Dissertations / Theses on the topic 'Air entrainment'
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Hadjerioua, Boualem. "Air entrainment and oxygenation by overfalling nappes." Diss., The University of Arizona, 1994. http://hdl.handle.net/10150/186852.
Full textHarrison, Roger. "Entrainment of Air into Thermal Spill Plumes." Thesis, University of Canterbury. Civil and Natural Resources Engineering, 2009. http://hdl.handle.net/10092/2865.
Full textVeverka, Peter John. "An investigation of interfacial instability during air entrainment." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/5800.
Full textTerrill, Eric J. "Acoustic measurements of air entrainment by breaking waves /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1998. http://wwwlib.umi.com/cr/ucsd/fullcit?p9907829.
Full textO'Connell, Aileen. "Observations of air entrainment and the limits of coatability." Thesis, Heriot-Watt University, 1989. http://hdl.handle.net/10399/915.
Full textBlenkinsopp, Christopher Edwin. "Air entrainment, splash and energy dissipation in breaking waves." Thesis, University of Southampton, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435725.
Full textFung, Po Kan. "A fundamental study of air entrainment in steam condensers." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253839.
Full textLamarre, Eric. "An experimental study of air entrainment by breaking waves." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12685.
Full textByrne, Kirstin. "Air/Gas entrainment in sewer force mains| A case study." Thesis, California State University, Long Beach, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=1523045.
Full textAir and gas pocket entrainment in pressurized sewer systems are a major issue for many wastewater agencies due to decreased capacity, increased pumping and maintenance costs, corrosion, and reduction in efficiency. The Orange County Sanitation District has been concerned about air pocket formation in their Newport Force Main Network. In this study, we performed field tests to determine if air pockets existed within OCSD’s large diameter force main from the Bitter Point Pump Station to Plant 2 and the effects of air entrapment on the hydraulic performance of the system. Several flow scenarios were analyzed during the field tests, which were performed with air valves open and air valves closed to compare flow and pressure fluctuations when air cannot escape the system. The effective flow area was analyzed to determine the decrease experienced when large quantities of air were present within the force main. Little information is available in regards to field studies performed on air and gas pocket formation outside of a controlled laboratory, so the type of tests and the methodology proposed in this study could be used as guidelines by other agencies facing similar problems.
Gómez, Ledesma Ramón. "An experimental investigation on the air entrainment by plunging jets." College Park, Md. : University of Maryland, 2004. http://hdl.handle.net/1903/1953.
Full textThesis research directed by: Mechanical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
Pump, Cody N. "Air entrainment relationship with water discharge of vortex drop structures." Thesis, University of Iowa, 2011. https://ir.uiowa.edu/etd/1062.
Full textMortensen, Joshua D. "Factors Affecting Air Entrainment of Hydraulic Jumps within Closed Conduits." DigitalCommons@USU, 2009. https://digitalcommons.usu.edu/etd/531.
Full textUys, Ehbenezer Chris. "Entrainment in an air/water system inside a sieve tray column." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/4237.
Full textENGLISH ABSTRACT: Mass transfer efficiency in distillation, absorption and stripping depends on both thermodynamic efficiency and hydrodynamic behaviour. Thermodynamic efficiency is dependent on the system kinetics while hydrodynamics is the study of fluid flow behaviour. The focus of this thesis is the hydrodynamic behaviour in tray columns, which affects entrainment. In order to isolate hydrodynamic behaviour from the thermodynamic behaviour that occurs inside sieve tray columns, investigations are conducted under conditions of zero mass transfer. When the gas velocity is sufficiently high to transport liquid droplets to the tray above, entrainment occurs. The onset of entrainment is one of the operating limits that determines the design of the column and thus impacts on the capital cost. By improving the understanding of the parameters that affect entrainment, the design of the tray and column can be improved which will ultimately increase the operability and capacity while reducing capital costs. Existing correlations predicting entrainment in sieve tray columns are based on data generated mainly from an air/water system. Previous publications recommend that more testing should be performed over larger ranges of gas and liquid physical properties. An experimental setup was therefore designed and constructed to test the influence of the following parameters on entrainment: 1. gas and liquid physical properties 2. gas and liquid flow rates 3. tray spacing The experimental setup can also measure weeping rates for a continuation of this project. The hydrodynamic performance of a sieve tray was tested with air and water over a wide range of gas and liquid flow rates and at different downcomer escape areas. It was found that the downcomer escape area should be sized so that the liquid escaping the downcomer always exceeds a velocity of approximately 0.23 m/s in order to create a sufficient liquid seal in the downcomer. For liquid velocities between 0.23 and 0.6 m/s the area of escape did not have an effect on the percentage of liquid entrained. It was also established that entrainment increases with increasing gas velocity. The rate at which entrainment increases as the gas velocity increase depends on the liquid flow rate. As soon as the liquid flow rate exceeded 74 m3/(h.m) a significant increase in entrainment was noted and the gas velocity had to be reduced to maintain a constant entrainment rate. This is because the increased liquid load requires a longer flow path length for the froth to fully develop. The undeveloped froth, caused by the short (455 mm) flow path, then creates a non-uniform froth that is pushed up against the column wall above the downcomer. Consequently, the froth layer is closer to the tray above resulting in most of the droplets ejected from the froth reaching the tray above and increasing entrainment. By reducing the gas velocity, the froth height and ejecting droplet velocity is reduced, resulting in a decrease in entrainment. The results from the experiments followed similar trends to most of the entrainment prediction correlations found in literature, except for the change noted in liquid flow rates above 74 m3/(h.m). There was, however, a significant difference between the experimental results and the correlations developed by Hunt et al. (1955) and Kister and Haas (1988). Although the gas velocities used during the air/water experiments were beyond the suggested range of application developed by Bennett et al. (1995) their air/water correlation followed the results very well. The entrainment prediction correlation developed by Bennett et al. (1995) for non-air/water systems was compared with the experimental air/water results to test for system uniformity. A significant difference was noted between their non-air/water prediction correlation and the air/water results, which motivates the need for a general entrainment prediction correlation over a wider range of gas and liquid physical properties. Based on the shortcomings found in the literature and the observations made during the experiments it is suggested that the influence of liquid flow path length should be investigated so that the effect on entrainment can be quantified. No single correlation was found in the literature, which accurately predicts entrainment for a large range of liquid loads (17 – 112 m3/(h.m)), high superficial gas velocities (3 – 4.6 m/s) and different gas and liquid physical properties. It is therefore recommended that more work be done, as an extension of this project, to investigate the influence of gas and liquid physical properties on entrainment (under zero mass transfer conditions) for a large range of liquid (5 – 74 m3/(h.m)) and gas (2 – 4.6 m/s) flow rates. In order to understand the effect of droplet drag on entrainment, tray spacing should be varied and increased to the extent where droplet ejection velocity is no longer the mechanism for entrainment and droplet drag is responsible for droplet transport to the tray above. Since it is difficult and in most cases impossible to measure exact gas and liquid loads in commercial columns, another method is required to measure or determine entrainment. Since liquid hold-up was found to be directly related to the entrainment rate (Hunt et al. (1955), Payne and Prince (1977) and Van Sinderen et al. (2003) to name but a few), it is suggested that a correlation should be developed between the dynamic pressure drop (liquid hold-up) and entrainment. This will contribute significantly to commercial column operation from a hydrodynamic point of view.
Kmack, Richard Matthew. "Characterization of air voids in fresh cement paste through ultrasonic nondestructive testing." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24794.
Full textCommittee Chair: Jacobs, Laurence; Committee Co-Chair: Kurtis, Kimberly; Committee Member: DesRoches, Reginald.
Majidi, Seyyed Hojjat. "Modeling of air entrainment and oxide inclusion formation during pouring of metal castings." Diss., University of Iowa, 2018. https://ir.uiowa.edu/etd/6611.
Full textLi, Jiajia. "Contributions to modeling of bubble entrainment for ship hydrodynamics applications." Diss., University of Iowa, 2015. https://ir.uiowa.edu/etd/1875.
Full textXue, Fei. "MOMENT BALANCE OF AN AXISYMMETRIC JET AND THE EFFECT OF AIR ENTRAINMENT FROM AMBIENT." Thesis, University of Gävle, Faculty of Engineering and Sustainable Development, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-6826.
Full textChen, Qingyuan. "An experimental study of air entrainment in a blade coating system with a pressurised pond applicator." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/5807.
Full textStoor, T. (Tuomas). "Air in pulp and papermaking processes." Doctoral thesis, University of Oulu, 2006. http://urn.fi/urn:isbn:9514280784.
Full textAl-Sahhaf, Ahmad Ali. "Investigation of the entrainment and infiltration rates through air curtains of open low-front refrigerated display cabinets." Thesis, Brunel University, 2013. http://bura.brunel.ac.uk/handle/2438/7456.
Full textKoehr, Bernard E. "An experimental study of the mechanism of air entrainment by planar liquid jets at a free surface." Available to US Hopkins community, 2002. http://wwwlib.umi.com/dissertations/dlnow/3068176.
Full textTeng, Penghua. "CFD MODELLING OF TWO-PHASE FLOWS AT SPILLWAY AERATORS." Licentiate thesis, KTH, Vattendragsteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-202392.
Full textQC 20170224
Wright, Nathan W. "Air Vent Sizing in Low-Level Outlet Works for Small- to Medium-Sized Dams." DigitalCommons@USU, 2013. http://digitalcommons.usu.edu/etd/1531.
Full textVos, Adele. "Unsteady flow conditions at dam bottom outlet works due to air entrainment during gate closure : Berg River dam model." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/71850.
Full textENGLISH ABSTRACT: A trial closure of the emergency gate of the Berg River Dam was undertaken by the Trans- Caledon Tunnel Authority (TCTA) on 12 June 2008. The air vent downstream of the emergency gate was designed to introduce air to mitigate the negative pressures that were expected in the conduit during emergency gate operations. The emergency gate has to close when the radial gate at the downstream end of the outlet conduit fails. Contrary to the theoretical design, the measured air vent velocities in the field indicated that, while the emergency gate was closing, very large volumes of air were apparently continuously being released from the air vent, commencing when the gate was about 30% closed (i.e. 70% open). This is in contrast to what the design intended, namely that air should have been drawn into the vent. This thesis is concerned with the testing of a 1:14.066 physical model representing the outlet works and air vent of the Berg River Dam as a means to determine the reasons for the release of large volumes of air from the air vent during the trial closure in 2008. It also seeks solutions to mitigate the excessive airflow from the air vent. It was concluded that the air velocity in the air vent was independent of the rate of closure of the emergency gate, but to increase with increasing water head. The problem at the Berg River Dam was determined to be one of air blowback. Modifications were made to the configuration of the model in order to determine whether the configuration of the outlet works caused air to be released from the air vent. It was determined that the downward sloping roof at the outlet of the conduit, used to accommodate the radial gate chamber, was the cause of the air blowback phenomenon. An additional air vent was fitted directly onto the conduit at the constriction was found to be ineffective in reducing the air blowback. It was concluded that there are no rational structural change that can prevent or inhibit a recurrence of the blowback phenomenon in the Berg River Dam outlet conduit. The recommendation follows that the outlet conduit should not be constricted by any structural or mechanism further downstream in the conduit.
AFRIKAANSE OPSOMMING: ʼn Toetssluiting van die noodsluis van die Bergrivierdam is op 12 Junie 2008 deur die TCTA (Trans-Caledon Tunnel Authority) uitgevoer. Die lugskag stroomaf van die noodsluis is ontwerp om lug in te voer om die verwagte negatiewe drukke tydens die noodsluissluiting te beperk. Die noodsluis moet sluit indien die radiaalsluis aan die einde van die uitlaatpyp sou faal. In teenstelling met die teoretiese ontwerp, het die gemete lugsnelhede in die lugskag in die veld aangedui dat groot volumes lug voortdurend uit die lugskag vrygelaat word wanneer die noodsluis ongeveer 30% toe is (dit wil sê 70% oop). Dit is in teenstelling met die ontwerp, want die lugskag is ontwerp vir die insuig van lug. Hierdie tesis het ten doel om die redes vir die vrylating van groot volumes lug uit die lugskag vas te stel met behulp van ʼn 1:14.066 fisiese skaalmodel van die uitlaatwerke en lugskag van die Bergrivierdam soos getoets tydens die inwydingstoetssluiting in 2008. Die toetse op die model het getoon dat die lugsnelheid in die lugskag onafhankik van die sluistoemaak tyd is, maar verhoog met die toename in die watervlak. Die Bergrivier dam probleem was bepaal as die van lug terugslag. Die model is gewysig ten einde te bepaal of die spesifieke samestelling van die uitlaatwerke die oorsaak van die vrystelling van lug uit die lugskag is. Die analises en verandering aan die uitleg toon aan dat die skuins afwaartse dak van die uitlaattonnel om die radiaalsluiskamer te huisves die rede was vir die vrylating van die lug uit die lugskag. ‘n Addisionele lugskag was gebou in die dak van die uitlaattonnel reg bo die sametrekking, maar was oneffektief om die terug vloei van lug te verminder. Die gevolgtrekking is dat daar geen rasionele strukturele verandering aangebring kan word aan die Bergrivier dam om die vrystelling van lug uit die lugskag te verhoed of te verminder nie. ’n Aanbeveling vir toekomstige ontwerpe is dus dat die uitlaattonnel nie beperkend by die uitlaatend moet wees nie.
Montre, Trevor Allen. "Experimental Investigation of a 2-D Air Augmented Rocket: Effects of Nozzle Lip Thickness on Rocket Mixing and Entrainment." DigitalCommons@CalPoly, 2011. https://digitalcommons.calpoly.edu/theses/662.
Full textLiu, Ting. "Modelling air―water flows in bottom outlets of dams." Doctoral thesis, KTH, Vattendragsteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-141182.
Full textQC 20140211
Ageorges, ValentIn. "Écoulement et entraînement d’air autour d’un cylindre vertical partiellement immergé." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMLH23.
Full textThe flow past ships or an emerged body such as bridge pilar, is a fundamental, familiar and fascinating sight.Measurements and modelling of this simple flow can have relevance to offshore structures and renewable energy systems. The interaction of such structures with marine environment lead to drag, lift forces and free-surface effects.Our current problem is simplified by considering cylindrical geometry. This work presents experimental results, in which vertical cylinders are translated at constant speed through water initially at rest, and numerical results using YALES2 computing code based on finite volume method. The cylinders are partially immersed, then the motion induces turbulent wake and free-surface deformation. The flow is governed by the Reynolds and Froude numbers defined with cylinder diameter. The explored range of parameters are in the regime of turbulent wake with experiments carried out for Reynolds number up to 240 000, and Froude number up to 2.4. The focus here is on drag force measurements and strong free-surface deformation up to rupture and air-entrainment. Two modes of air-entraiment have been observed: (i) in the wake of the cylinder and (ii) in a cavity along the cylinder wall. Results are as follows. First, a scaling for the critical velocity for air-entrainment in the cavity proportional to D1/5 proposed by Benusiglio is recovered. Secondly, drag coefficients measured by piezoelectric sensors are smaller in two phase flow compared to monophasic case, and air-entrainment in the cavity enhances this decrease. Numerically, YALES2 uses level-set method for the descirption of the free-surface, and is able to reproduce air-entrainment phenomenon, free-surface deformations and flow dynamics around the cylinder. The present work expands the range of dimensionless parameters and highlights free-surface effects on drag forces
Elgadafi, Mansour M. "Angled curtain coating: An experimental study. An experimental investigation into the effect of die angle on air entrainment velocity in curtain coating under a range of operating conditions." Thesis, University of Bradford, 2010. http://hdl.handle.net/10454/4464.
Full textShibata, Yusuke. "High speed very thin films with reverse roll coatings : an experimental investigation of reverse roll coating of fluids using rigid and deformable rolls at high speeds." Thesis, University of Bradford, 2012. http://hdl.handle.net/10454/5753.
Full textHaapala, A. (Antti). "Paper machine white water treatment in channel flow:integration of passive deaeration and selective flotation." Doctoral thesis, Oulun yliopisto, 2010. http://urn.fi/urn:isbn:9789514263682.
Full text内山, 知実, Tomomi UCHIYAMA, 正章 成瀬, and Masaaki NARUSE. "自由落下粒子群が形成する粒子噴流の三次元渦法解析." 日本機械学会, 2005. http://hdl.handle.net/2237/9206.
Full text内山, 知実, Tomomi UCHIYAMA, 佳伸 北野, and Yoshinobu KITANO. "自由落下粒子群が形成する粒子噴流の数値解析." 日本機械学会, 2003. http://hdl.handle.net/2237/9212.
Full textElgadafi, Mansour Masoud. "Angled curtain coating : an experimental study : an experimental investigation into the effect of die angle on air entrainment velocity in curtain coating under a range of operating conditions." Thesis, University of Bradford, 2010. http://hdl.handle.net/10454/4464.
Full textMounaud, Laurent Georges. "A Parametric Study of the Effect of Fire Source Elevation in a Compartment." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/30916.
Full textMaster of Science
Guyot, Grégory. "Contribution à la caractérisation des processus d’entraînement d’air dans les circuits d’aménagements hydro-électriques." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAI081.
Full textWe study the entrainment of air created by large-dipped jets. Direct applications in the field of hydroelectricity are energy optimization of plants, environmental management around infrastructures and prediction of extreme flood impacts downstream of dams. For such applications, it is necessary to quantify the penetration depth of the bubble cloud, predict the distribution of bubbles and the amount of air entrained. Predictive models describing these three points would be key engineering tools. The literature review shows that many models, particularly those applied to penetration depth or entrained air flow, exist but are limited to a narrow range of parameters. A first experiment was carried out on circular jets with a diameter of about ten centimeters and a drop length of 2.6 m. Comparison of the results with the existing models reveals that these models do not correctly capture the penetration depth, the size of the generated bubbles or the entrained air flow rate. This experiment shows that the jets flap and have an aerated structure at impact, with significant corrugations. In a second smaller scale experiment, we have characterized the influence of the jet movement on the penetration depth. It appears that the oscillation of the jet can lead to a decrease of the penetration depth, but this influence is not sufficient to explain the differences between experiments and models in the large scale experiment. We then designed and operated a third experiment to analyze jets with nozzle speeds between 2 and 30 m/s, nozzle diameters between 24 and 213 mm for a drop height of about 10 m. It is also possible to investigate bubble clouds with this experiment, since the jets are received in a 5 m diameter pit with a depth of up to 23 m. The cross-comparison of measurements made by analyzing high-frequency videos of jet drop, force at impact and optical probe measurements in bubble clouds evidence that the state of the jet at impact has a significant influence on air entrainment. We clearly identify jets with different shapes and air flows than those previously studied. Our analysis also allows us to propose a simple model without any adjustment parameters, based on a balance of forces applied to the bubble cloud. This model predicts the penetration depth of the bubble cloud for a wide range of jet scales
Maier, Marcus R. "Onsets of liquid and gas entrainment during discharge from a stratified air-water region through two horizontal side branches with centerlines falling in an inclined plane." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0003/MQ32176.pdf.
Full textŠafrata, Pavel. "Studium možností zlepšení mrazuvzdornosti betonů." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2017. http://www.nusl.cz/ntk/nusl-265735.
Full textFerreira, Laura Maria Canno 1977. "Analise experimental da curva de ligação poço-tunel em vertedor com emboque tipo tulipa." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/257857.
Full textTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
Made available in DSpace on 2018-08-09T18:19:12Z (GMT). No. of bitstreams: 1 Ferreira_LauraMariaCanno_D.pdf: 6902999 bytes, checksum: 3e1f02a65f335b50df38d55fa7ab47bd (MD5) Previous issue date: 2007
Resumo: Estruturas de queda com poços verticais podem ser utilizadas para drenagem urbana, dissipação de energia e como vertedores em barragens. No último caso, tem-se os vertedores com emboque tipo tulipa, formados por um perfil vertedor seguido de um poço vertical, que se liga a um túnel por meio de uma curva. A curva é um ponto crítico do dimensionamento do vertedor, pois, é onde o escoamento o deflete, causando elevadas pressões na sua parte convexa e subpressões na parte côncava. Este trabalho tem, como objetivo, o estudo experimental de um vertedor tipo tulipa, para definir uma melhor geometria para a curva de ligação poço-túnel. Um estudo experimental foi feito, empregando-se o modelo do vertedor de Paraitinga, em escala 1:51,02, utilizando novas geometrias para a curva, para avaliar as pressões e o arraste de ar. Pôde constatar-se a nfluência da geometria da curva, sendo que as novas curvas resultaram em um escoamento mais regular, acompanhando o traçado da curva, com pressões menores na parte convexa, além de uma maior vazão de afogamento do vertedor. Foram propostas equações para o cálculo da vazão de ar em função da concentração média do ar no escoamento. Através do estudo experimental comparativo entre as diferentes curvas se sugere o emprego da curva clotóide para ser usada na ligaçao poço-túnel
Abstract: Vertical dropshafts can be used in drainage systems, energy dissipator and as dam spillways. In this case, they are called morning glory, and consists of an inlet followed by a shaft which joins a tunnel through a bend. The bend is a critical point in spillway sizing, therefore the flow deflects in this region and causes high pressures in the convex part of the bend and negative pressures in the concavous part. This paper cares for the experimental study to define a better geometry for the shaft spillway vertical bend. An experimental study has been carried out, using the spillway model of Paraitinga dam, which scale was 1:51,02, using new bend geometries, to evaluate pressures flow and air entrainment. The influence of the bend geometry has been noticed, and the new curves resulted in a more regular flow, that followed the trace of the curve, with smaller pressures in the convex part, besides a higher flow to submerge the spillway. Equations have been proposed to calculate air entrainment flow as a function of the average concentration of air. Through the experimental study to compare the different curves, one suggest the use of use clotóide curve, as a bend shaft
Doutorado
Recursos Hidricos
Doutor em Engenharia Civil
Delacroix, Sylvain. "Caractérisation de la génération et de la propagation de bulles autour de la carène des navires scientifiques." Thesis, Brest, 2015. http://www.theses.fr/2015BRES0014/document.
Full textOne of the main assignments of Ifremer is to study the seabed and the resources undersea, through a large oceanographic fleet used across the globe. For that purpose, ships are equipped with different kinds of SONAR (SOund Navigation And Ranging) to obtain the information sought in the water column. In some sea conditions, waves and ship motions generate significant air entrainment below the surface. Bubble clouds are then carried under the hull by the flow. The interaction between these bubbles and the acoustic waves may result in data loss, and therefore in a considerable reduction of the vessel’s productivity. The tools used to study this phenomenon are currently limited : the numerical models are not efficient enough to simulate at a time air entrainment at the bow and the two phase flow around the hull. On the other hand conventional towing tank tests are not entirely satisfactory. During this PhD research work, a specific test method to study this phenomenon has been developed and implemented at the Ifremer wave and current tank. This method requires the synchronization between a wave generator and a movement generator (hexapod) that enables to force the model motions, calculated in advance by numerical simulations. With this configuration, the effects of waves or motions characteristics on the bubbles generation can be studied independently. A complete instrumentation allowed to acquire images sequences to characterize the air entrainment at the bow of the model. Two distinct mechanisms have been observed : the generation of bubbles by vortex shedding or by the breaking bow wave. A post-processing method has been developed to analyse these mechanisms, for many test configurations. A parametric study was performed to calculate the frequency of bubbles generation for each test parameter. PIV measurements allowed to correlate the dynamic of bubbles clouds with the own flow dynamic. The overall results provide new elements for the understanding and the study of the phenomenon, with the final objective of obtaining a reliable tool that facilitates the design of research vessels
Lima, Marco Ant?nio Batista de. "Formula??o e caracteriza??o de pastas espumadas por incorpora??o de ar e estabilizantes minerais." Universidade Federal do Rio Grande do Norte, 2011. http://repositorio.ufrn.br:8080/jspui/handle/123456789/12969.
Full textCementing operations may occur at various stages of the life cycle of an oil well since its construction until its definitive abandonment. There are some situations in which the interest zones are depleted or have low fracture pressure. In such cases, the adoption of lowdensity cement slurries is an efficient solution. To this end, there are basically three ways to reduce the density of cement slurries: using microspheres, water extending additives or foamed cement. The objective of this study is to formulate, to study and to characterize lowdensity foamed cement, using an air entrainment surfactant with vermiculite or diatomite as water extenders and stabilizers. The methodology consists on preparation and evaluation of the slurries under the American Petroleum Institute (API) and the Brazilian Association of Technical Standards (ABNT) guidelines. Based on calculated densities between 13 and 15 ppg (1.559 and 1.799 g/cm3), the slurries were prepared with fixed surfactant concentration, varying the concentrations of vermiculite and diatomite and were compared with the base slurries. The results of plastic viscosity, yield point and gel strength and the compressive strength for 24 h showed that the slurries presented suitable rheology and mechanical strength for cementing operations in oil wells, and had their densities reduced between 8.40 and 11.89 ppg (1.007 and 1.426 g/cm3). The conclusion is that is possible, under atmospheric conditions, to obtain light weighted foamed cement slurries with satisfactory rheological and mechanical properties by means of air entrainment and mineral additions with extenders and stabilizers effects. The slurries have great potential for cementing operations; applicability in deep wells, in low fracture gradient formations and in depleted zones and bring cost savings by reducing the cementing consumption
As opera??es de cimenta??o podem ocorrer em diversas etapas do ciclo de vida de um po?o, desde a sua constru??o at? seu abandono definitivo. H? situa??es em que as zonas de interesse se apresentam depletadas ou com baixa press?o de fratura. Nesses casos, a ado??o de pastas cimentantes de baixa densidade constitui solu??o eficiente. Para tanto, h? basicamente tr?s maneiras de reduzir a densidade de pastas de cimento: usando microesferas, aditivos estendedores de ?gua ou pastas espumadas. O objetivo deste trabalho ? formular, estudar e caracterizar pastas cimentantes espumadas de baixa densidade, utilizando um surfactante incorporador de ar juntamente com adi??es de vermiculita ou diatomita como estendedores e estabilizantes. A metodologia do trabalho consiste na prepara??o e avalia??o das pastas por meio de procedimentos adotados pelo American Petroleum Institute (API) e pela Associa??o Brasileira de Normas T?cnicas (ABNT). Partindo de densidades calculadas entre 13 e 15 lb/gal (1,559 e 1,799 g/cm3), as pastas foram preparadas com dosagem fixa do surfactante, variando as concentra??es de vermiculita e diatomita e foram comparadas com pastas base. Os resultados dos ensaios que determinam viscosidade pl?stica, limite de escoamento e for?as g?is, bem como os de resist?ncia ? compress?o para tempos de 24 h mostraram que as pastas apresentaram reologia e resist?ncia mec?nica adequadas para opera??es de cimenta??o em po?os de petr?leo, al?m de terem suas densidades reduzidas entre 8,40 e 11,89 lb/gal (1,007 e 1,426 g/cm3). Conclui-se que ? poss?vel, sob condi??es atmosf?ricas, obter pastas cimentantes espumadas de baixa densidade com propriedades reol?gicas e mec?nicas satisfat?rias, por meio de incorpora??o de ar e adi??es minerais com efeitos estendedores e estabilizantes. As pastas possuem grande potencial para opera??es de cimenta??o, t?m aplicabilidade em po?os profundos, forma??es de baixo gradiente de fratura e zonas depletadas e trazem redu??es de custo pela diminui??o do consumo de cimento
Bhamidipati, Kanthi Latha. "Detection and elimination of defects during manufacture of high-temperature polymer electrolyte membranes." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/43616.
Full textLobosco, Raquel Jahara. "Investigação teórico-numérica da aeração em estruturas de vertedouros em degraus com uso de software livre." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/18/18138/tde-07102014-152612/.
Full textIn many pratical aplications of engineering the interfacial layer between two fluids has a strong relevance in the process of right measurements of the flow. Espeficically in the enviromental and hydraulics engineering the interface between air and water is the property related with oxigen and areation of the flow. With focus on the dynamics of the turbulent processes, the proposed study is applied to sub-pressure problems in spillways. It investigates the gases exchange in the air- water interface in the dispersed phase and evaluate the water quality downstream. The major goal is to describe a relation between the boundary layer development and the flow regimes with discharge. To represent the distribution of void fractions of the dispersed phase, the physical formulation concepts of stepped spillways and entrapped air were used. The arguments and reasons to justify the proposed concentration profile formulation are based on the numerical provided void fraction distribution. The results as well as the physical model are in good agrement with described literature data. The Numerical approach of the fluid dynamics problem differs from major of described literature studies because it is based on the surface breakup.
Fonty, Thomas. "Modélisation de l’entraînement d’air dans l'eau avec la méthode SPH." Thesis, Paris Est, 2019. http://www.theses.fr/2019PESC1013.
Full textFlows over hydraulic works – a nappe falling over a spillway, a wave breaking on a dike, etc. – undergo strong mixtures of air and water that lead to the appearance of white waters with complex dynamics. Faithfully capture the phenomenon of air bubbles entrainment/entrapment in the flowing water is therefore pivotal for the design of those works. Both experimental and numerical modeling prove to be complex due to high density ratio between phases and the multiscale nature of those flows involving turbulence and surface tension effects. The SPH (Smoothed Particle Hydrodynamics) method, a fully Lagrangian approach that models the flow as a set of moving particles without any mesh, is particularly well-suited to simulate such highly-distorted flows. Nevertheless, the current computational limits still prevent one from finely simulating industrial application cases with large domains in hydraulics. In this work, we aim at simulating macroscopically those flows with a mixture model in which each SPH particle stands for a moving volume of air and water. The derivation of the continuous equations of this mixture model is first detailed, then a state of the art of multiphase simulations in SPH is presented. Equipped with this continuous model and the existing discretization tools, a two-phase SPH mixture model is then derived and implemented on GPU (Graphics Processing Unit). A focus is made on original elements developed in the discretization, especially the derivation of a scheme with good numerical properties to follow the phase volume variations and the writing of an open boundary framework for mixtures. Turbulence, prominent for the air entrainment phenomenon, is modeled with a k-ϵ model including a buoyancy term. This model is validated against bidimensional academic test cases of increasing complexity, namely an oil-water separation, a two-phase Poiseuille flow, the Rayleigh-Taylor instability and a sand dumping case, proving its versatility. The air entrainment phenomenology is then described and the model is applied to common structures in hydraulics such as plunging jets and stepped spillways by introducing a specific closure for the relative velocity between phases. Finally, first industrial application cases with complex geometries and dynamics are presented
Yazan, Kazim. "Effects Of Retempering With Superplasticizer On Properties Of Prolonged Mixed Mineral Admixture Containing Concrete At Hot Weather Conditions." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/3/12606751/index.pdf.
Full textIslam, G. "Evaluating reactivity and sorptivity of fly ash for use in concrete construction." Thesis, University of Dundee, 2012. https://discovery.dundee.ac.uk/en/studentTheses/94122abd-aa82-4c91-85ea-079505e14489.
Full textAlsaiari, Abdulmohsen Omar. "Augmentation of Jet Impingement Heat Transfer on a Grooved Surface Under Wet and Dry Conditions." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/98502.
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de, Rooy S. C. "Improved efficiencies in flame weeding." Lincoln University, 1992. http://hdl.handle.net/10182/18.
Full textGuibu, Pereira Gabriel. "Modélisation numérique d'écoulements turbulents avec entraînement d'air au sein d'ouvrages hydrauliques." Thesis, Strasbourg, 2019. http://www.theses.fr/2019STRAD023.
Full textThe mixing and dispersion of air into water is a frequently observed feature of flows occurring in nature and in man-made hydraulic structures. The addition of immersed air bubbles in the water modifies substantially the flow's characteristics, which may have a desirable or harmful effect depending on the context. Furthermore, the assessment of the air currents is of value in the study of confined spaces. For instance, this is important in the design of air vents in structures such as dropshafts in sewage systems. This thesis focuses on identifying and developing three-dimensional computational models for a better description of air-water interactions and two-phase flows in the context of hydraulic structures. A hybrid two-phase modelling approach is implemented in this thesis, thus allowing the simultaneous representation of segregated and dispersed flow regimes. The results from different methods employed for the aerated flow simulations are finally confronted with experimental data
Khan, Muhammad. "RANS and LES of multi-hole sprays for the mixture formation in piston engines." Phd thesis, Ecole Centrale de Lyon, 2014. http://tel.archives-ouvertes.fr/tel-01002111.
Full textWaniewski, Tricia Ann. "Air entrainment by bow waves." Thesis, 1999. https://thesis.library.caltech.edu/1559/1/Waniewski_ta_1999.pdf.
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