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1
Falcioni, Renan, Glaucio Leboso Alemparte Abrantes dos Santos, Luis Guilherme Teixeira Crusiol, Werner Camargos Antunes, Marcelo Luiz Chicati, Roney Berti de Oliveira, José A. M. Demattê, and Marcos Rafael Nanni. "Non−Invasive Assessment, Classification, and Prediction of Biophysical Parameters Using Reflectance Hyperspectroscopy." Plants 12, no. 13 (July 2, 2023): 2526. http://dx.doi.org/10.3390/plants12132526.
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Hyperspectral technology offers significant potential for non-invasive monitoring and prediction of morphological parameters in plants. In this study, UV−VIS−NIR−SWIR reflectance hyperspectral data were collected from Nicotiana tabacum L. plants using a spectroradiometer. These plants were grown under different light and gibberellic acid (GA3) concentrations. Through spectroscopy and multivariate analyses, key growth parameters, such as height, leaf area, energy yield, and biomass, were effectively evaluated based on the interaction of light with leaf structures. The shortwave infrared (SWIR) bands, specifically SWIR1 and SWIR2, showed the strongest correlations with these growth parameters. When classifying tobacco plants grown under different GA3 concentrations in greenhouses, artificial intelligence (AI) and machine learning (ML) algorithms were employed, achieving an average accuracy of over 99.1% using neural network (NN) and gradient boosting (GB) algorithms. Among the 34 tested vegetation indices, the photochemical reflectance index (PRI) demonstrated the strongest correlations with all evaluated plant phenotypes. Partial least squares regression (PLSR) models effectively predicted morphological attributes, with R2CV values ranging from 0.81 to 0.87 and RPDP values exceeding 2.09 for all parameters. Based on Pearson’s coefficient XYZ interpolations and HVI algorithms, the NIR−SWIR band combination proved the most effective for predicting height and leaf area, while VIS−NIR was optimal for optimal energy yield, and VIS−VIS was best for predicting biomass. To further corroborate these findings, the SWIR bands for certain morphological characteristic wavelengths selected with s−PLS were most significant for SWIR1 and SWIR2, while i−PLS showed a more uniform distribution in VIS−NIR−SWIR bands. Therefore, SWIR hyperspectral bands provide valuable insights into developing alternative bands for remote sensing measurements to estimate plant morphological parameters. These findings underscore the potential of remote sensing technology for rapid, accurate, and non-invasive monitoring within stationary high-throughput phenotyping systems in greenhouses. These insights align with advancements in digital and precision technology, indicating a promising future for research and innovation in this field.
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Guha, S., H. Govil, M. Tripathi, and M. Besoya. "EVALUATING CROSTA TECHNIQUE FOR ALTERATION MINERAL MAPPING IN MALANJKHAND COPPER MINES, INDIA." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-5 (November 19, 2018): 251–54. http://dx.doi.org/10.5194/isprs-archives-xlii-5-251-2018.
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<p><strong>Abstract.</strong> Landsat-8 Operational Land Imager (OLI) data has been successfully employed in the field of mineral exploration to detect important minerals. In this study, Crosta technique was applied to identify the diagnostic features of hydroxyl minerals, carbonate minerals and iron oxides in Malanjkhand copper mines, India. The Crosta technique was applied to six [blue, green, red, near-infrared (NIR), shortwave infrared1 (SWIR1), shortwave infrared2 (SWIR2) bands and two sets of four (blue, red, NIR, SWIR1; and blue, near-infrared, SWIR1, SWIR2) bands of OLI data. Results show that the areas with alteration zones are enhanced much better by using six bands of OLI data. The alteration differences are examined with the Crosta technique using four band combinations. Crosta technique is very useful in generating the images of hydroxyl minerals, carbonate minerals, and iron oxides.</p>
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Basinger, Nicholas T., Katherine M. Jennings, Erin L. Hestir, David W. Monks, David L. Jordan, and Wesley J. Everman. "Phenology affects differentiation of crop and weed species using hyperspectral remote sensing." Weed Technology 34, no. 6 (August 18, 2020): 897–908. http://dx.doi.org/10.1017/wet.2020.92.
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AbstractThe effect of plant phenology and canopy structure of four crops and four weed species on reflectance spectra were evaluated in 2016 and 2017 using in situ spectroscopy. Leaf-level and canopy-level reflectance were collected at multiple phenologic time points in each growing season. Reflectance values at 2 wk after planting (WAP) in both years indicated strong spectral differences between species across the visible (VIS; 350–700 nm), near-infrared (NIR; 701–1,300 nm), shortwave-infrared I (SWIR1; 1,301–1,900 nm), and shortwave-infrared II (SWIR2; 1,901–2,500 nm) regions. Results from this study indicate that plant spectral reflectance changes with plant phenology and is influenced by plant biophysical characteristics. Canopy-level differences were detected in both years across all dates except for 1 WAP in 2017. Species with similar canopy types (e.g., broadleaf prostrate, broadleaf erect, or grass/sedge) were more readily discriminated from species with different canopy types. Asynchronous phenology between species also resulted in spectral differences between species. SWIR1 and SWIR2 wavelengths are often not included in multispectral sensors but should be considered for species differentiation. Results from this research indicate that wavelengths in SWIR1 and SWIR2 in conjunction with VIS and NIR reflectance can provide differentiation across plant phenologies and, therefore should be considered for use in future sensor technologies for species differentiation.
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Zhang, Yunteng, and Zhiqiang Xiao. "A Method to Downscale MODIS Surface Reflectance Using Convolutional Neural Networks." Remote Sensing 15, no. 8 (April 16, 2023): 2102. http://dx.doi.org/10.3390/rs15082102.
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Surface reflectance is an important indicator for the physical states of the Earth’s surface. The Moderate Resolution Imaging Spectroradiometer (MODIS) surface reflectance product at 500 m resolution (MOD09A1) includes seven spectral bands and has been widely used to derive many high-level parameter products, such as leaf area index (LAI) and fraction of absorbed photosynthetically active radiation (FAPAR). However, the MODIS surface reflectance product at 250 m resolution (MOD09Q1) is only available for the red and near-infrared (NIR) bands, which greatly limits its applications. In this study, a downscaling reflectance convolutional neural network (DRCNN) is proposed to downscale the surface reflectance of the MOD09A1 product and derive 250 m surface reflectance in the blue, green, shortwave infrared (SWIR1, 1628–1652 nm) and shortwave infrared (SWIR2, 2105–2155 nm) bands for generating high-level parameter products at 250 m resolution. The surface reflectance of the MOD09A1 and MOD09Q1 products are preprocessed to obtain cloud-free continuous surface reflectance. Additionally, the surface reflectance in the blue, green, SWIR1 and SWIR2 bands from the preprocessed MOD09A1 product were upsampled to obtain surface reflectance in the corresponding bands at 1 km resolution. Then, a database was generated from the upsampled surface reflectance and the preprocessed MOD09A1 product over the On Line Validation Exercise (OLIVE) sites to train the DRCNN. The surface reflectance in the blue, green, SWIR1 and SWIR2 bands from the preprocessed MOD09A1 product and the surface reflectance in the red and NIR bands from the preprocessed MOD09Q1 product were entered into the trained DRCNN to obtain the surface reflectance in the blue, green, SWIR1 and SWIR2 bands at 250 m resolution. The downscaled surface reflectance from the DRCNN were compared with the surface reflectance from the MOD09A1 product and Landsat 7. The results show that the DRCNN can effectively downscale the surface reflectance of the MOD09A1 product to generate the surface reflectance at 250 m resolution.
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Rukhovich, Dmitry I., Polina V. Koroleva, Alexey D. Rukhovich, and Mikhail A. Komissarov. "Informativeness of the Long-Term Average Spectral Characteristics of the Bare Soil Surface for the Detection of Soil Cover Degradation with the Neural Network Filtering of Remote Sensing Data." Remote Sensing 15, no. 1 (December 26, 2022): 124. http://dx.doi.org/10.3390/rs15010124.
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The long-term spectral characteristics of the bare soil surface (BSS) in the BLUE, GREEN, RED, NIR, SWIR1, and SWIR2 Landsat spectral bands are poorly studied. Most often, the RED and NIR spectral bands are used to analyze the spatial heterogeneity of the soil cover; in our opinion, it is outmoded and seems unreasonable. The study of multi-temporal spectral characteristics requires the processing of big remote sensing data based on artificial intelligence in the form of convolutional neural networks. The analysis of BSS belongs to the direct methods of analysis of the soil cover. Soil degradation can be detected by ground methods (field reconnaissance surveys), modeling, or digital methods, and based on the remote sensing data (RSD) analysis. Ground methods are laborious, and modeling gives indirect results. RSD analysis can be based on the principles of calculation of vegetation indices (VIs) and on the BSS identification. The calculation of VIs also provides indirect information about the soil cover through the state of vegetation. BSS analysis is a direct method for analyzing soil cover heterogeneity. In this work, the informativeness of the long-term (37 years) average spectral characteristics of the BLUE, GREEN, RED, NIR, SWIR1 and SWIR2 bands of the Landsat 4–8 satellites for detecting areas of soil degradation with recognition of the BSS using deep machine learning methods was estimated. The objects of study are the spectral characteristics of kastanozems (dark chestnut soils) in the south of Russia in the territory of the Morozovsky district of the Rostov region. Soil degradation in this area is mainly caused by erosion. The following methods were used: retrospective monitoring of soil and land cover, deep machine learning using convolutional neural networks, and cartographic analysis. Six new maps of the average long-term spectral brightness of the BSS have been obtained. The information content of the BSS for six spectral bands has been verified on the basis of ground surveys. The informativeness was determined by the percentage of coincidences of degradation facts identified during the RSD analysis, and those determined in the field. It has been established that the spectral bands line up in the following descending order of information content: RED, NIR, GREEN, BLUE, SWIR1, SWIR2. The accuracy of degradation maps by band was determined as: RED—84.6%, NIR—82.9%, GREEN—78.0%, BLUE—78.0%, SWIR1—75.5%, SWIR2—62.2%.
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Ouma, Yashon O., Lone Lottering, and Ryutaro Tateishi. "Soil Erosion Susceptibility Prediction in Railway Corridors Using RUSLE, Soil Degradation Index and the New Normalized Difference Railway Erosivity Index (NDReLI)." Remote Sensing 14, no. 2 (January 12, 2022): 348. http://dx.doi.org/10.3390/rs14020348.
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This study presents a remote sensing-based index for the prediction of soil erosion susceptibility within railway corridors. The empirically derived index, Normalized Difference Railway Erosivity Index (NDReLI), is based on the Landsat-8 SWIR spectral reflectances and takes into account the bare soil and vegetation reflectances especially in semi-arid environments. For the case study of the Botswana Railway Corridor (BRC), the NDReLI results are compared with the RUSLE and the Soil Degradation Index (SDI). The RUSLE model showed that within the BRC, the mean annual soil loss index was at 0.139 ton ha−1 year−1, and only about 1% of the corridor area is susceptible to high (1.423–3.053 ton ha−1 year−1) and very high (3.053–5.854 ton ha−1 year−1) soil loss, while SDI estimated 19.4% of the railway corridor as vulnerable to soil degradation. NDReLI results based on SWIR1 (1.57–1.65 μm) predicted the most vulnerable areas, with a very high erosivity index (0.36–0.95), while SWIR2 (2.11–2.29 μm) predicted the same regions at a high erosivity index (0.13–0.36). From empirical validation using previous soil erosion events within the BRC, the proposed NDReLI performed better than the RUSLE and SDI models in the prediction of the spatial locations and extents of susceptibility to soil erosion within the BRC.
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Xu, Dandan, Dong Zhang, Dan Shi, and Zhaoqing Luan. "Automatic Extraction of Open Water Using Imagery of Landsat Series." Water 12, no. 7 (July 6, 2020): 1928. http://dx.doi.org/10.3390/w12071928.
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Open surface freshwater is an important resource for terrestrial ecosystems. However, climate change, seasonal precipitation cycling, and anthropogenic activities add high variability to its availability. Thus, timely and accurate mapping of open surface water is necessary. In this study, a methodology based on the concept of spatial autocorrelation was developed for automatic water extraction from Landsat series images using Taihu Lake in south-eastern China as an example. The results show that this method has great potential to extract continuous open surface water automatically, even when the water surface is covered by floating vegetation or algal blooms. The results also indicate that the second shortwave-infrared band (SWIR2) band performs best for water extraction when water is turbid or covered by surficial vegetation. Near-infrared band (NIR), first shortwave-infrared band (SWIR1), and SWIR2 have consistent extraction success when the water surface is not covered by vegetation. Low filter image processing greatly overestimated extracted water bodies, and cloud and image salt and pepper issues have a large impact on water extraction using the methods developed in this study.
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Malina, Edward, Haili Hu, Jochen Landgraf, and Ben Veihelmann. "A study of synthetic <sup>13</sup>CH<sub>4</sub> retrievals from TROPOMI and Sentinel-5/UVNS." Atmospheric Measurement Techniques 12, no. 12 (November 29, 2019): 6273–301. http://dx.doi.org/10.5194/amt-12-6273-2019.
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Abstract. Retrievals of methane isotopologues have the potential to differentiate between natural and anthropogenic methane sources types, which can provide much needed information about the current global methane budget. We investigate the feasibility of retrieving the second most abundant isotopologue of atmospheric methane (13CH4, roughly 1.1 % of total atmospheric methane) from the shortwave infrared (SWIR) channels of the future Sentinel-5/ultra-violet, visible, near-infrared, shortwave infrared (UVNS) and current Copernicus Sentinel-5 Precursor TROPOspheric Monitoring Instrument (TROPOMI) instruments. With the intended goal of calculating the δ13C value, we assume that a δ13C uncertainty of better than 1 ‰ is sufficient to differentiate between source types, which corresponds to a 13CH4 uncertainty of <0.02 ppb. Using the well-established information content analysis techniques and assuming clear-sky, non-scattering conditions, we find that the SWIR3 (2305–2385 nm) channel on the TROPOMI instrument can achieve a mean uncertainty of <1 ppb, while the SWIR1 channel (1590–1675 nm) on the Sentinel-5 UVNS instrument can achieve <0.68 ppb or <0.2 ppb in high signal-to-noise ratio (SNR) cases. These uncertainties combined with significant spatial and/or temporal averaging techniques can reduce δ13C uncertainty to the target magnitude or better. However, we find that 13CH4 retrievals are highly sensitive to errors in a priori knowledge of temperature and pressure, and accurate knowledge of these profiles is required before 13CH4 retrievals can be performed on TROPOMI and future Sentinel-5/UVNS data. In addition, we assess the assumption that scattering-induced light path errors are cancelled out by comparing the δ13C values calculated for non-scattering and scattering scenarios. We find that there is a minor bias in δ13C values from scattering and non-scattering retrievals, but this is unrelated to scattering-induced errors.
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Falcioni, Renan, Werner Camargos Antunes, Roney Berti de Oliveira, Marcelo Luiz Chicati, José Alexandre M. Demattê, and Marcos Rafael Nanni. "Assessment of Combined Reflectance, Transmittance, and Absorbance Hyperspectral Sensors for Prediction of Chlorophyll a Fluorescence Parameters." Remote Sensing 15, no. 20 (October 22, 2023): 5067. http://dx.doi.org/10.3390/rs15205067.
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Photosynthesis is a key process in plant physiology. Understanding its mechanisms is crucial for optimizing crop yields and for environmental monitoring across a diverse range of plants. In this study, we employed reflectance, transmittance, and absorbance hyperspectral sensors and utilized multivariate statistical techniques to improve the predictive models for chlorophyll a fluorescence (ChlF) parameters in Hibiscus and Geranium model plants. Our objective was to identify spectral bands within hyperspectral data that correlate with ChlF indicators using high-resolution data spanning the electromagnetic spectrum from ultraviolet to shortwave infrared (UV–VIS–NIR–SWIR). Utilizing the hyperspectral vegetation indices (HVIs) tool to align importance projection for wavelength preselection and select the most responsive wavelength by variable importance projection (VIP), we optimized partial least squares regression (PLSR) models to enhance predictive accuracy. Our findings revealed a strong relationship between hyperspectral sensor data and ChlF parameters. Employing principal component analysis, kappa coefficients (k), and accuracy (Acc) evaluations, we achieved values exceeding 86% of the predicted ChlF parameters for both Hibiscus and Geranium plants. Regression models for parameters such as Ψ(EO), ϕ(PO), ϕ(EO), ϕ(DO), δRo, ρRo, Kn, Kp, SFI(abs), PI(abs), and D.F. demonstrated model accuracies close to 0.84 for R2 and approximately 1.96 for RPD. The spectral regions linked with these parameters included blue, green, red, infrared, SWIR1, and SWIR2, emphasizing their relevance for noninvasive evaluations. This research demonstrates the ability of hyperspectral sensors to noninvasively predict chlorophyll a fluorescence (ChlF) parameters, which are essential for assessing photosynthetic efficiency in plants. Notably, hyperspectral absorbance data were more accurate in predicting JIP-test-based chlorophyll a kinetic parameters. In conclusion, this study underscores the potential of hyperspectral sensors for deepening our understanding of plant photosynthesis and monitoring plant health.
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Rostami, Amirhossein, Reza Shah-Hosseini, Shabnam Asgari, Arastou Zarei, Mohammad Aghdami-Nia, and Saeid Homayouni. "Active Fire Detection from Landsat-8 Imagery Using Deep Multiple Kernel Learning." Remote Sensing 14, no. 4 (February 17, 2022): 992. http://dx.doi.org/10.3390/rs14040992.
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Active fires are devastating natural disasters that cause socio-economical damage across the globe. The detection and mapping of these disasters require efficient tools, scientific methods, and reliable observations. Satellite images have been widely used for active fire detection (AFD) during the past years due to their nearly global coverage. However, accurate AFD and mapping in satellite imagery is still a challenging task in the remote sensing community, which mainly uses traditional methods. Deep learning (DL) methods have recently yielded outstanding results in remote sensing applications. Nevertheless, less attention has been given to them for AFD in satellite imagery. This study presented a deep convolutional neural network (CNN) “MultiScale-Net” for AFD in Landsat-8 datasets at the pixel level. The proposed network had two main characteristics: (1) several convolution kernels with multiple sizes, and (2) dilated convolution layers (DCLs) with various dilation rates. Moreover, this paper suggested an innovative Active Fire Index (AFI) for AFD. AFI was added to the network inputs consisting of the SWIR2, SWIR1, and Blue bands to improve the performance of the MultiScale-Net. In an ablation analysis, three different scenarios were designed for multi-size kernels, dilation rates, and input variables individually, resulting in 27 distinct models. The quantitative results indicated that the model with AFI-SWIR2-SWIR1-Blue as the input variables, using multiple kernels of sizes 3 × 3, 5 × 5, and 7 × 7 simultaneously, and a dilation rate of 2, achieved the highest F1-score and IoU of 91.62% and 84.54%, respectively. Stacking AFI with the three Landsat-8 bands led to fewer false negative (FN) pixels. Furthermore, our qualitative assessment revealed that these models could detect single fire pixels detached from the large fire zones by taking advantage of multi-size kernels. Overall, the MultiScale-Net met expectations in detecting fires of varying sizes and shapes over challenging test samples.
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Yogyanti, Galih Citra. "Burned area mapping in Dendang District, Tanjung Jabung Timur Regency using sentinel-2." Calamity: A Journal of Disaster Technology and Engineering 1, no. 1 (July 31, 2023): 41–50. http://dx.doi.org/10.61511/calamity.v1i1.2023.150.
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Remote Sensing is a way to provide information efficiently both in terms of cost and time. In addition, the use of remote sensing in mapping the burned area can be carried out on a large scale but with a fast time for the prevention of land fires. Monitoring of forest fires is carried out to see locations that often become fire hotspots every year and to prevent frequent land and forest fires.The method used in this study is to map the burned area using multi-temporal data using the Normalized burning Ratio and Normalized burning Ratio 2 indices from Sentinel-2 images in May and September 2019. The trend data can be used to evaluate the moratorium on forest business permits or a peatland. Sentinel 2 has a higher spatial resolution of 20 meters compared to other multispectral images that can be accessed easily and free of charge, so it is suitable to be applied in areas that are not too large and minimizes the value of estimation errors, using Sentinel 2 imagery which has 13 channels will Selected several channels that can be used for index transformation, namely the NBR (Normalized Burn Ratio) and NBR2 (Normalized Burn Ratio2) indexes, both indices utilize Near Infrared, SWIR1, and SWIR2 channels which can provide information about the area after land fires,The research results obtained that burned areas are often identified as barren land, such as peat canals or vacant land. This is because the spectral reflection characteristics of objects in burnt areas are the same as those in non-vegetated land areas when the NBR index is transformed using the NIR, SWIR1 and SWIR2 channels.
Keywords: Forest and land fires, NBR Indices, Sentinel-2.
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Ahmed, Zubair, P. P. Nageswara Rao, and P. Srikanth. "Area Estimation of Mango and Coconut Crops using Machine Learning in Hesaraghatta Hobli of Bengaluru Urban District, Karnataka." Journal of Geomatics 17, no. 1 (April 28, 2023): 85–92. http://dx.doi.org/10.58825/jog.2023.17.1.75.
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Timely and accurate estimation of acreage and production of horticulture crops is necessary for deciding how much, where and when to export these commodities in the national and global markets. Remote sensing has been one of the methods adopted, in addition to conventional sampling methods, for improving the estimates. Parametric image classification algorithms have been used by many researchers for identification and area estimation of horticulture crops. But these algorithms result in several unclassified pixels leading to over/underestimates. This study has been undertaken to estimate the area of two horticulture crops (i.e., mango and coconut) of Hesaraghatta hobli of Bengaluru urban district using Convolutional Neural Network (CNN) on Google Colaband Random Forest (RF) algorithms on Google Earth Engine (GEE). Remotely sensed data acquired by the Multi-Spectral Instrument (MSI) onboard Sentiel-2A satellite was used. Spectral signatures of horticulture crops and other associated cover types have been generated to identify the cover types and for selecting appropriate band combinations. Two different band combinations were used for area estimation of selected horticulture crops: i) Near-InfraRed (NIR), Red, and Green all three having a spatial resolution of 10 m, ii) Red edge-3, Short-Wave InfraRed1 (SWIR1) and Short-Wave InfraRed2 (SWIR2) having 20 m spatial resolution. Area estimates of horticulture crops and associated cover types were validated with respect to ground truth and statistical reports from Karnataka State Directorate of Horticulture (KSDH). It was found that the CNN model performed better than RF using NIR, Red, and Green band combination with an overall accuracy of 84%, but it failed to give similar accuracies with Red edge 3, SWIR1, and SWIR2 band combination. We attempted transfer learning using the trained CNN model at two different study areas far away from the study area and found encouraging results.
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Терехин, Э. А. "Многолетняя динамика спектрально-отражательных свойств участков лесовосстановления в лесах юга Среднерусской возвышенност." Региональные геосистемы 44, no. 2 (July 15, 2020): 210–20. http://dx.doi.org/10.18413/2712-7443-2020-44-2-210-220.
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Представлены результаты анализа многолетней динамики спектрально-отражательных признаков на участках лесовозобновления бывших сплошнолесосечных рубок. Оценка спектрального отклика выполнена на основе разновременных данных Landsat 1985–2015 гг. в различных диапазонах спектра. Исследование проведено для широколиственных лесов, типичных для юга Среднерусской возвышенности. Выполнено сравнение спектрального отклика лесных участков, отличающихся доминирующей породой. Для лесных массивов с преобладанием в верхних ярусах дуба или ясеня не выявлено статистически значимых различий в инфракрасных коэффициентах спектральной яркости. В инфракрасных диапазонах спектра (SWIR1 и SWIR2) установлена тенденция к последовательному снижению отражательных признаков по мере формирования лесных сообществ на бывших вырубках. Формирование насаждений возрастом 23–25 лет приводит к снижению на 15 % отражательных характеристик в диапазоне 1,55–1,75 мкм и на 30 % – в диапазоне 2,09–2,35 мкм. Увеличение возраста лесных насаждений приводит к снижению коэффициентов вариации спектральных признаков
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Clarke, Jenni. "Swirl by swirl." Early Years Educator 22, no. 5 (December 2, 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.
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Lee, Hyungyu, Jungsoo Lee, Donghwa Kim, and Jinsoo Cho. "Pre-swirl Nozzle Geometry Optimization to Increase Discharge Coefficient Using CFD Analysis." KSFM Journal of Fluid Machinery 20, no. 1 (February 1, 2017): 21–28. http://dx.doi.org/10.5293/kfma.2017.20.1.021.
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Reddy, S. L. K., C. V. Rao, P. R. Kumar, R. V. G. Anjaneyulu, and B. G. Krishna. "A NOVEL METHOD FOR WATER AND WATER CANAL EXTRACTION FROM LANDSAT-8 OLI IMAGERY." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-5 (November 19, 2018): 323–28. http://dx.doi.org/10.5194/isprs-archives-xlii-5-323-2018.
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<p><strong>Abstract.</strong> Constituents of hydrologic network, River and water canals play a key role in Agriculture for cultivation, Industrial activities and urban planning. Remote sensing images can be effectively used for water canal extraction, which significantly improves the accuracy and reduces the cost involved in mapping using conventional means. Using remote sensing data, the water Index (WI), Normalized Difference Water Index (NDWI) and Modified NDWI (MNDWI) are used in extracting the water bodies. These techniques are aimed at water body detection and need to be complemented with additional information for the extraction of complete water canal networks. The proposed index MNDWI-2 is able to find the water bodies and water canals as well from the Landsat-8 OLI imagery and is based on the SWIR2 band. In this paper, we use Level-1 precision terrain corrected OLI imagery at 30 meter spatial resolution. The proposed MNDWI-2 index is derived using SWIR2 (B7) band and Green (B3) band. The usage of SWIR2 band over SWIR1 results in very low reflectance values for water features, detection of shallow water and delineation of water features with rest of the features in the image. The computed MNDWI-2 index values are threshold by making the values greater than zero as 1 and less than zero as zero. The binarised values of 1 represent the water bodies and 0 represent the non-water body. This normalized index detects the water bodies and canals as well as vegetation which appears in the form of noise. The vegetation from the MNDWI-2 image is removed by using the NDVI index, which is calculated using the Top of Atmosphere (TOA) corrected images. The paper presents the results of water canal extraction in comparison with the major available indexes. The proposed index can be used for water and water canal extraction from L8 OLI imagery, and can be extended for other high resolution sensors.</p>
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Ain, Arindom. "CNN-Enhanced Multi-Indices Patch-Based Classification: A Case Study of Guwahati City." International Journal for Research in Applied Science and Engineering Technology 9, no. 12 (December 31, 2021): 1824–40. http://dx.doi.org/10.22214/ijraset.2021.39593.
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Abstract: Land use and land cover (LULC) provides a way to classify objects on the surface of Earth. This paper aims to identify the varying land cover classes by stacking of 6 spectral bands and 10 different generated indices from those bands together. We have considered the multispectral images of Landsat 7 for our research. It is seen that instead of using only basic spectral bands (blue, green, red, nir, swir1 and swir2) for classification, stacking relevant indices of multiple target classes like ndvi, evi, nbr, BU, etc. with basic bands generates more precise results. In this study, we have used automated clustering techniques for generating 5 different class labels for training the model. These labels are further used to develop a predictive model to classify LULC classes. The proposed classifier is compared with the SVM and KNN classifiers. The results show that this proposed strategy gives preferable outcomes over other techniques. After training the model over 50 epochs, an accuracy of 93.29% is achieved. Keywords: Land use, land cover, CNN, ISODATA, indices
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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, Amanda Sickafoose, Li Hsia Yeo, Samuel Courville, Eric Palmer, and Robert Gaskell. "Spectrophotometric and Topographic Correlations within the Mare Ingenii Swirl Region: Evidence for a Highly Mobile Lunar Regolith." Planetary Science Journal 4, no. 12 (December 1, 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 (July 5, 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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Hess, M., C. Wöhler, M. Bhatt, A. A. Berezhnoy, A. Grumpe, K. Wohlfarth, A. Bhardwaj, and V. V. Shevchenko. "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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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 (April 1, 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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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 (October 5, 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.
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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 (October 9, 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 (November 15, 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 (June 28, 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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Kim, Ki-Hyun, In-Haeng Song, and Soon-Ho Choi. "Design Technique of Post Swirl Stator in Container Vessels by CFD." Journal of the Society of Naval Architects of Korea 44, no. 2 (April 20, 2007): 93–100. http://dx.doi.org/10.3744/snak.2007.44.2.093.
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Domingue, Deborah, John Weirich, Frank Chuang, Samuel Courville, Roger Clark, Amanda Sickafoose, Eric Palmer, and Robert Gaskell. "Photometric Properties within the Reiner Gamma Swirl: Constraining Formation Mechanisms." Planetary Science Journal 5, no. 7 (July 1, 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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Balakrishnan, P., and K. Srinivasan. "Pipe jet noise reduction using co-axial swirl pipe." Aeronautical Journal 121, no. 1238 (March 6, 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 (January 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 (July 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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Chen, Wei, Haoyuan Hong, Mahdi Panahi, Himan Shahabi, Yi Wang, Ataollah Shirzadi, Saied Pirasteh, et al. "Spatial Prediction of Landslide Susceptibility Using GIS-Based Data Mining Techniques of ANFIS with Whale Optimization Algorithm (WOA) and Grey Wolf Optimizer (GWO)." Applied Sciences 9, no. 18 (September 8, 2019): 3755. http://dx.doi.org/10.3390/app9183755.
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The most dangerous landslide disasters always cause serious economic losses and human deaths. The contribution of this work is to present an integrated landslide modelling framework, in which an adaptive neuro-fuzzy inference system (ANFIS) is combined with the two optimization algorithms of whale optimization algorithm (WOA) and grey wolf optimizer (GWO) at Anyuan County, China. It means that WOA and GWO are used as two meta-heuristic algorithms to improve the prediction performance of the ANFIS-based methods. In addition, the step-wise weight assessment ratio analysis (SWARA) method is used to obtain the initial weight of each class of landslide influencing factors. To validate the effectiveness of the proposed framework, 315 landslide events in history were selected for our experiments and were randomly divided into the training and verification sets. To perform landslide susceptibility mapping, fifteen geological, hydrological, geomorphological, land cover, and other factors are considered for the modelling construction. The landslide susceptibility maps by SWARA, SWARA-ANFIS, SWARA-ANFIS-PSO, SWARA-ANFIS-WOA, and SWARA-ANFIS-GWO models are assessed using the measures of the receiver operating characteristic (ROC) curve and root-mean-square error (RMSE). The experiments demonstrated that the obtained results of modelling process from the SWARA to the SAWRA-ANFIS-GWO model were more accurate and that the proposed methods have satisfactory prediction ability. Specifically, prediction accuracy by area under the curve (AUC) of SWARA, SWARA-ANFIS, SWARA-ANFIS-PSO, SWARA-ANFIS-GWO, and SWARA-ANFIS-WOA models were 0.831, 0.831, 0.850, 0.856, and 0.869, respectively. Due to adaptability and usability, the proposed prediction methods can be applied to other areas for landslide management and mitigation as well as prevention throughout the world.
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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 (February 1, 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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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 (April 1, 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 (December 1, 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 (January 31, 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 (April 1, 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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Gao, Yan, Songguang Yang, Lianyu Yuan, Yuhai Cui, and Keqiang Wu. "Comparative Analysis of SWIRM Domain-Containing Proteins in Plants." Comparative and Functional Genomics 2012 (2012): 1–8. http://dx.doi.org/10.1155/2012/310402.
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Chromatin-remodeling complexes affect gene expression by using the energy of ATP hydrolysis to locally disrupt or alter the association of histones with DNA. SWIRM (Swi3p, Rsc8p, and Moira) domain is an alpha-helical domain of about 85 residues in chromosomal proteins. SWIRM domain-containing proteins make up large multisubunit complexes by interacting with other chromatin modification factors and may have an important function in plants. However, little is known about SWIRM domain-containing proteins in plants. In this study, 67 SWIRM domain-containing proteins from 6 plant species were identified and analyzed. Plant SWIRM domain proteins can be divided into three distinct types: Swi-type, LSD1-type, and Ada2-type. Generally, the SWIRM domain forms a helix-turn-helix motif commonly found in DNA-binding proteins. The genes encoding SWIRM domain proteins inOryza sativaare widely expressed, especially in pistils. In addition,OsCHB701andOsHDMA701were downregulated by cold stress, whereasOsHDMA701andOsHDMA702were significantly induced by heat stress. These observations indicate that SWIRM domain proteins may play an essential role in plant development and plant responses to environmental stress.
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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 (September 1, 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 (July 1, 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 (August 2, 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.