Dissertations / Theses on the topic 'Shear transfet'
To see the other types of publications on this topic, follow the link: Shear transfet.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Shear transfet.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Valle, Mariano Oñar. "Shear transfer in fiber reinforced concrete." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/72749.
Full text
2
Wallenfelsz, Joseph A. "Horizontal Shear Transfer for Full-Depth Precast Concrete Bridge Deck Panels." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/31943.
Full textAbstract:
Full-depth precast deck panels are a promising alternative to the conventional cast-in-place concrete deck. They afford reduced construction time and fewer burdens on the motoring public. In order to provide designers guidance on the design of full-depth precast slab systems with their full composite strength, the horizontal shear resistance provided at the slab-to-beam interface must be quantified through further investigation. Currently, all design equations, both in the AASHTO Specifications and the ACI code, are based upon research for cast-in-place slabs. The introduction of a grouted interface between the slab and beam can result in different shear resistances than those predicted by current equations.
A total of 29 push off tests were performed to quantify peak and post-peak shear stresses at the failure interface. The different series of tests investigated the surface treatment of the bottom of the slab, the type and amount of shear connector and a viable alternative pocket detail.
Based on the research performed changes to the principles of the shear friction theory as presented in the AASHTO LRFD specifications are proposed. The proposal is to break the current equation into two equation that separate coulomb friction and cohesion. Along with these changes, values for the coefficient of friction and cohesion for the precast deck panel system are proposed.Master of Science
3
Pai, Sai Ganesh Sarvotham. "Force transfer around openings in CLT shear walls." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/51632.
Full textAbstract:
During an earthquake, shear walls can experience damage around corners of doors and windows due to development of stress concentration. Reinforcements provided to minimize this damage are designed for forces that develop at these corners known as transfer forces. In this thesis, the focus is on understanding the forces that develop around opening corners in cross laminated timber (CLT) shear walls and reinforcement requirements for the same.
In the literature, four different analytical models are commonly considered to determine the transfer force for design of wood-frame shear walls. These models have been reviewed in this thesis. The Diekmann model is found to be the most suitable analytical model to determine the transfer force around a window-type opening.
Numerical models are developed in ANSYS to analyse the forces around opening corners in CLT shear walls. CLT shear walls with cut-out openings are analysed using a three-dimensional brick element model and a frame model. These models highlight the increase in shear and torsion around opening corners due to stress concentration. The coupled-panel construction practice for CLT shear walls with openings is analysed using a continuum model calibrated to experimental data. The analysis shows the increase in strength and stiffness of walls, when tie-rods are used as reinforcement. Analysis results also indicate that the tie-rods should be designed to behave linearly for optimum performance of the wall.
Finally, a linear regression model is developed to determine the stiffness of a simply-supported CLT shear wall with a window-type opening. This model provides insight into the effect of various geometrical and material parameters on the stiffness of the wall. The process of model development has been explained, which can be improved further to include the behaviour of anchors.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
4
Younes, Imad Sabeh. "Transfer matrix analysis of frame-shear wall systems." Thesis, University of Southampton, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280922.
Full text
5
Rong, Wang. "Instability of shear fluids with mass transfers." Doctoral thesis, Universite Libre de Bruxelles, 1991. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/213013.
Full text
6
Karabulut, Halit. "Condensation heat transfer in the presence of vapour shear." Thesis, Heriot-Watt University, 1991. http://hdl.handle.net/10399/819.
Full text
7
Habouh, Mohamed I. "SHEAR TRANSFER STRENGTH OF CONCRETE PLACED AGAINST HARDENED CONCRETE." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1439564977.
Full text
8
Kamaraldin, Khaled. "Punching shear and moment transfer in reinforced concrete flat slabs." Thesis, University of Westminster, 1990. https://westminsterresearch.westminster.ac.uk/item/94vwq/punching-shear-and-moment-transfer-in-reinforced-concrete-flat-slabs.
Full text
9
Sadrizadeh, Sasan. "Instabilities in Pulsating Pipe Flow of Shear-Thinning and Shear-Thickening Fluids." Thesis, Linköpings universitet, Mekanisk värmeteori och strömningslära, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-82037.
Full textAbstract:
In this study, we have considered the modal and non-modal stability of fluids with shear-dependent viscosity flowing in a rigid straight pipe. A second order finite-difference code is used for the simulation of pipe flow in the cylindrical coordinate system. The Carreau-Yasuda model where the rheological parameters vary in the range of 0.3 < n < 1.5 and 0.1 < λ < 100 is represents the viscosity of shear- thinning and shear thickening fluids. Variation of the periodic pulsatile forcing is obtained via the ratio Kω/Kο and set between 0.2 and 20. Zero and non-zero streamwise wavenumber have been considered separately in this study. For the axially invariant mode, energy growth maxima occur for unity azimuthal wave number, whereas for the axially non-invariant mode, maximum energy growth can be observed for azimuthal wave number of two for both Newtonian and non-Newtonian fluids. Modal and non-modal analysis for both Newtonian and non-Newtonian fluids show that the flow is asymptotically stable for any configuration and the pulsatile flow is slightly more stable than steady flow. Increasing the maximum velocity for shear-thinning fluids caused by reducing power-low index n is more evident than shear-thickening fluids. Moreover, rheological parameters of Carreau-Yasuda model have ignored the effect on the peak velocity of the oscillatory components. Increasing Reynolds number will enhance the maximum energy growth while a revers behavior is observed by increasing Womersley number.
10
Banta, Timothy E. "Horizontal Shear Transfer Between Ultra High Performance Concrete And Lightweight Concrete." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/31446.
Full textAbstract:
Ultra high performance concrete, specifically Ductal® concrete, has begun to revolutionize the bridge design industry. This extremely high strength material has given smaller composite sections the ability to carry larger loads. As the forces being transferred through composite members are increasing in magnitude, it is vital that the equations being used for design are applicable for use with the new materials. Of particular importance is the design of the horizontal shear reinforcement connecting the bridge deck to the top flange of the beams. Without adequate shear transfer, the flexural and shearing capacities will be greatly diminished. The current design equations from ACI and AASHTO were not developed for use in designing sections composed of Ductal® and Lightweight concrete.
Twenty-four push-off tests were performed to determine if the current horizontal shear design equations could accurately predict the horizontal shear strength of composite Ductal® and Lightweight concrete sections. Effects from various surface treatments, reinforcement ratios, and aspect ratios, were determined. The results predicted by the current design equations were compared to the actual results found during testing. The current design equations were all found to be conservative. For its ability to incorporate various cohesion and friction factors, it is recommended that the equation from AASHTO LRFD Specification (2004) be used for design.Master of Science
11
Sridharan, Harini. "COUPLED DYNAMICS OF HEAT TRANSFER AND FLUID FLOW IN SHEAR RHEOMETRY." University of Akron / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron1597346164780318.
Full text
12
Bensalem, Kamel. "The structural integrity of precast concrete floor systems used as horizontal diaphragms." Thesis, University of Nottingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391132.
Full text
13
Baumard, Théo. "Modelling the influence of infrared preheating and temperature uniformity in forming of powder-impregnated thermoplastic composites Experimental characterization and modeling of the temperature and rate-dependent shear behaviour of powder-impregnated glass fiber/PA66 woven semipregs." Thesis, Ecole nationale des Mines d'Albi-Carmaux, 2019. http://www.theses.fr/2019EMAC0010.
Full textAbstract:
Le thermoformage non-isotherme de composites thermoplastiques, qui consiste à chauffer une préforme consolidée à une température supérieure à la fusion de la matrice avant de la transférer dans une presse d’estampage, est un procédé bien adapté à la production grande série de pièces structurelles pour l’industrie automobile (avec des temps de cycle < 1 min). L’utilisation d’outils numériques pour prédire l’apparition de défauts en fonction des paramètres procédés utilisés est d’un grand intérêt pour éviter l’emploi de procédures d’optimisation expérimentales couteuses de type essais/erreur. Ces travaux de thèse ont porté sur le développement d’une simulation de la mise en forme de composites poudrés PA66/verre, incluant la modélisation explicite de l’étape de préchauffage infrarouge, afin d’étudier l’effet de l’homogénéité du champ de température sur la présence de défauts de forme. Les propriétés thermophysiques et optiques du matériau ont été caractérisées expérimentalement à deux niveaux de consolidation. La structure du matériau non consolidé conduit à un chauffage moins uniforme, comparé à une préforme préconsolidée. Un modèle éléments finis, basé sur la méthode des radiosités pour la prise en compte des transferts radiatifs a été utilisé pour simuler l’étape de préchauffage ; la démarche a été validée par comparaison avec des essais menés sur un pilote de four infrarouge. L’effet de l’affaissement de la préforme sur la distribution de température a été évalué numériquement, et une procédure d’optimisation pour déterminer les paramètres du four en fonction d’un champ de température requis a été présentée. Le comportement mécanique du composite tissé a été modélisé à l’échelle macroscopique par une loi hypoélastique, implémentée dans Abaqus/Explicit. Les paramètres du modèle ont été déterminés à l’aide d’essais en traction et cisaillement en fonction de la température et de la vitesse de sollicitation. Des simulations non-isothermes de la mise en forme de pièces hémisphériques ont été réalisées, et montrent un bon accord avec les données expérimentales obtenues à l’aide d’un pilote de formage à l’échelle laboratoireNon-isothermal thermoforming of thermoplastic composites, in which a preconsolidated blank is heated above the melting temperature of the matrix before being formed in a press, is a process well adapted to the high production rates of automotive structural parts, allowing for cycle times < 1 min. Numerical tools to predict the apparition of manufacturing-induced defects based on the process parameters used are of an obvious industrial interest to avoid relying on a cost and time intensive trial-and-error approach. This thesis focused on the development of a comprehensive simulation of the forming of powder-impregnated PA66/glass composites, modelling explicitly the infrared preheating step to investigate the effect of temperature homogeneity on shape defects. The thermophysical and optical properties of the material were characterized experimentally at two levels of consolidation, and as a function of temperature when relevant. The structure of the non-consolidated material leads to a less uniform heating, compared to preconsolidated blanks. A finite element model based on the radiosity method to compute the radiative heat transfer was used to simulate the preheating step; this approach was validated against experimental results from a custom-built infrared oven. The model has been used to investigate the effect of blank sag on temperature distribution, and an optimization method to determine the oven parameters based on a desired temperature field has been presented. The mechanical behaviour of the woven composite during forming was modelled with a hypoelastic continuum approach, implemented in Abaqus/Explicit. The model parameters were determined from experimental tensile tests and in-plane shear tests at various temperatures and shear rates. Non-isothermal simulations of the forming of hemispherical parts were conducted, using the temperature field predicted from the preheating simulation as an input, and showed good agreement with that observed on parts formed on a lab-scale thermoforming setup
14
Fong, Dickson Wen Jing. "Punching shear in waffle slabs in the presence of biaxial moment transfer." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/51640/.
Full textAbstract:
An extensive amount of works have been carried out to develop the current understanding in punching shear mechanism noted in reinforced concrete slabs. However, despite the increasing popularity of waffle slabs, the current understanding about punching behaviour is mainly focused on solid flat slabs, and only limited amount of works have been carried out on waffle slabs and in the presence of biaxial moment. Thus, there is a need to carry out a research in this area to aid the understanding about punching mechanism of waffle slabs in the presence of biaxial moment for the internal column and edge column connections. The experimental work carried out in this research included destructive testing of thirty-eight 1/10th scale model waffle slab specimens, which consists of fifteen internal column slabs and twenty-three edge column slabs. The main variables were, for the internal column slab, the principle angles of biaxial moment transfer, the column eccentricity, the column orientation and the size of solid sections, and for the edge column slab, the principle angles of biaxial moment transfer, the column eccentricity, the column location and the size of solid sections. From the experimental investigations, three distinct failure mechanisms were observed: the concentric punching at internal column mechanism; the eccentric punching at internal column mechanism; and the edge punching mechanism. In general, the observed punching shear failure mechanisms of waffle slabs were found identical to solid flat slabs; but the punching shear capacities reduced due to some losses in potential failure surface within the waffle section. The principle angle of biaxial moment transfer was found varying the shear surface area that was being mobilized, thus affecting the punching capacity of the slabs. An analytical study was carried out, using an upper-bound plastic model, to simulate the observed punching shear mechanisms, and hence, to predict the punching capacity of the slabs. A theoretical model was developed for each of the identified failure mechanism. In addition, three design models based on the current UK code, Eurocode 2, have been developed. In all cases, these models have achieved good agreements with the test results.
15
Heard, William Franklin. "Diagonal and horizontal stiffeners for shear transfer in rigid frame square knees." Master's thesis, Mississippi State : Mississippi State University, 2006. http://library.msstate.edu/etd/show.asp?etd=etd-11092006-214442.
Full text
16
Guidorzi, Michael. "Study of the mechanisms of shear transfer in fiber-reinforced concrete elements." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amslaurea.unibo.it/5922/.
Full text
17
Aoune, Azzeddine. "Experimental and theoretical studies of condensation on a horizontal tube row with vapour shear." Thesis, Heriot-Watt University, 1991. http://hdl.handle.net/10399/811.
Full text
18
Echegaray, Oviedo Javier Andrés. "Upgrading the push-off test to analyze the contribution of steel fiber on shear transfer mechanisms." Doctoral thesis, Universitat Politècnica de València, 2014. http://hdl.handle.net/10251/43723.
Full textAbstract:
The shear behavior of a specimen made of reinforced concrete is complex. The resisting mechanisms are affected by different factors such as section form, slimness of the specimen, longitudinal and transversal reinforcement arrangement, adhesion between concrete and steel, among others. Addition of steel fibers to the concrete improves the ductility as well as the tensile behavior; providing good control during the cracking process. Fibers also enhance the shear behavior of structural elements, increasing ultimate resistance and ductility.
Push-off tests had been used to study the mechanisms of concrete shear transfer. Shear strength of the specimen depends on the contribution of both concrete and reinforcement. Aggregate interlock has a significant contribution to the concrete shear capacity. In the last decades new kinds of concrete have been developed for industrial use, such as high strength concrete (HSC), self-compacting concrete (SCC) or fiber reinforced concrete (FRC), among others. In these new materials aggregate interlock phenomenon may be different when compared to conventional concrete (CC). There is a lack of information in literature about the mechanisms of shear transfer in fiber reinforced concrete elements.Echegaray Oviedo, JA. (2014). Upgrading the push-off test to analyze the contribution of steel fiber on shear transfer mechanisms [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/43723
TESIS
19
Davids, William G. "Modeling of rigid pavements : joint shear transfer mechanisms and finite element solution strategies /." Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/10157.
Full text
20
Huo, Bingyu. "Experimental and analytical study of the shear transfer in composite shallow cellular floor beams." Thesis, City University London, 2012. http://openaccess.city.ac.uk/1965/.
Full textAbstract:
This research investigated the longitudinal shear transfer mechanism in composite shallow cellular floor beams. The shear transfer mechanism is different with the headed shear studs used in composite construction. The shear resisting properties and behaviour of the shear transfer mechanism has not been studied previously. Experimental and analytical studies were carried out with the aims of improving and optimizing the design details, and advancing the method of shear connection in shallow floor beam construction. The composite shallow cellular floor beam investigated in this research is a new type of beam fabricated by welding two highly asymmetric cellular tees along the web. The shear connections of this type of composite beam are formed by the web openings, which transfer longitudinal shear force. Four types of these shear connections were studied: concrete-infill-only, tie-bar, ducting and web-welded-stud shear connections. In total, 24 push-out tests were performed in two test series to investigate the load-slip behaviour and shear resistance of the shear connections under direct shear force. The failure mechanisms of the two forms of shear connections were extensively studied, which lead to the development of a design method for the composite action. The concrete infill element passing through the web opening is subject to a complex three-dimensional stress state, and it is difficult to analyse it using the mathematical model rather than empirical formula. Finite Element Analysis of the concrete-infill-only shear connection was performed with a parametric study to further verify the design method that has been developed. Two flexural tests were carried out on a full-scale composite shallow cellular floor beam with a solid slab. The shear connections investigated in the flexural tests were: concrete-infill-only and tie-bar shear connections passed through the web. The behaviour and performance of the shear connections in the flexural tests were compared with those in the push-out tests. The degree of shear connection of the two flexural tests was determined in the back analysis using plastic theory with measured material properties. Based on the findings of the push-out tests and flexural tests, two design methods of deflection check and moment resistance were developed for composite shallow cellular floor beams at the serviceability limit state and the ultimate limit state respectively. The deflection check design method is based on the uncracked section properties of the composite beam. The moment resistance design method developed in this thesis is compatible with the design methods of BS5950 and Eurocode 4 (EC4).
21
Wang, Xiaohua. "Characterization of Mesoscopic Fluid-like Films with the Novel Shear-force/Acoustic Microscopy." PDXScholar, 2010. https://pdxscholar.library.pdx.edu/open_access_etds/736.
Full textAbstract:
The shear force mechanism has been utilized as a distance regulation method in scanning probe microscopes. However, the origin of shear force is still unclear. One of the most important reasons for the shear-force damping is due to the presence of a water contamination layer at the sample surface in ambient conditions. Understanding the behavior of such mesoscopic fluid-like films is of significance for studies of not only scanning probe microscopy but also other complex surface phenomena, such as nanotribology, lubrication, adhesion, wetting, and the microfluidity of biological membranes. This thesis investigates, in particular, the dynamics of mesoscopic fluids confined between two sliding solid boundaries. When fluids are constrained to nanometer-sized regions, their physical properties can greatly differ from those displayed by bulk liquids. To gain an insight into the fundamental characteristics of the confined fluid films, we exploit the versatile capabilities of the novel shear-force/acoustic near-field microscope (SANM), which is able to concurrently and independently monitor the effects of the fluid-mediated interactions acting on both the microscope's probe and the sample to be analyzed. Two signals are monitored simultaneously during each experimental cycle: the tuning fork signal, which is the oscillation amplitude of the probe and gives access to the shear force; and acoustic signal, which is detected by an acoustic sensor placed under the sample. Systematic experiments are carried out to investigate the effects of probe geometry, environmental humidity, and chemical properties of probe and sample surface (water affinity: hydrophobicity or hydrophilicity) on the probe-sample interactions, expressing the influence of the fluid-like contamination films.
22
Obst, Andreas W. "Nonlinear static and transient analysis of generally laminated beams." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-10102009-020113/.
Full text
23
Hoffie, Andreas Frank. "Convection Calibration of Schmidt-Boelter Heat Flux Gages in Shear and Stagnation Air Flow." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/31422.
Full textAbstract:
This work reports the convection calibration of Schmidt-Boelter heat flux gages in shear and stagnation air flow. The gages were provided by Sandia National Laboratories and included two one-inch diameter and two one-and-one-half-inch diameter Schmidt-Boelter heat flux gages. In order to calibrate the sensors a convection calibration facility has been designed, including a shear test stand, a stagnation test stand, an air heater and a data acquisition system. The current physical model for a combined radiation and convection heat transfer environment uses an additional thermal resistance around the heat flux gage. This model clearly predicts a non-linear dependency of the gage sensitivity over a range of heat transfer coefficients. A major scope of this work was to experimentally verify the relation found by the model assumptions. Since the actual heat sink temperature is not known and cannot be measured, three different cases have been examined resulting in three different sensitivities for one pressure value, which is the gage sensitivity for the not cooled case and the gage sensitivity for the cooled case, based on the plate temperature or on the cooling water temperature. All of the measured sensitivities for shear as well as for stagnation flow fit well in the theory and show the non-linear decay for increasing heat transfer coefficient values. However, the obtained data shows an offset in the intersection with the sensitivity at zero heat transfer coefficient. This offset might arise from different radiation calibration techniques and different surface coatings of test gage and reference standard.Master of Science
24
Ganji, Nagesh Lankaranu Hamid M. "Parametric study of load transfer in two-bolted single lap hybrid (bonded/bolted) shear joints." Diss., A link to full text of this thesis in SOAR, 2007. http://soar.wichita.edu/dspace/handle/10057/1133.
Full textAbstract:
Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering."May 2007." Title from PDF title page (viewed on Dec. 20, 2007). Thesis adviser: Hamid M. Lankarani. Includes bibliographic references (leaves 62-64).
25
Valdez, Soto Luis Fernando, and Soto Luis Fernando Valdez. "Finite Element Modeling of Tall Building Structures with Transfer Diaphragms Due to Offset Shear Walls." Thesis, The University of Arizona, 2017. http://hdl.handle.net/10150/625272.
Full textAbstract:
Diaphragms are elements of the seismic force resisting system in charge of stabilizing structures by tying in vertical elements, transferring inertial forces from one vertical element of the seismic force-resisting system to another and transferring shear forces from one vertical element to another. When vertical elements of the seismic force resisting system are offset horizontally conditions, the diaphragm that connects them must transfer large story shears in what is known as a transfer condition. Transfer conditions are often unavoidable and remain one of the least understood and most consequential aspects of building response in an earthquake. Poor performance of transfer structures in recent earthquakes further underscores the importance of determining the true behavior of transfer structures under seismic loading.
In order to begin to understand the behavior of transfer structures under seismic loading, finite element models were created for a 12 story building with offset shear walls. The models created represent one half of the building structure lumped into the two frames containing the shear walls in each half of the building. The first set of models (Phase 1) were developed starting from a nonlinear shear wall model. The model was incrementally made more complex, starting by adding a rigid, elastic transfer structure, and then elastic columns. Afterwards nonlinearity was added to the columns and finally typical floor diaphragms were added to the building. While results from these models showed similar curves for shear vs displacement and moment vs rotation for all models, issues with the fiber models used for the last model of this phase deemed the model too complex for the analyses required, particularly when modal analyses were performed on the structure.
The next set of models was developed from two two-dimensional models, one for each frame. Incrementally, the model was made more complex, starting by modeling the frames in three dimensions, with diaphragms being modeled as beams initially and then as shells. Seismic design loads were applied to this model in order to determine the shear and moment profiles of the building, as well as the shear transfer occurring at every story. Nonlinearity was added to the base of the building, yielding similar results to the elastic models with respect to the shear and moment profiles, but very different results for the shear vs displacement and moment vs rotation curves for the Phase 1 models.
26
Mirtalaie, Kamal. "Shear transfer between precast prestressed bridge beams and in-situ concrete crosshead in continuous structures." Thesis, University of Leeds, 1988. http://etheses.whiterose.ac.uk/310/.
Full textAbstract:
A detailed investigation was made to study the shear transfer between precast prestressed beams and in-situ concrete in a relatively new method of construction of continuous bridge decks where the ends of precast beams are connected to an integral in-situ crosshead away from the supports. Two series of tests were carried out. In the first series 1/3 scale models of the M. o. T, C&CA M-8 sections were used, and these were modified in the second series to study the effect of the beam's top flanges within the connection. One of the most important mechanisms of shear transfer proved to be the top flanges of the precast beam. For the precast beams with top flanges (first series), and with a 300mm beam embedment length, it was discovered that: a) The shear force is transferred from a small length at the end of the beam. b) The in-situ concrete nibs (concrete surrounding the web) can take this shear force without stirrups. c) There is no need either to project all the bars from the precast into the in-situ concrete or to prestress the connection transversely as a means of improving shear transfer. d) It was possible to transfer the whole shear force at the connection with a reduced embedment length of 100mm with nib stirrups. For the precast beam without top flanges, the transfer of the shear force at the connection required other improving details. In this respect transverse prestressing and web shear connectors were utilized effectively. The effect of projecting bars was also examined. In the general behaviour of composite continuous beams subjected to shear a detailed comparison was made between different Code predictions for the web cracking shear and web crushing strength. A mathematical model is also proposed to predict the stirrup stress according to shear span, effective depth and stirrup ratio when failure is controlled by web crushing. Stirrup stress measurement in the vicinity of continuous support made it possible to predict the enhanced shear strength and a design method is proposed for the continuous beams. A comparion is also made between different Code predictions in this respect. To obtain more information about the strength of web shear connectors used in the secod series, a separate dowel shear specimen was designed. Different interface conditions including bond, dowel bar size and strength and the effect of shrinkage were examined. A design method is proposed together with a comparison with different Code predictions.
27
Lyszczan, Peter [Verfasser], and Dietmar [Akademischer Betreuer] Göhlich. "Shear Load Transfer and Relaxation in Bolted Joints with Fractured Surfaces / Peter Lyszczan. Betreuer: Dietmar Göhlich." Berlin : Universitätsbibliothek der Technischen Universität Berlin, 2012. http://d-nb.info/1020274123/34.
Full text
28
Lynch, Stephen P. "Endwall Heat Transfer and Shear Stress for a Nozzle Guide Vane with Fillets and a Leakage Interface." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/31912.
Full textAbstract:
Increasing the combustion temperatures in a gas turbine engine to achieve higher efficiency and power output also results in high heat loads to turbine components downstream of the combustor. The challenge of adequately cooling the nozzle guide vane directly downstream of the combustor is compounded by a complex vortical secondary flow at the junction of the endwall and the airfoil. This flow tends to increase local heat transfer rates and sweep coolant away from component surfaces, as well as decrease the turbine aerodynamic efficiency. Past research has shown that a large fillet at the endwall-airfoil junction can reduce or eliminate the secondary flow. Also, leakage flow from the interface gap between the combustor and the turbine can provide some cooling to the endwall. This study examines the individual and combined effects of a large fillet and realistic combustor-turbine interface gap leakage flow for a nozzle guide vane. The first study focuses on the effect of leakage flow from the interface gap on the endwall upstream of the vane. The second study addresses the influence of large fillets at the endwall-airfoil junction, with and without upstream leakage flow. Both studies were performed in a large low-speed wind tunnel with the same vane geometry. Endwall shear stress measurements were obtained for various endwall-airfoil junction geometries without upstream leakage flow. Endwall heat transfer and cooling effectiveness were measured for various leakage flow rates and leakage gap widths, with a variety of endwall-airfoil junction geometries.
Results from these studies indicate that the secondary flow has a large influence on the coverage area of the leakage coolant. Increased leakage flow rates resulted in better cooling effectiveness and coverage, but also higher heat transfer rates. The two fillet geometries tested affected coolant coverage by displacing coolant around the base of the fillet, which could result in undesirably high gradients in endwall temperature. The addition of a large fillet to the endwall-airfoil junction, however, reduced heat transfer, even when upstream leakage flow was present.
Master of Science
29
Agarwal, Neeraj. "Transient Shear Flow Rheology of Concentrated Long Glass Fiber Suspensions in a Sliding Plate Rheometer." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/34784.
Full textAbstract:
Transient viscosity growth measurements at the startup of shear flow were performed on long glass fiber-filled polypropylene. Samples were prepared with fibers pre-oriented either in 1-direction, 3-direction or random in 1-3 plane, where the 1-direction is the direction of shear motion, the 2-direction is perpendicular to the shear plane and the 3-direction is the neutral direction. A sliding plate rheometer incorporating a shear stress transducer was constructed in the lab. It was shown that this device works well for the tested materials including a Newtonian oil, a low density polyethylene (LDPE) and short glass fiber-filled polypropylene. The transient viscosity growth behavior for long glass fiber suspensions was subsequently investigated. The results suggested that both, fiber length and fiber concentration have pronounced effect on the steady state suspension viscosity. It was also observed that the transient behavior of the pre-oriented samples was highly dependent on the initial orientation state of the fibers.Master of Science
30
Singh, Harminder. "Modelling of shear sensitive cells in stirred tank reactor using computational fluid dynamics." Thesis, University of Canterbury. Chemical and Process Engineering, 2011. http://hdl.handle.net/10092/5684.
Full textAbstract:
Animal cells are often cultured in stirred tank reactors. Having no cell wall, these animal cells are very sensitive to the fluid mechanical stresses that result from agitation by the impeller and from the rising and bursting of bubbles, which are generated within the culture medium in the stirred tank to supply oxygen by mass transfer to the cells. If excessive, these fluid mechanical stresses can result in damage/death of animal cells. Stress due to the rising and bursting of bubbles can be avoided by using a gas-permeable membrane, in the form of a long coiled tube (with air passing through it) within the stirred tank, instead of air-bubbles to oxygenate the culture medium. Fluid mechanical stress due to impeller agitation can be controlled using appropriate impeller rotational speeds. The aim of this study was to lay the foundations for future work in which a correlation would be developed between cell damage/death and the fluid mechanical stresses that result from impeller agitation and bubbling. Such a correlation could be used to design stirred-tank reactors at any scale and to determine appropriate operating conditions that minimise cell damage/death due to fluid mechanical stresses.
Firstly, a validated CFD model of a baffled tank stirred with a Rushton turbine was developed to allow fluid mechanical stresses due to impeller agitation to be estimated. In these simulations, special attention was paid to the turbulence energy dissipation rate, which has been closely linked to cell damage/death in the literature. Different turbulence models, including the k-ε, SST, SSG-RSM and the SAS-SST models, were investigated.
All the turbulence models tested predicted the mean axial and tangential velocities reasonably well, but under-predicted the decay of mean radial velocity away from the impeller. The k-ε model predicted poorly the generation and dissipation of turbulence in the vicinity of the impeller. This contrasts with the SST model, which properly predicted the appearance of maxima in the turbulence kinetic energy and turbulence energy dissipation rate just off the impeller blades. Curvature correction improved the SST model by allowing a more accurate prediction of the magnitude and location of these maxima. However, neither the k-ε nor the SST models were able to properly capture the chaotic and three-dimensional nature of the trailing vortices that form downstream of the blades of the impeller. In this sense, the SAS-SST model produced more physical predictions. However,this model has some drawbacks for modelling stirred tanks, such as the large number of modelled revolutions required to obtain good statistical averaging for calculating turbulence quantities. Taking into consideration both accuracy and solution time, the SSG-RSM model was the least satisfactory model tested for predicting turbulent flow in a baffled stirred tank with a Rushton turbine.
In the second part of the work, experiments to determine suitable oxygen transfer rates for culturing cells were carried out in a stirred tank oxygenated using either a sparger to bubble air through the culture medium or a gas-permeable membrane. Results showed that the oxygen transfer rates for both methods of oxygenation were always above the minimum oxygen requirements for culturing animal cells commonly produced in industry, although the oxygen transfer rate for air-bubbling was at-least 10 times higher compared with using a gas-permeable membrane. These results pave the way for future experiments, in which animal cells would be cultured in the stirred tank using bubbling and (separately) a gas-permeable membrane for oxygenation so that the effect of rising and bursting bubbles on cell damage/death rates can be quantified. The effect of impeller agitation on cell damage/death would be quantified by using the gas permeable membrane for oxygenation (to remove the detrimental effects of bubbling), and changing the impeller speed to observe the effect of agitation intensity.
In the third and final part of this work, the turbulent flow in the stirred tank used in the oxygenation experiments was simulated using CFD. The SST turbulence model with curvature correction was used in these simulations, since it was found to be the most accurate model for predicting turbulence energy dissipation rate in a stirred tank. The predicted local maximum turbulence energy dissipation rate of 8.9x10¹ m2/s3 at a rotational speed of 900 rpm was found to be substantially less than the value of 1.98x10⁵ m2/s3 quoted in the literature as a critical value above which cell damage/death becomes significant. However, the critical value for the turbulence energy dissipation rate quoted in the literature was determined in a single-pass flow device, whereas animal cells in a stirred tank experience frequent exposure to high turbulence energy dissipation rates (in the vicinity of the impeller) due to circulation within the stirred tank and long culture times. Future cell-culturing experiments carried out in the stirred tank of this work would aim to determine a more appropriate critical value for the turbulence energy dissipation rate in a stirred tank, above which cell damage/death becomes a problem.
31
Croswell, Joseph W. "On the energetics of primary and secondary instabilities in plane Poiseuille flow." Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/64563.
Full textAbstract:
The phenomenon of transition in a laminar flow has been a topic of continued interest for many years. Recent experiments in shear flows have revealed a series of instabilities that lead to breakdown to turbulence. We have completed an analysis of the mechanisms which drive the primary (TS wave) and secondary instabilities in plane Poiseuille flow. This was accomplished by studying the solutions of linear primary and secondary stability theory with energy methods. We found that primary instability occurred when the viscous stresses overpowered dissipative forces near the channel walls. For the secondary instability, we saw that the TS wave catalyzes the instability and then mediates the transfer of brge amounts of energy from the mean flow into the three-dimensional disturbance, thus driving the instability. In addition, we have compiled an extensive catalog of the loc!l.l energy and vorticity field distributions which result from each instability.Master of Science
32
Melnyk, Angela Dorothy. "Load transfer characteristics between posterior fusion devices and the lumbar spine under shear loading : an in vitro investigation." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/31943.
Full textAbstract:
Introduction: Clinical studies have demonstrated beneficial results of posterior arthrodesis for the treatment of degenerative spondylolisthesis (DS). The optimal stiffness of these fusion systems to enhance load-sharing and fusion rate while minimizing adjacent segment stresses is unknown. To our knowledge, posterior instrumentation for DS has not been tested under anterior shear loads, a highly relevant loading direction for DS.
Objectives: To determine the amount of shear load supported by posterior lumbar fusion devices of varying stiffness under shear loading.
Methods: The effect of implant stiffness and specimen condition on implant load was assessed in a biomechanical study. Fifteen human cadaveric lumbar functional spinal units were tested under a static 300 N axial compression load and a cyclic anterior shear load (5-250 N). Implants (High-Stiffness (HS): ∅ 5.5 mm Titanium, Medium-Stiffness (MS): ∅ 6.35 x 7.2 mm Oblong PEEK, Low-Stiffness (LS): ∅ 5.5 mm Round PEEK, and Ultra-Low-Stiffness (ULS): ∅ 5.5 mm Rod X), instrumented with strain gauges to measure loads, were tested in each of three specimen conditions simulating degenerative changes: intact, facet destabilization and disc destabilization.
Results: Transducers measured implant shear loads to within ±5 N. All implants supported significantly greater shear loads as the specimen was destabilized. The LS and ULS implants supported significantly less load than the HS and MS implants for all specimen conditions. Mean implant loads as a percent of the applied shear load in order of increasing specimen destabilization for the HS implant were: 43, 67 and 76%, for the MS implant were: 32, 56 and 77%, for the LS implant were: 18, 35 and 50%, and for the ULS implant were: 16, 39 and 42%. Standard errors were below 8%.
Discussion: An accurate shear load transducer was developed; the methodology is adaptable to many implant designs and materials. Implant shear stiffness significantly affected the shear load-sharing characteristics of the fusion devices. Low-stiffness implants transferred significantly greater loads to the spine, and may possibly enhance the transition to the adjacent, uninstrumented spine in vivo.
33
Mohammed, U. "Experimental studies and mathematical modelling of the draping and shear deformation of woven fabrics in resin transfer moulding." Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/604/.
Full text
34
Roche, Vincent. "Du manteau au système géothermal de haute température : Dynamique de subduction et anomalies thermiques en Méditerranée orientale." Thesis, Orléans, 2018. http://www.theses.fr/2018ORLE2007/document.
Full textAbstract:
Les ressources géothermales de haute température se localisent principalement le long des zones de subduction. Considérée comme amagmatique, la Province géothermale du Menderes (Turquie) offre l’opportunité d’étudier des systèmes géothermaux sans nécessairement invoquer une source de chaleur magmatique dans les premiers kilomètres de la croûte. Cette étude montre que les températures anormalement élevées dans la zone d’arrière-arcs sont principalement liées à la dynamique particulière de la subduction est-méditerranéenne (i.e. retrait et déchirure). Les résultats de modèles numériques suggèrent que le shear heating et les flux mantelliques modifient temporairement la quantité du flux de chaleur à la base de croûte. Par ailleurs, des études de terrain sur l’ensemble de la région (Cyclades, Dodécanèse et Anatolie occidentale) montrent une évolution tectonique et thermique similaire depuis le Crétacé, marquée minéralogiquement par une succession d’épisodes de HP-BT puis de HT-BP. Toutefois, l’apport des données TRSCM et radiochronométriques (⁴⁰Ar-³⁹Ar, U-Pb) souligne un évènement thermique majeur contemporain à la mise en place du dôme métamorphique du Menderes. Cet événement que l’on explique par un changement drastique de la dynamique de subduction (i.e. déchirure du panneau plongeant sous le Massif du Menderes), se développe au Miocène. Des structures d’échelle crustale (i.e. détachements)accommodent la mise en place du Massif du Menderes et contrôlent la circulation des fluides dans la croûte, depuis la zone de transition fragile-ductile jusqu’à la surface, sans nécessairement impliquer la contribution de systèmes magmatiques dans la croûte supérieure. La Province géothermale du Menderes est considérée comme une province de haute température de taille mondiale car elle résulte de la dynamique de subduction qui contrôle spatialement et temporellement l’intensité de l’anomalie thermique mais également la mise en place de structures perméables(détachements) d’échelle crustale favorisant la circulation des fluidesHigh temperature geothermal resources are mainly located along subduction zones. The Menderes geothermal Province (Turkey) offers the opportunity to study amagmatic geothermal systems, without necessarily invoking a magmatic heat source in the upper crust. This study shows that high temperatures in the back-arc domain are primarily related to subduction dynamics (i.e. rollback and tearing). Numerical models suggest that shear heating and mantle flows increase temporarily the amount of heat flow at the base of the crust. Furthermore, field studies on the entire Aegean region (Cyclades, Dodecanese and Western Anatolia) show a similar tectonic and thermal evolution since the Cretaceous, characterized by a succession of episodes of HP-LT and HT-LP metamorphism. Moreover, the contribution of TRSCM and radiochronometric data (⁴⁰Ar-³⁹Ar, U-Pb) reveals the formation of a largethermal pulse contemporaneous with the exhumation of the Menderes MCC. This event occurs in the Miocene and may be explained by a drastic change in subduction dynamics (i.e. slab tearing under the Menderes Massif).Crustal-scale structures (i.e. detachments) induce the emplacement of the Menderes MCC, and also control deep fluids circulation in the crust from brittle-ductile transition zone to the surface without magmatic contribution inthe upper crust. As a consequence, the Menderes geothermal Province is recognized as a most important active geothermal province in the world because it results from subduction dynamics. This dynamics thus controls thespatial and temporal distribution of thermal anomaly and extension, inducing crustal-scale permeable structures(detachments) that enhance fluids circulation
35
Mokwatlo, Sekgetho Charles. "Analysis of succinic acid-producing biofilms of Actinobacillus succinogenes." Diss., University of Pretoria, 2020. http://hdl.handle.net/2263/76114.
Full textAbstract:
Biofilms of the bovine rumen bacterium Actinobacillus succinogenes have demonstrated their exceptional capabilities as biocatalysts for high productivity, titre and yield production of succinic acid (SA). Succinic acid is set to become a significant building block chemical in the biobased economy. Although substantial progress has been made towards understanding the productive aspect of this microorganism with regard to its metabolic limits and performance on unrefined biorefinery stream substrates, more research is still required to address other challenges. One aspect is to understand how the biofilm biocatalyst is affected by bioreactor conditions, which would help in developing stable and highly active biofilms. For this reason the aim of this thesis was (i) to characterise how the accumulation of acid metabolites in continuous operation impacts A. succinogenes biofilms with respect to biofilm development, biofilm structure and cell activity within the biofilm, (ii) to show how shear conditions in the fermenter can be used to manipulate the biofilm structure and viable cell content of biofilms, leading to improved cell-based succinic acid productivities, and lastly (iii) to investigate the internal mass transfer effects on biofilm performance, further showing the role played by differences in shear and acid accumulation conditions in this respect.
The first part of the study addressed the interaction between the biofilm and the accumulation of metabolites produced. The results showed that biofilms of A. succinogenes develop rapidly and with high activity when cultivated under low product accumulation (LPA) conditions (< 10 g L-1 SA). High product accumulation (HPA) conditions considerably slowed down biofilm development, and increased cell mortality. Under HPA conditions some cells exhibited severe elongation while maintaining a cross-sectional diameter like the rod/cocci-shaped cells predominantly found in LPA conditions. The elongated cells formed in HPA conditions were found to be more viable and thus more resistant than the clusters of rod-shaped or cocci-shaped cells. The global microscopic structure of the HPA biofilms also differed significantly from that of the LPA biofilms. Although both exhibited shedding after 4 days of growth, the LPA biofilms were more homogenous (less patchy), thicker and had high viability throughout the biofilm depth.
In the second part of the study, two custom-designed bioreactors were used to evaluate the effect of shear on the biofilms. The first bioreactor allowed for in situ removal of small biofilm samples used for microscopic imaging. The second bioreactor allowed for complete removal of all biofilm and was used to analyse biofilm composition and productivity. Results clearly indicated that high shear biofilm cultivation in LPA conditions has beneficial morphological, viability and cell-based productivity characteristics. The smooth, low-porosity biofilms obtained under high shear and LPA conditions had an average cell viability of 79% (over a 3-day cultivation period) compared with the low shear value of 57%, also developed under LPA conditions. The EPS content of the high shear biofilm was 58% compared with 7% of the low shear equivalent. The cell-based (EPS excluded) succinic acid productivity for the high shear biofilm was 2.4 g g-1DCW h-1 compared with the 0.8 g g-1DCW h-1 for the low shear biofilm. This threefold increase in productivity obtained from the second bioreactor corresponded to the cell viability differences obtained from the first bioreactor. Clear evidence was provided for shear-induced shaping of the biofilm which resulted in improved volumetric glucose turnover attributes within the biofilm matrix.
The last section of the study investigated internal mass transfer effects in biofilm fermentations of Actinobacillus succinogenes by performing batch fermentations using attached and resuspended biofilms as biocatalysts. In the latter, the biofilms were resuspended after initial development to simulate mass transfer-free fermentations. Intrinsic kinetics for succinic acid production obtained from resuspended fermentations predicted faster production rates than for the attached biofilm runs (biofilm thicknesses in the range of 120–200 µm), indicating internal mass transfer limitations. A developed biofilm reaction diffusion model gave good prediction of attached biofilm batch operation results by accounting for internal mass transfer in the biofilm. Biofilm effectiveness factors ranged from 75% to 97% for all batches at the inception of batch conditions, but increased with the progression of batch operation due to the increased succinic acid titres which inhibited the production rates. Analysis of pseudo-steady-state continuous fermentation data from the literature, as well as from the second part of the study, using the model developed, showed that active biofilm thickness and effectiveness factors were dependent on the shear conditions and succinic acid titres in the biofilm reactors. A simplified algorithm was developed to estimate the pseudo-steady-state glucose penetration and biofilm effectiveness of A. succinogenes biofilms without the requirement to solve the overall mass transfer model. The results clearly showed that internal mass transfer needs to be considered in biofilm fermentations involving A. succinogenes as high biomass concentrations may not always equate to increased productivities if mass transfer effects dominate.Thesis (PhD)--University of Pretoria, 2020.
NRF
Chemical Engineering
PhD
Unrestricted
36
Kopf, Florian [Verfasser]. "Experimental and Numerical Geometry Optimization of Hollow Fiber Membranes for Efficient Mass Transfer at Low Shear Stress / Florian Kopf." München : Verlag Dr. Hut, 2017. http://d-nb.info/1149580453/34.
Full text
37
Tsotras, Achillefs. "On the interaction between modal behaviour and shear force behaviour of a pneumatic tyre." Thesis, Loughborough University, 2010. https://dspace.lboro.ac.uk/2134/6031.
Full textAbstract:
The in-plane phenomena of interaction between the tyre structural response and contact force generation are investigated in this work. The challenges of the physical tyre simulation are identified, primarily associated with the computational load imposed by the need to capture the space distributed mechanisms that prescribe the above interaction. The method of modal expansion and reduction is proposed for the moderation of this load. The theoretical framework for the transformation of a tyre modal representation into a transient contact and shear force generation model is developed. Various modelling approaches are examined with regards to their modal prediction characteristics. Linear and non linear structural features as well as the physical properties that define the broad range modal behaviour are identified. A discretised form of the ring model is derived and combined with a foundation of viscoelastic tread elements for simulating the transient contact behaviour of the tyre. The resulting pattern of the modes' excitation justifies the validity of the modal reduction method and reveals the relative importance of various mechanisms and physical properties in tyre contact behaviour. The interaction between the friction controlled shear slip of the tread, the belt compliance and the sidewall buckling is found to be reflected on the two-dimensional contact pressure distribution patterns. A method able to simulate the dynamic transient rolling and slipping operating conditions is developed, although the small displacement assumption of the modal approach is dropped. The method, which is based on the combined modal-time and space-time domain solutions, is applied on the study of the physical mechanism of the launch process. The examination of the model under steady state kinematic conditions reveals the saturation of the traction force for profound levels of slip, which highlights the contribution of the structural mechanisms on the macroscopically observed shear force performance of the tyre. The variation of the modes' level of excitation, as induced by the operating conditions, is proposed for the capture of the physical properties effect on tyre behaviour and performance.
38
Suwa, Akihiko 1972. "Simulation of phase domain breakup and coalescence in strong shear and transient flows using lattice-Boltzmann method." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/50408.
Full text
39
Gomez, Giraldo Evelio Andres. "Observations of energy transfer mechanisms associated with internal waves." University of Western Australia. Centre for Water Research, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0045.
Full textAbstract:
[Truncated abstract] Internal waves redistribute energy and momentum in stratified lakes and constitute the path through which the energy that is introduced at the lake scale is cascaded down to the turbulent scales where mixing and dissipation take place. This research, based on intensive field data complemented with numerical simulations, covers several aspects of the energy flux path ranging from basin-scale waves with periods of several hours to high frequency waves with periods of few minutes. It was found that, at the basin-scale level, the horizontal shape of the lake at the level of the metalimnion controls the period and modal structure of the basin-scale natural modes, conforming to the dispersion relationship of internal waves in circular basins. The sloping bottom, in turn, produces local intensification of the wave motion due to focusing of internal wave rays over near-critical slopes, providing hot spots for the degeneration of the basin-scale waves due to shear instabilities, nonlinear processes and dissipation. Different types of high-frequency phenomena were observed in a stratified lake under different forcing conditions. The identification of the generation mechanisms revealed how these waves extract energy from the mean flow and the basin-scale waves. The changes to the stratification show that such waves contribute to mixing in different ways . . . Detailed field observations were used to develop a comprehensive description of an undocumented energy flux mechanism in which shear-instabilities with significant amplitudes away from the generation level are produced in the surface layer due to the shear generated by the wind. The vertical structure of these instabilities is such that the growing wave-related fluctuations strain the density field in the metalimnion triggering secondary instabilities. These instabilities also transport energy vertically to the thermocline where they transfer energy back to the mean flow through interaction with the background shear.
40
Gunasekaran, Sidaard. "Relationship Between the Free Shear Layer, the Wingtip Vortex and Aerodynamic Efficiency." University of Dayton / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1470231642.
Full text
41
Yuen, K. W. H. "A study of boundary shear stress, flow resistance and momentum transfer in open channels with simple and compound trapezoidal cross sections." Thesis, University of Birmingham, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492540.
Full textAbstract:
The characteristics of fully developed turbulent flow in smooth open channels of simple trapezoidal cross-section have been examined experimentally in the range 0.5 < Fr < 3.5,1.9 x 104 < Re < 6.2 x 105 and 0.3 < 2b/H < 15.0. Subcritical flow in a compound trapezoidal channel has also been studied for relative depths between 0.05 < Dr 0.5. The effect of secondary flows and the interaction between the main channel and the flood plain flows have been shown to influence the boundary shear stress and velocity distributions significantly. For simple channels, the boundary shear stress distributions have been correlated with the geometry parameters 2b/H or Pb/Pw, and empirically derived equations are presented giving the percentage of the total shear force carried by the wall. Ancillary equations are also presented giving the correlation between the geometry parameters and the mean and maximum shear stresses. Attention is also focussed on the effect of the hydraulic parameters on flow resistance. A comparison is made between the data and traditional formulations for smooth pipes and rectangular channels. The Froude number effect is also examined and found to be important. For compound channels, the transfer of momentum between the main channel and the flood plain has been studied in detail. Boundary shear force results have been used to calculate the apparent shear forces on vertical, horizontal and inclined interfaces. An empirically derived equation relating the geometry parameters and the boundary shear force on the flood plain bed and walls is presented. In order to quantify the momentum transfer within the whole section, the Navier-Stokes equation for steady uniform flow is used, and an analytical solution to the depth averaged form of the equation compared with the experimental results. A comparison of the depth-averaged values of flow resistance with those values obtained from a one-dimensional formulation is also made, and distinct differences noted. Improvement may be made by using the resistance radius in place of the traditional hydraulic radius. Use is made of the apparent shear force results in assessing channel discharge calculation methods which are based on sub-dividing the flow area. Equations are presented giving the main channel discharge for both vertical and horizontal division planes. The methods for evaluating the critical depth in a compound channel are also reviewed and assessed against experimental data. The free overfall for simple trapezoidal channels has been studied and an analytical relationship obtained between the ratio of brink depth to critical depth and the channel bed slope. Experimental data confirm this relationship.
42
Nam, Soonkie. "Effects of Reservoir Releases on Slope Stability and Bank Erosion." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/77114.
Full textAbstract:
Reservoir release patterns are determined by a number of purposes, the most fundamental of which is to manage water resources for human use. Managing our water resources means not only controlling the water in reservoirs but also determining the optimum release rate taking into account factors such as reservoir stability, power generation, water supply for domestic, industrial, and agricultural uses, and the river ecosystem. However, riverbank stability has generally not been considered as a factor, even though release rates may have a significant effect on downstream riverbank stability. Riverbank retreat not only impacts land properties but also damages structures along the river such as roads, bridges and even buildings. Thus, reservoir releases need to also take into account the downstream riverbank stability and erosion issues.
The study presented here investigates the riverbank stability and erosion at five study sites representing straight as well as inside and outside channel meander bends located on the lower Roanoke River near Scotland Neck, North Carolina. Extensive laboratory and field experiments were performed to define the hydraulic and geotechnical properties of the riverbank soils at each site. Specifically, soil water characteristic curves were determined using six different techniques and the results compared to existing mathematical models. Hydraulic conductivity was estimated using both laboratory and in situ tests. Due to the wide range of experimentally obtained values, the values determined by each of the methods was used for transient seepage modeling and the modeling results compared to the actual ground water table measured in the field. The results indicate that although the hydraulic conductivities determined by in situ tests were much larger than those typically reported for the soils by lab tests, numerical predictions of the ground water table using the in situ values provided a good fit for the measured ground water table elevation. Shear strengths of unsaturated soils were determined using multistage suction controlled direct shear tests. The test method was validated, and saturated and unsaturated shear strength parameters determined. These parameters, which were determined on the basis of results from both laboratory and field measurements, and the associated boundary conditions, which took into account representative flow rates and patterns including peaking, drawdown and step-down scenarios, were then utilized for transient seepage analyses and slope stability analyses performed using SLIDE, a software package developed by Rocscience. The analyses confirmed that the riverbanks are stable for all flow conditions, although the presence of lower permeability soils in some areas may create excess pore water pressures, especially during drawdown and step-down events, that result in the slope becoming unstable in those locations. These findings indicate that overall, the current reservoir release patterns do not cause adverse impacts on the downstream riverbanks, although a gradual drawdown after a prolonged high flow event during the wet season would reduce unfavorable conditions that threaten riverbank stability.Ph. D.
43
Kolli, Kranthi Kumar. "Domain Effects in the Finite / Infinite Time Stability Properties of a Viscous Shear Flow Discontinuity." Connect to this title, 2008. http://scholarworks.umass.edu/theses/204/.
Full text
44
Eaves, Thomas Scott. "Generalised nonlinear stability of stratified shear flows : adjoint-based optimisation, Koopman modes, and reduced models." Thesis, University of Cambridge, 2016. https://www.repository.cam.ac.uk/handle/1810/260824.
Full textAbstract:
In this thesis I investigate a number of problems in the nonlinear stability of density stratified plane Couette flow. I begin by describing the history of transient growth phenomena, and in particular the recent application of adjoint based optimisation to find nonlinear optimal perturbations and associated minimal seeds for turbulence, the smallest amplitude perturbations that are able to trigger transition to turbulence. I extend the work of Rabin et al. (2012) in unstratified plane Couette flow to find minimal seeds in both vertically and horizontally sheared stratified plane Couette flow. I find that the coherent states visited by such minimal seed trajectories are significantly altered by the stratification, and so proceed to investigate these states both with generalised Koopman mode analysis and by stratifying the self-sustaining process described by Waleffe (1997). I conclude with an introductory problem I considered that investigates the linear Taylor instability of layered stratified plane Couette flow, and show that the nonlinear evolution of the primary Taylor instability is not coupled to the form of the linearly unstable mode, in contrast to the Kelvin-Helmholtz instability, for example. I also include an appendix in which I describe joint work conducted with Professor Neil Balmforth of UBC during the 2015 WHOI Geophysical Fluid Dynamics summer programme, investigating stochastic homoclinic bifurcations.
45
Memon, Muhammad Omar. "Wingtip Vortices and Free Shear Layer Interaction in the Vicinity of Maximum Lift to Drag Ratio Lift Condition." University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1492701624726378.
Full text
46
Diemuodeke, Ogheneruona Endurance. "Modelling of Liquid Breakup Mechanisms in Engineering Systems." Thesis, Cranfield University, 2014. http://dspace.lib.cranfield.ac.uk/handle/1826/9289.
Full textAbstract:
Effective design of liquid fuel injection systems is a function of good understanding of liquid breakup mechanisms. A transient liquid breakup model is developed on the classical interfacial breakup theory by modifying the classical linear perturbation process to include time-dependent base and perturbed flow parameters. The non-isothermal condition on liquid jet instability and breakup is theoretically modelled; with the particular consideration of a spatially variation of surface tension along the liquid-gas interface. The model combines the classical interface hydrodynamic instability and breakup theory and heat-transfer through semi-infinite medium. Analytical liquid breakup model, which combines transient and non-isothermal effects on liquid jet breakup, is suggested. The suggested model could be simplified to the transient breakup model and the non-isothermal breakup model equivalents. A novel mechanistic model, which is based on a simple momentum balance between the injected jet and the aerodynamic drag force, is suggested for breakup length. A new model, which combines energy criterion and dual-timescale for turbulent shear in droplet dispersion, is suggested for droplet breakup criteria on the basis of critical Webber number. All developed models showed good predictions of available experimental data, and established empirical correlation, within the operational conditions of contemporary ICEs, specifically diesel engines. Continued research in these areas could benefit the development of the next generation of liquid fuel injectors and combustors – by accounting for transient effects and non-isothermal conditions in liquid jet breakup, and turbulent shear in droplet breakup.
47
Yepez, Silva-Santisteban Bernardo Onagar. "Estudo dos parametros de engenharia de processo que afetam a fisiologia e a produção de inulinase por Kluyveromyces marxianus ATCC 16045." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/256550.
Full textAbstract:
Orientador: Francisco Maugeri FilhoTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
Made available in DSpace on 2018-08-05T17:05:43Z (GMT). No. of bitstreams: 1 YepezSilva-Santisteban_BernardoOnagar_D.pdf: 1839103 bytes, checksum: 44dfdd6f4dc2a025d2bcdbcf149d2ef1 (MD5) Previous issue date: 2006
Doutorado
Doutor em Engenharia de Alimentos
48
Souzy, Mathieu. "Mélange dans les suspensions de particules cisaillées à bas nombre de Reynolds." Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4719/document.
Full textAbstract:
J'ai étudié expérimentalement, à l'échelle de la taille des particules, les mécanismes à l'origine de l'intensification des transferts ayant lieu dans les suspensions cisaillées de particules non-inertielles et non-Browniennes. Dans un premier temps, l'expérience de Taylor est revisitée en étudiant l'évolution d'une goutte de colorant soumise à un cisaillement périodique. Au-delà d'une amplitude critique de déformation, la présence des particules brise la réversibilité du système et induit une forte dispersion de la goutte de colorant. Ensuite, en m'intéressant au transfert en proche paroi, j'ai montré que la rotation des particules sur la paroi induit un transport à flux constant d'un scalaire jusque dans le bulk de la suspension, brisant la couche limite diffusive. Une solution analytique du profil de concentration dans cette zone est proposée, en bon accord avec les expériences. Finalement, des mesures PIV haute résolution du fluide interstitiel dans le bulk de la suspension ont été réalisées. A partir de ces champs de vitesses, on a reconstruit l'historique d'étirement de lignes matérielles du fluide et ainsi déterminé les lois d'étirement, information fondamentale pour la compréhension du processus de mélange. La présence des particules change les lois d'étirement qui passent de linéaires dans un fluide pur, à exponentielles en présence de particules. Un modèle d'étirements multiplicatifs est proposé, qui prédit quantitativement l'évolution de la moyenne, de la variance, et la forme log-normale des distributions d'étirements mesurées expérimentalement. L'inhomogénéité des étirements dans les suspensions cisaillées implique une large distribution du temps de mélangeMainly based on experiments, I investigated at a particle scale the mechanisms at the origin of the transfer enhancement in sheared non-Brownian and non-inertial particulate suspensions. First, I revisited Taylor's experiment, investigating the evolution of a drop of dye in a periodic shear. Beyond a critical strain amplitude, the presence of the particles breaks the reversibility of the system and the drop of dye is rapidly dispersed in the surrounding medium. Then, investigating the transfer process in the wall vicinity, I showed that in this region, the rotation of the particles convectively transport a scalar at a constant rate directly from the wall towards the bulk of the suspension, breaking the diffusive boundary layer. An analytical solution for the concentration profile in this region is proposed, in good agreement with experimental measurements. Lastly, high-resolution PIV measurements of the fluid phase were performed in the bulk of the suspension. Using these velocity fields, we reconstructed the stretching histories of fluid material lines to determine the stretching laws, crucial for the understanding of the mixing process. The presence of the particles changes the very nature of the stretching laws from linear, in a pure fluid, to exponential in the presence of particles. A multiplicative stretching model is proposed, which quantitatively predicts the experimentally measured evolution of the mean and the variance of the elongations of the fluid material lines as well as their evolution towards a log-normal distribution. The strong stretching inhomogeneity in sheared suspensions results in a broad distribution of the mixing time
49
Golightly, Christopher Robert. "Engineering properties of carbonate sands : the geological origins, classification, engineering, shear and triaxial stress path properties of four carbonate sands. The analysis of the transfer function for pile skin friction." Thesis, University of Bradford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285066.
Full text
50
Oliveira, Elisandra Miranda de. "Transferência dos esforços cisalhantes em juntas de pavimentos rígidos." Universidade Federal de Goiás, 2008. http://repositorio.bc.ufg.br/tede/handle/tede/6783.
Full textAbstract:
Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2017-01-26T10:17:46Z
No. of bitstreams: 2
Dissertação - Elisandra Miranda de Oliveira - 2008.pdf: 8045679 bytes, checksum: bbc3ccef6840ca7cc9f60fd22a61ed85 (MD5)
license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5)Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-01-26T10:18:11Z (GMT) No. of bitstreams: 2 Dissertação - Elisandra Miranda de Oliveira - 2008.pdf: 8045679 bytes, checksum: bbc3ccef6840ca7cc9f60fd22a61ed85 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5)
Made available in DSpace on 2017-01-26T10:18:12Z (GMT). No. of bitstreams: 2 Dissertação - Elisandra Miranda de Oliveira - 2008.pdf: 8045679 bytes, checksum: bbc3ccef6840ca7cc9f60fd22a61ed85 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2008-09-17
Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq
The joint is part of the constructive process of the rigid pavement. In its implementation the section of concrete located below it is weakened and eventually becoming the most vulnerable of the pavement can arise where the possible diseases that may affect their strength and durability. Despite the importance that the joint has in the life of the rigid pavement it is not exploited, and therefore became the main subject of this study. This work is an experimental study of the sawed joint in rigid pavement of concrete with evaluation of the transference of shear strength through the saweds joints. The experimental program consisted of test of fourteen simple concrete plates with sawed joint, and adoption of the following variable: presence of smooth dowel of Ø 12,5mm, variation of the length of dowel (500 mm, 400 mm and 300 mm), variation of the thickness of the plates (120 mm and 160 mm), variation of the strength to the compression of the concrete (20 MPa and 30 MPa) and of the type of used concrete (conventional and autoadensável). These plates had been supported on natural and assayed rubber layers with static shipment application in one of the sides of the together one until the rupture of the plate. The results had shown that: the use of dowel in these meetings increases the efficiency in the transference of efforts; the increase in the thickness of the plate increases the resistant capacity of the together one, the efficiency in the transference of efforts and possesss minors displacements of the plate during the application of the shipment; the dowel with reduced size are efficient, but the bars of 400 mm present resulted next to the one to the bar in commercial size, 500 mm; the plates in autoadensável concrete after the fissuration practically do not present contribution of the concrete in the transference of efforts for the intertravamento of aggregates; the sawed joint depth of the together one has influence in the way of rupture of the plate and tack relation enters the bar of transference and concret.
A junta faz parte do processo construtivo do pavimento de concreto. Na sua execução a seção de concreto localizada abaixo dela fica enfraquecida e acaba se tornando o ponto mais vulnerável do pavimento onde podem surgir as possíveis patologias que venham a afetar a sua resistência e durabilidade. Apesar da importância que a junta possui na vida útil do pavimento de concreto este assunto é pouco explorado, e por isso se tornou o objeto principal deste estudo. Este trabalho é um estudo experimental das juntas serradas em pavimento rígido de concreto com avaliação da transferência de esforços cisalhantes através das juntas serradas. O programa experimental constou de ensaios de quatorze placas em concreto simples com junta serrada, e adoção das seguintes variáveis: presença de barra de transferência lisa de Ø 12,5mm, variação do comprimento das barras de transferência (500 mm, 400 mm e 300 mm), variação da espessura das placas (120 mm e 160 mm), variação da resistência característica à compressão do concreto (20 MPa e 30 MPa) e do tipo de concreto utilizado (convencional e autoadensável). Essas placas foram apoiadas sobre camadas de borracha natural e ensaiadas com aplicação de carregamento estático em um dos lados da junta até a ruptura da placa. Os resultados mostraram que: o uso de barras de transferência nessas juntas aumenta a eficiência na transferência de esforços; o aumento na espessura da placa aumenta a capacidade resistente da junta, a eficiência na transferência de esforços e possuem menores deslocamentos da placa durante a aplicação do carregamento; as barras com tamanho reduzido são eficientes, mas as barras de 400 mm apresentam resultados próximos ao da barra em tamanho comercial, 500 mm; as placas em concreto autoadensável após a fissuração praticamente não apresentam contribuição do concreto na transferência de esforços pelo intertravamento dos agregados; a profundidade da junta serrada tem influência no modo de ruptura da placa e relação de aderência entre a barra de transferência e o concreto.