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Carrillo, De Hert Sergio. "Drop size distribution analysis of mechanically agitated liquid-liquid dispersions." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/drop-size-distribution-analysis-of-mechanically-agitated-liquidliquid-dispersions(02a0af25-3d1c-47e0-8a4e-8b2cc98cdaea).html.
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Many daily life products consist of mixtures of oil and water. When an immiscible material is dispersed an interface in-between the two phases is created which gives rise to rheological phenomena which can be exploited for product formulation; this is the case in products such as hand-creams and food products. Furthermore emulsions are used to transport hydrophobic materials, for example, many pharmaceuticals are injected as emulsions into the bloodstream. The performance of such products depends on their microstructure, which is determined by its formulation and how its constituents are mixed together; therefore the microstructure depends on the properties of the dispersed phases, the emulsifier used, the equipment used and its processing conditions. Emulsified products are seldom mono-dispersed due to the complex drop breakup mechanism in the turbulent fields inside the equipment in which the phases are forced together. The chaotic breakup mechanism of highly viscous dispersed phases yield complex and broad drop size distributions (DSD) as a result of the dominating viscous cohesive stresses inside the parent drop. Former studies have used the Sauter mean diameter and/or the size of the largest drop as the characteristic measure of central tendency of the DSD to correlate their results and to prove mechanistic or phenomenological models; however these parameters in isolation are insufficient to characterise the whole DSD of highly polydisperse emulsions. In this dissertation a vast amount of silicon oils of different viscosity were used as dispersed phase to study the effect of various processing conditions and formulations on the resulting DSD. The effect of several formulation and processing parameters were studied for two different mixing devices: stirred vessels and in-line high-shear mixers. (1) For stirred vessels, the effect of stirring speed, continuous phase viscosity and dispersed phase volume fraction were studied in combination with the viscosity of the dispersed phase for steady-state systems. (2) For in-line high-shear mixers a model that links batch and multi-pass continuous emulsification for multimodal DSD was derived from a transient mass balance. Processing parameters such as time and volume, flow rate and number of passes through the mixer, and stirring speed were studied for a wide dispersed phase viscosity range. The analytical methodology implemented included the use of one or more probability density functions to describe the shape of the DSD. The models proposed gave reasonable approximations of the Sauter mean diameter and allowed to study the drop size changes and the relative amount of different types of drops resulting from different breakup mechanisms.
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Rajapakse, Achula, and s9508428@student rmit edu au. "Drop size distribution and interfacial area in reactive liquid-liquid dispersion." RMIT University. Civil Environmental and Chemical Engineering, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080717.163619.
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Emulsion explosives have become the preferred choice as blasting agents for numerous industries including mining, agriculture, and construction. One of the most important components in such an emulsion is an emulsifier, which controls the emulsification properties of the explosive. The present study involves the production of one such emulsifier, which is produced by reacting two immiscible liquids, PIBSA (polyisobutylene succinic anhydride) and MEA (monoethanolamine). The study examines the effect of design variable such as the impeller speed, impeller type and the dispersed phase volume fraction on interfacial area. Experiments were carried out in a 0.15 m diameter fully baffled stirred tank using a 6-bladed Rushton turbine impeller and a marine propeller. Drop size was determined using a microscope with a video camera and image processing system. The transient concentration of PIBSA was determined using FTIR analysis and used to estimate the volume fraction of the dispersed phase (Ö). The effective interfacial area was calculated using the Sauter mean drop diameter, d32 and Ö. Impeller speeds ranging from 150 to 600 rpm and dispersed phase volume fractions, Ö ranging from 0.01 to 0.028 were examined in the experimental study. It was found that that the evolution of Sauter mean drop diameter, d32 has four different trends depending on Ö and impeller speed. At high impeller speeds and high Ö, d32 values decrease initially and reach constant values after a long period of time. This trend is consistent with the findings in previous investigations. Under certain operating conditions, d32 values increase initially with stirring time to reach a maximum value and then decrease to reach a steady state value. The presence of these trends has been attributed to the effect of changing physical properties of the system as a result of chemical reaction. Results indicate that, in general, Sauter mean drop diameter d32 decreases with an increase in agitation intensity. However a decrease in the dispersed phase volume fraction is found to increase d32. These trends are found to be the same for both impeller types studied. Comparing the drop size results produced by the two impellers, it appears that low-power number propeller produces s ignificantly smaller drops than the Rushton turbine. It was found that the concentrations of reactants decrease with time for all impeller speeds thereby leading to a decrease in interfacial area with the progress of the reaction. Interfacial area values obtained at higher impeller speeds are found to be lower in spite of lower d32 values at these speeds. Also, these values decrease with time and become zero in a shorter duration indicating the rapid depletion of MEA. The interfacial area values obtained with the propeller at a given impeller speed are lower as compared to those for Rushton turbine. They also decrease and become zero in a shorter duration as compared to those for Rushton turbine suggesting propeller¡¦s performance is better in enhancing the reaction rate.
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Alqurashi, Faris. "Extension of spray flow modelling using the drop number size distribution moments approach." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/extension-of-spray-flow-modelling-using-the-drop-number-size-distribution-moments-approach(9c11e7da-f583-492d-b6a9-29b6fee71438).html.
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This work is an extension to the spray model of Watkins and Jones (2010). In their model, the spray is characterized by evaluating the three moments Q_2, Q_3 and Q_4 of general gamma number size distribution from their transport equations. The sub-models of drop drag, drop break-up and drop collisions were simulated in terms of gamma distributions. The model is considered as non-vaporising and compared with cases which have low ambient gas temperature and also is strict to a particular set of sub-models for drop drag and break up which they are applicable to produce integrable functions. In this work the model is adjusted to allow a variety of sub-models to be implemented. Three models (TAB, ETAB, DDB) are considered for drop breakup which have been basically introduced to be used with the Droplet Discrete Method (DDM) approach. So in order to implement these models with the model of Watkins and Jones the source terms of the breakup are calculated by grouping the droplets in each cell into parcels which contain a certain number of droplets with similar physical properties (size, velocity, temperature ...). The source terms of each parcel are calculated and multiplied by the number of droplets in these parcels and a numerical integration is then used to obtain the resultant effect of the drop breakup in each cell. The number of drops in each cell is determined from the gamma size distribution. Also three hybrid breakup models (KH-RT, Turb-KH-RT, Turb-TAB) which include two distinct steps: primary and secondary break up model are implemented. The Kelvin- Helmholtz (KH) and the turbulence induced breakup (Turb) models were used to predict the primary break up of the intact liquid core of a liquid jet while the secondary break up is modelled using the TAB model and competition between the KH and the RT models. Both models are allowed to work simultaneously. However it is assumed that if the disintegration occurs due to the RT the KH break up does not occur. In case of drag sub-model, a dynamic drag model is introduced which accounts for the effects of drop distortion and oscillation due to the effects of high relative velocity between the liquid and the surrounding gas. In this model the drag coefficient is empirically related to the magnitude of the drop deformation. The magnitude of drop deformation was calculated by using the TAB model. In this work, the effects of mass and heat transfer on the spray are modelled. An additional equation for the energy of the liquid is solved. The mass transfer rate is evaluated using the model of Godsave (1953) and Spalding (1953) while the Faeth correlation (1983) is used to model heat transfer between the two phases. For all equations of heat and mass transfer between phases, the drop Nusselt and Sherwood number are calculated by using the correlation of Ranz and Marshall. In this model also the liquid surface-average temperature T_l2 which is calculated by Watkins (2007) is used to determine the heat and mass transfer between phases instead of liquid volume-average temperature. It was derived by assuming a parabolic temperature profile within individual drops. All the equations are treated in Eulerian framework using the finite volume method. The model has been applied to a wide range of sprays and compared to a number of experiments with different operating conditions including high liquid injection pressure and high ambient gas density and temperature. A reasonable agreement is found by the ETAB model with most of the data while the TAB and the DDB models continually underestimate the penetration and drop sizes of the spray. The hybrid breakup models perform well and show better agreement with the available experimental data than the single breakup models. In term of high temperature cases, the model correctly captures the effect of evaporation on the different spray properties especially with hybrid break up model.
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Hadi, Hadi Abbas. "Dropwise condensation : experimental and theoretical investigation." Thesis, Heriot-Watt University, 1996. http://hdl.handle.net/10399/1193.
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Wennerdahl, Emelie. "Utvärdering av regnmätning och droppstorleksfördelning från en distrometer." Thesis, Uppsala universitet, Luft-, vatten och landskapslära, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-256926.
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Nederbördsmätning är viktigt inom många områden och en relativt ny teknik är enoptisk distrometer som med hjälp av laserteknik mäter nederbördspartiklarnasdroppstorlek och fallhastighet. Syftet med detta arbete var att undersöka hur välThies distrometer stämmer överens med nederbördsmätning från ett vippkärl ochmanuella mätningar från institutionen för geovetenskaper vid Uppsala universitet.Institutionen för geovetenskaper överväger att gå över till denna teknik och därmedbehövdes distrometern utvärderas för olika faktorer som kan påverka instrumentet.Vid jämförelse mellan instrumenten visade det sig att distrometern totalt sett samladein mer nederbörd än de andra mätarna. Det är svårt att avgöra vad skillnaden mellaninstrumenten kan bero på men felkällor så som avdunstning och vätning hos vippkärletoch manuella mätningar kan ge mindre nederbörd. En annan orsak kan varafelkalibrering av datan från distrometern. Inga samband hittades för vindhastighet,vindriktning och typ av nederbörd mellan de tre instrumenten. En vidare undersökning gjordes för droppstorleksfördelningen för att ge exempelpå fördelar med en distrometer. Droppstorleksfördelningen från distrometernjämfördes med exponentialfördelningen framtagen av Marshall & Palmer (1948).Resultatet visade sig stämma överens med tidigare studier, fördelningen stämmerbra överens för stratiforma väder, men sämre för konvektiva och snö.Measuring precipitation is important in many areas of research. A relatively newtechnology for measuring precipitation is the optical disdrometer, which measures thefalling velocity and drop size of particles by using lasers. The purpose of this workwas to compare data from a disdrometer with data from a tipping bucket and amanual measurement series from the Department of Earth Sciences at UppsalaUniversity. The comparison between the instruments showed that the disdrometermeasured more precipitation than the tipping bucket and the manual measurements.A reason for this can be due to evaporation and wetting from the tipping bucket andmanual measurement. Errors in calibration of data from the disdrometer may alsohave influence. Furthermore, an analysis of the drop size distribution was done in order todetermine areas of special use for the device. The drop size distribution calculatedfrom the distrometer was compared with the Marshall and Palmer (1948) distribution.The results showed that the MP-distribution was a good fit for stratiform weather;however, for convective clouds and snow the fit was not satisfactory and some otherrelationship should be used instead.
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Stevens, Kimberly Ann. "Two-Phase Interactions on Superhydrophobic Surfaces." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/7711.
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Superhydrophobic surfaces have gained attention as a potential mechanism for increasing condensation heat transfer rates. Various aspects related to condensation heat transfer are explored. Adiabatic, air-water mixtures are used to explore the influence of hydrophobicity on two-phase flows and the hydrodynamics which might be present in flow condensation environments. Pressure drop measurements in a rectangular channel with one superhydrophobic wall (cross-section approximately 0.37 X 10 mm) are obtained, revealing a reduction in the pressure drop for two-phase flow compared to a control scenario. The observed reduction is approximately 10% greater than the reduction that is observed for single-phase flow (relative to a classical channel). Carbon nanotubes have been used to create superhydrophobic coatings due to their ability to offer a relatively uniform nanostructure. However, as-grown carbon nanotubes often require the addition of a thin-film hydrophobic coating to render them superhydrophobic, and fine control of the overall nanostructure is difficult. This work demonstrates the utility of using carbon infiltration to layer amorphous carbon on multi-walled nanotubes to achieve superhydrophobic behavior with tunable geometry. The native surface can be rendered superhydrophobic with a vacuum pyrolysis treatment, with contact angles as high as 160 degrees and contact angle hysteresis less than 2-3 degrees. Drop-size distribution is an important aspect of heat transfer modeling that is difficult to measure for small drop sizes. The present work uses a numerical simulation of condensation to explore the influence of nucleation site distribution approach, nucleation site density, contact angle, maximum drop size, heat transfer modeling to individual drops, and minimum jumping size on the distribution function and overall heat transfer rate. The simulation incorporates the possibility of coalescence-induced jumping over a range of sizes. Results of the simulation are compared with previous theoretical models and the impact of the assumptions used in those models is explored. Results from the simulation suggest that when the contact angle is large, as on superhydrophobic surfaces, the heat transfer may not be as sensitive to the maximum drop-size as previously supposed. Furthermore, previous drop-size distribution models may under-predict the heat transfer rate at high contact angles. Condensate drop behavior (jumping, non-jumping, and flooding) and size distribution are shown to be dependent on the degree of subcooling and nanostructure size. Drop-size distributions for surfaces experiencing coalescence-induced jumping are obtained experimentally. Understanding the drop-size distribution in the departure region is important since drops in this size are expected to contribute significantly to the overall heat transfer rate.
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Frasson, Renato Prata de Moraes. "Understanding the partitioning of rainfall by the maize canopy through computational modelling and physical measurements." Diss., University of Iowa, 2011. https://ir.uiowa.edu/etd/2702.
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The interception and redirection of rainfall by vegetation has implications for many fields such as remote sensing of soil moisture, satellite observation of rainfall, and the modeling of runoff, climate, and soil erosion. Although the modeling of rainfall partitioning by forests has received attention in the past, partitioning caused by crops has been overlooked. The present work proposes a two front experimental and computational methodology to comprehensively study rainfall interception and partitioning by the maize canopy. In the experimental stage, we deployed two compact weather stations, two optical disdrometers, and five tipping bucket rain gauges. Two of the tipping bucket rain gauges were modified to measure throughfall while two were adapted to measure stemflow. The first optical disdrometer allowed for inspection of the unmodified drop-size and velocity distributions, whereas the second disdrometer measured the corresponding distributions under the canopy. This indicates that the outcome of the interaction between the hydrometeors and the canopy depends on the drop diameter.
In the computational stage, we created a model that uses drop-size and velocity distributions as well as a three-dimensional digital canopy to simulate the movement of raindrops on the surfaces of leaves. Our model considers interception, redirection, retention, coalescence, breakup, and re-interception of drops to calculate the stemflow, throughfall, and equivalent height of precipitation stored on plants for a given storm. Moreover, the throughfall results are presented as two-dimensional matrices, where each term corresponds to the accumulated volume of drops that dripped at a given location. This allows insight into the spatial distribution of throughfall beneath the foliage. Finally, we examine the way in which the maize canopy modifies the drop-size distribution by recalculating the drop velocity based on the raindrop's size and detachment height and by storing the counts of drops in diameter-velocity classes that are consistent with the classes used by disdrometers in the experimental study.
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Broukal, Jakub. "Effervescent Breakup and Combustion of Liquid Fuels: Experiment and Modelling." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-234230.
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Tato práce se zaměřuje na oblast effervescentních sprejů a jejich aplikace na kapalné spalování s důrazem na průmyslové spalovací komory. Oba aspekty – modelování a experiment – jsou řešeny. Práce obsahuje obecný úvod, ve kterém jsou vysvětleny základní jevy rozpadu kapaliny a vířivého spalování a dále je představena effervescentní atomizace. Poté jsou popsány použité experimentální postupy jak pro měření spreje, tak pro měření tepelných toků do stěn při spalování. V následující kapitole jsou popsány numerické modely a jejich podstata je vysvětlena. Jsou zde uvedeny modely pro rozpad spreje, turbulenci a spalování použité během výzkumu. Vlastní výsledky práce jsou uvedeny formou samostatných článků (vydaných nebo přijatých) s dodatečnou částí věnovanou nepublikovaným relevantním výsledkům. Bylo zjištěno, že standardní modely sprejů jsou do jisté míry schopny popsat effervescentní spreje. Nicméně aby bylo možné predikovat plamen kapalného spreje, jsou zapotřebí detailnější modely sprejů, které dokáží přesně zachytit změnu průměrů kapek v radiálním a axiálním směru. Experimentální měření effervescentních sprejů bylo provedeno pomocí navrhnuté metodiky. Výsledky měření byly analyzovány s důrazem na radiální a axiální vývoj průměrů kapek a některé nové jevy byly popsány. Nepřímá úměrnost mezi gas-liquid-ratio a středním průměrem kapek byla potvrzena. Dále by popsán jev, kdy pro různé axiální vzdálenosti které dojde k úplnému převrácení závislosti středního průměru na axiální vzdálenosti. V závěru je uvedeno shrnutí, které rekapituluje hlavní výsledků a závěry. V závěrečných poznámkách je nastíněn možný budoucí postup. Experimentální data pro ověřování budoucích effervescentních modelů jsou poskytnuta.
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Aiazzi, Lorenzo. "Combined analysis of C-band polarimetric radar and disdrometer data of convective and stratiform precipitation." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/22121/.
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The aim of the present Thesis is to observe the characteristics of the precipitation and to check the quality of the radar data under different meteorological conditions. This aim is achieved through a combined analysis of the data collected by two instruments that have different operating principles: a C-band polarimetric radar and a PARSIVEL2 disdrometer. Radar variables are compared with the characteristics and the microphysics evolution of the precipitation retrieved by the disdrometer. The disdrometer is located in the city center of Bologna, at about 28 km far from the radar site. The combined analysis of the two instruments is done for a dataset that includes 11 months of the years 2019 and 2020. The dataset contains convective and stratiform precipitation events. The lower radar elevations are affected by anthropogenic interferences that slightly reduce the dataset extension. The analyses show a good correlation between the reflectivity factors retrieved by the radar and by the disdrometer through the Drop Size Distribution (DSD). The correlation coefficient between the two estimations is 0.84. A verification of the operational algorithm of the hydrometeor classification is obtained through the radar data. Moreover, the convective and stratiform discrimination developed through the disdrometer data is consistent with the polarimetric variables of the radar. For example, the distribution of the differential reflectivity peaks for higher values in a regime of convective precipitation in comparison to the stratiform regime. The convective distribution of the differential reflectivity has a median of 1.5 dB, while the stratiform one has a median of 0.9 dB. Lastly, the case study of a thunderstorm occurred in Bologna on May 28th 2019 is described. This case study shows precipitation structures of different intensities and different types of hydrometeors, allowing a verification of the previous results and a more-detailed analysis of the DSD characteristics.
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Åsberg, Mathias. "Kvantifiering av simulerat regn i vindtunnel." Thesis, Mittuniversitetet, Avdelningen för kvalitets- och maskinteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-34788.
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Vindtunneln som drivs av Sports Tech Research Centres är en unik anläggning för att bedriva forskning på både atletiska utövare och utrustning. Vindtunnelns avancerade system möjliggör för forskning och tester på material och produkter kan utföras i en verklighetstrogen miljö. Det finns även sedan byggnationen ett regnsystem installerat i vindtunneln. Detta system är inte uppmätt efter viktiga faktorer och ingen vetskap om det simulerade regnets egenskaper eller likhet med naturligt förekommande regn finns. Syftet med arbetet var att utföra mätningar på det befintliga regnsystemet med avseende på storlek och fallhastighet för dropparna. Arbetets syfte var även att jämföra de uppmätta regn egenskaperna mot vetenskapliga modeller som beskriver ett naturligt regn. Där målet med arbetet var att ta fram ett underlag på det befintliga regnet i vindtunneln. Testerna utfördes med en optisk distrometer som mätte de fallande vattendropparna med en laser. Distrometern användes för att mäta storlek samt fallhastighet på vattendropparna. Distrometer placerades vid tester på olika höjder i vindtunneln, regnet undersöktes även vid varierande vattenflöde och vindhastigheter. Resultatet visade på att simulerade regnet hade en lägre hastighet i förhållande till den uppmätta droppstorleken högt i tunneln. Hastigheten på dropparna lågt i tunneln visade mer följa modellernas beskrivning av en naturligfallhastighet. Droppstorleksfördelningen visades inte överstämma mot naturligt regn utan visar på en högre mängd stora droppar än vad som är naturligt förekommande. Intensiteten i vindtunneln var som lägst 62 mm/h vilket väldigt högt sett från naturligt regn. Utifrån dessa parametrar följer inte det simulerade regnet ett naturligt förekommande regn.The wind tunnel operated by Sport Tech Research Centres, are a unique facility to conduct research on athletic practitioners and their equipment. The advanced systems in the wind tunnel allows for research and testing of materials and product in a realistic environment. Since the construction of the wind tunnel a rain system was fitted. This system is not measured for important factors and no knowledge of the simulated rainfall properties or similarities to naturally occurring rain exists. The aim of this work was to perform measurements of the existing rainfall system with regards to size and falls speed of the droplets. The purpose was also to compare the measure rain properties to scientific models describing natural rainfall. The goal of the work was to get a foundation of the existing rain in the wind tunnel. The tests were performed with an optic disdrometer that measured the falling water particles with a laser. The disdrometer measured size and fall speed of the droplets. The tests were carried out on different heights in the wind tunnel, the rain was also investigated at varying water pressure and wind speeds. The result shows that the simulated rainfall had lower speed relative to the measured drop size high in the tunnel. Fall speed of droplets low in the tunnel showed more according to the model’s description of a natural rain fall speed. Drop size distribution was shown not to be consistent with natural rainfall. The distribution shows a higher amount of large drops than is naturally occurring. Rainfall intensity was measured to 62 mm/h as lowest which is very high compared to natural rain. Based on these parameters the simulated rain is not a naturally occurring rainfall.
Betyg: 180803
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Bufo, Moacir José 1938. "Coalescencia de imisciveis em filme de agua residuaria." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266420.
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Orientador: Liliane Maria Ferrareso LonaTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
Made available in DSpace on 2018-08-07T08:12:19Z (GMT). No. of bitstreams: 1 Bufo_MoacirJose_D.pdf: 987875 bytes, checksum: 8fa242d4879a20b9592f76cbbb4e5681 (MD5) Previous issue date: 2006
Resumo: Águas residuárias urbanas e industriais, cujo destino final em nível mundial é o rio, sempre apresentam imiscíveis na forma de película e gotas, sejam de óleos comestíveis ou óleos lubrificantes ou solventes petroquímicos. A grande dificuldade em separar estes imiscíveis está no diâmetro de gotas inferior a 40 microns. A melhor tecnologia, hoje, produz água tratada ainda com gotas de 20 microns e com teor de imiscível igual a 10 mg/litro. O autor do presente trabalho, em 1984, acidentalmente criou um coalescedor a filme, e realizou ensaios numa instalação em escala piloto, para encontrar uma solução para um problema de imiscível em água, de uma indústria petroquímica. Os ensaios qualitativos realizados mostraram que a tecnologia é eficiente para separar imiscíveis em água. Os estudos, naquela época, não tiveram continuidade. O regime de operação da instalação piloto era contínuo. A aparelhagem da piloto era totalmente em vidro. O controle destes ensaios foi por meio visual que é bastante significativo pelo fato de ser um controle simnão, isto é, ou tem turbidez ou não tem turbidez. A água residuária entrando no coalescedor era homogênea e na saída do coalescedor havia a formação de duas camadas distintas com uma interface de separação. A camada inferior apresentava uma turvação e a camada superior não apresentava turvação. Este fato mostra de forma inquestionável de que ocorreu um processo de aglutinação de partículas ou coalescência. Desta forma, o objetivo deste trabalho é dar continuidade ao trabalho iniciado em 1984, visando desenvolver uma metodologia para explicar o fenômeno da coalescência neste tipo de coalescedor e também desenvolver um modelo para o seu dimensionamento, visto que o fluxograma do processo já está estabelecido. Este trabalho é assim definido como teórico, uma vez que já existe o trabalho experimental realizado em 1984. A consulta em literatura tem três enfoques: O primeiro é conhecer o fenômeno da coalescência em termos científico. O segundo enfoque foi conhecer o estado da arte da tecnologia de coalescedor. O terceiro foi uma compilação de todos aqueles conhecimentos científicos e tecnológicos julgados pertinentes para a condução deste estudo. Adotouse, neste trabalho, o método de dedução indutiva e a antiga técnica da equação da proporcionalidade para propor um mecanismo e uma equação cinética da coalescência em filme de líquido. Também foi usada a equação da continuidade de NavierStokes para determinar o perfil de concentração das gotas ao longo do filme, visando gerar um modelo de dimensionamento para o coalescedor proposto. Foi constatado que o comportamento de imiscível em água é específico para cada espécie química e também depende da intensidade de energia aplicada ao meio. Por este motivo, a consolidação da tecnologia de separação de gotas de imiscível proposta só poderá ser realizada mediante um estudo numa instalação em escala industrial. Qualquer estudo em escala piloto vem somente confirmar o que já foi realizado e no máximo fornecer valores isolados de concentração de gotas de imiscível
Abstract: Urban and industrial wastewaters always have immiscible chemicals. These immiscibles are chemicals such as edible oils, lubricant oil and petrochemical solvents. The final destinations of these wastewaters is the river. It is very difficult to separate immiscibles with diameter drop less than 40 µm from the wastewater. The best separation technology available today still produces clean water with drops below 20 microns and with immiscible content of 10 mg/l. In 1984 the author of this work accidentally created one coalescence film equipment. The pilot scale test results were successful in separating immiscibles from wastewater in a petrochemical plant. The glass pilot plant operated continuously. The kind of control plant it is visual to detect the turbidity. The homogenous liquid wastewater is fed to the top of the coalescence equipment. The liquid issue. the bottom of equipment had two phases. The lower phase was turbid and the upper phase was not. Unfortunately the investigation was stopped at the time. Based on the research developed in 1984, the objective of this work is to study the phenomena of coalescence of the liquid film and to develop a kinetic coalescence model and a design model for a coalescence equipment. This present work is theoretical based on the experimental date (process flowsheet and design equipment) obtained in 1984. There are three main objectives: the first objective is to understand the coalescence phenomena; the second is to understand the development of coalescer technology; the third is to compile all relevant scientific and technological knowledge for this research. The investigation used the inductive deduction method and the old proportional equation technique to suggest a mechanism and kinetic equation to describe the film coalescence phenomenon. The NavierStokes equation was used to determine the drop concentration profile in the film, in order to produce a way to design the equipment. One conclusion is that each immiscible chemical behave differently in water. The applied energy also plays a role. Another pilot plant will only confirm what has been done and give isolated immiscible products drop concentration
Doutorado
Desenvolvimento de Processos Químicos
Mestre em Engenharia Química
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Viljoen, D. J. "Evaluation and performance prediction of cooling tower spray zones." Thesis, Link to the online version, 2006. http://hdl.handle.net/10019/1286.
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Olesen, Mark Jørn. "Prediction of drop-size distributions based on ligament breakup." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/nq22488.pdf.
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Boodoo, Sudesh. "Estimation of drop-size distributions from deconvolved doppler radar data." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=69698.
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A 915 MHz Doppler radar was able under certain conditions to provide Doppler spectra containing separate and distinct modes due to scattering by rain and by the clear air. The rain spectra are broadened and shifted on the velocity axis due to turbulent air motions. Information in the clear air mode is used to correct for these effects, leaving in the rain spectra the reflectivity-weighted distribution of drop fall speed, from which the drop-size distribution can be computed.The fast Fourier transform and two iterative methods of deconvolution were applied to simulated Doppler spectra. We concluded that the iterative methods of deconvolution are more appropriate than the fast Fourier transform. Of the two iterative methods, Jansson's method of deconvolution, including prefiltering of the data, was found to give better results than Van Cittert's method.
Jansson's method was applied to biomodal spectra obtained from the HARP project of 1990 in Hawaii and to spectra obtained from a similar radar operated in Montreal. Evident is the different characteristics of rainfall in both regions and the appropriateness of the same deconvolution method to different classes of spectra.
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Schlauch, Sonja. "Modeling and simulation of drop size distributions in stirred liquid-liquid systems." [S.l.] : [s.n.], 2007. http://opus.kobv.de/tuberlin/volltexte/2007/1518.
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Tridon, Frédéric. "Mesure des précipitations à l'aide d'un radar en bande X non-cohérent à haute résolution et d'un radar en bande K à visée verticale. Application à l'étude de la variabilité des précipitations lors de la campagne COPS." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2011. http://tel.archives-ouvertes.fr/tel-00777843.
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L'estimation quantitative des précipitations à l'échelle locale est une nécessité sociétale, à cause de l'augmentation des dégâts provoqués par des inondations exacerbées par l'urbanisation croissante. Or, des estimations locales sont particulièrement difficiles à réaliser à cause de la forte variabilité des précipitations. De plus, ce genre d'estimation est sollicité par de petits organismes tels qu'une commune, pour lesquels il n'est pas envisageable d'utiliser des instruments à la pointe de la recherche technologique à cause de leur coût prohibitif. Ainsi, il est nécessaire de développer des méthodes d'estimation quantitative des précipitations applicables à un dispositif expérimental de prix abordable. Dans ce but, un dispositif expérimental innovant est utilisé dans cette thèse. Il est constitué d'instruments de mesure directe, au sol, tels que des pluviomètres et des disdromètres, et d'un prototype de radar à balayage horizontal basé sur un radar nautique commercial, associé à un MRR (Micro Rain Radar) à visée verticale qui fournissent une estimation en altitude de la pluie, respectivement sur une surface donnée et le long d'un profil vertical. Le radar à balayage horizontal est un radar en bande X, c'est-à-dire qu'il fonctionne à une longueur d'onde lui procurant une très haute résolution radiale, mais qui est très atténuée par les précipitations. Le MRR permet d'obtenir une description précise de la microphysique des précipitations et sert de relais entre les mesures au sol et les mesures en altitude du radar en bande X. Ces deux radars étant novateurs, une grande partie de cette thèse consiste à valider leurs mesures : étalonnage, filtrage d'échos aberrants, correction de l'atténuation, etc. Une fois les mesures rendues exploitables, cette thèse se focalise sur l'étude de la variabilité des précipitations afin de proposer et développer différentes méthodes de classification, selon leur type ou leur variations locales, et de vérifier leur potentiel pour l'amélioration de l'estimation des précipitations. Les résultats montrent que cet objectif ne peut être atteint que si la qualité des mesures des radars est encore améliorée : moins d'échos parasites pour le radar en bande X et prise en compte du vent vertical pour le MRR.
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Padron, Gustavo A. "Effect of surfactants on drop size distributions in a batch, rotor-stator mixer." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/2160.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2005.Thesis research directed by: Chemical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Lee, Gyu Won. "Errors in rain mearurement by radar : effect of variability of drop size distributions." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19509.
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In this work, the various sources of errors in radar rain estimation are quantified and procedures are developed to reduce them. The few topics explored here are: the variability of drop size distributions (DSDs), radar calibration, and errors in polarimetric rain estimation. The findings resulting from this study include 1) a new filtering technique that reduces the spurious DSD sampling variability while maintaining the physical variability, 2) a generalization of previously suggested DSD models in terms of scaling concepts, 3) the experimental evidence of the physical interpretation of DSD evolution and of R-Z relationships, 4) the time scale dependence of the DSD variability and its implication for radar rain estimation, 5) the quantification of error sources in polarimetric rain estimation and its feasibility in operational environment, and 6) a complete set of stable radar calibration methods and their theoretical limits. All error statistics from this work will be used as a guideline in radar rain estimation.
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Pilon, Mark J. (Mark Joseph). "A numerical and observational study of bimodal surface raindrop size distributions /." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66028.
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Hsieh, Wei-Chun. "Representing droplet size distribution and cloud processes in aerosol-cloud-climate interaction studies." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29619.
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Thesis (Ph.D)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2009.Committee Chair: Athanasios Nenes; Committee Member: Andrew G. Stack; Committee Member: Irina N. Sokolik; Committee Member: Judith A. Curry; Committee Member: Mike Bergin; Committee Member: Rodney J. Weber. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Rowan, Michael A. "The utility of drip Irrigation for the distribution of on-site wastewater effluent." The Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1078848711.
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Hohl, Lena Katharina [Verfasser], Matthias [Akademischer Betreuer] Kraume, Matthias [Gutachter] Kraume, and Alberto [Gutachter] Brucato. "Dispersion and phase separation in liquid multiphase systems : influence of three phase conditions on drop size distributions / Lena Katharina Hohl ; Gutachter: Matthias Kraume, Alberto Brucato ; Betreuer: Matthias Kraume." Berlin : Technische Universität Berlin, 2019. http://d-nb.info/1178524930/34.
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Ahmed, Aqeel. "LES of atomization and cavitation for fuel injectors." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMR048/document.
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Cette thèse présente la Simulation des Grandes Echelles (LES) de l’injection, de la pulvérisation et de la cavitation dans un injecteur pour les applications liées aux moteurs à combustion interne. Pour la modélisation de l’atomisation, on utilise le modèle ELSA (Eulerian Lagrangian Spray Atomization). Le modèle résout la fraction volumique du combustible liquide ainsi que la densité de surface d’interface liquide-gaz pour décrire le processus complet d’atomisation. Dans cette thèse, l’écoulement à l’intérieur de l’injecteur est également pris en compte pour une étude ultérieure de l’atomisation. L’étude présente l’application du modèle ELSA à un injecteur Diesel typique, à la fois dans le contexte de RANS et de LES.Le modèle est validé à l’aide de données expérimentales disponibles dans Engine Combustion Network (ECN). Le modèle ELSA, qui est normalement conçu pour les interfaces diffuses (non résolues), lorsque l’emplacement exact de l’interface liquide-gaz n’est pas pris en compte, est étendu pour fonctionner avec une formulation de type Volume of Fluid (VOF) de flux à deux phases, où l’interface est explicitement résolu. Le couplage est réalisé à l’aide de critères IRQ (Interface Resolution Quality), qui prennent en compte à la fois la courbure de l’interface et la quantité modélisée de la surface de l’interface. Le modèle ELSA est développé en premier lieu en considérant les deux phases comme incompressibles. L’extension à la phase compressible est également brièvement étudiée dans cette thèse. Il en résulte une formulation ELSA compressible qui prend en compte la densité variable de chaque phase. En collaboration avec l’Imperial College de Londres, la formulation de la fonction de densité de probabilité (PDF) avec les champs stochastiques est également explorée afin d’étudier l’atomisation. Dans les systèmes d’injection de carburant modernes, la pression locale à l’intérieur de l’injecteur tombe souvent en dessous de la pression de saturation en vapeur du carburant, ce qui entraîne une cavitation. La cavitation affecte le flux externe et la formulation du spray. Ainsi, une procédure est nécessaire pour étudier le changement de phase ainsi que la formulation du jet en utilisant une configuration numérique unique et cohérente. Une méthode qui couple le changement de phase à l’intérieur de l’injecteur à la pulvérisation externe du jet est développée dans cette thèse. Ceci est réalisé en utilisant le volume de formulation de fluide où l’interface est considérée entre le liquide et le gaz; le gaz est composé à la fois de vapeur et d’airambiant non condensableThis thesis presents Large Eddy Simulation (LES) of fuel injection, atomization and cavitation inside the fuel injector for applications related to internal combustion engines. For atomization modeling, Eulerian Lagrangian Spray Atomization (ELSA) model is used. The model solves for volume fraction of liquid fuel as well as liquid-gas interface surface density to describe the complete atomization process. In this thesis, flow inside the injector is also considered for subsequent study of atomization. The study presents the application of ELSA model to a typical diesel injector, both in the context of RANS and LES. The model is validated with the help of experimental data available from Engine Combustion Network (ECN). The ELSA model which is normally designed for diffused (unresolved) interfaces, where the exact location of the liquid-gas interface is not considered, is extended to work with Volume of Fluid (VOF) type formulation of two phase flow, where interface is explicitly resolved. The coupling is achieved with the help of Interface Resolution Quality (IRQ) criteria, that takes into account both the interface curvature and modeled amount of interface surface. ELSA model is developed first considering both phases as incompressible, the extension to compressible phase is also briefly studied in this thesis, resulting in compressible ELSA formulation that takes into account varying density in each phase. In collaboration with Imperial College London, the Probability Density Function (PDF) formulation with Stochastic Fields is also explored to study atomization. In modern fuel injection systems, quite oftenthe local pressure inside the injector falls below the vapor saturation pressure of the fuel, resulting in cavitation. Cavitation effects the external flow and spray formulation. Thus, a procedure is required to study the phase change as well as jet formulation using a single and consistent numerical setup. A method is developed in this thesis that couples the phase change inside the injector to the external jet atomization. This is achieved using the volume of fluid formulation where the interface is considered between liquid and gas; gas consists of both the vapor and non condensible ambient air
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Chen, Yi-ru, and 陳奕如. "The Characteristic of Drop Size Distribution During SoWMEX." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/02073854756182171013.
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碩士國立中央大學
大氣物理研究所
97
In 2008,a joint field experiment named SoWMEX/TiMREX was conducted in southern Taiwan.Most previous studies of the DSD in Taiwan focus on the north, and therefore this experiment is expected to help analyze the DSD in the south. Six disdrometers located in Quan-Xin,Ma-Ja,Quan-Fu,Fan-Hua,and Chin-San were utilized. This study analyzes precipitation events from May 16 to June 30 and discusses the properties of the DSD for different precipitation types. No matter what distinguishing precipitation types method used,the result shows the drop number concentration of convective precipitation is an order of magnitude larger than that of stratiform rain, and the range of the convective DSD is larger as well. When these two types are distinguished with 20 mm/hr as a rain rate boundary, the drop number concentration of convective rainfall is more than that of stratiform rain for drop sizes more than 2.0 mm, and less for drop sizes smaller than 2.0 mm. In addition, the rainfall and D_m observed in Chin-San are larger than the others because of its higher altitude. Compared with the Dm-Nw relation deduced by Bringi et al.(2003),there are similar results with the stratiform rainfall in southern Taiwan, while the convective rain is maritime-like and close to that observed in northern Taiwan. The rainfall properties of the Mei-yu season in 2008 is analyzed using an 2DVD located in Quan-Xin. The total rainfall duration is 8383 minutes, within which the stratiform rain is 5523 minutes(65%) and the convective rain is 2500 minutes(34%).The total rainfall accumulation is 987 mm, within which the stratiform one is 190.11mm(19%) and the convective one is 794.14 mm(80%). Therefore it’s shown that, in the Mei-yu season, the statiform rain is the major contribution to the rainfall duration while the short-time convective rainfall contributed to the most accumulation rainfall . DSD parameter statistics shows, slope parameterΛ, mean mass diameter Dm, liquid water content LWC and reflectivity dBZ are all larger in the convective rain than in the stratiform one, but the event frequency and shape parameter μ of the stratiform rainfall is larger instead.But the results derived from N0-R relation method has converse with the others while in convective type.
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Chiang, Mon-Liang, and 蔣孟良. "Investigation of Drop Size Distribution of Different Systems of Precipitation." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/94907538836291606081.
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Tsai, Chih-Chien, and 蔡直謙. "Budget Analysis of Drop Size Distribution: A Case Study during SoWMEX/TiMREX." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/hhg8y7.
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碩士國立中央大學
大氣物理研究所
97
3-D wind and DSD can be retrieved using dual polarization Doppler radar data. In addition to warm-rain microphysical processes such as nucleation, condensation, evaporation, coalescence and breakup, advection and sedimentation also lead to variation of DSD. The DSD at two time steps and the 3-D wind between allow a budget analysis of the drop number concentration, separating microphysical and kinematic effects. This article analyzes a convective cell observed by NCAR’s SPOL radar when it performed intensive sector scans toward its south during IOP-8 of SoWMEX/TiMREX. The data processing steps include interpolating radar data, calculating the average system speed, correcting the observation time lag, retrieving 3-D wind, retrieving DSD and calculating the budget equation at different stages of the convective cell. The 3-D wind is recovered by the single-Doppler velocity retrieval method of Liou (2007). The DSD is retrieved by the constrained gamma method of Brandes et al. (2003). The evolution of the convective cell is divided into 3 stages, during which the budget analysis of rain water content in the reflectivity core is as follows. During the intensifying stage, the total derivative of rain water content is positive for all drop sizes, which infers coalescence and condensation are the dominant microphysical processes. During mature stage I, the total derivative is negative for small and big drops but positive for median ones, which infers, besides condensation, coalescence and breakup dominate for small and big drops respectively. During mature stage II, the total derivative is nearly zero for all sizes, which infers opposite microphysical processes are well-matched. During the dissipating stage, the total derivative is negative for all sizes, which results, in doubt, from evaporation due to entrainment of drier air.
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Zeng, Zhao-Cheng, and 曾昭誠. "Analysis and Retrieval of Drop Size Distribution in 2016 Taipei Summer Storm Experiment." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/f2eth8.
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碩士國立中央大學
大氣科學學系
105
Polarimetric radar system provide high temporal and high-spatial resolution data and disdrometers can show the characteristic of Drop Size Distribution (DSD). Base on the information of disdrometer data, dual Polarimetric Radar data can be used to retrieve the parameters of DSD. The DSD varies from case to case or even in the different periods of a case. Therefore, understanding the variety of DSD is helpful to improve the accuracy of DSD parameters retrieved by radar. The data of Taiwan Experimental Atmospheric Mobile Radar (TEAM-R) and Impact Disdrometer (JWD) observations collected in Taipei Summer Storm Experiment (TASSE) during early September of 2016 was used. From the disdrometer data, the three Gamma distribution parameters including the intercept N_0, the shape (μ) and rate (Λ) parameters can be calculated through moment method. Through the scattering calculation the relations between polarimetric variables and gamma distribution parameters can be derived. The constrain relation between the shape (μ) and rate (Λ) parameters is necessary to retrieve the three Gamma distribution parameters from polarmetric variables Z_DR and K_dp. In this study, two constrain relations were applied: first one is the well known relation proposed by Brandes et al, , the second one is from the statistics during the three days disdrometer observation of thunderstorms in TASSE. The retrieved three dimensional distribution of DSD are compared between these two retrieval applications. A third approach is directly fitting the DSD Gamma parameters with the polarimetric variables to retrieve three Gamma parameters from fitting functions. Because the limitation of very large drop in disdrometer, the third method is not be able to retrieve reasonable DSD at large Z_DR situation. The retrieved three dimensional DSDs in different stages of thunderstorm reveal very bounty microphysical information. The relatively smaller concentration and drop diameter were found in the initiation stage, while the deep convection was developed one to two order of magnitude of concentration were found through the convective core. More cases studies and much longer statistics and validation should be conducted in the near future.
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Chien, Chiao-Ling, and 簡巧菱. "The characteristics of drop size distribution in different seasons and rain-types in Taiwan." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/5r67fq.
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碩士國立中央大學
大氣物理研究所
94
Characterization of variations in the raindrop size distribution (DSD) is required for microphysical studies. The DSD varies in different rain types and different spatial distribution. And variations in reflectivity-rainfall (Z-R) relations are strongly dependent on DSD variations. Other integral rainfall parameters such as liquid water content, reflectivity, and rain-rate are also functions of DSD. For these reason, it is important to analyze the DSD in different places and rain types. DSD data collected with a Joss-Waldvogel disdrometer (JWD) and a 2d-video disdrometer (2DVD) in NCU from February, 2002 to May, 2006, is used to analyze the variations in gamma parameters of raindrop spectra. Besides, to compare the spatial difference of DSD, we also analyzed JWD data in five stations (i.e. Feitsui, Nankang, NCU, Shiyun and Suiman) from June, 2004 to May, 2006. On average, as the rain-rate increased, more large drops were found in 2DVD and JWD. Although JWD underestimated the small drops, the small drops had little impact on the rain-rate and reflectivity differences between the 2DVD and JWD. For the comparison between five stations in northern Taiwan, the rainfall characteristics of Feitsui were more light rain and more small drops. Nankang had less small drops because small drops were masked by background noise. More heavy rainfall events occurred in Suiman and Shiyun due to its geographical features. And the average raindrop size in Suiman and Shiyun was larger than the other three stations. DSD data from 2DVD and JWD had been analyzed to determine the variability of drop size in different seasons and precipitation types. For winter and front type, the rain-rate was smaller and the raindrops tended to smaller drop size. For Mei-yu front, the raindrop spectra were broader than the other seasons or types except the afternoon thundershower type. And the raindrop size was larger than winter. For typhoon type, the raindrops tended to medium size. As rain-rate greater than 60(mm/hr), the right side of raindrop spectra became narrow and the concentration of large drops decreased. For afternoon thundershower, it had more heavy rainfall events. The drop size was the largest and its spectra were the broadest of all types. The composite statistics based on disdrometer suggested that the median volume diameter and generalized intercept for rain-rate less than 10(mm/hr) lied on a straight line with negative slope, which similar to stratiform rain type discussed by Bringi et al. (2003). And as rain-rate larger than 10(mm/hr), the two parameters lied between “maritime-like” and “continental-like” clusters. In squall line case study, the analysis showed that stratiform precipitation has weaker reflectivity, narrower raindrop spectra, and smaller drop size. For convective precipitation, it had stronger reflectivity, broader raindrop spectra, and larger drop size. In typhoon Aere case, during the spiral band passage, the raindrop spectra became broader and the raindrop size was larger compared to the raindrop size during the passage of eye wall.
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Dolman, Bronwyn Kaye. "Raindrop size distribution retrievals in the tropics and mid latitudes." Thesis, 2010. http://hdl.handle.net/2440/65561.
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Weather radar capabilities have improved dramatically over the last 50 years. Following World War II, surplus military radars were turned to the study of weather. Since then, they have evolved to the modern standard of rainfall estimations available to the general public in real time. Forecasters rely on weather radars not only for routine forecasting, but also for tracking rapidly evolving, potentially hazardous, severe weather events. These storms have the potential to cause flash floods and hence loss of crops, livestock, and human life. Most weather radars estimate rainfall by converting the measured reflectivity to a rainrate via an empirical relationship (Z-R relationship). There are limitations in the accuracy of the rainfall estimates derived from these scanning radars. Variations in the raindrop size distribution (DSD), that is, the spread of sizes of raindrops falling at a given location, affect the measured reflectivity, and thus the rain rate estimate. The DSD can vary both temporally and spatially, and also with latitude. Investigation of the DSD and its evolution can be used to investigate the effectiveness of Z-R relationships in varied meteorological conditions and locations. Well-established techniques exist for retrieving the DSD using vertically pointing VHF Doppler radars. These radars can simultaneously detect a clear-air echo due to fluctuations in temperature and humidity, and a precipitation echo. Mean vertical air motion and spectral width are estimated from the clear air spectrum, and used to correct the precipitation spectrum through a deconvolution procedure. The corrected precipitation spectrum is then converted to a size spectrum, and the DSD calculated. The DSD and associated integral parameters such as rainrate and liquid water content can then be used to infer the microphysical processes dominating the cloud and precipitation structure. This knowledge can then be used to investigate various Z-R relationships. This thesis presents DSD retrievals from VHF profilers located in Adelaide and Darwin. Each profiler is installed within the footprint of a scanning weather radar, allowing direct comparison of the same air space. These radars provide a unique opportunity to study the evolution of the DSD with the profiler, and use this to investigate variations in time and height of the Z-R relationship. The locations of the radars also permits investigation of the differing nature of DSD evolution in the tropics compared to the mid-latitudes. The TWP-ICE field campaign was conducted in Darwin and surrounding areas in January and February 2006. The campaign involved many instruments, both insitu and remote sensing, including a fleet of aircraft and ship. The University of Adelaide Atmospheric Physics Group installed a VHF wind profiler operating at 54.1 MHz near Darwin airport for the experiment. This radar sampled the same air space as a C-band polarimetric scanning radar (CPol), which performed horizontal scans at increasing elevations, along with vertical scans over the profiler site every 10 minutes. Results from 8 events, differing in age, type, dominant microphysical process and seasonal regime are presented in this thesis. A VHF profiler permanently located near Adelaide airport provides an observational capability similar to Darwin, but in the mid-latitudes where the processes dictating rainfall are vastly different. This radar also operates at 54.1 MHz, and is installed within the footprint of an operational weather watch radar. Pseudo vertical scans can be constructed from the successive horizontal scans allowing direct comparisons. This profiler is the first generation of the profiler in Darwin. It is not as powerful and cannot detect low intensity rainfall. Due to this and the drought South Australia experienced between 2006 and 2008, data from Adelaide are limited. Two events are presented. Seasonal trends in the tropics, that is break conditions as opposed to the monsoon, are compared and contrasted. These trends are then compared to the limited Adelaide data. By analysing the evolution in both time and height of the DSD, and the dependence on season and latitudinal location, this thesis leads to a better understanding of the microphysical processes dictating rainfall in the tropics and
mid-latitudes.Thesis (Ph.D.) -- University of Adelaide, School of Chemistry and Physics, 2010
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Lu, You-jia, and 盧又嘉. "The Characteristic of Drop Size Distribution associated with the landfall of the typhoon Fanapi in 2010." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/55327012375254397944.
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碩士國立中央大學
大氣物理研究所
100
Many studies have indicated that there are different characteristics of the drop size distribution(DSD) according to the rainfall situation. The DSD can determine the rainfall integer parameters, including liquid water content(W), reflectivity factor(Z) and rainfall rate(R), etc. Therefore, it is very important to analyze the characteristics of DSD. Joss-Waldvogel disdrometers was conducted in this study to investigate the characteristics of DSD associated with the landfall of the typhoon Fanapi in 2010. There are four Joss-Waldvogel disdrometers had been deployed in the south ( Kaohsiung Jiasian station and Jilai station) and the north (Feitsui station and Hsiayun station) respectively. Base on the distribution and variation of radar reflectivity, we can attribute the precipitation associated with typhoon Fanapi to four different rainbands: the peripheral circulation, the strong convection rainbands before the eye passing through, the strong convection rainbands after the eye passing through and spiral rainbands. The characteristics of DSD in different rainbands during typhoons invading Taiwan will be investigated in this study. The results from this study about DSD indicate that there are more small drops concentration in the precipitation associated with peripheral circulation than in other rainbands. There are more large drops and small drops concentration in the strong convection rainbands before the eye area passing through than in the strong convection rainbands after the eye passing through. When comparing the rainfall integer parameters, there is good relation between the slope(Λ) and the shape index(μ). The bigger μ value in the strong convection rainbands after the eye passing through means less small drop concentration. The smaller μ value in the strong convection rainbands before the eye passing through means more small drop concentration. Since the Λ values are smaller in all the rainbands associated with strong convection rainbands before and after the eye passing through means more midsize drops concentration and large drops concentration in the strong convection rainbands. This findings are consistent with DSD investigation. Because the intercept parameter (N_0) is influenced by μ value, we normalize it and get the generalized intercept parameter(N_w). Comparing with previous studies about the relation between mass-weighted diameter D_m and the generalized intercept parameter N_w, the precipitation accompany with peripheral circulation of the typhoon was closed to maritime convective type. The precipitation type of the strong convection rainbands is in the range of continental convective type. The spiral rainbands was approximately the same with the distribution of stratiform type.
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Owolawi, Pius Adewale. "Rain rate and rain drop size distribution models for line-of-sight millimetric systems in South Africa." Thesis, 2006. http://hdl.handle.net/10413/1520.
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Radio frequencies at millimeter wavelengths suffer greatly from rain attenuation. It is therefore essential to study rainfall characteristics for efficient and reliable design of radio networks at frequencies above 10GHz. These characteristics of rain are geographically based, which need to be studied for estimation of rain induced attenuation. The ITU-R, through recommendations P.837 and P.838, have presented global approaches to rain-rate variation and rain-induced attenuation in line-of-sight radio links. Therefore, in this dissertation characteristics of rainfall rate and its applications for South Africa are evaluated. The cumulative distributions of rain intensity for 12 locations in seven regions in South Africa are presented in this dissertation based on five-year rainfall data. The rain rate with an integration time of 60 minutes is converted into an integration time of 1 minute in accordance with ITU-R recommendations. The resulting cumulative rain intensities and relations between them are compared with the global figures presented in ITU-R Recommendation P.837, as well as with the work in other African countries, notably by Moupfuma and Martin. Based on this work, additional rain-climatic zones are proposed alongside the five identified by ITU-R for South Africa. Finally, the study compares the semi-empirical raindrop-size distribution models such as Laws and Parsons, Marshall and Palmer, Joss, Thams and Waldvogel, and Gamma distribution with the estimated South Africa models.Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2006.
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Raikar, Neha B. "Prediction and manipulation of drop size distribution of emulsions using population balance equation models for high-pressure homogenization." 2010. https://scholarworks.umass.edu/dissertations/AAI3409835.
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Emulsions constitute a wide range of natural as well as processed products. Pharmaceutical applications of emulsions include oral administration, parenteral delivery, ophthalmic medicine, topical and transdermal creams, and fluorocarbon-in-water emulsions for blood oxygenation. In the foods area many of the products like mayonnaise, margarine, ice-creams are emulsions by nature and some products can also be used for delivery of active ingredients (e.g. nutraceuticals) with potential health benefits. Emulsions are also encountered at many stages of petroleum recovery, transportation, and processing. Typically, emulsions are manufactured in a two-step process. First a coarse emulsion called a premix is made which is passed through a high-pressure homogenizer. Intense energy supplied in the high pressure homogenizer causes breakage of the coarse emulsion to a fine one with a tighter distribution. Population balance equation (PBE) models are useful for emulsions since they allow prediction of the evolution of the drop size distribution on specification of the two rate processes i.e., breakage of drops due to the flow field and coalescence of colliding drops. In our work, we developed a PBE model to describe emulsion breakage in a high pressure homogenizer. The focus of the work was breakage and conditions to keep coalescence to minimum were implemented. Two breakage rates representing two mechanisms i.e., turbulent inertial and turbulent viscous breakage were necessary for reproducing the bimodal nature of the distributions. We used mechanistic functions in the PBE model to develop a predictive model which could be extended to changes in formulation variables as well as process variables. Starting with the assumption of binary breakage, the model was refined to include multiple drop breakage. The developed model was found to be extensible to reasonable changes in oil concentration, surfactant concentration, continuous phase viscosity and constant ratio of oil to surfactant. Anomalies in pressure prediction encountered earlier were also corrected for by including some additional features like heating, maximum stable diameter, and number of daughter drops. A preliminary attempt was also made to use the developed model for designing experiments for making target emulsions with pre-specified properties.
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(11192166), Marcus Terrell. "INVESTIGATING THE EFFECT OF SIZE SORTING ON THE VERTICAL VARIATION OF RAIN DROP SIZE DISTRIBUTIONS USING PARSIVEL DISDROMETERS AND WSR-88D RADARS DURING VORTEX-SE." Thesis, 2021.
Find full textAbstract:
Rain drop size distributions (DSDs) in severe convective storms are highly variable in time and space. DSDs can be derived from polarimetric radar observations at high spatiotemporal resolution but these observations are often lacking near the surface owing to radar horizon issues. Disdrometers provide “ground-truth” measurements and validation of radar-derived DSDs but are by nature limited point measurements. Moreover, substantial evolution of the DSD can occur between the lowest radar elevation angle and the surface. Recent studies have shown that hydrometeor size sorting (HSS) is an important and even dominant process contributing to DSD evolution in severe storms; many physical processes such as the strength of the updraft, transient effects, and storm-relative mean winds are contributing factors to continued size sorting. In this study, we focus on strong storm-relative mean winds that induce sustained size sorting owing to the different residence times of hydrometeors of different sizes as they fall in severe storms. The resulting differential advection leads to a distinct horizontal spread of hydrometeors of different sizes at the bottom of a given layer. The goal of this study is to evaluate the impact of size sorting on DSD evolution from the radar level to the surface. To accomplish this, we develop and apply a raindrop trajectory model to compute the evolution of DSDs between radar observations aloft and the surface. For simplicity and to isolate the effects of size sorting, we neglect processes such as breakup, collection, and evaporation, and assume a horizontally homogeneous wind profile. We use disdrometer and radar data, which measure DSDs at the surface and provide the observed quantities aloft, respectively. The disdrometer data was collected from portable disdrometers as a collaboration between Purdue University, University of Oklahoma, University of Massachusetts, and the National Severe Storms Laboratory during the VORTEX-SE 2017 field campaign. NEXRAD data from KHTX Huntsville, AL and KGWX Columbus Air Force Base, MS was retrieved from the National Centers for Environmental Information (NCEI).
We evaluate three separate cases, a tornadic QLCS on 30 April 2017, a cluster storm on 27 March 2017, and a squall line on 25 March 2017. After the radar data is pre-processed, we retrieve the DSDs from the radar by assuming a gamma distribution and discretize them into PARSIVEL bins to produce a gridded dataset of DSDs. We then apply the raindrop trajectory model to compute the DSDs at the surface which are then compared directly with disdrometer observations. Analysis and comparisons from all cases yield similar results in that-the sorted radar DSDs at the surface are overall closer to the disdrometer observations than the original radar DSDs aloft. Results also show that the spatial variation of DSDs is higher at the surface due to size sorting by the storm-relative mean winds.
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Lu, Chung-Hua, and 呂崇華. "Using dual-polarization radar measurements to analyse the microphysics characteristics of the drop size distribution of Mei-yu frontal rainfall." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/8rcjs4.
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碩士國立中央大學
大氣物理研究所
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The major purpose of this research is to understand the microphysics characteristics of Mei-yu frontal system over Taiwan area using NCU C-band dual-polarization (C-Pol) radar measurements. A sequence of quality control procedures are carried out by using the differential phase measurements (ΦDP) to correct the system bias and attenuation of reflectivity (ZH) and differential reflectivity (ZDR). The corrected radar parameters were verified, the improvement after correction procedure is pronounced. The method for retrieving drop size distribution (DSD) parameters is to assume that the drop size distribution (DSD) is represented by a gamma distribution, and an empirical relation between the distribution shape (μ) and slope (Λ) parameters. Then the three gamma parameters ( 、 、 ) can be derived from the polarimetric variables (ZH、ZDR and KDP) through an forward numerical calculation of scattering model. Retrieved physical characteristics of the drop size distribution (DSD) were generally well matched with disdrometer observations. The retrieval data is applied to the selected Mei-yu frontal precipitation cases to analyze the microphysics characteristics of the rainfall system. The research results indicate that two strong convective cases are dominated by relatively large drops number and relatively large drops size respectively at the same rainfall rate. Two cases have great variation in the drop size distribution (DSD). At high rain rates, the D0 values reach a steady value what are believed to be equilibrium DSDs in which breakup and accretion are roughly in balance. Besides, the radar measurements suggest that the correlation coefficient (ρhv) in both convective rain and stratiform rain will lower under mixed-phase precipitation.
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藤吉, 康志. "雪片の融解分裂による粒径分布の変化の解明." 1994. http://hdl.handle.net/2237/13004.
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Miller, Richard Allen. "A method of producing drop size distributions in emulsions." Thesis, 1993. http://hdl.handle.net/1911/13805.
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A method of producing, collecting, and measuring drop size distributions in liquid-liquid emulsions has been developed. The emulsion is produced in a standardized cylindrical mixing tank. Dispersed phase droplets are encapsulated with a thin polymer film through a polycondensation reaction. Once encapsulated, the droplets behave as solid particles and may be removed from the mixing tank and measured. Data collected in the laboratory is used to support a proposed second law function, which may be used to test the validity of correlations that predict drop size distributions in emulsions.
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Schlauch, Sonja [Verfasser]. "Modeling and simulation of drop size distributions in stirred liquid-liquid systems / vorgelegt von Sonja Schlauch." 2007. http://d-nb.info/983652899/34.
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Firda, John Michael. "Application of dual-frequency millimeter-wave Doppler spectra for the retrieval of drop-size distributions in precipitation." 1997. https://scholarworks.umass.edu/dissertations/AAI9809331.
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This dissertation presents a procedure that uses dual-frequency millimeter-wave Doppler spectra to retrieve the drop-size distribution of rain. Using two frequencies rather than one makes it possible to extract information about the drop-size distribution with less dependence on models. The two data sets can be compared to each other in addition to existing models. Vertical air motion is determined by Mie scattering effects, and turbulence is removed by correlating the two retrieved distributions. An iterative procedure uses retrieved drop-size distributions to estimate vertical air motion, reducing the dependence on a model drop-size distribution. Drop-size distributions and vertical air motion are retrieved at high spatial and temporal resolutions. Data was gathered to test the algorithm with the University of Massachusetts' Cloud Profiling Radar System (CPRS) during April 1995 at the Ground Based Remote Sensing - Intensive Observation Period (GBRS-IOP) sponsored by the Department of Energy - Atmospheric Radiation Measurement (DOE-ARM) program. The measurements represent the first simultaneous Doppler spectra at these frequencies. The experiment took place in April of 1995 at the ARM Cloud and radiation Testbed (CART) site in Lamont, OK. The radar obtains colocated spectra at 33.12 and 94.92 GHz by using a single one-meter-diameter lens antenna. Radio-sonde and surface measurements of temperature and pressure, provided by the ARM-site, were used in the retrieval algorithm. Rain from stratiform and convective clouds was analyzed. The stratiform rain case had a relatively uniform rain-rate with small variations in mean velocity, implying that the vertical winds did not vary significantly over time. The convective case showed frequent variations in mean velocity with greater intensity than the stratiform case, as well as short cells of increased precipitation. The algorithm's results were reasonably good for rain-rates higher than 1 $mmhr\sp{-1}$, and vertical air motion estimates were found to be relatively insensitive to the initial drop-size distribution model used after iterating the algorithm with retrieved drop-size distributions.