Дисертації з теми "Cavitating Flows"
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся з топ-50 дисертацій для дослідження на тему "Cavitating Flows".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Переглядайте дисертації для різних дисциплін та оформлюйте правильно вашу бібліографію.
Wang, Yi-Chun Brennen Christopher E. "Shock waves in bubbly cavitating flows /." Diss., Pasadena, Calif. : California Institute of Technology, 1996. http://resolver.caltech.edu/CaltechETD:etd-02282006-144334.
Повний текст джерелаAhmed, Zayed. "Quantitative flow measurement and visualization of cavitation initiation and cavitating flows in a converging-diverging nozzle." Thesis, Kansas State University, 2017. http://hdl.handle.net/2097/35522.
Повний текст джерелаDepartment of Mechanical and Nuclear Engineering
B. Terry Beck
Mohammad H. Hosni
Cavitation is the formation of vapor phase from the liquid phase by reduction in its absolute pressure below the saturation pressure. Unlike boiling, where the temperature of the liquid is increased to cause vaporization, the reduction in the pressure alone can cause the liquid to turn into vapor. Cavitation is undesirable in many engineering applications as it is associated with reduction in efficiency and is known to cause damage to pump and propeller components. However, the endothermic nature of cavitation could be utilized to create a region of low temperature that could be utilized to develop a new refrigeration cycle. The work presented in this thesis is part of ongoing research into the potential cooling capacity of cavitation phenomena, where the cavitation in a converging-diverging nozzle is being investigated. Due to the constricting nature of the throat of the converging-diverging nozzle, the liquid velocity at the throat is increased, obeying the continuity law. With an increase in velocity, a reduction in absolute pressure is accompanied at the throat of the nozzle according to the Bernoulli’s principle. The local absolute pressure at the throat can go lower than the saturation vapor pressure, thereby causing the fluid to cavitate. The effect of water temperature on the flowrates, the onset of cavitation within the nozzle, and the resulting length of the cavitation region within the nozzle are the subject of this thesis. Experimental results and analysis are presented which also show that near the onset of cavitation, the flowrate can go beyond the choked flowrate, causing the local pressure in the throat to go well below zero for an extended amount of time in the metastable state, before nucleating (cavitating) into a stable state. Flow visualization using a high speed digital camera under different operating conditions was aimed at investigating the region of cavitation onset, which appears to be associated with boundary layer separation just downstream of the nozzle throat. In order to delay the boundary layer separation point in the downstream section of the nozzle, the diffuser region of the nozzle was modified to enable two flow paths, where one path would suck the flow near the inner walls of the nozzle and the other would allow the bulk of the flow to pass through. This was achieved with the use of inserts. Various inserts were tested in an attempt to capture the effect of inserts on the cavitation phenomena. Their effect on the flowrates, length of two phase region, and cavitation onset are presented in this thesis.
Preston, Alastair Thomas Colonius Timothy E. "Modeling heat and mass transfer in bubbly cavitating flows and shock waves in cavitating nozzles /." Diss., Pasadena, Calif. : California Institute of Technology, 2004. http://resolver.caltech.edu/CaltechETD:etd-12182003-150738.
Повний текст джерелаSezal, İsmail Hakkı. "Compressible dynamics of cavitating 3-D multi-phase flows." München Verl. Dr. Hut, 2009. http://mediatum2.ub.tum.de/node?id=684068.
Повний текст джерелаŞenocak, Inanç. "Computational methodology for the simulation of turbulent cavitating flows." [Gainesville, Fla.] : University of Florida, 2002. http://purl.fcla.edu/fcla/etd/UFE1001181.
Повний текст джерелаJeshani, Mahesh. "Optical characterisation of cavitating flows in diesel fuel injection equipment." Thesis, City University London, 2013. http://openaccess.city.ac.uk/3414/.
Повний текст джерелаPodbevsek, Darjan. "Optical probing of thermodynamic parameters and radical production in cavitating micro-flows." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1210/document.
Повний текст джерелаA constriction in the microchannel can be used to establish a two-phase flow, when a sufficient liquid flux is introduced. This is known as hydrodynamic cavitation. The latent heat resulting from the growing and collapsing vapor bubbles makes it interesting to observe the temperature conditions in the flow downstream of the constriction. Using fluorescence microscopy, with the addition of temperature sensitive nano probes into the working fluid, we can determine the temperature at a single point, averaged over the integration time. Coupled with a confocal microscope, we were able to produce two and three dimensional temperature maps of the steady state flow in the microchannel by the use of ratiometric intensity measurements. This technic allows us to observe temperature gradients in two-phase flow as well yielding the void fraction information. Areas of substantial cooling are observed downstream the constriction in the two-phase flow, linked to the bubble growth, while heating regions due to condensations are missing. A complementary, yet less sensitive probe-less technique using the inherent Raman scattering signal of the liquid, was used to confirm the findings. A separate study evaluating a new group of luminescent materials for optical temperature and pressure probes is performed and discussed herein. Finally, the luminol chemiluminescent reaction with radicals produced by the cavitating flow, is used to obtain a corresponding photon yield. By counting the photons produced, an estimate on the radical yield can be obtained. Additionally, rudimentary mapping of the chemiluminescence signal allows the localization of the bubble collapse regions
Gaschler, Maria [Verfasser], and Moustafa [Akademischer Betreuer] Abdel-Maksoud. "Numerical modelling and simulation of cavitating marine propeller flows / Maria Gaschler ; Betreuer: Moustafa Abdel-Maksoud." Hamburg : Universitätsbibliothek der Technischen Universität Hamburg-Harburg, 2017. http://d-nb.info/1136955143/34.
Повний текст джерелаEgerer, Christian [Verfasser], Nikolaus A. [Akademischer Betreuer] [Gutachter] Adams, and Stefan [Gutachter] Hickel. "Large-Eddy Simulation of Turbulent Cavitating Flows / Christian Egerer ; Gutachter: Stefan Hickel, Nikolaus A. Adams ; Betreuer: Nikolaus A. Adams." München : Universitätsbibliothek der TU München, 2016. http://d-nb.info/1124154744/34.
Повний текст джерелаBeban, Bruno [Verfasser], Nikolaus A. [Akademischer Betreuer] Adams, Romuald [Gutachter] Skoda, and Nikolaus A. [Gutachter] Adams. "Numerical Simulation of Submerged Cavitating Throttle Flows / Bruno Beban ; Gutachter: Romuald Skoda, Nikolaus A. Adams ; Betreuer: Nikolaus A. Adams." München : Universitätsbibliothek der TU München, 2019. http://d-nb.info/1187443921/34.
Повний текст джерелаÖrley, Felix [Verfasser], Nikolaus A. [Akademischer Betreuer] [Gutachter] Adams, and Stefan [Gutachter] Hickel. "Numerical Simulation of Cavitating Flows in Diesel Injection Systems / Felix Örley ; Gutachter: Stefan Hickel, Nikolaus A. Adams ; Betreuer: Nikolaus A. Adams." München : Universitätsbibliothek der TU München, 2016. http://d-nb.info/1120584299/34.
Повний текст джерелаMihatsch, Michael Simon [Verfasser], Nikolaus A. [Akademischer Betreuer] Adams, Manolis [Gutachter] Gavaises, and Nikolaus A. [Gutachter] Adams. "Numerical Prediction of Erosion and Degassing Effects in Cavitating Flows / Michael Simon Mihatsch ; Gutachter: Manolis Gavaises, Nikolaus A. Adams ; Betreuer: Nikolaus A. Adams." München : Universitätsbibliothek der TU München, 2017. http://d-nb.info/1151322172/34.
Повний текст джерелаSchmidt, Steffen Joachim [Verfasser], Nikolaus A. [Akademischer Betreuer] [Gutachter] Adams, and Terwisga Tom J. C. [Gutachter] van. "A low Mach number consistent compressible approach for simulation of cavitating flows / Steffen Joachim Schmidt ; Gutachter: Tom J. C. van Terwisga, Nikolaus A. Adams ; Betreuer: Nikolaus A. Adams." München : Universitätsbibliothek der TU München, 2015. http://d-nb.info/1121206689/34.
Повний текст джерелаChebli, Rezki. "Simulation 2D et 3D des écoulements cavitants : développement d'un algorithme original dans Code_Saturne et étude de l'influence de la modélisation de la turbulence." Thesis, Paris, ENSAM, 2014. http://www.theses.fr/2014ENAM0040/document.
Повний текст джерелаCavitation is one of the most demanding physical phenomena influencing the performance of hydraulic machines. It is therefore important to predict correctly its inception and development, in order to quantify the performance drop it induces, and also to characterize the resulting flow instabilities. The aim of this work is to develop an unsteady 3D algorithm for the numerical simulation of cavitation in an industrial CFD solver « Code_saturne ». It is based on a fractional step method and preserves the minimum/maximum principle of the void fraction. An implicit solver, based on a transport equation of the void fraction coupled with the Navier-Stokes equations is proposed. A specific numerical treatment of the cavitation source terms provides physical values of the void fraction (between 0 and 1) without including any artificial numerical limitation. The influence of RANS turbulence models on the simulation of cavitation on 2D geometries (Venturi and Hydrofoil) is then studied. It confirms the capability of the two-equation eddy viscosity models, k-epsilon and k-omega-SST, with the modification proposed by Reboud et al. (1998) to reproduce the main features of the unsteady sheet cavity behavior. The second order model RSM-SSG, based on the Reynolds stress transport, appears able to reproduce the highly unsteady flow behavior without including any arbitrary modification. The three-dimensional effects involved in the instability mechanisms are also analyzed. This work allows us to achieve a numerical tool, validated on complex configurations of cavitating flows, to improve the understanding of the physical mechanisms that control the three-dimensional unsteady effects involved in the mechanisms of instability
Jayaprakash, Arvind Prakash. "Cavitating Flow over Stationary and Oscillating Hydrofoils." Cincinnati, Ohio : University of Cincinnati, 2008. http://www.ohiolink.edu/etd/view.cgi?acc%5Fnum=ucin1205164937.
Повний текст джерелаCommittee/Advisors: Urmila Ghia PhD (Committee Chair), Kirti Ghia PhD (Committee Co-Chair), Milind Jog PhD (Committee Member). Title from electronic thesis title page (viewed Sep.3, 2008). Includes abstract. Keywords: Cavitation; Stationary; Oscillating; Hydrofoils. Includes bibliographical references.
JAYAPRAKASH, ARVIND PRAKASH. "Cavitating Flow over Stationary and Oscillating Hydrofoils." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1205164937.
Повний текст джерелаWilms, Jeffrey. "Flow visualization of cavitation." Thesis, Kansas State University, 2013. http://hdl.handle.net/2097/32158.
Повний текст джерелаDepartment of Mechanical and Nuclear Engineering
Mohammad Hosni
A typical refrigeration loop is composed of an evaporator, compressor, condenser, and an expansion valve. There are many possible refrigerants that can be used, but the physical properties of water make it ineffective in the traditional refrigeration loop. But if water could be used it would have many advantages as it is abundant, cheap, and is safe for the environment. This research focuses on a different kind of refrigeration loop using water. This new refrigeration loop utilizes water flowing through a nozzle, initiating cavitation. Cavitation is generally defined as creating vapor from liquid, not through adding heat, but by decreasing the pressure. In a converging/ diverging nozzle, as the cross sectional area is constricted, the velocity of the flow will increase, decreasing the pressure. Therefore, by flowing water through the nozzle it will cavitate. Transforming liquid into gas requires a certain amount of energy, defined as the latent heat. When a liquid is turned to vapor by an increase in the temperature, the latent heat is provided by the heat transfer to the system. As no energy is being added to the nozzle to cause the cavitation, the energy transfer to create the vapor comes from the remaining liquid, effectively causing a temperature drop. This research focused on the flow visualization of water cavitating as it travelled through a converging/ diverging nozzle. Under different flow conditions and different nozzle geometries, the cavitation manifested itself in different formations. When gasses were entrained in the water they formed bubbles, which acted as nucleation sites as they moved through the nozzle. This was called travelling bubble cavitation. In venturi nozzles the cavitation nucleated off of the wall, forming attached wall cavitation. When water flowed out of an orifice, a turbulent mixture of liquid and vapor, orifice jet, was formed which caused vapor to form around it. This was known as shear cavitation. When the water was rotated prior to the throat of an orifice, the orifice jet expanded radially and formed swirl cavitation. In addition to studying how the cavitation was formed, the void fraction and velocity were measured for attached wall cavitation.
Fine, Neal E. "Nonlinear analysis of cavitating propellers in nonuniform flow." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/12564.
Повний текст джерелаWhitfield, Claire Margaret Frances. "Investigation of cavitating flow luminescence for analytical spectroscopy." Thesis, University of Plymouth, 2015. http://hdl.handle.net/10026.1/3464.
Повний текст джерелаHaese, Peter Michael. "Interior source methods for planar and axisymmetric supercavitating flows." Title page, contents and abstract only, 2003. http://web4.library.adelaide.edu.au/theses/09PH/09phh136.pdf.
Повний текст джерелаWu, Jiongyang. "Filter-based modeling of unsteady turbulent cavitating flow computations." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0011587.
Повний текст джерелаSzymczak, Michel. "Flow visualization of cavitating, high-speed, submerged water jets." Thesis, University of Ottawa (Canada), 1988. http://hdl.handle.net/10393/5159.
Повний текст джерелаTanguay, Michel Colonius Timothy E. "Computation of bubbly cavitating flow in shock wave lithotripsy /." Diss., Pasadena, Calif. : California Institute of Technology, 2004. http://resolver.caltech.edu/CaltechETD:etd-05282004-130028.
Повний текст джерелаYazici, Bora. "Numerical And Experimental Investigation Of Flow Through A Cavitating Venturi." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/3/12607924/index.pdf.
Повний текст джерелаHarp, Susan R. "A computational method for evaluating cavitating flow between rough surfaces." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/16838.
Повний текст джерелаFine, Neal E. "Computational and experimental investigations of the flow around cavitating hydrofoils." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/35344.
Повний текст джерелаHart, Douglas P. Acosta Allan J. Brennen Christopher E. "Cavitation and wake structure of unsteady tip vortex flows /." Diss., Pasadena, Calif. : California Institute of Technology, 1993. http://resolver.caltech.edu/CaltechETD:etd-03272007-131947.
Повний текст джерелаBrewer, Wesley H. (Wesley Huntington). "A computational and experimental study of viscous flow around cavitating propulsors." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/38100.
Повний текст джерелаBourg, David M. "Development of the Distributed Points Method with Application to Cavitating Flow." ScholarWorks@UNO, 2008. http://scholarworks.uno.edu/td/904.
Повний текст джерелаMAHALATKAR, KARTIKEYA. "CAVITATING FLOW OVER OSCILLATING HYDROFOILS AND HYDROFOIL-BASED SHIP STABILIZATION SYSTEM." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1154301156.
Повний текст джерелаAsher, William. "Fluid dynamics of cavitating sonic two-phase flow in a converging-diverging nozzle." Thesis, Kansas State University, 2014. http://hdl.handle.net/2097/17621.
Повний текст джерелаDepartment of Mechanical and Nuclear Engineering
Steven Eckels
Both cavitating and flashing flows are important phenomena in fluid flow. Cavitating flow, a common consideration in valves, orifices, and metering devices, is also a concern in loss of coolant accidents for liquid water in power plants when saturation pressures are below atmospheric pressure. Flashing flow is a common consideration for devices such as relief and expansion valves and fluid injectors as well as for loss of coolant accidents in which the coolant’s saturation pressure is above atmospheric. Of the two phenomena, flashing flow has received greater interest due to its applicability to safety concerns, though cavitating flow is perhaps of greater interest in terms of energy efficiency. It is possible for cavitating and flashing flow to actually become sonic. That is, the local velocity of a fluid can exceed the local speed of sound due to the unique properties of two-phase mixtures. When a flow becomes sonic, it is possible for the flow to accelerate and impose additional energy losses that would not otherwise occur. Models of this aspect of two-phase flow are not well developed, typically only being presented for the case of constant area ducts. In this paper two models for cavitating sonic flow are developed and described by applying the integral forms of the mass, momentum, and energy equations to a control volume of variable cross-sectional area. These models, based on the homogeneous equilibrium model (HEM) and separated flow model, are then applied to experimental data taken by the author with R-134a as the fluid of interest. Experimental data were taken with four instrumented converging-diverging nozzles of various geometries using a custom testing rig that allowed for precise control and measurement of flow parameters such as mass flow, temperature, and pressure. The resultant data from the models are then examined, focusing on the resultant velocities, Mach numbers, quality, and shear stresses.
Mishima, Shigenori. "Design of cavitating propeller blades in non-uniform flow by numerical optimization." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/41006.
Повний текст джерелаMiah, Wadud. "Numerical modelling of material interfaces and cavitation in high speed flows." Thesis, Imperial College London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427920.
Повний текст джерелаAlrifaai, Hatim. "Experimental Investigation of Cavitation Using Refrigerant in a Two-Phase Flow System." Thesis, Kansas State University, 2017. http://hdl.handle.net/2097/38553.
Повний текст джерелаDepartment of Mechanical and Nuclear Engineering
Mohammad H. Hosni
Cavitation is a phase change process and its conversion of fluid from liquid to vapor requires pressure reduction. In this thesis, cavitation of R134a refrigerant is evaluated experimentally. This work is part of an ongoing project that seeks to develop a novel cooling cycle based on the cooling potential of the fluid during cavitation. A blowdown system was designed, built, and used for conducting the experiments. This system included a special test section containing a unique converging-diverging nozzle system designed for this investigation. In the end, cavitation was achieved by flowing the test fluid through a converging-diverging nozzle. As the fluid flows through the nozzle throat, the velocity increases while the pressure decreases and cavitation occurs when its static pressure drops below its vapor pressure. The onset of cavitation was evaluated by measuring pressure, temperature, and refrigerant flow rate, and by visualizing the flow using a high-speed video camera.
Ndamuso, N. "Parametric studies of cavitation dependence on hydrocarbon and biodiesel fuel injection flows." Thesis, City, University of London, 2017. http://openaccess.city.ac.uk/19228/.
Повний текст джерелаTomov, Petar. "Étude expérimentale et numérique de la cavitation et la cavitation aérée. Vers une application à l’alimentation en carburant d’un moteur d’avion." Thesis, Paris, ENSAM, 2016. http://www.theses.fr/2016ENAM0011/document.
Повний текст джерелаDepending on the configuration of the plane, its flight altitude, the type of fuel, different physical phenomena significantly change the characteristics of the fuel supply to the engine. Indeed, it primarily occurs a fuel degassing phenomenon that could be coupled to the cavitation phenomenon. As a result, the thus obtained multiphase flows contain micro bubbles, larger bubbles or vapor pockets which might induce engines malfunctions. The latter result in thrust fluctuations which can lead to a loss of power. The scientific context of the industrial problem lies in the development of a numerical and experimental representation of the cavitation and degassing phenomena on a smaller scale. As a result, it is of primary importance for one to understand the mechanisms of occurrence of gas and cavitation in the given industrial configuration. In order to deal with those issues, two test benches have been developed, as well as an in-house numerical code capable of simulating aerated cavitation phenomenon. Therefore, three different pure cavitation regimes and three other aerated cavitation are shown, as a result of the experimental work. The multiphase flow observations are based on a statistical post-processing of images taken by a high-speed camera. Moreover, two 2D aerated cavitation numerical simulations, as well as the first 3D pure cavitation simulation have been shown
Lauer, Eric [Verfasser]. "Numerical simulation and investigation of high-speed bubble-dynamics in cavitating flow. / Eric Lauer." München : Verlag Dr. Hut, 2013. http://d-nb.info/1045989126/34.
Повний текст джерелаKozák, Jiří. "Cavitation Induced by Rotation of Liquid." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-409529.
Повний текст джерелаYuhua, Yan. "Cavitation phenomena and the admittance of air in the flow through an orifice." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.257548.
Повний текст джерелаKinnas, Spyridon Athanasios. "Non-linear corrections to the linear theory for the prediction of the cavitating flow around hydrofoils." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/15257.
Повний текст джерелаMICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.
Bibliography: leaves 116-120.
by Spyridon Athanasios Kinnas.
Ph.D.
Schümichen, Michel, Frank Rüdiger, Jochen Fröhlich, and Jürgen Weber. "Simulation of the cavitating flow in a model oil hydraulic spool valve using different model approaches." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-199607.
Повний текст джерелаPettersson, Kristoffer. "Design of aerators for prevention of cavitation – The Höljes Dam." Thesis, KTH, Vattendragsteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-99352.
Повний текст джерелаSarkar, Snigdha. "Numerical Investigation of Vapor and Gaseous Cavitation in Squeeze-Film Damper Bearings." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1523636346718425.
Повний текст джерелаBachmann, Mathieu [Verfasser]. "Dynamics of cavitation bubbles in compressible two-phase fluid flow / Mathieu Bachmann." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2013. http://d-nb.info/1036241467/34.
Повний текст джерелаShahmohamadi, Hamed. "Multi-phase thermal cavitation flow in rough conforming and partially conforming conjunctions." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/18460.
Повний текст джерелаTeng, 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.
Повний текст джерелаQC 20170224
Pinho, Jorge. "Experimental investigation of cavitation in a safety relief valve using water: extension to cryogenic fluids." Doctoral thesis, Universite Libre de Bruxelles, 2015. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209095.
Повний текст джерелаIn order to investigate the above effects of cavitation in a SRV, two different orifice sized valves (API 2J3 type and a transparent model based on an API 1 1/2G3 type) are tested in two different experimental facilities expressly built for this purpose. Instead of using a spring, the design of both valves allows the adjustment of the disc at any desired lift. Hence the static behavior of the valves is investigated. Both facilities, operating at different magnitude scales, allow the study of single phase and cavitating flow conditions required to properly determine the most important hydraulic characteristics, and access on any potential scaling effect between both sized SRVs. Experimental techniques used for the determination of the hydraulic characteristics include temperature, flow rate, fluid forces and pressure measurements both upstream and downstream the test sections.
Results show a similar influence of cavitation on the flow characteristics of both valves, minimizing any potential scaling effect. The liquid pressure recovery factor FL, which is normally used to identify a choked flow condition in a control valve, is experimentally determined for the first time in a SRV. The existence of a local minimum located at small openings of the lift indicates a change on the flow characteristics of both valves, which is related to the location of the minimum cross section of the flow that does not remain constant for every lift position. An extended experimental campaign is performed to analyse the effect of the blowdown ring adjustment located around the nozzle of the API 2J3 valve. Results confirm that the position of the ring has an important contribution for the hydraulic forces acting on the valve disc.
In the second part of the research, precise optical diagnostic techniques are successfully applied in the transparent valve to locally characterize the flow topology in a SRV experiencing cavitation. These results are innovative and enrich the experimental database available in the literature for the characterization and understanding of the flow physics in such devices. In a first configuration, high speed visualization is applied to observe qualitatively the flow pattern and the inception of liquid vaporization. Particle tracking results suggest that vapor bubbles are formed in the core of vortices detached from the shear layers attached to the valve. These rotational structures promote lower pressure regions allowing the liquid to vaporize. In the second configuration, particle image velocimetry is applied to extract the velocity field in both single phase and cavitating flow conditions. Results of PIV confirm the existence of a submerged jet just downstream the minimum section. This jet is characterized by two non-symmetric shear layers at its sides. Under cavitation conditions, PIV results confirm that vapor bubbles are formed preferentially inside the jet shear layers. The phenomenon of mass flux limitation caused by cavitation is reproduced at small openings of the valve and interaction with the flow topology is highlighted. It is observed that limitation of the flow occurs when the vena contracta is shifted towards the minimum geometrical section of the flow. Finally, instabilities of the flow downstream the critical section are investigated in the frequency domain by means of time resolved data. Results suggest that vortex shedding mechanism is dominated by a constant Strouhal number which is slightly affected by the valve opening.
In the last part of the research, the methodology used in water is extended and applied to cryogenic liquids. Two different geometries are investigated experimentally and numerically using water and liquid nitrogen as working fluids. Results suggest that both the flow coefficient (determined at single flow conditions), and the liquid recovery factor (used to identify choked flows), are independent on the fluid properties and therefore, an hydraulic similarity relation can be proposed.
This research project was carried out at the von Karman Institute for Fluid Dynamics (VKI), in Belgium, in close collaboration and with the funding of Centre Technique des Industries Mécaniques (CETIM) in France.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
Schmidt, Aaron James. "Quantitative measurement and flow visualization of water cavitation in a converging-diverging nozzle." Thesis, Kansas State University, 2016. http://hdl.handle.net/2097/32587.
Повний текст джерелаDepartment of Mechanical and Nuclear Engineering
B. Terry Beck
Mohammad H. Hosni
Cavitation is the change of a liquid to a two-phase mixture of liquid and vapor, similar to boiling. However, boiling generates a vapor by increasing the liquid temperature while cavitation generates vapor through a decrease in pressure. Both processes are endothermic, removing heat from the surroundings. Both the phase change and heat absorption associated with cavitation provide many engineering applications, including contributing to a new type of refrigeration cycle under development. Cavitation can occur at or below the vapor pressure; conditions that delay cavitation and allow for a metastable liquid are not well understood. A converging-diverging nozzle was designed and fabricated to create a low pressure region at the nozzle throat. The converging section of the nozzle increased the water velocity and decreased the pressure, according to Bernoulli’s principle. A cavitation front was formed slightly past the nozzle throat. The cavitation location suggested that the water was metastable near the nozzle throat. Flow through the system was controlled by changing the nozzle inlet and outlet pressures. The flowrate of water was measured while the outlet pressure was lowered. The flowrate increased as the outlet pressure dropped until cavitation occurred. Once cavitation initiated, the flow became choked and remained constant and independent of the nozzle outlet pressure. High-speed imagery was used to visualize the flow throughout the nozzle and the formation and collapse of cavitation in the nozzle’s diverging section. High-speed video taken from 1,000 to 35,000 frames per second captured the formation of the cavitation front and revealed regions of recirculating flow near the nozzle wall in the diverging section. Particle Image Velocimetry (PIV) was used to measure the velocity vector field throughout the nozzle to characterize flow patterns within the nozzle. PIV showed that the velocity profile in the converging section and throat region were nearly uniform at each axial position in the nozzle. In the diverging section, PIV showed a transient, high-velocity central jet surrounded by large areas of recirculation and eddy formation. The single-phase experimental results, prior to cavitation onset, were supplemented by Computational Fluid Dynamics (CFD) simulations of the velocity distribution using Fluent software.
Brewer, Wesley Huntington. "On simulating tip-leakage vortex flow to study the nature of cavitation inception." Diss., Mississippi State : Mississippi State University, 2002. http://library.msstate.edu/etd/show.asp?etd=etd-04102002-134949.
Повний текст джерелаRuh, Christian. "Performance of boiling and hot sparged agitated reactors." Thesis, University of Surrey, 1997. http://epubs.surrey.ac.uk/844300/.
Повний текст джерела