Tesi sul tema "Floc properties"
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1
Kim, Jinho. "Floc properties in stirred suspensions". Thesis, University College London (University of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268458.
Testo completo
2
Selomulya, Cordelia Chemical Engineering & Industrial Chemistry UNSW. "The Effect of Shear on Flocculation and Floc Size/Structure". Awarded by:University of New South Wales. Chemical Engineering and Industrial Chemistry, 2002. http://handle.unsw.edu.au/1959.4/18226.
Testo completoAbstract (sommario):
The effect of shear on the evolution of floc properties was investigated to analyse the flocculation mechanisms. Little fundamental attention has been given to the shear influence that often creates compact aggregates, while the floc characteristics might differ in other aggregating conditions. It is thus crucial to understand how flocs evolve to steady state, if their properties are to be 'tailored' to suit subsequent solids-liquid separation processes. In this work, flocculation of monodisperse latex particles of various sizes (60, 380, and 810 nm diameter) via electrolyte addition was carried out in a couette-flow and also in shear fields generated by an axial-flow impeller (Fluid foil A310) and a radial-flow impeller (Rushton R100) in standard mixing tanks. A small-angle light scattering technique was used to acquire information regarding the time variation of floc properties in a non-intrusive manner. The structure was quantified by a measure of fractal dimension, signifying the degree of floc compactness. Estimates of the average floc mass were also obtained from the aggregate scattering patterns. By monitoring the changes in floc structure and mass, corresponding to the size evolution; mechanisms of floc formation, fragmentation, and restructuring were identified. Aggregates of 60 and 380 nm particles were observed to grew larger initially, before decreasing to their equilibrium sizes at moderate shear rates (32 - 100 s-1) in a homogeneous shear environment. Floc restructuring at large length scales occurred extensively, and was responsible for the drop in size, particularly at the early stage of the process. Aggregates of 810 nm particles did not, however, display this behaviour. Flocs of larger primary particles were presumably susceptible to breakage rather than deformation, as they were weaker under comparable conditions. Denser aggregates were found when restructuring transpired, while comparatively tenuous flocs were observed when formation and breakage kinetics were the governing mechanisms. The disparity in floc behaviour at higher shear rates (246 s-1 - 330 s-1) was less apparent. The intense hydrodynamic stresses in those instances inevitably caused fragmentation, regardless of the intrinsic particle properties; hence the observed floc compaction was the product of break-up and re-aggregation. A population balance model, incorporating variation in floc structure, displayed comparable trends in size evolution; verifying that restructuring indeed took an important role under certain flocculation conditions. Similar phenomena were likewise observed with the flocculation in stirred tanks. The results reinforced findings in literature; that while circulation time controlled the process kinetics; the floc size was determined by the turbulent stresses. In addition, the maximum shear levels also influenced the floc structures, with denser aggregates produced in a shear field generated using the radial-flow impeller at equivalent energy dissipation per-unit mass. A correlation between non-dimensional floc factor that embodied the aggregate size and structure, and aggregation factor comprising the significant parameters from flocculation conditions, was proposed. The proposed relationship takes into account aspects such as the aggregate structure, interparticle forces, and particle concentration that are often overlooked in existing relationships, which usually only relate the maximum floc size to the applied energy dissipation rate. It thus provides an improved manner of presenting general flocculation data, as well as a means to predict floc properties produced under a specific aggregation condition. Future studies with increasingly complex systems that resemble real conditions are recommended in order to establish a practical understanding of the flocculation mechanisms, for the purpose of optimising the aggregate properties.
3
Balls, Margaret. "Relationships between floc properties and NOM removal using a moorland water source". Thesis, University College London (University of London), 2014. http://discovery.ucl.ac.uk/1417138/.
Testo completoAbstract (sommario):
Natural organic matter, or NOM presents a treatment challenge to the conventional water treatment process and has been associated with the formation of disinfection by-products (DBP’s) such as Tri-halomethanes (THM’s) if not removed prior to the disinfection stage. Poor removal of NOM is also thought to lead to filter performance problems such as turbidity or particle count breakthrough, which represents an increased risk of passage of Cryptosporidium into the treated water. Understanding the complex nature of NOM floc and how its physico-chemical properties relate to the coagulation matrix within the water treatment process is therefore key to optimising NOM removal. This forms the basis of the study which was carried out entirely using a natural raw moorland source water, which is preferable over synthetic kaolin based systems. The experimental programme encompassed both bench-scale and pilot-scale tests, and investigated the effect of changes to a number of variables such as coagulant type, coagulation pH and Fe:DOC ratio on floc physico-chemical properties. The approach taken in this work, of monitoring NOM removal alongside floc properties obtained from the optical flocculation monitor revealed some key trends. Firstly under equivalent shear conditions the coagulant dose almost always correlated with the steady-state maximum floc size, and influenced the flocculation rate. Generally the ferric based systems with the largest and fastest forming floc correlated with the best NOM removal, but when the applied Fe:DOC range was narrow and within an optimal range it was difficult to pin-point the best dose. The organic coagulants polyDADMAC and Zetag 64 formed larger, amd more reversible floc than the ferric based systems but with poor NOM removal. Secondly under equivalent shear conditions the larger flocs exhibited the least resistance to breakage, regardless of the coagulant system. Finally with regard to floc physico-chemical properties and filter performance, some key trends were revealed. Zeta potential influenced both NOM removal and the filtered water quality with considerable improvement noted as the charge tended towards 0 mV, and poor performance in the form of breakthrough as the charge decreased to <-10 mV or >4 mV. Flocculant dosing prior to filtration increased floc reformation and prevented breakthrough when charge destabilisation was sub-optimal, and could prove a useful strategy to employ when experiencing challenging winter conditions.
4
Lee, Boon Chong. "The influence of nutrients on floc physicochemical properties and structure in activated sludge processes". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ28822.pdf.
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5
Kolda, Bridget C. "Impact of polymer type, dosage, and mixing regime and sludge type on sludge floc properties". Thesis, Virginia Tech, 1995. http://hdl.handle.net/10919/40662.
Testo completoAbstract (sommario):
This research investigated the impact of sludge type, polymer type (percent mole charge), dosage, mixing rate, and solution ionic strength on bound water content of sludge flocs. Data determined to evaluate the extent of dewatering included: percent dry solids, bulk density, bound water content (determined by dilatometric method), floc density (determined by isopycnic centrifugation), and cake solids concentrations. Calculated floc densities and bound water contents were compared with measured values. The polymer mole charge had marginal impact on bound water content. The optimal polymer dose as determined by dose curves did not necessarily result in the least bound water content. The mixing rate did not have an impact on bound water content of the chemical sludge, but did have an impact on bound water content of the biological sludge. However, the percentage of total water removed that was due to bound water removal was not affected by rate of mixing, polymer mole charge, or polymer dose. Altering solution ionic strength did not appear to improve bound water removal.
The calculated bound water content values determined using measured floc densities were consistently greater than the measured bound water content values determined by dilatometric method. The bound water content per the dilatometric method did not account for all the water present in the floes as determined by the isopycnic centrifugation method.
Master of Science
6
Cheung, Mee Chu. "Comparative study of the structural, chemical and physical properties of activated sludge floc from different full-scale wastewater treatment systems". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0013/MQ33959.pdf.
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7
Fall, Kelsey. "Influence Of Suspended Particle Size And Composition On Particle Image Processing, Estuarine Floc Fractal Properties, And Resulting Estuarine Light Attenuation". W&M ScholarWorks, 2020. https://scholarworks.wm.edu/etd/1593091656.
Testo completoAbstract (sommario):
Understanding the nature of suspended particles is crucial to explaining water clarity issues in many estuaries, including the Chesapeake Bay and its tidal tributaries. Typical near surface estuarine particles are not individual sediment grains, but rather are clusters of inorganic and organic components known as flocs. Because of their fragile nature, flocs are challenging to observe in-situ, so their influence on the optical properties of the system are not well-known. This dissertation used a combination of state-of-the-art optical instrumentation, including laser scattering and transmissometry, a high-definition particle imaging camera system (PICS), and irradiance meters, along with supporting laboratory analysis techniques to investigate the surface waters of the York River estuary. This work characterized estuarine floc properties while simultaneously identifying relationships between estuarine light attenuation, absorption, and scattering due to flocs as well as other water column constituents. The relative organic fraction of suspended solids was found to be an important control on the fractal nature of estuarine flocs, including primary particle size and density, as well as bulk floc properties. A new approach is presented here that simultaneously solves for multiple floc fractal characteristics (e.g., fractal dimension, primary particle size, and primary particle density) and identifies whether simple fractal models are appropriate to describe individual suspensions. Results indicate that suspensions in the York River estuary with lower organic fraction and higher total suspended solids (TSS) are dominated by larger flocs composed of smaller, denser primary particles. In contrast, suspensions with higher organic fraction and lower TSS are composed of smaller flocs with larger, less dense primary particles. Paradoxically, the organic-rich flocs containing larger, lower density primary particles are, in terms of solids content, actually denser overall. This is because the larger, organic-rich primary particles take up more space within the flocs, leaving less room for water. Diffuse light attenuation, scattering, and absorption were related to the nature of the flocs in the York estuary, as well as to other water column constituents. It was found that as TSS increases, larger, lower density flocs containing less organic matter and more water increasingly dominate. This causes scattering to increase more quickly than TSS. In contrast, absorption increased more slowly than TSS. This is because the organics more prevalent at low TSS absorb more light per mass than the inorganic solids that dominate suspensions with higher TSS. Under most conditions, total scattering was dominated by inorganic particles. However, the combined effects of other components (the water itself, colored dissolved organic matter, phytoplankton, plus non-algal organic solids) typically dominated both absorption and attenuation. The importance of phytoplankton and organic solids relative to inorganic solids from land runoff have important ramifications for water clarity management, specifically suggesting revaluation of strategies solely focused on reducing inorganic sediment input. Even with an advanced video-settling column (e.g. PICS), there are issues resolving smaller flocs and sampling very low TSS. A major challenge in processing particle images is correctly identifying and sizing particles of varying composition and size, while correctly separating in-focus particles from out-of-focus particles. A new automated analysis approach was created that efficiently resolves particles, while rejecting out-of-focus objects, and was implemented into the automated processing algorithm for the PICS. Field- and laboratory-based experiments were conducted to evaluate video-based size, settling velocity, and density estimates, and it was found that all three parameters were adequately measured with the PICS.
8
Koivuranta, E. (Elisa). "Optical monitoring of flocs and filaments in the activated sludge process". Doctoral thesis, Oulun yliopisto, 2016. http://urn.fi/urn:isbn:9789526211794.
Testo completoAbstract (sommario):
Abstract Flocculation plays a critical role in the activated sludge process, where flocs are removed by settling and where unsatisfactory flocculation is resulting in poor effluent quality. Control and operation of the process is also challenging as it is sensitive to external and internal disturbances. Furthermore, stricter environmental demands are also being placed on wastewater treatment and discharge quality thus solutions are needed to improve the current systems. A novel optical monitoring method employing a tube flow and a CCD camera was developed to characterize the flocs and filaments of the sludge, and the method was tested on samples from full-scale activated sludge plants. An online device operating on the same principle was also developed and this was tested over a period of eight months at municipal wastewater treatment plant. Optical monitoring was employed in the laboratory to study the breakage of activated sludge flocs. Based on the image analysis data, in the industrial plant the major breakage process was large-scale fragmentation. In the two municipal plants, it was surface erosion. The flocs had more filaments and were more irregular in shape in the industrial plant, which could be the reason for the large-scale fragmentation. The effect of floc morphology on the effluent clarity of the activated sludge process was studied in the industrial and municipal activated sludge plants by optical monitoring over periods of three months and eight months, respectively. The changes in floc morphology took place slowly in both plants. Four major factors that correlated with the purification results were the size and shape of the flocs and the quantities of small particles and filaments. The image analysis results suggested that the settling problem that occurred during the test periods in the industrial plant was caused by dispersed growth, whereas that in the municipal plant was caused by filamentous bulking. In conclusion, it is possible to use the developed method online in order to analyse the state of flocculation. Thus the method could be useful when developing online monitoring applications for quantifying floc characteristics and for diagnosing the causes of settling problems in the wastewater treatment plantsTiivistelmä Aktiivilieteprosessissa flokkulaatiolla on merkittävä rooli, sillä muodostuneet flokit poistetaan prosessista laskeutuksen avulla. Siten huono flokkulaatio johtaa puhdistetun jäteveden kiintoainemäärän lisääntymiseen. Prosessin säätö ja operointi on kuitenkin hankalaa, sillä aktiivilieteprosessi on herkkä ulkoisille ja sisäisille häiriöille. Jätevedenpuhdistukseen liittyvät ympäristövaatimukset ja päästöehdot vesistöihin ovat myös tiukentuneet, joten uusia menetelmiä tarvitaan parantamaan nykyisiä prosesseja. Tässä työssä kehitettiin uusi, optinen kuvantamismenetelmä karakterisoimaan flokkeja ja rihmoja. Menetelmä hyödyntää putkivirtausta ja CCD-kameraa ja sitä testattiin aktiivilietelaitosten näytteillä. Lisäksi kehitettiin samaa periaatetta noudattava online-laitteisto, jota testattiin kahdeksan kuukauden ajan. Optista kuvantamista testattiin laboratoriossa flokkien hajoamistutkimuksessa. Kuva-analyysitulosten perusteella kahden kunnallisen aktiivilietelaitoksen flokit hajosivat pintaeroosioon perustuvan mallin mukaan ja teollisen aktiivilietelaitoksen flokit hajosivat fragmentaatiomallin mukaan. Teollisen aktiivilietelaitoksen flokeissa oli enemmän rihmoja ja ne olivat epäsäännöllisemmän muotoisia, mikä voi olla syynä flokkien fragmentaatioon. Flokkien morfologian vaikutus jäteveden puhdistustuloksiin tutkittiin teollisessa (kolmen kuukauden ajan) ja kunnallisessa (kahdeksan kuukauden ajan) aktiivilietelaitoksessa optisella kuvantamismenetelmällä. Molemmissa laitoksessa muutokset flokkien morfologiassa tapahtuivat hitaasti. Neljä tärkeintä tekijää, jotka korreloivat puhdistustulosten kanssa, olivat flokkien koko ja muoto sekä pienten partikkelien ja rihmojen määrä. Kuva-analyysitulosten perusteella laskeutumisongelma teollisessa jätevesilaitoksessa johtui flokinmuodostajabakteerien liian pienestä määrästä ja kunnallisessa jätevesilaitoksessa rihmamaisten bakteerien liikakasvusta. Yhteenvetona voidaan todeta, että kehitettyä menetelmää on mahdollista käyttää online-mittarina sekä sen avulla voidaan arvioida flokkulaation tilannetta. Siten menetelmää on mahdollista hyödyntää flokkien ominaisuuksien karakterisoinnissa ja arvioidessa jätevedenkäsittelylaitoksen laskeutumisongelmien aiheuttajaa
9
Andrew, Philip L. "Experimental and numerical investigations of the off-design flow physics in a supersonic through-flow fan cascade". Diss., This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-07282008-134047/.
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10
Sutapa, Ignasius Dwi Atmana. "Propriétés physico-chimiques et décantabilité des boues activées en relation avec le transfert d'oxygène et la biofloculation". Vandoeuvre-les-Nancy, INPL, 1996. http://www.theses.fr/1996INPL068N.
Testo completoAbstract (sommario):
L’aération et la séparation des boues activées constituent les deux étapes clé pour le bon fonctionnement d'une station d'épuration. L’objectif de ce travail est double: caractériser les paramètres susceptibles d'influencer le processus de transfert d'oxygène dans le milieu de boues activées, et étudier l'aptitude à décanter de celles-ci en relation avec la biofloculation mise en jeu. L’étude du transfert d'oxygène montre que le facteur alpha dépend du degré d'épuration de la pollution introduite: ce facteur augmente lorsque la DCO et donc le OUR dans le milieu de culture diminuent. Mais le facteur prépondérant est la concentration en biomasse dans le bassin d'aération: plus cette concentration augmente, plus la viscosité du milieu est importante et plus le facteur alpha diminue. L’étude des flocs de boues activées montre qu'ils présentent une structure très complexe dans laquelle les micro-organismes sont piégés par une matrice de polymères exocellulaires. Ceux-ci, dont les exopolysaccharides, jouent un rôle important dans l'agglomération des micro-organismes. Les expériences montrent que les flocs biologiques placés dans des conditions de famine aérobie, défloculent en relargant des exopolymères dans le milieu interstitiel. Ces conditions de famine permettent, en outre, de supprimer les germes filamenteux, responsables d'une mauvaise décantation
11
Bian, Qi. "Bulk flow properties of wheat". Thesis, Kansas State University, 2014. http://hdl.handle.net/2097/18679.
Testo completoAbstract (sommario):
Master of ScienceDepartment of Grain Science and Industry
Kingsly Ambrose
Consistent and reliable flow of bulk wheat from hoppers and silos is very significant in wheat handling and processing. Bulk wheat flow challenges such as inconsistent flow, arching, etc., are common during handling. The irregular size and non-uniformity of physical properties, the presence of impurities affects the flow behavior during discharge. Chaff and insects infested kernels are the two most common impurities present in wheat. In this research, the effect of these two impurities on their physical and flow properties of wheat were studied. Physical and flow indicators, such as bulk, tapped, particle densities, angle of repose, Hausner’s ratio, Carr index, and porosity measures the flowability of uncompacted bulk solids. Meanwhile, flow properties tested by shear testing principle based on Jenike’s method, simulated bulk wheat under pressure in bins/hoppers. The dynamic properties tested quantify the energy required to flow, compressibility and permeability at dynamic handling situations. Due to the presence of impurities and moisture content differences, bulk density and angle of repose of wheat varied from 801.54kg/m3 to 718.36kg/m3, and 23.6° to 38.4°, respectively. Angle of internal friction and wall friction angle that reflect interaction between particles and particle with bins/hopper walls, ranged from 23.95° to 43.13° and 15.46° to 20.33°, respectively. In addition to instrumental flow property evaluation, the flow profile, discharge rate, and particle velocity during hopper flow of bulk wheat was studied using Particle Image Velocimetry method. Mass flow and funnel flow hopper dimensions were used for this flow profile analysis. The discharge rate decreased from 1.67 to 1.12 kg/s for mass flow and 1.42 to 0.86 kg/s for funnel flow when the chaff in bulk wheat increased from 0% to 7.5% (weight basis). Analysis of the active flow zone indicated that bulk wheat without chaff had a uniform flow compared to wheat with chaff in the bulk. The findings from this study will be useful for design of hopper bottom bins and handling equipment based on the wheat quality and percent moisture content.
12
Mueller, A. J. "Extensional flow of macromolecules in solution". Thesis, University of Bristol, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234875.
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13
Kristensen, Aleksander. "Flow properties of water-based drilling fluids". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for petroleumsteknologi og anvendt geofysikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-23107.
Testo completoAbstract (sommario):
The objective of this master thesis was to investigate the flow properties of water based drilling fluids, utilizing measurements in both the micro and macro scale. The research was performed on two realistic drilling fluids by the use of a viscometer, a rheometer and a realistic flow loop, where the latter represents the macro scale. The research outcome could possibly improve the understanding of flow behavior in wellbores, and remove uncertainties associated with annular friction. The two fluids utilized in the research was made up with the goal of having equal rheological qualities, when measured with a Fann 35 viscometer. A more thorough examination of the two fluid's rheology was then executed by using a Anton Paar MCR302 rheometer. The macroscopic properties was researched employing a flow loop, capable of simulating realistic wellbore conditions.The main outcome of this thesis is that even though two fluids appear to have the same rheoligical properties when measured on simple equipment, their fundamental different microscopic structure will exhibit variations when the fluids are utilized in real applications.Due to problems encountered when mixing the fluids, as well as problems with one of the fluids itself, not all intended experiments were conducted. The experiments should be replicated with an emphasis on temperature control, avoiding bubbles and foam, and be conducted within a shorter time period.
14
Hyde, Anthony Richard. "The flow properties of filamentous fermentation broths". Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333302.
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15
Akella, Ravi Chandra. "Information flow properties for cyber-physical systems". Diss., Rolla, Mo. : Missouri University of Science and Technology, 2009. http://scholarsmine.mst.edu/thesis/pdf/Akella_09007dcc806406a3.pdf.
Testo completoAbstract (sommario):
Thesis (M.S.)--Missouri University of Science and Technology, 2009.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed April 15, 2009) Includes bibliographical references (p. 34-36).
16
McBride, William James. "Division of multiphase flow at a horizontal bifurcation". Thesis, Queen's University Belfast, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324829.
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17
Massey, Kevin C. "Flow/acoustic coupling in heated and unheated free and ducted jets". Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/11971.
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18
Jepson, D. M. "Vertical annular flow : the effects of physical properties". Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316862.
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19
Al, Harrasi Mahmood Abdul Wahid Sulaiman. "Fluid flow properties of tight gas-condensate reservoirs". Thesis, University of Leeds, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.582106.
Testo completoAbstract (sommario):
Tight gas-condensate reservoirs contain large reserves, but can be extremely costly to develop. Understanding the fundamental controls on the fluid flow behaviour of tight gas and gas-condensate reservoirs has the potential to result in more cost-effective reservoir development and help increase the world's producible reserves. Therefore, the principal objective of the thesis is to improve understanding of multiphase flow within tight gas-condensate reservoirs. In order to achieve this objective a series of pore-to-core scale experiments under controlled conditions were performed, followed by numerical simulation. Three methodologies were used in this study: First, pore-scale experiments in glass micromodels with liquid-liquid systems were performed to improve understanding of the phase separation and flow mechanisms at pore level. Second, coreflood experiments were performed while in-situ saturation was monitored using an X-ray C'I' -scanner. A newly developed liquid-liquid system was used in these experiments. Flow through tight gas sandstones allowed the determination of relative penneabilities as well as determining their dependence on absolute permeability and capillary number. Third, production simulation modelling has been conducted to investigate the implications of the results. The micromodel experiments have proved extremely useful for characterizing the flow behaviour . of condensate systems. The results showed that the flow mechanisms and phases' distributions were affected largely by interfacial tension, pore structure and wettability.
20
Kojima, Takehiro. "Bulk flow properties of fine binary powder mixtures". Thesis, University of Cambridge, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648838.
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21
Zhu, Junlin. "Effective properties for flow in heterogeneous porous media". Diss., Virginia Tech, 1990. http://hdl.handle.net/10919/39416.
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22
Whang, Kyu-ho. "Static and Flow Properties of Dilute Polymer Solutions". Thesis, University of North Texas, 1991. https://digital.library.unt.edu/ark:/67531/metadc501073/.
Testo completoAbstract (sommario):
Small weight percentages of certain high-molecular weight polymers added to liquids in turbulent flow through conduits can result in dramatic friction reduction. Although many current and potential uses of the drag reduction phenomenon exist, there is a fundamental problem: drag reduction efficacy decreases rapidly with flow time due to the mechanical degradation in flow of the added polymer. In this thesis study, dilute aqueous solutions of polyacrylamide were tested under turbulent flow conditions in an attempt to determine where mechanical degradation in flow occurs.
23
Mitchell, Thomas Matthew. "The fluid flow properties of fault damage zones". Thesis, University of Liverpool, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485852.
Testo completoAbstract (sommario):
Quantification of the fluid flow properties of the Earth's crust is an essential precursor to the understanding of a wide range of geological processes, including earthquake generation and crustal strength, and the recovery of natural resources. Faults playa key role in the migration of fluids around the ;Earth's crust, and therefore the fluid flow properties of fractured rocks and how these properties evolve with time are of major importance. This thesis aims to improve our understanding of the hydraulic transport properties of large fault zones by presenting a large dataset of detailed field and microstructural observations and results from a suite of laboratory experiments to provide a basis for studying the distribution, and fluid flow properties, of damage surrounding large natural fault zones. Damage surrounding the core of faults is represented by both microfracturing of the rock matrix and by macroscopic fracture networks. Microfracture and macrofracture densities and orientations have been analysed on strike slip faults with displacements ranging over 3 orders of magnitude (~O.l2 m - 5000 m). These faults cut crystalline rock within the excellently exposed Atacama Fault Zone, Northern Chile. All faults consist of a fault core and associated damage zone. Damage zone width as defined by macrofractures and microfractures scale with displacement and fault length. Both microfractures (specifically fluid inclusion planes) and macrofractures within the damage zone show a log-linear .decrease in fracture density with perpendicular distance from the fault core. An empirical equation for microfracture density distribution based on the evolution of displacement has been derived for these faults. Preferred microfracture orientations in the damage zone suggest that this damage may predominantly be due to early processes related to enhanced stress at fault tips, in addition to cumulative wear processes from the juxtaposition of geometrical irregularities on the fault plane and damage from dynamic rupture. Fault core widths scale with displacement, with the largest displacement fault showing a wide multiple core zone. Detailed experimental studies of the development of permeability of crustal rock during deformation are essential in helping to understand fault mechanics and constrain larger scale models that predict bulk fluid flow within the crust. The strength, permeability and pore fluid volume evolution of initially intact crystalline rock under increasing differential load leading to macroscopic failure has been determined at water pore pressures of 50 MPa and varying effective pressures from 10 to 50 MPa. Permeability is seen to increase by, up to, and over two orders of magnitude prior to macroscopic failure, with the greatest increase seen at lowest effective pressures. Post-failure permeability is shown to be over three orders of magnitude higher than initial intact permeabilities and approaches the lower the limit of measurements of in situ bulk crustal permeabilities. Increasing amplitude cyclic loading tests show permeabilitystress hysteresis with high permeabilities maintained as differential stress is reduced and the greatest permeability increases are seen between 90-99% of the failure stress. Under hydrothermal conditions without further loading, it is suggested that much of this permeability can be recovered by healing and sealing, and pre-macroscopic failure fracture damage may heal relatively faster than post-failure macroscopic fractures. Pre-failure permeabilities are nearly seven to nine orders of magnitude lower than that predicted by some high pressure diffusive models suggesting that microfracture matrix flow cannot dominate, and agrees with inferences that bulk fluid flow and dilatancy must be dominated by larger scale structures, such as macrofractures. It is suggested that the permeability of a highly stressed fault tip process zone in low-permeability crystalline rocks could increase by more than 2 orders of magnitude, while stress drops related to fracture propagation close damage zone cracks, and some permeability is maintained due to hysteresis from permanent microfracture damage. Future work should aim to quantify experimentally-induced microfractures and. associated permeability measurements, and by relating the fracture densities surrounding natural fault zones with densities seen in experimental deformed samples with known permeabilities, modelling techniques can then be applied to gain estimates of bulk fluid flow of the fracture networks. This will provide a basis for predicting the influence of pore fluid pressures on important geological issues, such as crustal strength.
24
Arowosola, Babatunde Clement. "Influence of particle-scale properties and gravitational field on flow properties of granular materials". Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/13295/.
Testo completoAbstract (sommario):
The complexities in the processing behaviour of granular materials under different gravitational environments pose challenges to the researchers in a number of multidisciplinary fields. The micromechanical behaviour of granular materials is inherently heterogeneous due to its discrete nature. Generally, the macroscopic behaviour of granular materials can be determined by accounting for the inter-particle interactions that exist within. Although significant progress has been achieved in the past especially on the transport, handling and storage of granular materials in confined geometries under earth gravity using experimental and computational methods, the micromechanical behaviour of granular materials under low-gravitational environments is still poorly understood. Out of the several approaches proposed in the literature in understanding the complexities in granular materials, discrete element modelling (DEM) has evolved as an important tool in evaluating the role of particle scale properties on the flow and compaction characteristics of granular materials. The primary focus of this research is to understand the micromechanical properties of granular materials, primarily their flow and compaction characteristics under different gravitational environments. Hence, three dimensional DEM is applied in this study under earth, mars and lunar (EML) gravity conditions. In this study, in order to attain a fundamental level understanding of the flow behaviour of granular materials through confined geometries under varying gravity conditions, a comprehensive level of simulations were performed. Initially, sandstone materials as simulants used to represent space grains in space exploration activities are experimentally characterised to obtain two key input material parameters viz., particle size distribution and adhesion force between the grains. These key input parameters, in addition to their other physical properties reported in the literature are fed as input parameters in the three-dimensional DEM simulations for studying their flow and compaction characteristics under EML gravities. Further, investigations on the prediction of maximum shear stress distribution in a hopper containing granular materials under static filling were analysed under earth gravity using three dimensional DEM. The predicted results are compared with an advanced experimental approach using Photo-stress analysis tomography (PSAT). Studies show that the predicted DEM and experimental results for the maximum stress distribution are in good agreement under earth gravity. The hopper internal angle is seen to influence the stress profile quite significantly. Additionally, these DEM results agree qualitatively well with the common Walker’s theoretical predictions for the stress distribution along the hopper walls with dependence on hopper internal angle under earth gravity. The PSAT analysis, though performed only under earth gravity under static condition validates the usefulness of inputting measured particle-scale properties in the DEM simulations. Thereafter, different continuum approaches and DEM simulations are used to investigate the effect of particle scale properties and gravity on the flow characteristics of granular materials through hoppers. Continuum theories based on discrete layer approach and Kirya’s structural model for gravity effects on flow properties of grains in hoppers is performed and compared with that of DEM simulations. Most results obtained on the effect of various particle scale properties agree with existing studies in literature where available. Granular flow is seen to depend on gravity using both the continuum and DEM simulations and these results further agree qualitatively with predictions from a limited practical parabolic flight test operation. Based on this analysis and to further understand the influence of particle scale properties on granular flow, parametric analysis is carried out using DEM simulations. The analysis provides understanding of the complex behaviour of the grains and its response under EML gravity levels. Granular packing, granular bed density, cohesion, hopper geometry (orifice and internal angle), friction effect, angle of repose and combined adhesion strength and size distribution (for real samples) of the granular materials were all observed to have significant effect on granular flow under EML gravity levels distinctly. From all the analysis, the influence of gravity on granular flow is observed to be most sensitive under the lunar gravity. This could imply that the lunar in-situ resource utilization (ISRU) processes may require wider exit openings or non-gravity driving forces to have an effective output from the various processes as compared to process utilization on earth. To improve the granular flow, applying a granular flow aid is investigated for a horizontal piezo vibrator across the hopper containing granular bed under EML gravity levels using DEM. Analysis indicates that the piezo-vibrator technique could improve the flow of grains through a hopper under low gravity levels. To aid the design of the vibrator, its effective impact to improve flow is however shown to depend on the horizontal amplitude and frequency of the vibrator. Furthermore DEM simulations are performed to assess the quality of granular filling in a collection chamber from continuous flow and staggered flow outputs. Continuous flow mechanism is seen to be more effective in processing of grains as against staggering the flow especially under a low gravity level. Finally, the compaction properties of granular media with ice contents under different gravity levels is analysed using DEM simulations. Overall, this thesis presents vital information on the role of particle scale properties on flow and compaction characteristics of granular materials under varying gravity environments. In the future, the understandings reported in this thesis could help to design suitable flow and compaction processes in different engineering and science disciplines, especially in space/low gravity explorations to meet with the ever growing needs for technology advancements.
25
Parker, A. R. "Particle interactions in fluid suspensions". Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384501.
Testo completo
26
Mishra, Phoolendra Kumar. "Pumping test inference of saturated/unsaturated aquifer properties". Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/194085.
Testo completoAbstract (sommario):
Analytical solutions for aquifer response to pumping are commonly used to infer the hydraulic properties of aquifers. This dissertation develops new analytical solutions for the analysis of pumping test data from confined and unconfined aquifer.An analytical solution for flow to a partially penetrating well of infinitesimally small radius in a compressible unconfined aquifer is developed that allows inferring its saturated and unsaturated hydraulic properties from drawdowns recorded in the saturated and/or the unsaturated zone. The effects of unsaturated zoneconstitutive parameters and thickness on drawdowns in the saturated and unsaturated zones as functions of position and time is investigated; the solution is validated against numerical simulations of drawdown in a synthetic aquifer having unsaturated properties described by the van Genuchten (1980) - Mualem (1976)constitutive model; used to analyze drawdown data from a pumping test conducted by the US Geological Survey at Cape Cod,Massachusetts; and corresponding estimates of van Genuchten - Mualem parameters are compared with laboratoryvalues obtained for similar materials in the area.Drawdowns generated by extracting water from a large diameter (e.g. water supply) well are affected by wellbore storage. An analytical solution in Laplace transformed space for drawdown in a uniformanisotropic confined aquifer caused by withdrawing water at a constant rate from a partially penetrating well with storage is developed. When the pumping well is fully penetrating the solution reduces to that of Papadopulos and Cooper (1967); to that of Hantush (1964) when the pumping well has no wellbore storage; to the solution of Theis (1935) when both conditions are fulfilled; and to that of Yang et al. (2006) when the pumping well is partially penetrating, having finite radius but lacking storage. The solutionis validated against synthetic pumping test data and used to explore graphically the effects of partial penetration, wellbore storage and anisotropy on time evolutions of drawdown in the pumping well and in observation wells.The analytical solution for unconfined aquifers is extended to the case of a finite diameter pumping well with storage. The extended analytical solution is used to investigate the effects of storage in the pumping well and delayed piezometer response on drawdowns in the saturated and unsaturated zones as functions of position and time. The solution is validated against numerical simulations of drawdown in a synthetic aquifer having unsaturated properties described by the van Genuchten (1980) - Mualem (1976) model. It is then used to analyze a seven-day pumping test conducted by University of Waterloo researchers at the Canadian Forces Base Borden in Ontario, Canada; and to compare our results with those ofMoench (2008).
27
Hamburger, Thomas. "Aerosol microphysical properties during anticyclonic flow conditions over Europe". Diss., lmu, 2011. http://nbn-resolving.de/urn:nbn:de:bvb:19-127766.
Testo completo
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Vladu, Maria-Camelia. "Calcium sulphoaluminate hydrates : crystal growth, stability and flow properties". Thesis, University of Edinburgh, 2005. http://hdl.handle.net/1842/11506.
Testo completoAbstract (sommario):
The calcium sulphoaluminate hydrates are important components of Portland cement and constitute the principal matrix formers of some sulphoaluminate cements. Their practical importance lies in the involvement as intermediates and products of the hydration of portland cements under geothermal conditions. Ettringite is a complex mineral (Ca6[Al(OH)6]2(SO4)3.26H2O) formed during the initial stages of Portland cement hydration at ambient temperature, by reaction of sulphate ions released by gypsum (CaSO4.2H2O) with tricalcium aluminate (Ca3Al2O6). After exhaustion of gypsum, the remaining tricalcium aluminate in solution reacts with already formed ettringite transforming to monosulphate (Ca4Al2(SO4)(OH)12.xH2O). At higher temperature (>100°C), ettringite is unstable and transforms to monosulphate. Monosulphates are known to exist is at least four different hydrate forms (x = 8,10,12,14). In this study the stability of calcium sulphoaluminate hydrates were mapped in various environments (variable relative humidity, temperature and alkalinity). The monosulphate hydrates were obtained by hydrothermal synthesis using microwave radiation at 120°C. Their formation is via ettringite thermal decomposition in autoclave conditions under autogenous pressure. It has been shown that a series of calcium sulphoaluminate hydrates can be obtained depending on temperature and water activity. The interconversion of the calcium sulphoaluminate hydrates was found to be an easy and rapid process, whereby metastable phase are readily formed, indicating the lability of Ca-OH-Al-SO4 system. The kinetics and the mechanism of growth of calcium sulphoaluminate hydrates are known to influence the development of mechanical properties and the characteristics of cements. The ettringite crystal growth process was evaluated from the point of view of its influence on crystal morphology. General crystallisation methods for ettringite synthesis were developed starting from supersaturated solutions of pure phases and its morphology was found to vary with crystallisation factors (temperature for instance); ettringite crystals are generally hexagonal rods with different aspect ratios.
29
Polanco, Juan Ignacio. "Lagrangian properties of turbulent channel flow : a numerical study". Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1043/document.
Testo completoAbstract (sommario):
La perspective lagrangienne, décrivant un écoulement selon les trajectoires de traceurs fluides, est une approche naturelle pour étudier les phénomènes de dispersion dans les écoulements turbulents. En turbulence de paroi, le mouvement des traceurs est influencé par le cisaillement moyen et par une forte inhomogénéité et anisotropie en proche paroi. On étudie les propriétés lagrangiennes d’un écoulement de canal turbulent par simulation numérique directe à un nombre de Reynolds modéré. Les statistiques d’accélération lagrangienne sont comparées aux expériences de suivi de particules réalisées en parallèle à ce travail. Comme en turbulence homogène isotrope (THI), les composantes d’accélération le long des trajectoires lagrangiennes se décorrèlent sur des temps comparables aux plus petites échelles de l’écoulement, tandis que la norme de l’accélération reste corrélée plus longtemps. La persistance d’anisotropie à petite échelle loin de la paroi est constatée par l’existence d’une corrélation croisée non nulle entredeux composantes de l’accélération. On montre que, en conséquence des flux moyens d’énergie cinétique en turbulence de paroi, près des parois les traceurs se déplacent et s’étalent sur des plus grandes distances quand ils sont suivis en arrière dans le temps qu’en avant. La dispersion relative de paires de traceurs est aussi étudiée. Aux temps courts, la séparation des paires est balistique pour toutes les distances à la paroi. Comme en THI, les traceurs se séparent plus rapidement lorsqu’ils sont suivis en arrière dans le temps. Aux temps plus longs, le cisaillement moyen accélère la séparation dans la direction de l’écoulement moyen. Un modèle de cascade balistique initialement proposé pour la THI est adapté aux écoulements inhomogènesThe Lagrangian perspective, describing a flow from the trajectories of fluid tracers, isa natural framework for studying dispersion phenomena in turbulent flows. In wall-boundedturbulence, the motion of fluid tracers is affected by mean shear and by strong inhomogeneityand anisotropy near walls. We investigate the Lagrangian properties of a turbulent channel flowusing direct numerical simulations at a moderate Reynolds number. Lagrangian accelerationstatistics are compared to particle tracking experiments performed in parallel to this work. Asin homogeneous isotropic turbulence (HIT), the acceleration components along Lagrangianpaths decorrelate over time scales representative of the smallest scales of the flow, while theacceleration norm stays correlated for much longer. The persistence of small-scale anisotropy farfrom the wall is demonstrated in the form of a non-zero cross-correlation between accelerationcomponents. As a result of the average fluxes of kinetic energy in wall turbulence, tracers initiallylocated close to the wall travel and spread over longer distances when tracked backwardsin time than forwards. The relative dispersion of tracer pairs is finally investigated. At shorttimes, pair separation is ballistic for all wall distances. As in HIT, relative dispersion is timeasymmetric, with tracers separating faster when tracked backwards in time. At longer times,mean shear dominates leading to rapid separation in the mean flow direction. A ballisticcascade model previously proposed for HIT is adapted to inhomogeneous flows
30
Jacobs, Bruce Lee. "Effective properties of multiphase flow in heterogeneous porous media". Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/9697.
Testo completoAbstract (sommario):
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, February 1999.Includes bibliographical references (leaves 218-224).
The impact of heterogeneity on multiphase fl.ow is explored using a spectral perturbation technique employing a stationary, stochastic representation of the spatial variability of soil properties. A derivation of the system's effective properties - nonwetting phase moisture content, capillary pressure, normalized saturation and permeability - was developed which is not specific as to the form of the permeability dependence on saturation or capillary pressure. This lack of specificity enables evaluation and comparison of effective properties with differing characterization forms. Conventional characterization techniques are employed to parameterize the saturation, capillary pressure, relative permeability relationships and applied to the Cape Cod and Borden aquifers. An approximate solution for the characteristic width of a dense nonaqueous phase liquid (DNAPL) plume or air sparging contributing area is derived to evaluate the sensitivity of system behavior to properties of input processes. Anisotropy is predicted for uniform, vertical flow in the Borden Aquifer consistent with both prior experimental observations and Monte Carlo simulations. Increases of the mean capillary pressure (increasing nonwetting phase saturation) is accompanied by reductions in nonwetting phase anisotropy. Similar levels of anisotropy are not found in the case of the Cape Cod aquifer; the difference is attributed largely to the mean value of the log of the characteristic pressure which is shown to control the rate of return to asymptotic permeability and hence system uniformity. A positive relation between anisotropy and interfacial tension was observed, consistent with prior numerical simulations. Positive dependence of lateral spreading on input fl.ow rate is predicted for Cape Cod Aquifer with reverse response at Borden Aquifer due to capillary pressure dependent anisotropy of Borden Aquifer. The effective permeability for horizontal fl.ow with core scale heterogeneity was found to be velocity dependent with features qualitatively similar to experimental observations and numerical experiments. Application of Leverett scaling as generally implemented in Monte Carlo simulations under represents aquifer hetero geneity and for the Borden Aquifer, van Genuchten characterization reduces system anisotropy by several orders of magnitude. Anisotropy of the effective properties proved to be less sensitive to Leverett scaling if the Brooks-Corey characterization was used due to insensitivity in this case to the variance of the slope parameter.
by Bruce L. Jacobs.
Ph.D.
31
Franc, Jacques. "Two-phase flow properties upscaling in heterogeneous porous media". Phd thesis, Toulouse, INPT, 2018. http://oatao.univ-toulouse.fr/21684/1/FRANC_Jacques.pdf.
Testo completoAbstract (sommario):
The groundwater specialists and the reservoir engineers share the same interest in simulating multiphase flow in soil with heterogeneous intrinsic properties. They also both face the challenge of going from a well-modeled micrometer scale to the reservoir scale with a controlled loss of information. This upscaling process is indeed worthy to make simulation over an entire reservoir manageable and stochastically repeatable. Two upscaling steps can be defined: one from the micrometer scale to the Darcy scale, and another from the Darcy scale to the reservoir scale. In this thesis, a new second upscaling multiscale algorithm Finite Volume Mixed Hybrid Multiscale Methods (Fv-MHMM) is investigated. Extension to a two-phase flow system is done by weakly and sequentially coupling saturation and pressure via IMPES-like method.
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McGuire, Cameron. "Granular flow properties of food powders in extrusion processing". Thesis, Kansas State University, 2017. http://hdl.handle.net/2097/38220.
Testo completoAbstract (sommario):
Master of ScienceDepartment of Grain Science and Industry
Sajid Alavi
This study relates raw material particulate rheology to the granular flow in a single screw food extruder. Raw materials based on corn (i.e. meal, flour, and starch), wheat (i.e. farina, flour and starch), and sucrose (i.e. granulated, superfine, and powdered) were used as model particulate systems for the study. Various particulate-scale characteristics and flow parameters of these nine materials were determined using a powder rheometer. Properties such as basic flow energy, cohesion, flow function, and effective angle of internal friction were good indicators of flowability in an extruder. Corn meal exhibited lower energy requirements and a higher propensity for flow than corn flour (6.7mJ/g versus 10.7mJ/g, and “free-flowing” versus “cohesive,” according to Flow Function classifications), with wheat farina showing similar results when compared to wheat flour (5.8mJ/g versus 7.9mJ/g, and “highly free-flowing” versus “cohesive”), although both wheat systems showed lower energy requirements than their comparable corn systems. Sugar, being of a different base material and particle shape, behaved differently than these starch-based materials—flow energy decreased and propensity to flow increased as particle size decreased (51.7mJ/g versus 8.0mJ/g, and “free flowing” versus “highly free-flowing”). This large energy requirement for coarse sugar particles was attributed more to particle shape than composition, as the sharp edges of sugar can interlock and restrict movement through the sample. The starch-based results were validated in a particulate flow study involving the above model systems (corn meal, corn flour, wheat farina, and wheat flour) in a pilot-scale single screw extruder. Visualization data, obtained using a transparent plexiglass window during extrusion, confirmed that the flours exhibited higher flow energy requirements and a lower flow factor compared to coarser-particle size during extrusion, seen by the increased peak heights and barrel fill. Additionally, moisture changes were analyzed, showing an increase in energy required for starch-based materials as moisture increases and a decrease in energy for sucrose. Due to the hygroscopic nature of sucrose, moisture was absorbed more rapidly than starch products and the edges of individual particles softened, forming a soft solid. These physiochemical differences resulted in decreased energy requirements for sucrose as moisture was increased (51.7mJ/g to 13.6mJ/g), while corn meal and wheat farina yielded increased energy requirements (6.7mJ/g to 9.1mJ/g and 5.8mJ/g to 9.5mJ/g, respectively). Again, results of starch-based materials were validated using a plexiglass cover during extrusion, clearly showing an increase in barrel fill as moisture content increased for both materials, with corn meal flowing more readily than farina. Lastly, temperature of corn meal and farina was increased to show the difference in behavior of starch-based materials, where farina decreased in energy as temperature increased (14.4mJ/g to 12.1mJ/g ) while corn meal energy requirements increased (12.9mJ/g to 17.2mJ/g). With the results developed from these three experiments, and validated where physically possible, it was concluded that offline powder rheometry is a useful tool for predicting the behavior of food powders. These results were then developed into a computer-simulated model to allow for virtual and visual representation of the conveying action inside an enclosed steel barrel.
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Appiah, Kwadwo Ampofo. "Microstructural and microanalytical characterization of laminated (C-SiC) matrix composites fabricated by forced-flow thermal-gradient chemical vapor infiltration (FCVI)". Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/14910.
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Morell, Albert T. "Model for Flow Properties Across the Opening of Normal Bleed Holes in Supersonic Flow". University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1519909987871461.
Testo completo
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Sugami, Yuitsu. "ALTERNATIVE DIESELS FROM PLANT OILS AND THEIR EVALUATION OF FUEL PROPERTIES". 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225703.
Testo completo
36
Sutton, Kaylee B. "Post-Application Flow Properties of Architectural Paints: The Link Between Environmental Factors, Rheology, and Application Properties". University of Akron / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron1578905387807612.
Testo completo
37
Stewart, David G. "Thermophysical properties of gases and gas mixtures for critical flow nozzle applications". Thesis, University of Strathclyde, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248763.
Testo completo
38
Karaman, Turker. "Prediction Of Multiphase Flow Properties From Nuclear Magnetic Resonance Imaging". Phd thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610382/index.pdf.
Testo completoAbstract (sommario):
In this study a hybrid Pore Network (PN) model that simulates two-phase (water-oil) drainage and imbibition mechanisms is developed. The developed model produces Nuclear Magnetic Resonance (NMR) T2 relaxation times using correlations available in the literature. The developed PN was calibrated using experimental relative permeability data obtained for Berea Sandstone, Kuzey Marmara Limestone, Yeniköy Dolostone and Dolomitic Limestone core plugs. Pore network body and throat parameters were obtained from serial computerized tomography scans and thin section images. It was observed that pore body and throat sizes were not statistically correlated. It was also observed that the developed PN model can be used to model different displacement mechanisms. By using the synthetic data obtained from PN model, an Artificial Neural Network (ANN) model was developed and tested. It has been observed that the developed ANN tool can be used to estimate oil &ndash
water relative permeability data very well (with less than 0.05 mean square error) given a T2 signal. It was finally concluded that the developed tools can be used to obtain multiphase flow functions directly from an NMR well log such as Combinable Magnetic Resonance (CMR).
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Belyadi, Fatemeh. "Determining low permeability formation properties from absolute open flow potential". Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4879.
Testo completoAbstract (sommario):
Thesis (M.S.)--West Virginia University, 2006.Title from document title page. Document formatted into pages; contains viii, 63 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 36-42).
40
Goodman, Matthew R. "Properties of Stochastic Flow and Permeability of Random Porous Media". Thesis, The University of Arizona, 2010. http://hdl.handle.net/10150/193422.
Testo completoAbstract (sommario):
Thermosolutal fluid flow has a strong influence on the evolution of solidification microstructures. While porous media theory and volume-averaged permeability relations give a basis to quantify these phenomena, traditional methods of permeability estimation used for random porous media fail to adequately characterize the full relation of microstructural morphology to volume-average permeability. Most significantly, the link between microstructural parameters and permeability is treated as a deterministic function at all scales, ignoring the variability inherent in porous media.The variation in permeability inherent to random porous media is investigated by the numerical solution of Stokes equations on an ensemble of porous media, which represent of many scales of sampling and morphological character. Based on volume-averaging and statistical treatment, the stochastic character of tensoral permeability in porous media is numerically investigated. Quantification of permeability variation and autocorrelation structure are presented as conditions, which future realistic stochastic permeability fields must respect.
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Leese, Hannah. "Electroosmosis in nanoporous membranes : connecting material properties to flow behaviour". Thesis, University of Bath, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.601631.
Testo completoAbstract (sommario):
The development of nanoporous materials has received considerable attention in nanofluidic studies in recent years. Furthering earlier research, the present thesis offers a systematic study of two nanoporous materials-nanoporous alumina membranes and carbon nanotube membranes-with a view to establishing their electroosmotic and fluid-flow behaviour at the nanoscale. The nanoporous alumina membranes were studied for their own electroosmotic and fluid-flow properties, and utilised as templates for the production of the carbon nanotube membranes also investigated in this study. The advanced control provided by the fabrication processes of both materials allowed for systematic investigations into the effects of pore diameter and surface chemistry on both electroosmotic and pressure-driven flows. Nanoporous alumina membranes were developed with pore diameters of< 10 nm. The effect of nanostructure and surface chemistry on macro wetting properties was analysed in detail. Flow enhancements were observed in hydrophilic alumina nanochannels with inner diameters of 40 to 25 nrm. Atomic force microscopy force measurements provided further insight into fluid-solid interactions at the nanoscale. A systematic investigation of nanoporous alumina DC electroosmotic pumps with pore diameters down to 8 run was also undertaken with sodium tetraborate buffer operated at Δ V = 10 V. Concentration polarization was identified as the principal challenge to sustained electroosmotic flow. By optimising the electroosmotic process, particularly the rig design and buffer concentration, an EO pump was developed with a lifetime of up to 4 hours. Carbon nanotube membranes with a range of pore diameters were also investigated for their electroosmotic and pressure-driven flow properties. The synthesis of carbon nanotubes was optimised to obtain unblocked and functioning membranes. Flow enhancements were observed in engineered carbon nanotube membranes with pore diameters down to 16 run. Electroosmotic flow rates in carbon nanotube membranes were similar to those of nanoporous alumina. Two electrolytes-sodium tetraborate and sodium chloride-were investigated in electroosmotic flow experiments with carbon nanotube membranes. This allowed for further investigation of electroosmosis and electric double layer overlap.
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Palit, Imon Joydipto. "The effects of strategic behaviour on properties of order flow". Thesis, University of Essex, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.617086.
Testo completoAbstract (sommario):
This thesis seeks a better understanding of the role that endogenous dynamics plays in financial markets. We investigate the intra-day dynamics of trading in stock markets by means of computer simulations and empirical analysis of high-frequency data. We show that the strategic behaviour of interacting liquidity taking and providing agents plays an important role in explaining the phenomena of volatility clustering, long-memory in order flow and stable- U-shape intra-day volume dynamics that are-observed in pure order driven markets. We first construct a zero-intelligence model to reproduce order flow from naive trader behaviours in a market that uses the double auction market clearing mechanism. We simulate the market by generating random types of event drawn from empirical distributions calibrated against data from the Paris Bourse exchange. We find that whilst the model recovers some realistic features, it does not reproduce volatility clustering. This suggests strategic behaviour is an important feature of markets creating correlated order flow as a result of a subtle interplay of liquidity provision and taking. We then go on to test empirically whether an important part of this correlated order flow occurs due to order splitting. We show that the cause of long-memory at high frequency timescales is due to persistent liquidity taking by single agents. This is in line with the practice of algorithmic trading that strategically splits a large order into smaller pieces to avoid market impact and detection from other market participants. Finally we investigate how the practice of algorithmic order splitting can influence intra-day volume dynamics. We develop a model of intra-day trading volume dynamics and run Monte-Carlo simulations with estimated parameters. We find our model achieves realistic dynamics when compared with observed volume curves. This suggests strategic behaviour from algorithmic trading plays a major part in shaping intra-day trading volume dynamics.
43
Eastman, John. "The shear and extensional flow properties of polymer/surfactant solutions". Thesis, University of Bristol, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319075.
Testo completo
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Caba, Aaron C. "Characterization of Carbon Mat Thermoplastic Composites: Flow and Mechanical Properties". Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/29104.
Testo completoAbstract (sommario):
Carbon mat thermoplastics (CMT) consisting of 12.7 mm or 25.4 mm long, 7.2 micrometer diameter, chopped carbon fibers in a polypropylene (PP) or poly(ethylene terephthalate) (PET) thermoplastic matrix were manufactured using the wetlay technique. This produces a porous mat with the carbon fibers well dispersed and randomly oriented in a plane. CMT composites offer substantial cost and weight savings over typical steel construction in new automotive applications. In production vehicles, automotive manufacturers have already begun to use glass mat thermoplastic (GMT) materials that use glass fiber as the reinforcement and polypropylene as the matrix. GMT parts have limitations due to the maximum achievable strength and stiffness of the material. In this study the glass fibers of traditional GMT are replaced with higher strength and higher stiffness carbon fibers.
The tensile strength and modulus and the flexural strength and modulus of the CMT materials were calculated for fiber volume fractions of 10-25%. Additionally, the length of the fiber (12.7 mm or 25.4 mm) was varied and four different fiber treatments designed to improve the bond between the fiber and the matrix were tested. It was found that the fiber length had no effect on the mechanical properties of the material since these lengths are above the critical fiber length. The tensile and the flexural moduli of the CMTs were found to increase linearly with the FVF up to 25% FVF for some treatments of the fibers. For the other treatments the linearly increasing trend was valid up to 20% FVF, then stiffness either stayed constant or decreased as the FVF was increased from 20% to 25% . The strength versus FVF curves showed trends similar to those of the modulus versus FVF curves. It is shown that choosing an appropriate sizing can extend the usable FVF range of the CMT by at least 5%. Published micromechanical relations over-predicted the tensile modulus of the composite by 20-60%. An empirical fiber efficiency relation was fit to the experimental data for the tensile modulus and the tensile strength giving excellent agreement with the experimental results.
Flow tests simulating the compression molding process were conducted on the CMT to determine what factors affect the flow viscosity of the CMT. The melt viscosity of the neat PP was measured using cone and plate rheometry at temperatures between 180°C–210°C and was fit with the Carreau relation. The through thickness packing stress of the CMT mat was measured for FVFs of 8-40% and was found to follow a power law behavior based on the local bending of fibers up to a FVF of 20.9%. Above this FVF the power law exponent decreases, and this is attributed to fracture of some of the fibers. Heated platens were used to isothermally squeeze the CMT at axial strain rates of 0.02-6 s^-1. The plot of the load-displacement behavior for the 10% FVF CMT was similar in shape to that for a fluid with a yield stress. For FVFs of 15-25% the load-displacement curves showed a load spike at the beginning of the flow, then followed the curve for a fluid with a yield stress. The matrix was burned off the squeezed samples, and the remaining carbon mat was dissected and visually inspected. It was found that fiber breakage increased and fiber length decreased as the FVF of the sample was increased.Ph. D.
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Soszyński, Robert Marian. "The formation and properties of coherent flocs in fibre suspensions". Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/27544.
Testo completoAbstract (sommario):
Fibres in concentrated suspensions are in continuous contact with other fibres and may interlock through elastic bending to form coherent networks. Such interlocking is termed Type-C cohesion. The process by which Type-C cohesion forms among fibres and the resulting structure and tensile strength of individual floes of fibres have been examined in experimental study in which relatively straight, smooth nylon (6-6) fibres of aspect ratios from 65 to 189 were suspended in aqueous-sugar solutions. The fibres were in most cases neutrally buoyant. The suspensions were caused to flow in a partially filled, inclined-to-the-horizontal or horizontally-oriented cylinder rotated about its principal axis to produce a recirculating and moderately unsteady flow. At a well-defined and reproducible "threshold concentration" Type-C coherent floes formed. The floes were verified to be of Type-C by heat treatment. The heat treatment caused stress relaxation in elastically bent fibres resulting in reduced floe strength. Visual observations of floe formation and velocity measurements with Laser Doppler Anemometer indicated that the floes originated in the zone in which flow decelerated. In this zone floes formed by compaction of crowded fibres. The threshold concentration depended on fibre geometry and viscosity of the suspending liquid. Below an aspect ratio of approximately 50 and above a suspending liquid viscosity of approximately 0.013 Pa‧s, Type-C coherent floes did not form at any concentration of fibres. Under the test conditions of this work, the threshold concentration was unaffected by the cylinder rotational speed, cylinder diameter, and angle of incline to the horizontal, provided that sufficient shear was induced in the cylinder to create recirculating flow. The structure and strength of Type-C coherent floes were examined. The number of contact points per fibre was less than values estimated from theoretical, statistical models in the literature. The tensile strength of individual Type-C floes measured in a tester with a unique comb support showed values larger than strengths reported in the literature for either man-made or wood-pulp fibre networks. A mathematical model developed to describe tensile strength based on frictional fibre-to-fibre interaction accounted for only a part of the total floe strength.Applied Science, Faculty of
Chemical and Biological Engineering, Department of
Graduate
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Li, Zihao. "Experimental, Theoretical, and Numerical Investigations of Geomechanics/Flow Coupling in Energy Georeservoirs". Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/104895.
Testo completoAbstract (sommario):
The development of hydrocarbon energy resources from shale, a fine-grained, low-permeability geological formation, has altered the global energy landscape. Constricting pressure exerted on a shale formation has a significant effect on the rock's apparent permeability. Gas flow in low-permeability shales is significantly different from liquid flow due to the Klinkenberg effect caused by gas molecule slip at the nanopore wall surfaces. This has the effect of increasing apparent permeability (i.e., the measured permeability). Optimizing the conductivity of the proppant assembly is another critical component of designing subsurface hydrocarbon production using hydraulic fracturing. Significant fracture conductivity can be achieved at a much lower cost than conventional material costs, according to the optimal partial-monolayer proppant concentration (OPPC) theory. However, hydraulic fracturing performance in unconventional reservoirs is problematic due of the complex geomechanical environment, and the experimental confirmation and investigation of the OPPC theory have been rare in previous studies. In this dissertation, a novel multiphysics shale transport (MPST) model was developed to account for the coupled multiphysics processes of geomechanics, fluid dynamics, and the Klinkenberg effect in shales. Furthermore, A novel multi-physics multi-scale multi-porosity shale gas transport (M3ST) model was developed based on the MPST model research to investigate shale gas transport in both transient and steady states, and a double-exponential empirical model was also developed as a powerful substitute for the M3ST model for fitting laboratory-measured apparent permeability. Additionally, throughout the laboratory experiment of fracture conductivity with proppant, the four visible stages documented the evolution of non-monotonic conductivity and proppant concentration. The laboratory methods and empirical model were then applied to the shale plugs from Central Appalachia to investigate the formation properties there. The benefits of developing these regions wisely include a smaller surface footprint, reduced infrastructure requirements, and lower development costs. The developed MPST, M3ST, double-exponential empirical models and research findings shed light on the role of multiphysics mechanisms, such as geomechanics, fluid dynamics and transport, and the Klinkenberg effect, in shale gas transport across multiple spatial scales in both steady and transient states. The fracture conductivity experiments successfully validate the theory of OPPC and illustrate that proppant embedment is the primary mechanism that causes the competing process between fracture width and fracture permeability and consequently the non-monotonic fracture conductivity evolution as a function of increasing proppant concentration. The laboratory experimental facts and the numerical fittings in this study provided critical insights into the reservoir characterization in Central Appalachia and will benefit the reservoir development using non-aqueous fracturing techniques such as CO2 and advanced proppant technologies in the future.Doctor of Philosophy
Production of oil and gas from the extremely tight rock has changed the global energy industry, including job growth, energy security, and environment protection. However, the oil and gas production from the tight rock is difficult because of the complex rock properties. Hydraulic fracking can resolve the issue and contribute to the high production. The higher and safer production needs us to have a better understanding of oil and gas flow under the ground. A series of laboratory experiment were conducted, and a new shale gas transport model is introduced in this dissertation to explain the oil and gas flow under the complicated scenarios. The experimental results show that many factors can impact the oil and gas flow, and the model can match the experimental results very well. A few statistical methods are also used in the data analysis. The optimization of proppant pack is another important component of hydraulic fracking. Proppant particles are usually man-made ceramic tiny balls, which will be injected into the underground to keep the fractures from closing during the production. From the previous papers, it is possible to achieve high fracture conductivity at a much lower cost than traditional proppant costs. Many groups of laboratory experiment were conducted to demonstrate this guess. Many rock samples in the experiment are from Central Appalachian area, which can help the resource development in this area. The developed model and experimental research findings in this study provided critical insights into the role of the many physics mechanisms on shale gas transport, proppant optimization, and hydraulic fracking.
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Anwar, Adeel. "Enhancing properties of biodiesel via heterogeneous catalysis". Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/enhancing-properties-of-biodiesel-via-heterogeneous-catalysis(7e52f44f-4c50-4cd3-b5a8-cf6ce714b7d6).html.
Testo completoAbstract (sommario):
Biodiesel is a re-emerging biofuel as an alternative to the traditional petroleum derived diesel. There are however, several factors that currently hinder the widespread uptake. Majority of the biodiesel are currently produced from edible oils thereby sparking the food versus fuel debate, the cost of feedstock is significantly high, there are problems experienced in the traditional production process and the resulting fuel is of inadequate quality. This work focused on addressing the issue of poor cold flow properties to improve the overall quality of biodiesel. The skeletal isomerisation of linear fatty acid methyl esters (FAMEs) into branched chain isomers, using solid acid catalysts, appears to be the most comprehensive solution in enhancing the cold flow properties of biodiesel. However, obtaining high branched chain yields, mitigation of undesired side reactions, achieving shorter reaction times, using fewer processing steps and lower operating conditions have still not been achieved to a large extent. Moreover, no studies were found to date investigating isomerisation of FAMEs as a continuous process. A trickle bed reactor (TBR) system has been identified to be an effective continuous reactor. Its key features of being a three phase system and allowing a high degree of contact between the reactant and the catalyst offering a high conversion per unit volume provides an encouraging opportunity to lower reaction times, reaction steps and conditions whilst increasing branched chain yields. This thesis explores the use of the TBR system, for the first time, to enhance the cold flow properties of biodiesel through molecular modification using zeolite beta catalyst with Si/Al ratios of 180 and 12.5. A range of reactions have been investigated including isomerisation, dewaxing (hydroisomerisation and hydrocracking) and decarboxylation on biodiesels derived from camelina, palm and coconut oils. Significant progress has been made in this research area with a 7 °C drop in MP being achieved upon the dewaxing of the coconut biodiesel at 250 °C, 1.01 bar pressure, 0.2 ml/min LF and 37.5 ml/min GF. To achieve greater drops in melting points it has been suggested to investigate mesoporous catalysts as they will ensure greater facilitated molecular access to the active sites, resulting in a higher conversion by preventing pore blockages. All in all, a series of key findings and serendipitous discoveries have brought to surface an array of new challenges as well as paving the way for a host of exciting opportunities for future research. The ability to continuously produce high quality renewable fuel offers a fascinating prospective for various industrial associates such as Argent Energy, Olleco, Neste Oil and ConocoPhillips.
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Xu, Wenyue. "Towards numerical modeling of two-phase flow in seafloor hydrothermal systems". Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/26014.
Testo completo
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Milne, Fraser Dalton. "Topographic and material controls on the Scottish debris flow geohazard". Thesis, University of Dundee, 2008. https://discovery.dundee.ac.uk/en/studentTheses/eb4a6b03-8024-4818-8e92-ce1fd3c77209.
Testo completoAbstract (sommario):
Debris flows can be considered the most significant geological hazard in areas of high relief in Scotland having impacted upon slope foot infrastructure several times in recent years. The potency of this geohazard is anticipated to increase over the coming decades due to a climatologically enforced upturn in debris flow frequency. In thisresearch material and topographic controls on debris flow activity are investigated using a combination of field and laboratory based analysis of debris flows at six study sites across upland Scotland. Centrifuge modelling is also used to simulate theinitiation of debris flows in soils with varying particle size distributions.Spatial densities of debris flow measured in the field indicate that hillslopes underlain by sandstone and granitic bedrocks, which tend to be mantled by coarser sand rich soils, have a greater frequency of flows than those underlain by schist andextrusive lava bedrocks. Higher debris flow densities on slopes underlain by sandstone and granite lithologies are facilitated by high permeability in overlying regolith matrixes allowing more rapid increase in pore water pressures duringrainstorms although this is likely to be further influenced by packing and organic content. Centrifuge modelling of hillslope debris flows also demonstrate that sandier soils are generally geotechnically more susceptible to slope failure.The susceptibility of a hillslope to debris flow is strongly influenced by slope geometry and morphology. Hillslopes with persistently steep slopes and a high incidence of concavities, gullies and couloirs are topographically more predisposed todebris flow activity due to greater shear stresses and morphologically controlled, gravity induced concentrations of hillslope hydrology. The majority of material in channelised debris flows is entrained during the gully propagation stage of the massmovement. Consequently, such events can be considered accumulative channelised debris flows. Longer and steeper gullies with greater sediment capacities are more likely to yield larger flow mass movements. Coupling between open hillslopes andbedrock gullies is shown to be an essential component for conceptualisation of the debris flow geohazard.Due to the role they play in amplifying debris flow magnitude, hazard management should be focussed around bedrock gullies and stream channels. Highesthazard rankings should be assigned to slope foot infrastructure in proximity to gullied stream channels with high sediment capacities and long, steep profiles conducive to large accumulative channelised debris flows. To avoid detrimental aesthetic impact, hazard management should be strongly geared towards utilisation of lower impactexposure reduction techniques and less visually intrusive engineering approaches such as increasing culvert capacity to accommodate debris flows. During realignment or the planning of future transport infrastructure, culverts with capacities significantly exceeding those required for purely hydrodynamic considerations should be placed straight on to stream channels avoiding proximal gully bends.
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Jouini, Dhafer Ben Mahmoud Carleton University Dissertation Engineering Mechanical. "Experimental investigation of the ventilation air flow properties in an office space". Ottawa, 1992.
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