soil compaction possibly resulting from the interaction between the surface and cometary gas and subsequent magnetic shielding is able to explain all observed on-swirl vs. off-swirl spectral trends including the absorption band depth near 3 μm. Our results suggest that an external mechanism of interaction between a comet and the uppermost regolith layer might play a significant role in lunar swirl formation.
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Cho, Eunjin, Chae Kyung Sim, Seul-Min Baek, Minsup Jeong, and Young-Jun Choi. "Reddening and darkening trends of on/off swirls and the relationship with magnetic field strength." Publications of the Astronomical Society of Japan 73, no. 6 (2021): 1604–14. http://dx.doi.org/10.1093/pasj/psab096.
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Abstract Lunar swirls are albedo features associated with magnetic anomalies, and their formation mechanism has long been debated. Because spectral properties of lunar swirls provide information on space weathering environments and surface compositions, differences in the spectra between swirls and background regions can give a clue to their formation. We analyze space weathering for swirls in the lunar highlands and maria using the VIS-NIR spectral slope, 1550 nm reflectance, and 950 nm band depth. We find that highland swirls show lower reddening-to-darkening ratios than off-swirl regions, implying more decreases of nanophase iron relative to microphase iron on swirls. We also use magnetic field data to investigate the influence of the crustal magnetic field on the space weathering of a few selected swirls. The Reiner Gamma swirl becomes more immature as the magnetic field strength increases, although the entire swirl has a high albedo. Especially, the Reiner Gamma tail shows that the stronger magnetic field makes the surface undergo less spectral reddening. Our results support the solar wind stand-off hypothesis, which is that the solar wind deflected by the crustal field determines the optical property of the surface.
7
Zhang, Shenghui, Shuiting Ding, Peng Liu, and Tian Qiu. "Effect of Hot Streak on Aerothermal Performance of High Pressure Turbine Guide Vane under Different Swirl Intensities." Aerospace 9, no. 10 (2022): 579. http://dx.doi.org/10.3390/aerospace9100579.
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In advanced civil aero-engine, the gas exiting combustor typically features hot streak (HS) and swirl that affect the aerothermal performances of the high pressure (HP) nozzle guide vane (NGV). The purpose of this paper is to study the influences of HS on HP NGV aerothermal behaviors under swirl with various intensities. The numerical investigations were conducted on the first NGV of GE-E3 HP turbine. Four swirl intensities (|SN| = 0, 0.25, 0.50, 0.75) and two swirl orientations (positive and negative) were considered. The result indicates that the relative strengths between the swirl and its induced radial pressure gradient dominate the flow patterns on vane surfaces. Thus, the diverse streamlines distributions appear on the surfaces and the dominated factor on each surface does not vary with swirl intensity. The swirl redistributes the cold and hot fluid and thus generates the relatively hot oblique strip and cold region at the upstream of vane. The heat load on the vane that is not directly impinged by HS is dictated by the radial migration of the fluids originating from the regions aforementioned at |SN| = 0.25 and 0.50. However, at |SN| = 0.75, the transverse movement of HS due to the intense swirl causes additional thermal load. The heat load on the vane that faces HS is mainly determined by the radial migration of HS. The swirl alters the heat transfer distribution on vane surfaces remarkably. With positive swirl, the heat transfer coefficients at the lower span of suction side and pressure side are enhanced and weakened respectively. As expected, the opposite trends are observed in the negative swirl case. Swirl also affects boundary layer transition, and then affecting heat transfer. Positive and negative swirls both advance the transition on the suction side of vane directly impinged by the swirl, and with the increase of swirl intensity, transition onset shifts toward upstream.
8
Clarke, Jenni. "Swirl by swirl." Early Years Educator 22, no. 5 (2020): S12—S13. http://dx.doi.org/10.12968/eyed.2020.22.5.s12.
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Give children time to explore patterns in nature and develop their ability to appreciate and identify shape and design. Learning is maximised when it is led by children as part of in the moment planning, explains Jenni Clarke.
9
Weirich, John R., Deborah L. Domingue, Frank C. Chuang, et al. "The Search for Topographic Correlations within the Reiner Gamma Swirl." Planetary Science Journal 4, no. 11 (2023): 212. http://dx.doi.org/10.3847/psj/ace2b8.
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Abstract Lunar swirls have been traditionally considered to be unaffected by topographic changes. Yet, correlations between areas of high albedo and lower elevations are observed in regions of the Mare Ingenii swirl. Here, we apply similar techniques used at Mare Ingenii to determine if correlations between swirl units and topography also exist within Reiner Gamma. We generate topography using the techniques of stereophotoclinometry to Lunar Reconnaissance Orbiter Camera Narrow Angle Camera images to derive meter- to submeter-scale topography. We choose a 50 km2 study region with a 2.6 m ground sample distance (GSD), and within this region there is a 1 km2 subregion with a 0.8 m GSD. We use surface reflectance data at multiple viewing geometries to classify these regions into different swirl units using machine learning techniques. Statistical analyses of the data show mean height variations between on- and off-swirl of ∼4 m, with on-swirl at a lower elevation. It is not clear how this scale of elevation difference influences the formation of swirl units, but it supports postulations of dust migration and magnetic sorting contributing to their formation.
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Shih, T. I.-P., and Y. L. Lin. "Controlling Secondary-Flow Structure by Leading-Edge Airfoil Fillet and Inlet Swirl to Reduce Aerodynamic Loss and Surface Heat Transfer." Journal of Turbomachinery 125, no. 1 (2003): 48–56. http://dx.doi.org/10.1115/1.1518503.
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Computations, based on the ensemble-averaged compressible Navier-Stokes equations closed by the shear-stress transport (SST) turbulence model, were performed to investigate the effects of leading-edge airfoil fillet and inlet-swirl angle on the flow and heat transfer in a turbine-nozzle guide vane. Three fillet configurations were simulated: no fillet (baseline), a fillet whose thickness fades on the airfoil, and a fillet whose thickness fades on the endwall. For both fillets, the maximum height above the endwall is positioned along the stagnation zone/line on the airfoil under the condition of no swirl. For each configuration, three inlet swirls were investigated: no swirl (baseline) and two linearly varying swirl angle from one endwall to the other (+30 to −30 deg and −30 to +30 deg). Results obtained show that both leading-edge fillet and inlet swirl can reduce aerodynamic loss and surface heat transfer. For the conditions of this study, the difference in stagnation pressure from the nozzle’s inlet to its exit were reduced by more than 40% with swirl or with fillet without swirl. Surface heat transfer was reduced by more than 10% on the airfoil and by more than 30% on the endwalls. When there is swirl, leading-edge fillets became less effective in reducing aerodynamic loss and surface heat transfer, because the fillets were not optimized for swirl angles imposed. Since the intensity and size of the cross flow were found to increase instead of decrease by inlet swirl and by the type of fillet geometries investigated, the results of this study indicate that the mechanisms responsible for aerodynamic loss and surface heat transfer are more complex than just the intensity and the magnitude of the secondary flows. This study shows their location and interaction with the main flow to be more important, and this could be exploited for positive results.
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SINHA, SUPURNA. "ONSET OF SHEAR WAVES IN A BACTERIAL BATH: A NOVEL EFFECT." Fluctuation and Noise Letters 03, no. 04 (2003): L373—L377. http://dx.doi.org/10.1142/s0219477503001452.
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Recent experiments on particle diffusion in bacterial baths indicate the formation of correlated structures in the form of bacterial swirls. Here we predict that such a structural ordering would give rise to the new effect of propagating shear waves in a bacterial bath at length scales of the order of a swirl, which corresponds to time scales of the order of the lifetime of a swirl. Our prediction can be tested against future experiments in bacterial baths.
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Diabis, Farag A., Abd Rahim Abu Talib, Norkhairunnisa Mazlan, and Eris Elianddy Supeni. "Numerical Study on the Effect of Four-Lobe Swirl Generator and Its Transition Parts on Thermal Performance Enhancement and Fluid Flow." CFD Letters 17, no. 10 (2025): 120–48. https://doi.org/10.37934/cfdl.17.10.120148.
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Improving heat transfer in the field of thermal application is the targeted outcome of many researchers. The flow within smooth channels could not be mixed properly. Therefore, swirl flow techniques are taken into consideration because of their capability to promote the heat exchanger’s thermal efficiency by changing the flow's direction and creating a fluctuating flow between the channel's wall and core. The primary challenge that researchers frequently encounter with swirl flow techniques is the increased pressure loss. One of the most notable recent advancements is the lobed swirl generator, which achieves substantial swirl intensity with manageable pressure loss. Consequently, this study aims to explore and gain a deeper understanding of the thermal characteristics of the lobed swirl generator under various performance parameters. Consequently, the impact of a four-lobed swirl generator under a different twisted angle of (90 ≤ θ ≤ 450) and its transition part at essential parameters of transition multipliers (0.25 ≤ n ≤ 0.75) and variable helix (0.5 ≤ t ≤ 1.5) have been examined. The working fluid is water at the Reynolds number varies from 30,000 to 55,000 is conducted. The applicable shear-stress transport (SST) k-ω model has been adopted to model the turbulence swirling flow. According to the obtained results, the lobed swirl generator at (θ =360) and beta transition of (n = 0.5 mm) and (t =1 mm), the heat transfer and pressure loss increase compared with plain tube by 28.78 % and 17.35 %, respectively. By reducing the transition multipliers value to (n = 0.25 mm), a slight increase in heat transfer and pressure loss in the percentage by 40.32 % and 17.89 %, respectively are observed. The outcome demonstrated that lobed swirls could generate a centrifugal force under different conditions, which is the main significant character behind the heat transfer improvement.
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Rahmi, Khalifah Insan Nur, and Nur Febrianti. "Pemanfaatan Data Sentinel-2 untuk Analisis Indeks Area Terbakar (Burned Area)." Jurnal Penginderaan Jauh Indonesia 2, no. 1 (2022): 1–6. https://doi.org/10.12962/jpji.v2i1.260.
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Pemetaan area terbakar dapat diekstraksi dari citra penginderaan jauh menggunakan indeks area terbakar. Berbagai indeks telah dikembangkan untuk mengidentifikasi area terbakar antara lain dari NBR, NBR2, MIRBI, dan BAIS2. Penelitian ini bertujuan untuk mengetahui indeks yang paling baik membedakan area terbakar dan tidak terbakar skala detil. Area terbakar diidentifikasi dari delta indeks sebelum dan setelah kebakaran. Data yang dipergunakan adalah citra Sentinel-2 resolusi 20 meter sebelum kebakaran tanggal 01 Mei 2019, dan setelah kebakaran tanggal 08 September 2019. Indeks NBR menggunakan perkanalingan kanal SWIR dan NIR, indeks NBR2 dan MIRBI menggunakan perbandingan kanal SWIRL dan SWIRS, sementara indeks BAIS2 memainkan rentang spektral red edge, NIR dan SWIR. Hasil analisis indeks separabilitas menunjukan indeks MIRBI baik untuk membedakan area terbakar dengan lahan terbuka. Indeks NBR baik membedakan area terbakar dengan vegetasi dan lahan terbangun sementara indeks NBR2 baik untuk mebedakan area terbakar berasap dengan vegetasi dan lahan terbangun
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Sikh Ilham Nazmy, Zambri Harun, Zulkhairi Zainol Abidin, Mohd Izhar Ghazali, and Junaidy Ilyas. "Vortex Control Using Plate Type Floor Splitter in Pump Intake." Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 100, no. 1 (2022): 89–97. http://dx.doi.org/10.37934/arfmts.100.1.8997.
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Pump sump design is very crucial in ensuring a minimum requirement for its operation. Improper pump sump design will influence the development of vortices and swirls that can adversely affect the pump efficiency which subsequently could damage the pump. This can be mitigated by installing an anti-vortex device (AVD) beneath the intake pipe in the pump sump. The AVD works by suppressing the development of vortices and swirls in the flow of water into the intake pipe. ANSI/HI 9.8-2012 standard has outlined various AVD shapes and concepts that can be used. This experimental study was conducted to determine the appropriate parameters and configurations of twin plate floor splitter (TPFS) to suppress the development of vortex in the intake pipe. Geometries and other outlines in experiments were based on the guidelines by ANSI/HI 9.8-2012. The AVD model variations used were models with no floor splitter, single plate floor splitter (SPFS), and TPFS with 25 mm, 45 mm and 65 mm gap variations. The results showed that the distance between the two sides of twin plate affects the number of vortex generation and the swirl angle reduction. The number of vortices increased with the distance between the plates but with lower localized vortex intensity. However, the TPFS models that were used produced a swirl angle of less than 5° with the 25 mm variation producing the lowest swirl angle of 2.41°. The use of TPFS shows significantly improved performance in swirl angle reduction and vortex suppression as compared to no AVD case.
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Xie, Quan, Jiajia Liu, Chris J. Nelson, Robert Erdélyi, and Yuming Wang. "Photospheric Swirls in a Quiet-Sun Region." Astrophysical Journal 979, no. 1 (2025): 27. https://doi.org/10.3847/1538-4357/ad99d4.
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Abstract Swirl-shaped flow structures have been observed throughout the solar atmosphere, in both emission and absorption, at different altitudes and locations, and are believed to be associated with magnetic structures. However, the distribution patterns of such swirls, especially their spatial positions, remain unclear. Using the Automated Swirl Detection Algorithm, we identified swirls from the high-resolution photospheric observations, centered on Fe i 630.25 nm, of a quiet region near the Sun's central meridian by the Swedish 1-m Solar Telescope. Via a detailed study of the locations of the detected small-scale swirls with an average radius of ~300 km, we found that most of them are located in lanes between mesogranules (which have an average diameter of ~5.4 Mm) instead of the commonly believed intergranular lanes. The squared rotation, expansion/contraction and vector speeds, and proxy kinetic energy are all found to follow Gaussian distributions. Their rotation speed, expansion/contraction speed, and circulation are positively correlated with their radius. All these results suggest that photospheric swirls at different scales and locations across the observational 56 . ″ 5 × 57 . ″ 5 field of view could share the same triggering mechanism at preferred spatial and energy scales. A comparison with our previous work suggests that the number of photospheric swirls is positively correlated with the number of local magnetic concentrations, stressing again the close relation between swirls and local magnetic concentrations: the number of swirls should positively correlate with the number and strength of local magnetic concentrations.
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Wang, Hong Yuan, Yi Hua Xu, Xu Hu, and Zhuo Xiong Zeng. "Influence of Swirling Air on Ignition and Combustion Characteristics in Boron-Based Ducted Rocket." Applied Mechanics and Materials 684 (October 2014): 76–82. http://dx.doi.org/10.4028/www.scientific.net/amm.684.76.
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Three-dimensional two-phase flow in the typical double downside 90°afterburning chamber of boron based ducted rocket is numerically simulated by means of Realizable turbulence model, one-step eddy-dissipation combustion mode1 and the ignition and combustion mode of boron particles of KING with considering the film moving effect in the high-speed flow. The results show that co-swirl and counter-swirl air in the double side of inlet enters into afterburning chamber to make mixture of air and gas more fully and combustion efficiency increases with the increase of swirl number. Boron particles and total combustion efficiency with co-swirl is higher than counter-swirl when the swirl number is less than 0.179. On the contrary, the counter-swirl is higher than co-swirl when the swirl number greater than 0.385, the co-swirl is balance to the counter-swirl when the swirl number is about 0.2; the ignition time of boron particles is reduced with swirling air, its minimum can be attained when swirl number is 0.385.
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Benisek, Miroslav, Dejan Ilic, Djordje Cantrak, and Ivan Bozic. "Investigation of the turbulent swirl flows in a conical diffuser." Thermal Science 14, suppl. (2010): 141–54. http://dx.doi.org/10.2298/tsci100630026b.
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Results of the theoretical and experimental investigations of the turbulent mean swirl flows characteristics change along straight conical diffuser of incompressible fluid (air) are presented in this paper. The main swirl flow characteristics review is given. In addition: the specific swirl flow energy, the energy loss, the mean circulation, the swirl flow parameter, the ratio between the swirl and axial flow loss coefficients change along the diffuser are presented. Among other values: the Boussinesq number, outlet Coriolis coefficient and swirl flow loss coefficient dependences on inlet swirl flow parameter are also given. The swirl flow specific energy and outlet Coriolis coefficient calculation procedure are presented in this paper, as well as experimental test bed and measuring procedures. The swirl flow fields were induced by the axial fan impeller. Various swirl parameters were achieved by the impeller openings and rotational speeds.
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Domingue, Deborah, John Weirich, Frank Chuang, et al. "Spectrophotometric and Topographic Correlations within the Mare Ingenii Swirl Region: Evidence for a Highly Mobile Lunar Regolith." Planetary Science Journal 4, no. 12 (2023): 240. http://dx.doi.org/10.3847/psj/ace433.
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Abstract The spectrophotometric properties of two study areas in the Ingenii swirl region show that the combined effects of multiple processes are required to explain the regolith’s mineralogical and physical properties. Production of the swirl regions requires mobilization of the regolith in addition to preferential radiation shielding of subareas. The discovery of topographic correlations between on- and off-swirl (dark lanes) clearly shows that the on-swirl regions are statistically lower than the off-swirl dark lanes by 2–3 m. Photometric analyses show no microscale roughness differences between on- and off-swirl, suggesting no differences in the regolith’s fairy-castle structure between the two swirl regions. The photometric properties of one of the study areas suggest that off-swirl dark lanes may have a more complicated grain structure than on-swirl areas. Enhanced abundances of plagioclase are observed on-swirl in both study areas. Enhanced abundances of FeO and orthopyroxene are observed off-swirl in both areas. No variations in olivine or clinopyroxene abundance were observed for either study area. The discovery of topographic correlations coupled with the similarities in structural properties provides new constraints on the types of processes acting on lunar swirl surfaces.
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Sun, Yanzhe, Tianyou Wang, Ming Wen, Yufeng Li, Fuquan Tian, and Zhen Lu. "Prediction of the in-piston-bowl swirl ratio of diesel engines." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 233, no. 10 (2018): 2381–89. http://dx.doi.org/10.1177/0954407018781616.
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Steady flow tests are widely used to evaluate the performance of intake ports in generating swirl flow in diesel engines. Such test data, however, may deviate largely from the real in-piston-bowl swirl ratio due to the complex unsteady air motion in the compression stroke. In this study, a new method is proposed to predict the unsteady in-piston-bowl swirl ratio of diesel engines from steady flow test data by focusing on three key steps, including the swirl field at intake valve close timing, swirl enhancement due to squish flow, and swirl decay during the compression stroke. Experimental results on an optically accessible diesel engine under non-firing conditions show that, at intake valve close, the relationship between the swirl ratio and the vertical location was approximately linear and the mean swirl ratio could be fitted by a Bessel function; the correlation between the swirl decay coefficient and surface-to-volume ratio was built by fitting the experiment data. Furthermore, the in-piston-bowl swirl ratio during the compression stroke could then be derived according to the conservation of angular momentum.
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Xin, Xi, De Xin Liu, Liu Qing Wang, and Li Wang. "Influence of Variable Swirl Intake Manifolds for DI Diesel Engine on in-Cylinder Air Motion." Applied Mechanics and Materials 130-134 (October 2011): 95–98. http://dx.doi.org/10.4028/www.scientific.net/amm.130-134.95.
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This paper developed a new design of variable swirl intake manifolds for four-valve DI diesel engine by setting swirl control valves in the intake manifolds. The 3-D numerical model under the same experimental condition was established and particular flow information in intake manifolds and cylinder was achieved. Influence of variable swirl intake manifolds on intake flow characteristics and in-cylinder swirl characteristics were analyzed. The simulation results show that the swirl intensity in cylinder can be tuned by this device. The swirl intensity increases gradually with decrease flow coefficient and it can meet the requirements of swirl intensity for different operating conditions.
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Pazur, W., and L. Fottner. "The Influence of Inlet Swirl Distortions on the Performance of a Jet Propulsion Two-Stage Axial Compressor." Journal of Turbomachinery 113, no. 2 (1991): 233–40. http://dx.doi.org/10.1115/1.2929091.
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Aeroengine intakes containing S-shaped diffusers produce different types of inlet swirl distortions and essentially a combination of a twin swirl and a bulk swirl. The main object of this investigation was to assess the influence of inlet swirl distortions on the performance of a transonic two-stage axial compressor installed in a turbo jet bypass engine Larzac 04. A typical inlet swirl distortion was simulated by a delta-wing in front of the engine. An experimental method was investigated to measure the performance map of the installed low-pressure compressor for different engine operating lines. The influence of an inlet swirl distortion with different strengths on the performance map of the compressor was investigated experimentally. It is shown that the performance parameters decrease and a temperature distortion is generated behind the compressor. As the basis of the theoretical investigations of the performance map, including inlet swirl distortions, a computing model considering four compressors working in parallel was established. The model is based on the idea that an inlet swirl distortion can be substituted by two fundamental types of swirl components, i.e., a bulk swirl corotating, and a bulk swirl counterrotating to the revolution of the compressor. Computed performance maps of the compressor will be discussed and compared with the experimental data.
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Xu, Qijun, Jinfeng Wang, and Jing Xie. "3D Numerical Simulation and Performance Analysis of CO2 Vortex Tubes." Applied Sciences 11, no. 20 (2021): 9386. http://dx.doi.org/10.3390/app11209386.
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In view of the extensive application of swirl flow pipes (vortex tubes) in refrigeration systems, the parameters of swirl flow pipes were investigated to provide optimal cooling and heating conditions. Three-dimensional numerical simulations were carried out using available experimental data and models. The analysis verified that the heat pipe with a length of 175 mm performed better than the swirl flow pipe with a length of 125 mm, confirming experiments by Agrawal. Meanwhile, by comparing different pressures, it was found that in the single-nozzle swirl flow pipe, the greater the increase of pressure (0.1–1.0 MPa), the greater the burden on the vortex chamber and the more serious the wear is, which can be seen in the higher inlet pressure. In order to improve the durability of the swirl flow pipe, we suggest using a swirl flow pipe with more nozzles. Finally, according to the simulation results, with the rise of carbon dioxide pressure potential energy at the inlet, the cooling effect of the swirl flow is first increasing and then decreasing. When the swirl flow pipe is used as a refrigeration device to determine the minimum cooling temperature under the maximum pressure, the lowest temperature of the 125 mm swirl flow pipe was 252.4 K at 0.8 MPa, while the lowest temperature of the 175 mm swirl flow pipe was 246.0 K. Secondly, the distance from the inlet to the hot outlet of the swirl flow pipe had little effect on the cooling temperature and radial velocity, but increasing its distance increased the wall temperature of the swirl flow pipe because it increases the contact time between the airflow and the hot end of the tube wall. When the swirl flow pipe is used as a heat-producing device, increasing the tube length of the swirl flow pipe appropriately increases its maximum heat-producing temperature.
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Tu, Baofeng, Luyao Zhang, and Jun Hu. "Effect of swirl on the performance and stability of transonic axial compressor." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 232, no. 6 (2017): 608–21. http://dx.doi.org/10.1177/0957650917742320.
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To investigate the effect of twin swirl and bulk swirl on the performance and stability of a transonic axial compressor, a blade swirl generator was designed and simulated with a transonic single rotor using steady and unsteady numerical calculation methods. The bulk swirl intensity was adjusted by replacing the blades with different camber angles. The twin swirl intensity was decreased by reducing the blade number. The counter-rotating bulk swirl generated a significant drop in both the efficiency and stall margin, and resulted in an increase in the choked mass flow, and total pressure ratio. The co-rotating bulk swirl generated a decrease in the mass flow, total pressure ratio and stable operating range. The counter-rotating bulk swirl resulted in suction surface boundary layer separation beyond 50% of the span-wise height as well as more serious tip leakage blockage. The twin swirl resulted in a decrease in the total pressure ratio, maximum efficiency and stable operating range. The steady and unsteady numerical calculation results were consistent, though some differences were observed in the values. For the steady calculation, the maximum efficiency and choked mass flow decreased by 0.88% and 1.74%, respectively, and the mass flow at the stable boundary increased by 3.92% as compared to the uniform inlet flow at twin swirl intensity of 24°. During the unsteady calculation, the mass flow exhibited an increase of only 2.2% at the stable boundary. Under twin swirl and co-rotating bulk swirl and uniform inlet flow, the leading edge spillage of the tip leakage flow resulted in compressor instability. The counter-rotating bulk swirl changed the mechanism of instability. The characterisation of the swirl distortion presented a difference between the steady and unsteady calculations near the stable boundary. The unsteady calculation exhibited a lower mass flow at the stable boundary point and a higher total pressure ratio.
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Khan, Md Tanvir, Sharif M. Islam, and Zahir U. Ahmed. "Near-wall and Turbulence Behavior of Swirl Flows through an Aerodynamic Nozzle." Journal of Engineering Advancements 01, no. 02 (2020): 43–52. http://dx.doi.org/10.38032/jea.2020.02.003.
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It is often a challenge to achieve uniform flow in turbulent swirl flow and to predict the flow within the nozzle as measurement diagnostics face difficulty to capture both mean flow and turbulence. The purpose of this study is to numerically investigate the near wall flow characteristics and turbulent behavior for the effect of different tangential inlet numbers of an incompressible turbulent swirl air jet. In this regard, axial-plus-tangential flow based swirling nozzle is considered for the simulation using finite volume method, where turbulence is approximated by the Shear Stress Transport (SST) k-ω model. The results show that axial and tangential velocity at the wall vicinity response the most. Moreover, the turbulent flow characteristic for no swirl flow is nearly uniform, but for swirl flow it fluctuates abruptly near the inlet section where the swirl has introduced. The skin friction coefficient for 2TP is the maximum for swirl flow and for no swirl condition the skin friction coefficient is nearly uniform. Due to the swirl introduction the pressure drop characteristics near the nozzle center response quickly and near the wall vicinity this property changes slowly. The magnitude of swirl decay fluctuates before the nozzle converging section however after the nozzle converging section the swirl decay is nearly constant. The local swirl near the inlet is highly unpredictable although after the nozzle converging section the local swirl profile is nearly similar for 2TP, 3TP and 4TP.
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Wang, Xi, Peng Han, and Kun Liu. "Effect of multi-angle parameter on fluid flow characteristics of swirl-type oxygen lance." Metallurgical Research & Technology 119, no. 3 (2022): 314. http://dx.doi.org/10.1051/metal/2022029.
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The supersonic jet characteristics of the oxygen lance nozzle play an important role in converter melting. In this study, the jet characteristics of swirl-type oxygen lance were investigated by numerical simulation. The velocity field, jet coalescence behavior and jet impact cavity area of swirl-type oxygen lance with different inclination and swirl angles were analyzed. The results demonstrate that compared with the traditional oxygen lance, the swirl angle accelerates the attenuation of the jet. However, the tangential velocity of jet is conducive to the rapid melting of the slag in the steelmaking process. With the increase of swirl angle and inclination angle, the velocity of jet decreases, the temperature of jet increases and the independence between jets is improved. With the increase of the swirl angle, the tangential velocity of the swirl-type oxygen lance increases, but the possibility of slag adhering to the nozzle surface increases. The effective impact area varies non-monotonically with the swirl angle. The optimum inclination and swirl angle of the swirl-type oxygen lance for a 260 t converter are 15° and 10° respectively. When the oxygen flow rate increases, the decay of jet velocity decreases and the effective impact area increases.
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Domingue, Deborah, John Weirich, Frank Chuang, et al. "Photometric Properties within the Reiner Gamma Swirl: Constraining Formation Mechanisms." Planetary Science Journal 5, no. 7 (2024): 161. http://dx.doi.org/10.3847/psj/ad2179.
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Abstract The area in the Reiner Gamma swirl studied by Weirich et al. for topographic correlations also displays correlations with the Hapke-model-derived single-scattering albedo, surface roughness, and particle scattering properties with swirl unit. The correlations with single-scattering albedo associate compositional variations in plagioclase and FeO content with swirl unit. The correlations with photometric surface roughness show a rougher surface on-swirl, implying a potentially more porous surface on-swirl compared to off-swirl. This suggests the variations in single-scattering albedo are dominated by the compositional differences and not structural differences, such as compaction. Grain-size differences could still contribute to the albedo variations. Differences in particle scattering properties between on-swirl and off-swirl are counter-indicative of the trend expected from variations in space weathering, unless there is a process to initiate either size sorting or compositional differences. The photometric properties point to a complex interaction of multiple processes to form the swirl units, not a singular dominant process. Variations in weathering, dust mobilization and entrapment, and impact modification may all play a key role.
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Bhatia, Anmol, Kushaljit S. Sodhi, Akshay K. Saxena, and Niranjan Khandelwal. "Anticlockwise Swirl." Journal of Pediatric Gastroenterology and Nutrition 60, no. 3 (2015): e25. http://dx.doi.org/10.1097/mpg.0000000000000644.
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Jamal, Mohammad, Olivier Court, and Jeffrey Barkun. "Swirl Sign." Journal of the American College of Surgeons 209, no. 6 (2009): 789. http://dx.doi.org/10.1016/j.jamcollsurg.2009.05.031.
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Hjertager, B. H. "Swirl flows." International Journal of Heat and Mass Transfer 28, no. 5 (1985): 1055. http://dx.doi.org/10.1016/0017-9310(85)90288-1.
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Faeth, G. M. "Swirl flows." Combustion and Flame 63, no. 1-2 (1986): 311. http://dx.doi.org/10.1016/0010-2180(86)90133-1.
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Balakrishnan, P., and K. Srinivasan. "Pipe jet noise reduction using co-axial swirl pipe." Aeronautical Journal 121, no. 1238 (2017): 488–514. http://dx.doi.org/10.1017/aer.2017.5.
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ABSTRACTThe present experimental work highlights the acoustic far field and flow field characteristics of confined co-axial swirling pipe jets. Co-axial confinements with six vanes at angles of 0°, 20° and 40° are considered here. Two pipe lengths of L/D=0.5 and 2 are studied. The Mach numbers studied range from 0.85 to 1.83. An increase in the pipe length causes suppression of the transonic tones in non-swirl pipe jets. Swirl reduces the low frequency noise components and increases the high-frequency components compared to non-swirl jet. The broadband shock associated noise is mitigated by the swirl pipe jets. However, the screech tone is completely eliminated by the swirl pipe jets. Further, swirl pipe jets radiate low levels of noise at all the emission angles compared to non-swirl pipe jets, for both the pipe length cases at supersonic Mach numbers. Increase in the pipe length enhances the shock associated noise and OASPL for the non-swirl pipe jet. Centreline pitot survey and schlieren visualisation show a reduction in core length, reduction in the number of shock cells, weakening/destruction of the shock cells by the swirl pipe jets compared to the non-swirl pipe jets.
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Jebamani, Rathnaraj, and Narendra Kumar. "Studies on variable swirl intake system for DI diesel engine using computational fluid dynamics." Thermal Science 12, no. 1 (2008): 25–32. http://dx.doi.org/10.2298/tsci0801025j.
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It is known that a helical port is more effective than a tangential port to attain the required swirl ratio with minimum sacrifice in the volumetric efficiency. The swirl port is designed for lesser swirl ratio to reduce emissions at higher speeds. But this condition increases the air fuel mixing time and particulate smoke emissions at lower speeds. Optimum swirl ratio is necessary according to the engine operating condition for optimum combustion and emission reduction. Hence the engine needs variable swirl to enhance the combustion in the cylinder according to its operating conditions, for example at partial load or low speed condition it requires stronger swirl, while the air quantity is more important than the swirl under very high speed or full load and maximum torque conditions. The swirl and charging quantity can easily trade off and can be controlled by the opening of the valve. Hence in this study the steady flow rig experiment is used to evaluate the swirl of a helical intake port design for different operating conditions. The variable swirl plate set up of the W06DTIE2 engine is used to experimentally study the swirl variation for different openings of the valve. The sliding of the swirl plate results in the variation of the area of inlet port entry. Therefore in this study a swirl optimized combustion system varying according to the operating conditions by a variable swirl plate mechanism is studied experimentally and compared with the computational fluid dynamics predictions. In this study the fluent computational fluid dynamics code has been used to evaluate the flow in the port-cylinder system of a DI diesel engine in a steady flow rig. The computational grid is generated directly from 3-D CAD data and in cylinder flow simulations, with inflow boundary conditions from experimental measurements, are made using the fluent computational fluid dynamics code. The results are in very good agreement with experimental results.
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Lee, K.-H., T. Setoguchi, S. Matsuo, and H.-D. Kim. "An experimental study of underexpanded sonic, coaxial, swirl jets." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 218, no. 1 (2004): 93–103. http://dx.doi.org/10.1243/095440604322786974.
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The present study addresses experimental investigations of the near-field flow structures of an underexpanded sonic, dual, coaxial, swirl jet. The swirl stream is discharged from the secondary annular nozzle and the primary inner nozzle provides the underexpanded free jets. The interactions between the secondary swirl and primary underexpanded jets are quantified by a fine pitot impact and static pressure measurements and are visualized using a shadowgraph optical method. The pressure ratios of the secondary swirl and primary underexpanded jets are varied below 7.0. Experiments are conducted to investigate the effects of the secondary swirl stream on the primary underexpanded jets, compared with the secondary stream of no swirl. The results show that the presence of an annular swirl stream causes the Mach disc to move further downstream, with an increased diameter, and remarkably reduces the fluctuations of the impact pressures in the underexpanded sonic dual coaxial jet, compared with the case of the secondary annular stream with no swirl.
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Wang, Xuegao, Jun Hu, Jin Guo, Baofeng Tu, and Zhiqiang Wang. "An experimental investigation on the interaction between inlet swirl distortion and a low-speed axial compressor." Science Progress 103, no. 3 (2020): 003685042094092. http://dx.doi.org/10.1177/0036850420940920.
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The aim of this article mainly lies in two aspects. The first is to investigate the effect of inlet swirl distortion on the performance and stability of a low-speed compressor experimentally. The second is to quantify swirl pattern revolution through the compressor and find out background causes of the change in compressor performance. Swirl distortion makes the leading-edge incidence opposite between tip and hub regions, compared to that of clean flow. And the compressor performance change is ultimately determined by these two aspects. Results indicate that negative bulk swirl improves pressure rise, and the effect is on the contrary to the positive bulk swirl. Under the condition of paired swirl, pressure rise also presents a reduction. All these three types of swirl have little effect on the stall boundary. Although swirl distortion shows clear recovery at rotor exit, downstream components still work at off-design conditions due to the induced nonuniformity in axial velocity and total pressure.
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Liu, Yin Li, and Hao Tang. "Numerical Study on the Interaction Mechanism between Swirl and Reverse Flow Rate in a Twin Swirl Combustor." Advanced Materials Research 960-961 (June 2014): 341–48. http://dx.doi.org/10.4028/www.scientific.net/amr.960-961.341.
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An isothermal flow in a Twin Swirl Combustor (TSC) was simulated with the Renormalized Group (RNG) k-ε turbulence model. The swirling and recirculation intensity was studied under different structures and inlet conditions. The results confirmed that there was a significant negative correlation between the trend lines of the swirl number (S) and reversed flow rate (Xr). The gradient of reversed flow rate was larger in the front and middle parts of the combustor than that of swirl number. The end-surface-inlet structure had a better swirl and recirculation enhancement effect. With the end-surface-inlet structure, the internal swirl and reverse intensity could be flexibly adjusted by switching the swirl intensity of the primary air. Under the structure of staggered-inlet, there was a critical distance between primary and secondary air inlets. When exceeded, it would be more difficult to enhance the swirl and reverse flow effect by increasing the swirl intensity of the secondary air.
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Li, Jing, Guo Chang Zhao, Li Ping Song, and Lei Cao. "Influence of De-Swirl Angle on the Flow and Heat Transfer in Rotor-Stator Cavity System." Applied Mechanics and Materials 733 (February 2015): 544–47. http://dx.doi.org/10.4028/www.scientific.net/amm.733.544.
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Numerical simulations are used to investigate the influence of different de-swirl angles on the flow and heat transfer in rotor-stator cavity system The results show that: de-swirl angle has great influence on the swirl number; radial velocity increases with the increase of de-swirl angle; the smaller de-swirl angle is, the more smooth radial velocity distributes; it is favorable for disc flow and heat transfer when θ=45°.
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Fan, Yu, De Xin Liu, and Li Wang. "3D Numerical Simulation on the Variable Swirl Intake Process of Diesel Engine." Applied Mechanics and Materials 273 (January 2013): 143–47. http://dx.doi.org/10.4028/www.scientific.net/amm.273.143.
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To study the flow and swirl characteristics in the variable swirl intake system of a four-valve diesel engine, a numerical simulation with using the three dimensional CFD software AVL-FIRE, was calculated on the intake flow in three types of inlet of the engine. Two swirl-control valve plans are posed and a better plan was selected through the comparative study. The result shows that with a lager valve lift the flow characteristic of spiral inlet is better than that of tangential inlet, and in the opposite case the results are also opposite. The double inlets make the swirl torque increase. When a swirl-control valve is set in the spiral inlet, the variable swirl effect is better, and it ensures better flow capacity and larger swirl ratio range.
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Nielsen, K. K., D. W. Childs, and C. M. Myllerup. "Experimental and Theoretical Comparison of Two Swirl Brake Designs." Journal of Turbomachinery 123, no. 2 (2000): 353–58. http://dx.doi.org/10.1115/1.1354140.
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Experimental and theoretical data are presented for two interchangeable swirl brakes designed in connection with the Space Shuttle Main Engine (SSME) Alternate Turbopump Development (ATD) High-Pressure Fuel Turbopump (HPFTP) program. The experimental data includes rotordynamic data for a extensive variation of test variables. Comparison of the swirl brake performance revealed that a nonaerodynamic swirl brake design proved as efficient and at times better than an aerodynamic design. For this reason a theoretical investigation using computational fluid dynamics (CFD) was recently carried out. This modeling focused on predicting the seal inlet swirl ratio which is the primary swirl brake performance parameter. The nonaerodynamic swirl brake showed superior performance for a variety of test variable conditions. Strong separation vortices within the swirl vanes are the main reason for this finding.
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Kamaruddin, Salahuddin, Anusha Apparau, Norlisah Ramli, Kartini Rahmat, Jeannie Hsiu Ding Wong, and Khairul Azmi Abd Kadir. "CT swirl sign in primary intracerebral haemorrhage and association with haematoma expansion." Neurology Asia 29, no. 4 (2024): 963–71. https://doi.org/10.54029/2024mrp.
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Background & Objective: Haematoma expansion is an important predictor of poor clinical outcomes for primary acute intracerebral haemorrhage (ICH). Swirl sign is described as an area which is hypodense or isodense surrounded by hyperdense acute haemorrhage. This study aimed to describe swirl sign in ICH, its prevalence and to determine if the presence of swirl sign, swirl volume and the ratio of swirl to initial haematoma volume are associated with haematoma expansion and to predict clinical outcome in ICH. Methods: One hundred and sixty-three patients who had spontaneous ICH with initial (CT1) and repeat CT (CT2) within 96 hours were included. Presence of swirl sign, its volume and the ratio of swirl volume over haematoma volume in initial and repeat CT were calculated using semi auto-segmentation from ‘ITK snap’. Statistical analysis using Spearman’s correlation coefficient and chi-square test were done to assess the relationship between the data parameters with haematoma expansion as well as functional outcome and mortality at 1 month. Results: Chi-square test showed a significant association between the presence of swirl sign with the haematoma expansion (p < 0.001) and mRS score at 1 month (p < 0.05). Spearman correlation showed a significant moderate correlation between swirl sign and volume of haematoma expansion (r = 0.518, p < 0.001). Ratio of swirl volume/initial haematoma volume demonstrated low correlation but however significant with haematoma expansion (r=0.28 p < 0.05). Conclusion: Swirl sign, its volume as well as the ratio of swirl volume over initial haematoma are associated with haematoma expansion. It can be used as a predictor of mortality and functional outcome at one month.
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Joo, S. H., K. M. Chun, Y. Shin, and K. C. Lee. "An Investigation of Flame Expansion Speed With a Strong Swirl Motion Using High-Speed Visualization." Journal of Engineering for Gas Turbines and Power 125, no. 2 (2003): 485–93. http://dx.doi.org/10.1115/1.1564067.
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In this study, a simple linear supposition method is proposed to separate the flame expansion speed and swirl motion of a flame propagating in an engine cylinder. Two series of images of flames propagating in the cylinder with/without swirl motion were taken by a high frame rate digital video camera. A small tube (4 mm ID) was installed inside the intake port to deliver the fuel/air mixture with strong swirl motion into the cylinder. An LDV was employed to measure the swirl motion during the compression stroke. Under the assumption that flame propagates spherically from the each point of the flame front, a diameter of small spherical flames can be calculated from the two consecutive images of the flame without swirl motion in the cylinder. Using the normalized swirl motion of the mixture during the compression stroke and the spherical flame diameters, the flame expansion speed and swirl ratio of combustion propagation in the engine cylinder can be obtained. This simple linear superposition method for separating the flame expansion speed and swirl motion can be utilized to understand the flow characteristics, such as swirl and turbulence, during the combustion process.
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Hsu, Yun, and Christopher E. Brennen. "Effect of Swirl on Rotordynamic Forces Caused by Front Shroud Pump Leakage." Journal of Fluids Engineering 124, no. 4 (2002): 1005–10. http://dx.doi.org/10.1115/1.1511164.
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Unsteady forces generated by fluid flow through the impeller shroud leakage path of a centrifugal pump were investigated. The effect of leakage path inlet swirl (pump discharge swirl) on the rotordynamic forces was re-examined. It was observed that increasing the inlet swirl is destabilizing both for normal and tangential rotordynamic forces. Attempts to reduce the swirl within the leakage path using ribs and grooves as swirl brakes showed benefits only at low leakage flow rate.
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Yu, Jie, Xiong Chen, and Hong Wen Li. "Numerical Simulation of Cold Swirl Field for Solid Fuel Ramjet with NACA Airfoil." Applied Mechanics and Materials 716-717 (December 2014): 711–16. http://dx.doi.org/10.4028/www.scientific.net/amm.716-717.711.
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In order to study the swirl flow characteristics in the solid fuel ramjet chamber, a new type of annular vane swirler with NACA airfoil is designed. The cold swirl flow field in the chamber is numerically simulated with different camber and t attack angle, while the swirl number , swirl flow field structure, total pressure recovery coefficient were studied. According to numerical simulation result, the main factors in swirl number are camber and angle of attack, the greater angle of attack, the greater the camber ,the stronger swirl will be. Results show that the total pressure loss is mainly concentrated in the inlet section, the total pressure loss cause by vane swirler is small. Radial velocity gradient exists in swirling flow, and increases with the swirl number. With the influence of centrifugal force and combustion chamber structure, the radial velocity gradient increases.
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Pati, Sukumar, and Vishwanath Kumar. "Effects of temperature-dependent thermo-physical properties on hydrodynamic swirl decay in microtubes." Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering 233, no. 3 (2018): 427–35. http://dx.doi.org/10.1177/0954408918755782.
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In this paper, the influence of temperature-dependent thermo-physical properties is investigated on the decay of swirl in a laminar swirling flow of liquid through a heated microtube. The conservation equations for mass, momentum, and energy are numerically solved to obtain the velocity and temperature fields. The decay of swirl is quantified by the variation of the ratio of swirl number at a section to that at the inlet ( S/ S0) along the flow. The results reveal that constant property simulations result in faster swirl decay as compared to the variable-property simulations. Further, the implications of slip length, inlet swirl number, inlet swirl velocity profile, and Reynolds number on the swirl decay are presented. The results of the present analysis bear significant technological consequences in the design of micro-heat exchangers with intrinsic rotationalities.
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Wang, Y., W. Xu, H. Yin, Y. Zhang, and H. S. Dou. "Numerical study on the influence of pre-swirl angle on internal flow characteristics of centrifugal pumps." AIP Advances 12, no. 4 (2022): 045019. http://dx.doi.org/10.1063/5.0085903.
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The effect of inlet pre-swirl on the performance of a centrifugal pump is studied by numerical simulation. The governing equations are Navier–Stokes equations and the shear stress transport k–ω turbulence model. The numerical results show that the optimal operating point moves from the low flow region to the high flow region as the pre-swirl angle shifts from positive to negative. It is found by contours of Omega–Liutex that the positive pre-swirl angle is able to weaken the vortex on the blade suction and reduce the energy dissipation. On both the 0.5Q0 and 1.2Q0 operating conditions, the proportion of entropy production loss in the impeller and volute is about 60% and 30%, respectively. As the pre-swirl angle changes from negative to positive, the entropy production loss in the inlet and outlet pipes increases slowly, and the entropy production loss in the volute and impeller shows a decreasing trend and the peak area of entropy loss moves toward the outlet. Under the four pre-swirl angles, the main frequency is always the passing frequency of the blade. The pre-swirl angle affects the pressure fluctuation at the main frequency but has little effect at the secondary frequency. The change in velocity pulsation amplitude in the impeller in the positive pre-swirl angle is smaller than that in the negative pre-swirl angle. As a result, for the positive pre-swirl angle, the turbulent kinetic energy density in the impeller is low, and the energy loss is low, compared with negative pre-swirl. Under the low flow condition (0.5Q0), the change in velocity pulsation amplitude in the inertial range of the energy spectrum under negative pre-swirl is greater than that under positive pre-swirl.
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Fu, Jun, Yuan Tang, Wen Hua Yuan, Yi Ma, Wei Chen, and Guang Ming Li. "Research on the Angle of Swirl Chamber Diesel Engine with Dual Channel." Applied Mechanics and Materials 635-637 (September 2014): 598–602. http://dx.doi.org/10.4028/www.scientific.net/amm.635-637.598.
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Swirl chamber diesel engine’s insert piece of channel performance has a great influence on the swirl chamber indoor airflow movement condition. So based on the 175F series bell flat bottom type swirl chamber’s single connection channel improvement, the influence law of swirl chamber indoor air movement during the injection time by the double connection channel angle at the engine rated speed 2600r/min was studied. Simplified boundary conditions to establish its mathematical solution model for the swirl chamber, then the fluid simulation software was used to research the original scheme and double channel with angle of 50 ° and 30 °, 40 °, 60 ° schemes’ swirl chamber indoor air movement. Results show that the angle of 40 ° dual channel form, the loss of the throttle was reduced, and the swirl chamber air velocity increases obviously, the swirl chamber air velocity in injection time up to 125 m/s,which not only increased indoor vortexes energy but also contribute to oil and gas preferably blended, and near the nozzle the temperature lower 20 °C than the original machine, effectively reducing the nozzle heat load.
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Uy, Robert V., and Christopher E. Brennen. "Experimental Measurements of Rotordynamic Forces Caused by Front Shroud Pump Leakage." Journal of Fluids Engineering 121, no. 3 (1999): 633–37. http://dx.doi.org/10.1115/1.2823516.
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Unsteady forces generated by fluid flow through the impeller shroud leakage path of a centrifugal pump were investigated. Different pump shroud geometries were compared, and the effect of leakage path inlet swirl (pump discharge swirl) on the rotordynamic forces was examined for various ratios of fluid throughflow velocity to impeller tip speed. A short axial length leakage path reduced the measured forces, while curvature appeared to increase the destabilizing forces when inlet swirl was present. It was observed that changing the inlet swirl velocity does not appear to significantly affect the measured forces for a given leakage flow coefficient, but any nonzero inlet swirl is destabilizing when compared to cases with no inlet swirl.
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Whitfield, A., and A. H. Abdullah. "The Performance of a Centrifugal Compressor With High Inlet Prewhirl." Journal of Turbomachinery 120, no. 3 (1998): 487–93. http://dx.doi.org/10.1115/1.2841744.
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The performance requirements of centrifugal compressors usually include a broad operating range between surge and choke. This becomes increasingly difficult to achieve as increased pressure ratio is demanded. In order to suppress the tendency to surge and extend the operating range at low flow rates, inlet swirl is often considered through the application of inlet guide vanes. To generate high inlet swirl angles efficiently, an inlet volute has been applied as the swirl generator, and a variable geometry design developed in order to provide zero swirl. The variable geometry approach can be applied to increase the swirl progressively or to switch rapidly from zero swirl to maximum swirl. The variable geometry volute and the swirl conditions generated are described. The performance of a small centrifugal compressor is presented for a wide range of inlet swirl angles. In addition to the basic performance characteristics of the compressor, the onsets of flow reversals at impeller inlet are presented, together with the development of pressure pulsations, in the inlet and discharge ducts, through to full surge. The flow rate at which surge occurred was shown, by the shift of the peak pressure condition and by the measurement of the pressure pulsations, to be reduced by over 40 percent.
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Zhang, Shiqiang, Chunshu Li, Ruilin Liu, Jingyang Bao, and Miao Chi. "Effects of the variable valve lift difference on in-cylinder gas flow in a four-valve gasoline engine." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 233, no. 7 (2018): 1806–17. http://dx.doi.org/10.1177/0954407018789321.
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The in-cylinder gas flow is an important factor that affects the engine performance. The appropriate swirl can reduce cycle-to-cycle variations, increase flame propagation speed, and improve the combustion efficiency. Many technologies can induce significant swirl, but lead to intake flow loss. In this research work, the variable valve lift difference adjustment mechanism is developed to obtain and adjust in-cylinder swirl without weakening flow capacity in a four-valve gasoline engine. The in-cylinder swirl and tumble characteristics generated by the variable valve lift difference adjustment mechanism are studied by means of experiment and simulation. The results of the experiment and simulation show the intensity of tumble and swirl under the larger lift valve is increased with the increase in the phase difference between two intake cams at same camshaft angle, and a large-scale swirl is formed in the cylinder when the camshaft angles change from 40° to 80°, and another large scale swirl is formed during the camshaft angles change from 100° to 140°, but the rotating direction of the secondary swirl is inverse to that of first swirl. The scale and shape of the in-cylinder tumble and swirl are not changed significantly with the increase in the phase difference between two intake cams when the camshaft angles change from 80° to 100°. A brief discussion on the research results that improve the performance of actual gasoline engine is given.
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Gupta, A. K., M. J. Lewis, and M. Daurer. "Swirl Effects on Combustion Characteristics of Premixed Flames." Journal of Engineering for Gas Turbines and Power 123, no. 3 (2000): 619–26. http://dx.doi.org/10.1115/1.1339987.
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The effect of radial distribution of swirl has been examined on the thermal behavior of two different premixed flames using a double concentric premixed swirl burner. The double concentric swirl burner allowed systematic variation in the radial distribution of swirl (both co- and counter-) between the inner and outer annulus of the burner. The burner had two annular jets and a central nozzle. Information on the thermal field in two flames formed by co- or counter-swirl in the outer annulus and co-swirl in the inner annulus has been examined. Specifically mean and fluctuating temperatures, integral and micro thermal time scales, and probability density distribution of temperatures have been determined at various spatial positions in the flames. The micro-thermocouple output was compensated to provide high-frequency (about 1 kHz) response of the thermocouple. Direct flame photographs were taken to provide information about the global features of flames and flame stability. The global and thermal characteristic data presented here provided a complete insight on the thermal behavior of co- and counter-swirl flames. The results show that the direction of swirl (co- or counter-) used to stabilize a flame from annular jets provides a great influence on flame symmetry. The simultaneous combination of co- and counter-swirl in the burner showed a very nonsymmetrical behavior of the flame. The global and thermal data presented here confirmed these findings. The results suggest significant effect of co- and counter-swirl distribution in flames on the NOx emission levels.
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Ojaghloo, Mostafa, and Jonathan W. Naughton. "Impact of Swirl on the Round Wake." Journal of Physics: Conference Series 3016, no. 1 (2025): 012010. https://doi.org/10.1088/1742-6596/3016/1/012010.
Full textAbstract:
Abstract The influence of swirl on axisymmetric wakes is a critical area of study, with significant implications for both practical applications, such as wind turbine wakes, and fundamental fluid dynamics research, where even small changes in the mean flow can lead to substantial alterations in turbulence characteristics. Despite its importance, this topic has received limited attention in the literature. This study examines the influence of swirl on the downstream development of a controlled, rotationally symmetric wake. The wake was generated using a rotating porous disk mounted in a wind tunnel, and the flow field was measured using stereoscopic PIV across various swirl strengths. The results suggest that swirl begins to influence the wake at swirl numbers around 0.07, with its effects saturating at swirl numbers exceeding 0.2.