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Dissertations / Theses on the topic 'Rotating mechanism'
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1
White, David Allen. "Development of a high-speed rotating bar mechanism." Thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-12172008-063626/.
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2
Yang, Chunping. "Rotating Drum Biofiltration." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1092668752.
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3
Lunka, Alex A. "Development of a Novel Air-to-Liquid Mass Transfer Mechanism." Ohio University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1415121834.
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4
Begáň, Matej. "Kočka šrotového jeřábu - otočná část." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-442799.
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The diploma thesis deals with a design of a rotating part of a crane trolley of a scrap crane with a load capacity of 110,000 kg, which is situated in an exterior environment. The aim of the diploma thesis is a design and calculation verified design of the lifting mechanism, rotation mechanism and the design of a spacious traverse, which is used for the manipulation of the scrap trough and casting ladle.
5
Ban, Kyunha. "Mechanism and Significance of Slip and New Mixing Elements During Flow in Modular Intermeshing Co-Rotating Twin Screw Extruders." University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1218132059.
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6
Anza, Inigo. "Synthesis of Aluminum-Titanium Carbide Nanocomposites by the Rotating Impeller Gas-Liquid In-situ Method." Digital WPI, 2016. https://digitalcommons.wpi.edu/etd-dissertations/376.
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"The next generation of aluminum alloys will have to operate at temperatures approaching 300°C. Traditional aluminum alloys cannot perform at these temperatures, but aluminum alloys reinforced with fine ceramic particles can. The objective of this research is to develop a process to synthesize Al-TiC composites by the Rotating Impeller Gas-Liquid In-situ method. This method relies on injecting methane into molten aluminum that has been pre-alloyed with titanium. The gas is introduced by means of a rotating impeller into the molten alloy, and under the correct conditions of temperature, gas flow, and rotation speed, it reacts preferentially with titanium to form titanium carbide particles. The design of the apparatus, the multi-physics phenomena underlying the mechanism responsible for particle formation and size control, and the operation window for the process are first elucidated. Then a parametric study that leads to the synthesis of aluminum reinforced with TiC microparticles and nanoparticles is described. Finally, potential technical obstacles that may stand in the way of commercializing the process are discussed and ways to overcome them are proposed. "
7
Anand, Vijay G. "Rotating Detonation Combustor Mechanics." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1530798871271548.
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8
Pandravada, Ratnam. "Kinematics and motion planning of a rolling disk between two planar manipulators." Ohio : Ohio University, 1996. http://www.ohiolink.edu/etd/view.cgi?ohiou1178049004.
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9
Briega-Martos, Valentín. "Unraveling the oxygen reduction reaction mechanism: occurrence of a bifurcation point before hydrogen peroxide formation." Doctoral thesis, Universidad de Alicante, 2019. http://hdl.handle.net/10045/102311.
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En la presente tesis doctoral se realiza un estudio detallado sobre el mecanismo de la reacción de reducción de oxígeno (ORR) en electrodos monocristalinos de platino. Para ello, se han realizado medidas electroquímicas usando la configuración de electrodo rotatorio de menisco colgante (HMRDE) con superficies con distinta estructura superficial y variando condiciones de la disolución de trabajo como el pH, fuerza iónica o la ausencia o presencia de bromuros. La conclusión principal que se extra de estos experimentos es la posibilidad de la existencia de un punto de bifurcación en el mecanismo, implicando el intermedio OOH, antes de la formación de peróxido de hidrógeno. Además, también se estudia la ORR y la reacción de oxidación de ácido fórmico en electrodos monocristalinos de Pt en presencia de acetonitrilo, como estudio previo al estudio de estas reacciones en disolventes orgánicos con pequeñas cantidades de agua. Por último, se estudia la ORR en un Aza-CMP, lo cual permite obtener información fundamental que se puede aplicar en estudios sobre el mecanismo de la ORR en los sitios activos de materiales de carbón funcionalizados con nitrógeno.
10
Lumbers, Jeremy. "Rotating biological contactors : mechanisms, modelling and design." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/47161.
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11
Mohamed, Alhade Abdossllam. "Monitoring cracks in a rotating shaft." Thesis, University of Aberdeen, 2012. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=186894.
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Condition monitoring of rotating shafts is gaining importance in industry due to the need to increase machine reliability and decrease the possible loss of production due to machine breakdown. In this work, the use of vibration signals for the detection of a crack within a shaft was investigated. The research involved the measurement of vibration signals during laboratory tests on a long rotating shaft rig. The focus of the experimental work was on the effect of cracks on the dynamics and the initiation and growth of cracks in the shaft. Measurements were taken from the shaft system both with simulated cracks (notches) cut at 45° and 90° to the shaft axis and with real propagating cracks initiated by a pre-crack cut. All defects were located at the mid- point along the shaft. The vibration responses and stresses were measured for different depths of crack. The vibration responses of the three different defects were compared using PSDs of the data to identify the change in position and magnitude of the peaks in the spectrum under each defect. Experiments to study the effect of defect depth at different shaft rotation speeds were also carried out. Finally, a shaft with a breathing crack (continuously opening and closing as the shaft rotates) was also studied experimentally, with the crack growing under normal steady state operating conditions. After completing the experiment work, the shaft was broken and the type of fracture studied. The results for both simulated and actual crack growth showed that vibration frequencies decreased as a crack progressed, indicating the possibility of using the vibration signal for crack detection. A significant relationship was found between the stage of crack growth and the vibration results. A finite element (FE) model was constructed to explore the relationship between the natural frequencies and crack depth and position along the shaft and to explain and validate the results of the experimental work. The FE model showed similar trends to the experimental results and also allowed the effect of different crack positions to be explored. The PSD data was fed into an artificial neural network after a feature extraction procedure was applied to significantly reduce the quantity of data whilst at the same time retaining the salient information. Such an approach results in a considerably reduced training time for the network due to the reduced complexity. The proposed scheme was shown to successfully identify the different defect levels. This method greatly enhances the capacity of an automated diagnostic process by linking increased capability in signal analysis to the predictive capability of the artificial neural network.
12
Lovegrove, Alistair. "Bifurcations and istabilities in rotating two-layer fluids." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390486.
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13
Whitehurst, E. P. "Flow dissipation in rotating superfluid sup(3)He." Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356718.
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14
Seshasayanan, Kannabiran. "Rotating turbulent dynamos." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066158/document.
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Dans cette thèse, nous étudions l’effet de la turbulence en rotation sur l’instabilité dynamo. Nous étudions les différentes limites de la turbulence en rotation numériquement et théoriquement. D’abord, nous avons considéré l’effet dynamo engendré par les écoulements quasi-bidimensionnel (un écoulement avec trois composantes de vitesse qui dépendent de deux directions), qui modélise la limite de rotation très rapide. Nous avons étudié l’amplitude de saturation du champ magnétique en fonction du nombre de Prandt magnétique pour ce type d’écoulement. Un modèle théorique est développé et comparé avec les résultats numériques. Nous avons aussi regardé l’effet d’une vitesse bruitée sur le taux de croissance des différents moments du champ magnétique. Nous avons étudié l’écoulement 3D en rotation globale pour différents régimes du paramètre de contrôle. Pour l’écoulement hydrodynamique, nous avons étudié la transition vers une cascade inverse et les différents types de saturation de la cascade inverse. Nous avons regardé l’instabilité dynamo de ces écoulements. Nous avons montré que la rotation modifie le mode le plus instable et dans certains cas peut réduire le seuil de l’instabilité dynamoIn this thesis, we study the effect of rotating turbulent flows on the dynamo instability. We study the different limits of rotating turbulence using numerical simulations and theoretical tools. We first look at the dynamo instability driven by quasi-twodimensional flows (flows with three components varying along two directions), which models the limit of very fast rotation. We look at the saturation amplitude of the magnetic field as a function of the magnetic Prandtl number for such flows. A theoretical model for the dynamo instability is later developed and compared with the numerical results. We also study the effect of a fluctuating velocity field on the growth rate of different moments of the magnetic field. The three dimensional rotating flow is then studied for different range of parameters. For the hydrodynamic problem, we study the transition to an inverse cascade and the different saturation mechanism of the inverse cascade. Later the dynamoinstability driven by such flows is investigated. We show that the effect of rotation modifies the most unstable mode and in some cases can reduce the dynamo threshold
15
Laker, Travis S. "Secondary flows in a rotating serpentine circular duct." Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/15898.
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16
Pitt-Francis, Joseph M. "Dynamics of solid bodies in a rotating viscous fluid." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386716.
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17
Siegwart, David Kevin. "Classical and quantum chaos of dynamical systems : rotating billiards." Thesis, Durham University, 1990. http://etheses.dur.ac.uk/6228/.
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The theory of classical chaos is reviewed. From the definition of integrable systems using the Hamilton-Jacobi equation, the theory of perturbed systems is developed and the Kolmogorov-Arnold-Moser (KAM) theorem is explained. It is shown how chaotic motion in Hamiltonian systems is governed by the in tricate connections of stable and unstable invariant manifolds, and how it can be catagorised by algorithmic complexity and symbolic dynamics, giving chaotic measures such as Lyapunov exponents and Kolmogorov entropy. Also reviewed is Gutzwiller's semiclassical trace formula for strongly chaotic systems, torus quantisation for integrable systems, the asymptotic level density for stationary billiards, and random matrix theories for describing spectral fluctuation properties. The classical theory is applied to rotating billiards, particularly the free motion of a particle in a circular billiard rotating uniformly in its own plane about a point on its edge. Numerically, it is shown that the system's classical behaviour ranges from fully chaotic at intermediate energies, to completely integrable at very low and very high energies. It is shown that the strong chaos is due to discontinuities in the Poincare map, caused by trajectories which just glance the boundary-an effect of the curvature of trajectories. Weaker chaos exists due to the usual folding and stretching of the Hamiltonian flow. Approximate invariant curves for integrable motion are found, valid far from the presence of glancing trajectories. The major structures of phase space are investigated: a fixed point and its bifurcation into a two-cycle, and their stabilities. Lyapunov exponents for trajectories are calculated and the chaotic volume for a wide range of energies is measured. Quantum mechanically, the energy spectrum of the system is found numerically. It is shown that at the energies where the classical system is completely integrable the levels do not repel, and at those energies where it is completely chaotic there is strong level repulsion. The nearest neighbour level spacing distributions for various ranges of energy and values of Planck's constant are found. In the semiclassical limit, it is shown that, for energies where the classical system is completely chaotic, the level spacing statistics are Wigner, and where it is completely integrable, the level spacing statistics are Poisson. A model is described for the spacing distributions where the levels can be either Wigner or Poisson, which is useful for showing the transition from one to the other, and ad equately describes the statistics. Theoretically, the asymptotic level density for rotating billiards is calculated, and this is compared with the numerical results with good agreement, after modification of the method to include all levels.
18
Greed, Glenn Trevor. "Asymptotic theory for thermal instabilities in the rotating annulus." Thesis, University of Exeter, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337765.
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19
Barsoum, Nader N. "Analysis and computation of instability mechanisms in rotating electrical machinery." Thesis, University of Newcastle Upon Tyne, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328149.
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20
Gosselin, Frédéric. "Stability of a rotating cylindrical shell containing axial viscous flow." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99764.
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The present thesis studies the stability of a rotating cylindrical shell containing a co-rotating axial viscous flow. The system can be thought of as a long thin-walled pipe carrying an internal axial flow while the whole is in a frame of reference rotating at a prescribed rate. The equations of the previously solved inviscid model are rederived and the problem is studied further. The results obtained for purely axial flow are reproduced, but as expected from literature, it is impossible to obtain satisfactory results for the system subjected to rotation due to the presence of singularities in the flow pressure solution. A hypothetical physical explanation for these singularities is put forward and has similarities with the phenomenon of atmospheric flow blocking.Considering the unsuccessful results obtained with the inviscid theory, it is believed that the added realism brought in by the introduction of viscosity in the theory can lead to a successful model. Assuming a travelling-wave perturbation scheme, the linear Donnell-Mushtari thin shell equations are coupled with the fluid stresses obtained by solving numerically the incompressible Navier-Stokes equation for a laminar or turbulent flow. A novel triple-perturbation approach is established to consider the interaction between the fluid and the structure. This triple-perturbation approach is in essence a superposition of three fluid fields caused by the three components of the shell deformation for a given oscillation mode. It is found that the usual technique for linear aeroelasticity studies consisting of applying the fluid boundary conditions at the undeformed position of the wall instead of the instantaneous deformed position greatly alters the stability of the system. To remedy to this problem, three different corrections are applied and tested on the carefully derived model. The dynamics of the system subjected to purely axial flow with no rotation is successfully studied with the viscous model for both laminar and turbulent flow conditions. Because no experimental or previous theoretical data is available, it is impossible to validate the results obtained in the laminar regime. For the turbulent regime, as the Reynolds number is increased, the results tend more and more towards those obtained with the inviscid theory.
The results obtained for small rates of rotation show that both in the laminar and in the turbulent regime, the system tends to be stabilised when subjected to a small rate of rotation. On the other hand, this tendency should be reversed for higher rates of rotation, but it is impossible to show this due to the limitations of the root-finding method employed.
21
Facciolo, Luca. "A study on axially rotating pipe and swirling jet flows." Doctoral thesis, Stockholm : Royal Institute of Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3862.
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22
Lingwood, R. J. "Stability and transition of the boundary layer on a rotating disk." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307947.
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23
Landon, Steven D. "Development of Deployable Wings for Small Unmanned Aerial Vehicles Using Compliant Mechanisms." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1917.pdf.
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24
Xiong, Xiao-Jin. "Modeling, control and computer simulation of a rotating Timoshenko beam." Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=35652.
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In this work, we develop a mathematical model for a rotating Timoshenko beam, and then show its well-posedness. Further, we prove the exact controllability of its linearized model under different sets of controllers. Finally, we work out a computer simulation system for linear as well as nonlinear control problems.
25
Tseng, Chaw-Wu. "Vibration of rotating-shaft design spindles with flexible bases /." Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/7129.
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26
Jintanawan, Thitima. "Vibration of rotating disk-spindle systems with hydrodynamic bearings /." Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/7149.
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27
Kaya, Yasemin. "Analytical And Numerical Solutions To Rotating Orthotropic Disk Problems." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608868/index.pdf.
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Analytical and numerical models are developed to investigate the effect of orthotropy on the stress distribution in variable thickness solid and annular rotating disks. The plastic treatment is based on Hill&rsquos quadratic yield criterion, total deformation theory, and Swift&rsquo
s hardening law. The elastic-plastic stress distributions, residual stresses and radial displacement distributions are obtained after having analysed the cases of rotating solid disk, annular disk with rigid inclusion, annular disk subjected to either internal or external pressure. Thermal loading is also considered for the annular disk with rigid inclusion. Effects of different values of elastic and plastic orthotropy parameters are investigated. It is observed that the elastic orthotropy significantly affects the residual stresses in disks. The most remarkable effect of the plastic orthotropy is observed on the disk with rigid inclusion.
28
Newey, Michael Kent. "Mechanisms for axial band formation in a rotating drum of granular material." College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/4151.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2006.Thesis research directed by: Physics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
29
Crawford, Thomas Joseph. "An experimental study of the spread of buoyant water into a rotating environment." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/264526.
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This thesis examines previously unresolved issues regarding the fluid dynamics of the spread of buoyant water into a rotating environment. We focus in particular on the role that finite potential vorticity and background turbulence play in determining the flow properties. When water of an anomalous density enters into an oceanic basin, gravity-driven surface flows can be established as a result of the density difference. These flows are often of a sufficiently large scale that the dynamics are affected by the Coriolis force arising from the rotation of the earth. This causes the formation of a large outflow gyre near to the source which feeds into a propagating gravity current that is confined to the coast. Previous experimental work in this field has sought to simplify the problem through the use of a point source and a quiescent ambient. We extend this work to provide a better representation of the real-world flow by introducing a source of finite depth and background turbulence to the rotating ambient. This study seeks to answer three key questions that are critical to the understanding of the flow behaviour in this scenario. First, what is the effect of the finite potential vorticity of the outflow on the properties of the outflow vortex and the boundary current? Second, what role does the presence of the the outflow vortex play in determining the behaviour of the current? Third, what is the effect of background turbulence on the flow properties? To carry out the investigation, experiments were conducted in the laboratory and compared with a theoretical description of the flow. The currents are generated inside a rotating tank filled with saltwater by the continuous release of buoyant freshwater from a source structure located at the fluid surface. A horizontal source of finite depth is used to introduce finite potential vorticity into the outflow. The impact of background turbulence is examined by introducing an oscillating grid into the rotating tank. We find that the finite potential vorticity of the outflow plays an important role in determining the flow properties for sufficiently low Rossby and Froude number. As the value of these parameters is increased a zero potential vorticity model is able to capture the key elements of the flow behaviour. The outflow vortex is found to act as a time-varying source to the boundary current, with the current velocity fixed by the vortex velocity field. The vortex vorticity is seen to decrease with time, while the vortex radius continues to increase at late times despite the vortex having reached a limiting depth, which enables potential vorticity to be conserved and the current to be supplied with a non-zero velocity. Finally, the structure of the background turbulence is found to be key in determining the effect that it has on the flow properties, with different behaviours observed for three-dimensional and quasi- two-dimensional turbulence.
30
Romero, HernaÌndez Sergio. "Determination of windage losses on high-speed enclosed rotating discs with superposed flow." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270488.
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31
Jonsson, Jonathan. "Modelling adsorption rate in a rotating bed reactor." Thesis, Umeå universitet, Institutionen för fysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-152065.
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SpinChem AB designs rotating bed reactors (RBR:s) that are used to conduct reactions between solid and liquid phase. In this work a model have been developed that predicts the performance of the S2 RBR. Coupled with simulations the model could be used to improve current and future RBR designs. The model predicts the reaction rate inside the RBR during a de-colourization process where methylene blue was adsorped onto an adsorbent that was chosen during a screening study. The materials investigated were XAD1600N, MN102, activated carbon and IRN99 where the suitability of a material was judged upon the capacity and reproducibility of the process, and the reaction rate dependency on the mass transport. The DOE software MODDE Pro was used to design a parameter study that produced a function that describes the reaction rate of the process as a function of the RPM of the RBR and the temperature, pH and initial concentration of the methylene blue solution. Using simulations in ANSYS Fluent and modelling the function was then converted to the final model. It was then tested by comparing experimental results with simulations of the de-colourization process where the reaction rate inside the RBR was set using the model. IRN99 was chosen as the adsorbent of the process as its capacity was the highest of the four materials studied and its reaction rate displayed a sufficient mass transport dependence. The parameter study produced a function with a high R2, Q2 and reproducibility (>0.85) but displayed a low model validity (-0.2) as a result of the noise in the experimental data. The final model agrees well with the experimental results in the whole parameter space of experiments conducted. The model is meant to be a general model that could be applied to other RBR sizes. It could therefore be used to investigate the performance of new RBR models before they are built or improve current RBR:s. Other geometries has however not been tested during this work and therefore not much can be said about its accuracy when used in this way.SpinChem AB designar roterande bäddreaktorer (RBR:s) som används för att genomföra reaktioner mellan fast och flytande fas. I detta arbete har en modell utvecklats som förutspår prestandan hos en S2 RBR. Tillsammans med simuleringar kan modellen användas för att förbättra nuvarande och framtida RBR-modeller. Modellen förutspår reaktionshastigheten inuti RBR:en under en avfärgningsprocess där metylenblått adsorberades på ett adsorbent som valdes under en screeningsstudie. Materialet som undersöktes var XAD1600N, MN102, aktiverat kol och IRN99 där lämpligheten av ett material bedömdes på processens kapacitet och reproducerbarhet och reaktionshastighetens beroende på masstransport. DOE-mjukvaran MODDE Pro användes för att utforma en parameterstudie som gav en funktion som beskriver processens reaktionshastighet som en funktion av RBR:ens RPM och temperaturen, pH och initialkoncentrationen av metylenblålösningen. Genom att använda simuleringar i ANSYS Fluent och modellering kunde funktionen omvandlas till en modell som beskriver reaktionens hastighet inne i RBR:en. Den testades sedan genom att jämföra experimentella resultat med simuleringar av avfärgningsprocessen där reaktionshastigheten inuti RBR:en sattes med hjälp av modellen. IRN99 valdes som adsorbent av processen eftersom dess kapacitet var den högsta av de fyra studerade materialen och dess reaktionshastighet visade ett tillräckligt masstransportberoende. Parameterstudien gav en funktion med hög R2, Q2 och reproducerbarhet (> 0,85) men visade på en låg modellgiltighet (-0.2) vilket beror på brus i experimentdata. Den slutliga modellen stämmer väl överens med experimentresultaten i hela parameterrummet för de utförda experimenten. Modellen är avsedd att vara en allmän modell som kan tillämpas på andra RBR-storlekar. Det kan därför användas för att undersöka prestandan hos nya RBR-modeller innan de byggs eller förbättra nuvarande RBR:er. Andra geometrier har dock inte testats under detta arbete och därför kan inte mycket sägas om dess noggrannhet när den används på detta sätt.
32
Memon, M. D. "Numerical modelling and prediction of fluid flow and heat transfer in rotating disc geometries." Thesis, University of Sussex, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.484071.
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33
Zoueshtiagh, Farzam. "Experimental and computational study of spiral patterns in granular media underneath a rotating fluid." Thesis, University of Warwick, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247353.
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34
Arslan, Eray. "Effect Of A Temperature Cycle On A Rotating Elastic-plastic Shaft." Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12611573/index.pdf.
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The stress distribution in a rotating solid shaft with temperature dependent yield
stress subject to a temperature cycle is investigated. It is presumed that the shaft
is in a state of generalized plane strain and obeys Tresca&rsquos yield criterion and the flow rule associated with it. By the temperature cycle it is meant that the surface temperature of the shaft is increased to a limiting value, it is held at this temperature for a while, and then slowly decreased at the same rate to the reference temperature. The isothermal shaft is rotated up to around elastic limit rotation speed and then the temperature cycle is applied to the surface of the shaft. Even in an initially purely elastic shaft, two plastic regions with different forms of the yield condition emerge simultaneously at the centre and expand into the elastic region. However, the expansion of the plastic zone ceases soon thereafter, and an unloaded region spreads into the plastic core. It is shown that the stress distribution is altered significantly by the temperature cycle, hence also leading to non-zero residual stresses at stand-still.
35
Vemuri, Achyut. "Estimation of Instantaneous Speed for Rotating Systems: New Processing Techniques." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1470671420.
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36
Imayama, Shintaro. "Studies of the rotating-disk boundary-layer flow." Doctoral thesis, KTH, Strömningsfysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-158973.
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The rotating-disk boundary layer is not only a simpler model for the study of cross-flow instability than swept-wing boundary layers but also a useful simplification of many industrial-flow applications where rotating configurations are present. For the rotating disk, it has been suggested that a local absolute instability, leading to a global instability, is responsible for the small variation in the observed laminar-turbulent transition Reynolds number however the exact nature of the transition is still not fully understood. This thesis aims to clarify certain aspects of the transition process. Furthermore, the thesis considers the turbulent rotating-disk boundary layer, as an example of a class of three-dimensional turbulent boundary-layer flows. The rotating-disk boundary layer has been investigated in an experimental apparatus designed for low vibration levels and with a polished glass disk that gave a smooth surface. The apparatus provided a low-disturbance environment and velocity measurements of the azimuthal component were made with a single hot-wire probe. A new way to present data in the form of a probability density function (PDF) map of the azimuthal fluctuation velocity, which gives clear insights into the laminar-turbulent transition region, has been proposed. Measurements performed with various disk-edge conditions and edge Reynolds numbers showed that neither of these conditions a↵ect the transition process significantly, and the Reynolds number for the onset of transition was observed to be highly reproducible. Laminar-turbulent transition for a ‘clean’ disk was compared with that for a disk with roughness elements located upstream of the critical Reynolds number for absolute instability. This showed that, even with minute surface roughness elements, strong convectively unstable stationary disturbances were excited. In this case, breakdown of the flow occurred before reaching the absolutely unstable region, i.e. through a convectively unstable route. For the rough disk, the breakdown location was shown to depend on the amplitude of individual stationary vortices. In contrast, for the smooth (clean-disk) condition, the amplitude of the stationary vortices did not fix the breakdown location, which instead was fixed by a well-defined Reynolds number. Furthermore, for the clean-disk case, travelling disturbances have been observed at the onset of nonlinearity, and the associated disturbance profile is in good agreement with the eigenfunction of the critical absolute instability. Finally, the turbulent boundary layer on the rotating disk has been investigated. The azimuthal friction velocity was directly measured from the azimuthal velocity profile in the viscous sublayer and the velocity statistics, normalized by the inner scale, are presented. The characteristics of this three-dimensional turbulent boundary-layer flow have been compared with those for the two-dimensional flow over a flat plate and close to the wall they are found to be quite similar but with rather large differences in the outer region.QC 20150119
37
Bocchi, Edoardo. "Compressible-incompressible transitions in fluid mechanics : waves-structures interaction and rotating fluids." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0279/document.
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Ce manuscrit porte sur les transitions compressible-incompressible dans les équations aux dérivées partielles de la mécanique des fluides. On s'intéresse à deux problèmes : les structures flottantes et les fluides en rotation. Dans le premier problème, l'introduction d'un objet flottant dans les vagues induit une contrainte sur le fluide et les équations gouvernant le mouvement acquièrent une structure compressible-incompressible. Dans le deuxième problème, le mouvement de fluides géophysiques compressibles est influencé par la rotation de la Terre. L'étude de la limite à rotation rapide montre que le champ vectoriel de vitesse tend vers une configuration horizontale et incompressible.Les structures flottantes constituent un exemple particulier d'interaction fluide-structure, où un solide partiellement immergé flotte à la surface du fluide. Ce problème mathématique modélise le mouvement de convertisseurs d'énergie marine. En particulier, on s'intéresse aux bouées pilonnantes, installées proche de la côte où les modèles asymptotiques en eaux peu profondes sont valables. On étudie les équations de Saint-Venant axisymétriques en dimension deux avec un objet flottant à murs verticaux se déplaçant seulement verticalement. Les hypothèses sur le solide permettent de supprimer le problème à bord libre associé avec la ligne de contact entre l'air, le fluide et le solide. Les équations pour le fluide dans le domaine extérieur au solide sont donc écrites comme un problème au bord quasi-linéaire hyperbolique. Celui-ci est couplé avec une EDO non-linéaire du second ordre qui est dérivée de l'équation de Newton pour le mouvement libre du solide. On montre le caractère bien posé localement en temps du système couplé lorsque que les données initiales satisfont des conditions de compatibilité afin de générer des solutions régulières.Ensuite on considère une configuration particulière: le retour à l'équilibre. Il s'agit de considérer un solide partiellement immergé dans un fluide initialement au repos et de le laisser retourner à sa position d'équilibre. Pour cela, on utilise un modèle hydrodynamique différent, où les équations sont linearisées dans le domaine extérieur, tandis que les effets non-linéaires sont considérés en dessous du solide. Le mouvement du solide est décrit par une équation intégro-différentielle non-linéaire du second ordre qui justifie rigoureusement l'équation de Cummins, utilisée par les ingénieurs pour les mouvements des objets flottants. L'équation que l'on dérive améliore l'approche linéaire de Cummins en tenant compte des effets non-linéaires. On montre l'existence et l'unicité globale de la solution pour des données petites en utilisant la conservation de l'énergie du système fluide-structure.Dans la deuxième partie du manuscrit, on étudie les fluides en rotation rapide. Ce problème mathématique modélise le mouvement des flots géophysiques à grandes échelles influencés par la rotation de la Terre. Le mouvement est aussi affecté par la gravité, ce qui donne lieu à une stratification de la densité dans les fluides compressibles. La rotation génère de l'anisotropie dans les flots visqueux et la viscosité turbulente verticale tend vers zéro dans la limite à rotation rapide. Notre interêt porte sur ce problème de limite singulière en tenant compte des effets gravitationnels et compressibles. On étudie les équations de Navier-Stokes-Coriolis anisotropes compressibles avec force gravitationnelle dans la bande infinie horizontale avec une condition au bord de non glissement. Celle-ci et la force de Coriolis donnent lieu à l'apparition des couches d'Ekman proche du bord. Dans ce travail on considère des données initiales bien préparées. On montre un résultat de stabilité des solutions faibles globales pour des lois de pression particulières. La dynamique limite est décrite par une équation quasi-géostrophique visqueuse en dimension deux avec un terme d'amortissement qui tient compte des couches limitesThis manuscript deals with compressible-incompressible transitions arising in partial differential equations of fluid mechanics. We investigate two problems: floating structures and rotating fluids. In the first problem, the introduction of a floating object into water waves enforces a constraint on the fluid and the governing equations turn out to have a compressible-incompressible structure. In the second problem, the motion of geophysical compressible fluids is affected by the Earth's rotation and the study of the high rotation limit shows that the velocity vector field tends to be horizontal and with an incompressibility constraint.Floating structures are a particular example of fluid-structure interaction, in which a partially immersed solid is floating at the fluid surface. This mathematical problem models the motion of wave energy converters in sea water. In particular, we focus on heaving buoys, usually implemented in the near-shore zone, where the shallow water asymptotic models describe accurately the motion of waves. We study the two-dimensional nonlinear shallow water equations in the axisymmetric configuration in the presence of a floating object with vertical side-walls moving only vertically. The assumptions on the solid permit to avoid the free boundary problem associated with the moving contact line between the air, the water and the solid. Hence, in the domain exterior to the solid the fluid equations can be written as an hyperbolic quasilinear initial boundary value problem. This couples with a nonlinear second order ODE derived from Newton's law for the free solid motion. Local in time well-posedness of the coupled system is shown provided some compatibility conditions are satisfied by the initial data in order to generate smooth solutions.Afterwards, we address a particular configuration of this fluid-structure interaction: the return to equilibrium. It consists in releasing a partially immersed solid body into a fluid initially at rest and letting it evolve towards its equilibrium position. A different hydrodynamical model is used. In the exterior domain the equations are linearized but the nonlinear effects are taken into account under the solid. The equation for the solid motion becomes a nonlinear second order integro-differential equation which rigorously justifies the Cummins equation, assumed by engineers to govern the motion of floating objects. Moreover, the equation derived improves the linear approach of Cummins by taking into account the nonlinear effects. The global existence and uniqueness of the solution is shown for small data using the conservation of the energy of the fluid-structure system.In the second part of the manuscript, highly rotating fluids are studied. This mathematical problem models the motion of geophysical flows at large scales affected by the Earth's rotation, such as massive oceanic and atmospheric currents. The motion is also influenced by the gravity, which causes a stratification of the density in compressible fluids. The rotation generates anisotropy in viscous flows and the vertical turbulent viscosity tends to zero in the high rotation limit. Our interest lies in this singular limit problem taking into account gravitational and compressible effects. We study the compressible anisotropic Navier-Stokes-Coriolis equations with gravitational force in the horizontal infinite slab with no-slip boundary condition. Both this condition and the Coriolis force cause the apparition of Ekman layers near the boundary. They are taken into account in the analysis by adding corrector terms which decay in the interior of the domain. In this work well-prepared initial data are considered. A stability result of global weak solutions is shown for power-type pressure laws. The limit dynamics is described by a two-dimensional viscous quasi-geostrophic equation with a damping term that accounts for the boundary layers
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Di, Gennaro Sofia. "Quantum rotating black holes and extra dimensions." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/19851/.
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We employ the formalism of the Horizon Quantum Mechanics to describe the gravitational radius of compact sources by means of an operator and derive a Horizon Wave Function which will allow us to estimate the probability of formation of black holes in scattering processes. If the Planck scale is kept at its standard value, however, it will be impossible to test that regime with any foreseeable technology. We then review how the introduction of extra dimensions can potentially lower the Planck scale down to the TeV range in an attempt to solve the hierarchy problem. In this context, we proceed by studying black holes described by a generalisation of the Kerr metric for higher dimensional spacetime known as the Myers-Perry metric. Our computation of the probability that a rotating source in higher dimensions is a black hole suggests that, even if the fundamental Planck scale is as low as a few TeV's, we should not be able to detect any black hole in colliders as is indeed the case.
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Shafie, H. Khalil. "The geometry of Gaussian rotation space random fields /." Thesis, McGill University, 1998. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=35614.
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In recent years, very detailed images of the brain, produced by modern sensor technologies, have given the neuroscientist the opportunity to study the functional activation of the brain under different conditions. The main statistical problem is to locate the isolated regions of the brain where activation has occurred (the signal), and separate them from the rest of the brain where no activation can be detected (the noise). To do this the images are often spatially smoothed before analysis by convolution with a filter f (t) to enhance the signal to noise ratio, where t is a location vector in N dimensional space. The motivation for this comes from the Matched Filter Theorem of signal processing, which states that signal added to white noise is best detected by smoothing with a filter whose shape matches that of the signal. The problem is that the scale of the signal is usually unknown. It is natural to consider searching over filter scale as well as location, that is, to use a filter s-N/2ft/s with scale s varying over a predetermined interval [ s1,s2 ]. This adds an extra dimension to the search space, called scale space (see Poline and Mazoyer, 1994). Siegmund and Worsley (1995) establish the relation between searching over scale space with the problem of testing for a signal with unknown location and scale and find the approximate P-value of the maximum of the scale-space filtered image using the expected Euler characteristic of the excursion set. In this thesis we study the extension of the scale space result to rotating filters of the form | S|--1/4f (S --1/2t), where S is now an N x N positive definite symmetric matrix that rotates and scales the axes of the filter.
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Dalwadi, Mohit. "Flow and nutrient transport problems in rotating bioreactor systems." Thesis, University of Oxford, 2014. https://ora.ox.ac.uk/objects/uuid:1d7298b7-cdf5-4240-a79c-b7b69f662c1a.
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Motivated by applications in tissue engineering, this thesis is concerned with the flow through and around a free-moving porous tissue construct (TC) within a high-aspect-ratio vessel (HARV) bioreactor. We formalise and extend various results for flow within a Hele-Shaw cell containing a porous obstacle. We also consider the impact of the flow on related nutrient transport problems. The HARV bioreactor is a cylinder with circular cross-section which rotates about its axis at a constant rate, and is filled with a nutrient-rich culture medium. The porous TC is modelled as a rigid porous cylinder with circular cross-section and is fully saturated with the fluid. We formulate the flow problem for a porous TC (governed by Darcy's equations) within a HARV bioreactor (governed by the Navier-Stokes equations). We couple the two regions via appropriate interfacial conditions which are derived by consideration of the intricate boundary-layer structure close to the TC surface. By exploiting various small parameters, we simplify the system of equations by performing an asymptotic analysis, and investigate the resulting system for the flow due to a prescribed TC motion. The motion of the TC is determined by analysis of the force and torque acting upon it, and the resulting equations of motion (which are coupled to the flow) are investigated. The short-time TC behaviour is periodic, but we are able to study the long-time drift from this periodic solution by considering the effect of inertia using a multiple-scale analysis. We find that, contrary to received wisdom, inertia affects TC drift on a similar timescale to tissue growth. Finally, we consider the advection of nutrient through the bioreactor and TC, and investigate the problem of nutrient advection-diffusion for a simplified model involving nutrient uptake.
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Vukasinovic, Jelena. "Flow in the gap between a rotating screw and a co-axial stationary outer cylinder." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/17304.
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Ahlberg, Charlotte. "An experimental study of fiber suspensions between counter-rotating discs." Licentiate thesis, Stockholm : Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11644.
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Gamez, Victor Manuel. "Mechanics of batch slurry mixing by means of rotating impellers in a cylindrical vessel." FIU Digital Commons, 1998. http://digitalcommons.fiu.edu/etd/3446.
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Two slurries with solids concentration of 5 % (wt) and 20 % (w.), with approximate chemical and physical properties of melter feeds found in the Defense Waste Processing Facility of the Savannah River Site were prepared, characterized and mixed in a cylindrical vessel with impellers of different diameters pumping the flow in two different axial directions. The electrical power consumed by each impeller was measured and compared for both slurries. A sampling mechanism consisting of tubes positioned parallel to the vertical axis of the tank was also implemented to ascertain the level of homogeneity developed in the mix. The effects of the diameter of the sampling tubes and the sampling speed were evaluated for different impeller rotational speeds acting on the two slurries. Different startup techniques from a fully-settled condition were also assessed. Results indicate significantly lower power consumption when the impeller pumps the fluid downwards, more representative samples when the sampling tube diameter and sampling velocity are increased, and the lowest consumption of power at the startup from fully-settled conditions by the injection of air in the bed of solids.
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Colley, Andrew John. "An experimental investigation of the flow in the boundary layer above a rotating disc, with compliant characteristics, in water." Thesis, University of Warwick, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268297.
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Imayama, Shintaro. "Experimental study of the rotating-disk boundary-layer flow." Licentiate thesis, KTH, Mekanik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-95147.
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Rotating-disk flow has been investigated not only as a simple model of cross flow instability to compare with swept-wing flow but also for industrial flow applications with rotating configurations. However the exact nature of laminar-turbulent transi- tion on the rotating-disk flow is still major problem and further research is required for it to be fully understood, in particular, the laminar-turbulent transition process with absolute instability. In addition the studies of the rotating-disk turbulent boundary- layer flow are inadequate to understand the physics of three-dimensional turbulent boundary-layer flow. In present thesis, a rotating-rotating disk boundary-layer flow has been inves- tigated experimentally using hot-wire anemometry. A glass disk with a flat surface has been prepared to archieve low disturbance rotating-disk environment. Azimuthal velocity measurements using a hot-wire probe have been taken for various conditions. To get a better insight into the laminar-turbulent transition region, a new way to describe the process is proposed using the probability density function (PDF) map of azimuthal fluctuation velocity. The effect of the edge of the disk on the laminar-turbulent transition process has been investigated. The disturbance growth of azimuthal fluctuation velocity as a function of Reynolds number has a similar trend irrespective of the various edge conditions. The behaviour of secondary instability and turbulent breakdown has been in- vestigated. It has been found that the kinked azimuthal velocity associated with secondary instability just before turbulent breakdown became less apparent at a cer- tain wall normal heights. Furthermore the turbulent breakdown of the stationary mode seems not to be triggered by its amplitude, however, depend on the appearance of the travelling secondary instability. Finally, the turbulent boundary layer on a rotating disk has been investigated. An azimuthal friction velocity has been directly measured from the azimuthal velocity profile in the viscous sub-layer. The turbulent statistics normalized by the inner and outer sclaes are presented.QC 20120529
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Bilson, Matthew James. "Momentum and scalar transport in the straight pipe and rotating cylinder : a comparison of transport mechanisms /." St. Lucia, Qld, 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17836.pdf.
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Shibuya, Satoru. "Undrained behaviour of granular materials under principal stress rotation." Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/7979.
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Lubbers, Jonathan Louis. "PERCH LANDING MANEUVERS AND CONTROL FOR A ROTATING-WING MAV." UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_theses/152.
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This thesis addresses flight control of the perch landing maneuver for micro-aerial vehicles. A longitudinal flight model is constructed for a pigeon-sized aircraft. In addition to a standard elevator control surface, wing-rotation also considered as a non-standard actuator for increasing low-speed aerodynamic braking. Optimal state and control trajectories for the perch landing maneuver are computed using commercial software. A neighboring optimal control law is then developed and implemented in a set of flight simulations. Simulations are run with both a quasisteady and an unsteady aerodynamic model. The effectiveness of wing rotation and of the neighboring optimal control law is discussed, as is the importance of unsteady aerodynamics during the maneuver. Wing rotation was found to be minimally effective in this case, but it showed potential to be more effective in further research. The unsteady aerodynamic model has significant influence over the success or failure of the maneuver.
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Lundberg, Karl. "Development of a CFD Model for a Rotating Bed Reactor in Large Volumes." Thesis, Umeå universitet, Institutionen för fysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-136101.
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Den roterande bäddreaktornSpinChem® RBR S2 kan fyllas med solida partiklar och sänkas ned och roteras ien vätska. Detta gör att kemiska reaktioner mellan vätskan och partiklarna iRBR:en kan äga rum.Flödet från en RBR S2 i en 76 dm3 stor vattentank undersöktes med hjälp avsimuleringar i ANSYS Fluent 18.0. Den tid som krävdes för ett färgämne attsprida sig jämnt i vattentanken på grund av flödet från RBR:en mättes i ettexperiment och jämfördes med motsvarande simuleringar. Mixningstiderna frånexperimentet visade att det krävdes i genomsnitt 161 s för färgämnet att blijämnt fördelat, medan simuleringarna överskattade denna tid med ungefär 89 %.En simuleringsmodell för att avgöra hur mycket av en vätska som varit i kontaktmed partiklarna i RBR:en efter en given tid togs fram och testades.Simuleringarna visade att ungefär 8660 s krävdes för att 95 % av vätskan ivattentanken skulle ha varit i kontakt med partiklarna. Denna tid verifieradesdock inte med experiment.The rotating bed reactorSpinChem® RBR S2 can be filled with solid particles and submerged into a liquidwhere it is rotated, which allows for chemical reactions to occur between theliquid and the particles.The flow in a 76 dm3 large tank of water due to the rotating RBR S2 wasinvestigated using simulations performed in ANSYS Fluent 18.0. The timerequired for a colouring agent to become uniformly mixed in the tank due to theflow from the device was measured in a practical experiment and was compared tosimulations. The mixing times obtained in the practical experiment were onaverage approximately 161 s, whereas the times obtained in the simulationoverpredicted this with approximately 89 %.A simulation model for determining how much of a liquid has been in contactwith the particles in the RBR after a given amount of time was suggested andtested. The simulation results showed that approximately 8660 s was requriedfor 95 % of the liquid to be in contact with the porous bed, although this timewas not verified experimentally.
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Soltani, Fariborz. "Kinematic Synthesis Of Spatial Mechanisms Using Algebra Of Exponential Rotation Matrices." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12605867/index.pdf.
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The major part of this thesis has been devoted to path and motion generation synthesis of spatial mechanisms. For the first time kinematic synthesis methods have been developed based on the algebra of exponential rotation matrices. Besides modeling spatial pairs such as spheric, cylindric and Hook's joints by combinations of revolute and prismatic joints and applying Denavit-Hartenberg'
s convention, general loop closure equations have been presented for path and motion generation synthesis of any spatial mechanism with lower kinematic pairs. In comparison to the existing synthesis methods the main advantage of the methods presented in this thesis is that, general loop closure equations have been presented for any kind of spatial mechanism with lower kinematic pairs. Besides these methods enable the designer to benefit the advantages of the algebra of exponential rotation matrices. In order to verify the applicability of the synthesis methods presented in this thesis, the general loop closure equations of RSHR, RCCR and RSSR-SC mechanisms have been determined and then using these equations six numerical examples have been solved. Some tables have been presented based on the determined loop closure equations which reveal useful information about the number of precision points or positions that can be considered for the kinematic synthesis of the above mentioned mechanisms and the number of free parameters. In numerical examples, the mechanisms have been synthesized based on the general loop closure equations and the synthesis algorithms presented in the thesis. Although in some cases semi-analytical solutions have been obtained, in most of the cases, the loop closure equations were solved by computer programs written by Mathcad. The input angle-output angle diagrams drawn at the end of each numerical example illustrate the motion continuity of the mechanisms and that branching has been avoided. Detailed information has been given about the computer programs and the difficulties which may arise while synthesizing spatial mechanisms. In addition to the above mentioned points, a mobility analysis has been done for the RCCR mechanism and some inequalities have been obtained in terms of the link lengths. The swing angle diagram of the RCCR linkage has been drawn too.