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Full Text, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Eng & Built Env, Science, Environment, Engineering and Technology, A reinforced concrete (RC) flat plate is a type of structural system widely used in the construction of about 80-90% of residential high-rise buildings in Australia and similarly overseas. Flat plate construction is however prone to punching shear failure at slab-column joints which may trigger a catastrophic progressive collapse of the entire structure. In a flat plate structure, unbalanced moments at the slab-column joints are unavoidable. These bending moments are commonly caused by asymmetric loading, unequal spans or horizontal forces like wind or earthquake. The existence of unbalanced moments could increase the vulnerability of a flat plate structure to punching shear failure. In addition, the load originally resisted by a potentially damaged column will be transferred to the adjacent joints, at which a large additional shear stress and unbalanced bending moment will be generated, eventually leading to more complex mechanical performance and failure mechanism of the joints. Limited collapse-resistant design guidelines are available for this type of structure. Moreover, its punching shear and post-punching failure mechanisms in the context of a progressive collapse are still in need of in-depth study. To investigate the punching and post-punching shear mechanisms of slab-column joints subjected to concentric loading (with balanced moments), previous static tests on four slab-column joint specimens with slab in-plane restraints have been analysed. The effects of different punching directions (upward punching and downward punching) and embedded beams on the post-punching performance of the joints were studied. Furthermore, a 3D nonlinear finite element modelling approach for concentrically loaded joints was developed using software LS-DYNA and verified against the test results. Based on the numerical study, the contributions of the concrete and reinforcement in resisting the collapse of the slab-column joints were evaluated. To investigate the mechanical behavio

With the increasing need for commercial and residential buildings, post-tensioned (PT) flat plates have become a preferred choice for floor systems, because of the numerous advantages over non-prestressed slabs such as better efficiency, reduced slab self-weight, as well as crack and deflection control. To improve the competitive advantage of PT flat plates through improved economy and performance, a study was undertaken. This study investigated the performance and behavior of three one-third scale models of a nine-panel two-way unbonded post-tensioned flat plate. One of the slabs had conventional reinforcement with uniform-banded tendon layout, another had conventional reinforcement with banded-banded tendon layout while the last had banded-banded tendon layout reinforced with steel fiber. The specimens were loaded to service limit state, factored load and then to failure, using a whiffle tree loading system that approximated a uniformly distributed load. Experimental results were compared to analytical results from finite element and yield line analysis. The performance of the banded-banded specimens was very similar to the uniform-banded specimens at service and factored load. The failure loads for all specimens were considerably higher than the design factored load of 197 psf. Steel fiber was able to replace conventional reinforcement and the performance of the specimens with steel fibers was satisfactory, and comparable to their corresponding conventional reinforced specimens at service and factored limit state. Analytical results from finite element analysis showed a fairly reasonable agreement with experimental results. The results from the experimental tests showed that the use of steel fiber in post-tensioned flat plates is a viable and safe technology that will lead to improved performance and economy. The experimental results seem to indicate that the requirement of conventional reinforcement may be unnecessary in the negative moment regions and also in t

With the increasing need for commercial and residential buildings, post-tensioned (PT) flat plates have become a preferred choice for floor systems, because of the numerous advantages over non-prestressed slabs such as better efficiency, reduced slab self-weight, as well as crack and deflection control. To improve the competitive advantage of PT flat plates through improved economy and performance, a study was undertaken. This study investigated the performance and behavior of three one-third scale models of a nine-panel two-way unbonded post-tensioned flat plate. One of the slabs had conventional reinforcement with uniform-banded tendon layout, another had conventional reinforcement with banded-banded tendon layout while the last had banded-banded tendon layout reinforced with steel fiber. The specimens were loaded to service limit state, factored load and then to failure, using a whiffle tree loading system that approximated a uniformly distributed load. Experimental results were compared to analytical results from finite element and yield line analysis. The performance of the banded-banded specimens was very similar to the uniform-banded specimens at service and factored load. The failure loads for all specimens were considerably higher than the design factored load of 197 psf. Steel fiber was able to replace conventional reinforcement and the performance of the specimens with steel fibers was satisfactory, and comparable to their corresponding conventional reinforced specimens at service and factored limit state. Analytical results from finite element analysis showed a fairly reasonable agreement with experimental results. The results from the experimental tests showed that the use of steel fiber in post-tensioned flat plates is a viable and safe technology that will lead to improved performance and economy. The experimental results seem to indicate that the requirement of conventional reinforcement may be unnecessary in the negative moment regions and also in t

A reinforced concrete (RC) flat plate is a type of structural system widely used in the construction of about 80-90% of residential high-rise buildings in Australia and similarly overseas. Flat plate construction is however prone to punching shear failure at slab-column joints which may trigger a catastrophic progressive collapse of the entire structure. In a flat plate structure, unbalanced moments at the slab-column joints are unavoidable. These bending moments are commonly caused by asymmetric loading, unequal spans or horizontal forces like wind or earthquake. The existence of unbalanced moments could increase the vulnerability of a flat plate structure to punching shear failure. In addition, the load originally resisted by a potentially damaged column will be transferred to the adjacent joints, at which a large additional shear stress and unbalanced bending moment will be generated, eventually leading to more complex mechanical performance and failure mechanism of the joints. Limited collapse-resistant design guidelines are available for this type of structure. Moreover, its punching shear and post-punching failure mechanisms in the context of a progressive collapse are still in need of in-depth study. To investigate the punching and post-punching shear mechanisms of slab-column joints subjected to concentric loading (with balanced moments), previous static tests on four slab-column joint specimens with slab in-plane restraints have been analysed. The effects of different punching directions (upward punching and downward punching) and embedded beams on the post-punching performance of the joints were studied. Furthermore, a 3D nonlinear finite element modelling approach for concentrically loaded joints was developed using software LS-DYNA and verified against the test results. Based on the numerical study, the contributions of the concrete and reinforcement in resisting the collapse of the slab-column joints were evaluated. To investigate the mechanical behavio, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Eng & Built Env, Science, Environment, Engineering and Technology, Full Text

[ES] El presente trabajo aborda el estudio del pandeo y post-pandeo de placas y paneles rectangulares, propios de la estructura semi-monocasco predominante en los diseños aeronáuticos actuales. Se añade la influencia de una imperfección inicial coincidente con el modo de pandeo de la estructura y el comportamiento elasto-plástico del material. En primera instancia se analiza el pandeo y post-pandeo de una placa elástica e imperfecta bajo diferentes condiciones de contorno. A continuación, se introduce la posibilidad de que el material entre en zona elasto-plástica bien al inicio de pandeo o bien en post-pandeo, lo que constituye dos problemáticas diferentes. Además, se comparan soluciones experimentales con diferentes teorías elasto-plásticas modernas aún debatidas en la actualidad. Posteriormente, se repite el estudio completo de post-pandeo para placas largas y se realiza la comparativa con placas cuadradas. Se finaliza el trabajo abordando un análisis completo de pandeo y post-pandeo en un panel integral, en el que se incluyen la teoría elasto-plástica y la imperfección inicial. Se presta especial atención a la distinción entre modos de pandeos locales y globales, así como los peligros asociados a este último. Para el análisis de cada caso se contrastan métodos analíticos, el método de los elementos finitos y, en algunos casos, soluciones experimentales y referencias externas. El cálculo analítico se aborda con ayuda del software comercial Mathematica, el numérico con Abaqus y el post-procesado de gráficas con Illustrator., [EN] The study of buckling and post-buckling of rectangular plates and panels, specific of the semi-monocoque structure, is discussed. The possibility of an initial imperfection that matches with the buckling mode of the structure and the elasto-plastic behaviour of the material is included. Firstly, the buckling and post-buckling of an elastic and imperfect plate is analyzed under different boundary conditions. Then, the possibility of elasto-plastic behaviour for both buckling or post-buckling is studied, raising two different problems. Different controversial modern elasto-plastic theories are also compared with experimental solutions. Subsequently, the full post-buckling study is repeated for long plates and compared with the results of square plates. The work is concluded addressing a complete analysis of buckling and post-buckling for an integral panel, including both the elasto-plastic theory and the initial imperfection. Particular attention is paid to the distinction between local and global buckling modes, as well as to the risks associated with the last one. In every study, analytical methods, the finite element method and, in some cases, experimental solutions are contrasted. The analytical calculation is approached with the support of the commercial software Mathematica, the numerical one with Abaqus and the post-processing of plots with Illustrator.

[ES] El presente trabajo aborda el estudio del pandeo y post-pandeo de placas y paneles rectangulares, propios de la estructura semi-monocasco predominante en los diseños aeronáuticos actuales. Se añade la influencia de una imperfección inicial coincidente con el modo de pandeo de la estructura y el comportamiento elasto-plástico del material. En primera instancia se analiza el pandeo y post-pandeo de una placa elástica e imperfecta bajo diferentes condiciones de contorno. A continuación, se introduce la posibilidad de que el material entre en zona elasto-plástica bien al inicio de pandeo o bien en post-pandeo, lo que constituye dos problemáticas diferentes. Además, se comparan soluciones experimentales con diferentes teorías elasto-plásticas modernas aún debatidas en la actualidad. Posteriormente, se repite el estudio completo de post-pandeo para placas largas y se realiza la comparativa con placas cuadradas. Se finaliza el trabajo abordando un análisis completo de pandeo y post-pandeo en un panel integral, en el que se incluyen la teoría elasto-plástica y la imperfección inicial. Se presta especial atención a la distinción entre modos de pandeos locales y globales, así como los peligros asociados a este último. Para el análisis de cada caso se contrastan métodos analíticos, el método de los elementos finitos y, en algunos casos, soluciones experimentales y referencias externas. El cálculo analítico se aborda con ayuda del software comercial Mathematica, el numérico con Abaqus y el post-procesado de gráficas con Illustrator., [EN] The study of buckling and post-buckling of rectangular plates and panels, specific of the semi-monocoque structure, is discussed. The possibility of an initial imperfection that matches with the buckling mode of the structure and the elasto-plastic behaviour of the material is included. Firstly, the buckling and post-buckling of an elastic and imperfect plate is analyzed under different boundary conditions. Then, the possibility of elasto-plastic behaviour for both buckling or post-buckling is studied, raising two different problems. Different controversial modern elasto-plastic theories are also compared with experimental solutions. Subsequently, the full post-buckling study is repeated for long plates and compared with the results of square plates. The work is concluded addressing a complete analysis of buckling and post-buckling for an integral panel, including both the elasto-plastic theory and the initial imperfection. Particular attention is paid to the distinction between local and global buckling modes, as well as to the risks associated with the last one. In every study, analytical methods, the finite element method and, in some cases, experimental solutions are contrasted. The analytical calculation is approached with the support of the commercial software Mathematica, the numerical one with Abaqus and the post-processing of plots with Illustrator.

[ES] El presente trabajo aborda el estudio del pandeo y post-pandeo de placas y paneles rectangulares, propios de la estructura semi-monocasco predominante en los diseños aeronáuticos actuales. Se añade la influencia de una imperfección inicial coincidente con el modo de pandeo de la estructura y el comportamiento elasto-plástico del material. En primera instancia se analiza el pandeo y post-pandeo de una placa elástica e imperfecta bajo diferentes condiciones de contorno. A continuación, se introduce la posibilidad de que el material entre en zona elasto-plástica bien al inicio de pandeo o bien en post-pandeo, lo que constituye dos problemáticas diferentes. Además, se comparan soluciones experimentales con diferentes teorías elasto-plásticas modernas aún debatidas en la actualidad. Posteriormente, se repite el estudio completo de post-pandeo para placas largas y se realiza la comparativa con placas cuadradas. Se finaliza el trabajo abordando un análisis completo de pandeo y post-pandeo en un panel integral, en el que se incluyen la teoría elasto-plástica y la imperfección inicial. Se presta especial atención a la distinción entre modos de pandeos locales y globales, así como los peligros asociados a este último. Para el análisis de cada caso se contrastan métodos analíticos, el método de los elementos finitos y, en algunos casos, soluciones experimentales y referencias externas. El cálculo analítico se aborda con ayuda del software comercial Mathematica, el numérico con Abaqus y el post-procesado de gráficas con Illustrator., [EN] The study of buckling and post-buckling of rectangular plates and panels, specific of the semi-monocoque structure, is discussed. The possibility of an initial imperfection that matches with the buckling mode of the structure and the elasto-plastic behaviour of the material is included. Firstly, the buckling and post-buckling of an elastic and imperfect plate is analyzed under different boundary conditions. Then, the possibility of elasto-plastic behaviour for both buckling or post-buckling is studied, raising two different problems. Different controversial modern elasto-plastic theories are also compared with experimental solutions. Subsequently, the full post-buckling study is repeated for long plates and compared with the results of square plates. The work is concluded addressing a complete analysis of buckling and post-buckling for an integral panel, including both the elasto-plastic theory and the initial imperfection. Particular attention is paid to the distinction between local and global buckling modes, as well as to the risks associated with the last one. In every study, analytical methods, the finite element method and, in some cases, experimental solutions are contrasted. The analytical calculation is approached with the support of the commercial software Mathematica, the numerical one with Abaqus and the post-processing of plots with Illustrator.

When reinforced concrete (RC) flat plate systems are used as gravity force resisting systems in regions of high seismic activity, they are required to accommodate the seismically induced drifts without jeopardizing their gravity load capacity. The elastic nature of fibre-reinforced polymer (FRP) reinforcement raises concerns about the seismic response of FRP-RC flat plate systems. The present study provides the first attempt to tackle this area. A pioneer research program was conducted to investigate the feasibility of using FRP reinforcement in slab-column edge connections subjected to simulated seismic loads. The program consisted of three phases: experimental, analytical, and numerical. The experimental phase involved the construction and testing of seven full-scale glass FRP (GFRP)-RC edge connections under simultaneous gravity and reversed-cyclic lateral loads. The test parameters were the flexural reinforcement type (steel and GFRP) and ratio (0.7 and 1.4%), the gravity shear ratio (0.4, 0.5, and 0.6), and the GFRP shear reinforcement type (shear studs and corrugated bars). In the analytical phase, models predicting the punching capacity of FRP-RC connections from literature were reviewed. Besides the connections tested in the experimental phase, a database comprising 68 interior and 19 edge specimens subjected to gravity loads was compiled and used to assess the models. A universal model capable of predicting the capacity of interior and edge connections subjected to gravity or cyclic loads was proposed. The numerical phase incorporated the construction and validation of a finite element model (FEM) simulating the seismic behaviour of FRP-RC edge connections. This FEM was used to conduct a parametric study investigating the influence of gravity shear ratio, column size, slab thickness, and flexural reinforcement type and ratio on the seismic response of edge connections. The results showed that GFRP reinforcement can be used in edge connections subjected to s

When reinforced concrete (RC) flat plate systems are used as gravity force resisting systems in regions of high seismic activity, they are required to accommodate the seismically induced drifts without jeopardizing their gravity load capacity. The elastic nature of fibre-reinforced polymer (FRP) reinforcement raises concerns about the seismic response of FRP-RC flat plate systems. The present study provides the first attempt to tackle this area. A pioneer research program was conducted to investigate the feasibility of using FRP reinforcement in slab-column edge connections subjected to simulated seismic loads. The program consisted of three phases: experimental, analytical, and numerical. The experimental phase involved the construction and testing of seven full-scale glass FRP (GFRP)-RC edge connections under simultaneous gravity and reversed-cyclic lateral loads. The test parameters were the flexural reinforcement type (steel and GFRP) and ratio (0.7 and 1.4%), the gravity shear ratio (0.4, 0.5, and 0.6), and the GFRP shear reinforcement type (shear studs and corrugated bars). In the analytical phase, models predicting the punching capacity of FRP-RC connections from literature were reviewed. Besides the connections tested in the experimental phase, a database comprising 68 interior and 19 edge specimens subjected to gravity loads was compiled and used to assess the models. A universal model capable of predicting the capacity of interior and edge connections subjected to gravity or cyclic loads was proposed. The numerical phase incorporated the construction and validation of a finite element model (FEM) simulating the seismic behaviour of FRP-RC edge connections. This FEM was used to conduct a parametric study investigating the influence of gravity shear ratio, column size, slab thickness, and flexural reinforcement type and ratio on the seismic response of edge connections. The results showed that GFRP reinforcement can be used in edge connections subjected to s

Rowing is a competitive sport where victory is determined by fine margins. In the past, the focus has been on optimizing the shell. Due to the increasing regulations placed on the shell design, the scope for manoeuvring in this area is greatly limited. This increases the necessity to focus on the less explored option of propulsion in rowing. The propulsion is caused by the momentum transfer from the rowers to the water with the help of oar blades. The design of these oar blades has also been extensively studied. However, knowledge on the effect of the air-water interface on the drag force on the oar blades is still lacking. Therefore, visualizing the flow around the oar blades will lead to better understanding of the flow structures, which would help in optimizing the drag force acting on the oar blades. In the present study, a simplified scenario of a rectangular flat plate moving normally to its plane along a straight line and parallel to the free surface has been studied using hydrogen bubble visualization and Particle Image Velocimetry (PIV). Using a 4-axes industrial robot and a force/torque transducer, the effect of the air-water interface on the drag force on the plate has been studied at a Reynolds number, based on the longest edge of the plate, of 6×104. The analysis of the drag force profiles at different plate depths led to the identification of a high drag case, which occurred at a plate depth h of 20 mm. The hydrogen bubble visualization indicated that in this specific case, the high drag was related to the formation of a compact wake behind the plate. Hydrogen bubble visualizations were also performed at two other plate depths, h = 0 and h = 100 mm, to determine the effect of the air-water interface on the flow structures and ultimately on the drag force acting on the plate. The visualization of the deep water case (h = 100 mm) captured the formation of a vortex ring, which was found to have uni, Mechanical Engineering

Rowing is a competitive sport where victory is determined by fine margins. In the past, the focus has been on optimizing the shell. Due to the increasing regulations placed on the shell design, the scope for manoeuvring in this area is greatly limited. This increases the necessity to focus on the less explored option of propulsion in rowing. The propulsion is caused by the momentum transfer from the rowers to the water with the help of oar blades. The design of these oar blades has also been extensively studied. However, knowledge on the effect of the air-water interface on the drag force on the oar blades is still lacking. Therefore, visualizing the flow around the oar blades will lead to better understanding of the flow structures, which would help in optimizing the drag force acting on the oar blades. In the present study, a simplified scenario of a rectangular flat plate moving normally to its plane along a straight line and parallel to the free surface has been studied using hydrogen bubble visualization and Particle Image Velocimetry (PIV). Using a 4-axes industrial robot and a force/torque transducer, the effect of the air-water interface on the drag force on the plate has been studied at a Reynolds number, based on the longest edge of the plate, of 6×104. The analysis of the drag force profiles at different plate depths led to the identification of a high drag case, which occurred at a plate depth h of 20 mm. The hydrogen bubble visualization indicated that in this specific case, the high drag was related to the formation of a compact wake behind the plate. Hydrogen bubble visualizations were also performed at two other plate depths, h = 0 and h = 100 mm, to determine the effect of the air-water interface on the flow structures and ultimately on the drag force acting on the plate. The visualization of the deep water case (h = 100 mm) captured the formation of a vortex ring, which was found to have uni, Mechanical Engineering

This work deals with punching shear behaviour of flat plates reinforced with glass fibre-reinforced polymers (GFRP) reinforcing bars. Six full-scale reinforced concrete (RC) slab-column interior connections were constructed and tested to failure. Two variables were investigated; the flexural reinforcement ratio when high strength concrete (HSC) is used and the type of GFRP shear reinforcement (headed studs and corrugated bars) when normal strength concrete (NSC) is used. All specimens were tested under concentric shear force and unbalanced bending moment with a constant moment-to-shear ratio. Increasing the reinforcement ratio increased punching capacity and post-cracking stiffness for HSC connections. Both types of shear reinforcement increased the punching capacity and deflection of NSC connections. Test results were compared with the predictions of the available fibre-reinforced polymer (FRP) design provisions in North American codes.

[EN] Advanced injection strategies for internal combustion engines have been extensively studied although there still exists a significant fundamental knowledge gap on the mechanism for high-pressure spray interaction with the piston surface and chamber wall in the internal combustion engine. The current study focuses on providing qualitative and quantitative information on spray-wall impingement and its characteristics by expanding the range of operating parameters under engine-like conditions. Parameters considered in the experiment are ambient gas and fuel injection conditions. The test included the non-vaporizing spray at the different ambient density (14.8, 22.8 and 30 kg/m3 ) and injection pressure (1200, 1500 and 1800 bar) with the isothermal condition (ambient, and plate temperatures of 423 K). The test was conducted in the constant-volume vessel with the 60-degree impinging spray angle relative to the plate. The free spray and impinged spray properties were qualitatively analysed based on Mie and schlieren images. The results showed that the lower ambient density and higher injection pressure tended to result in relatively higher impinged spray height. The expanding shape of the impinged spray on the wall showed the oval shape.

[EN] Advanced injection strategies for internal combustion engines have been extensively studied although there still exists a significant fundamental knowledge gap on the mechanism for high-pressure spray interaction with the piston surface and chamber wall in the internal combustion engine. The current study focuses on providing qualitative and quantitative information on spray-wall impingement and its characteristics by expanding the range of operating parameters under engine-like conditions. Parameters considered in the experiment are ambient gas and fuel injection conditions. The test included the non-vaporizing spray at the different ambient density (14.8, 22.8 and 30 kg/m3 ) and injection pressure (1200, 1500 and 1800 bar) with the isothermal condition (ambient, and plate temperatures of 423 K). The test was conducted in the constant-volume vessel with the 60-degree impinging spray angle relative to the plate. The free spray and impinged spray properties were qualitatively analysed based on Mie and schlieren images. The results showed that the lower ambient density and higher injection pressure tended to result in relatively higher impinged spray height. The expanding shape of the impinged spray on the wall showed the oval shape.

[EN] Advanced injection strategies for internal combustion engines have been extensively studied although there still exists a significant fundamental knowledge gap on the mechanism for high-pressure spray interaction with the piston surface and chamber wall in the internal combustion engine. The current study focuses on providing qualitative and quantitative information on spray-wall impingement and its characteristics by expanding the range of operating parameters under engine-like conditions. Parameters considered in the experiment are ambient gas and fuel injection conditions. The test included the non-vaporizing spray at the different ambient density (14.8, 22.8 and 30 kg/m3 ) and injection pressure (1200, 1500 and 1800 bar) with the isothermal condition (ambient, and plate temperatures of 423 K). The test was conducted in the constant-volume vessel with the 60-degree impinging spray angle relative to the plate. The free spray and impinged spray properties were qualitatively analysed based on Mie and schlieren images. The results showed that the lower ambient density and higher injection pressure tended to result in relatively higher impinged spray height. The expanding shape of the impinged spray on the wall showed the oval shape.

[EN] Advanced injection strategies for internal combustion engines have been extensively studied although there still exists a significant fundamental knowledge gap on the mechanism for high-pressure spray interaction with the piston surface and chamber wall in the internal combustion engine. The current study focuses on providing qualitative and quantitative information on spray-wall impingement and its characteristics by expanding the range of operating parameters under engine-like conditions. Parameters considered in the experiment are ambient gas and fuel injection conditions. The test included the non-vaporizing spray at the different ambient density (14.8, 22.8 and 30 kg/m3 ) and injection pressure (1200, 1500 and 1800 bar) with the isothermal condition (ambient, and plate temperatures of 423 K). The test was conducted in the constant-volume vessel with the 60-degree impinging spray angle relative to the plate. The free spray and impinged spray properties were qualitatively analysed based on Mie and schlieren images. The results showed that the lower ambient density and higher injection pressure tended to result in relatively higher impinged spray height. The expanding shape of the impinged spray on the wall showed the oval shape.

[EN] Advanced injection strategies for internal combustion engines have been extensively studied although there still exists a significant fundamental knowledge gap on the mechanism for high-pressure spray interaction with the piston surface and chamber wall in the internal combustion engine. The current study focuses on providing qualitative and quantitative information on spray-wall impingement and its characteristics by expanding the range of operating parameters under engine-like conditions. Parameters considered in the experiment are ambient gas and fuel injection conditions. The test included the non-vaporizing spray at the different ambient density (14.8, 22.8 and 30 kg/m3 ) and injection pressure (1200, 1500 and 1800 bar) with the isothermal condition (ambient, and plate temperatures of 423 K). The test was conducted in the constant-volume vessel with the 60-degree impinging spray angle relative to the plate. The free spray and impinged spray properties were qualitatively analysed based on Mie and schlieren images. The results showed that the lower ambient density and higher injection pressure tended to result in relatively higher impinged spray height. The expanding shape of the impinged spray on the wall showed the oval shape.

This work deals with punching shear behaviour of flat plates reinforced with glass fibre-reinforced polymers (GFRP) reinforcing bars. Six full-scale reinforced concrete (RC) slab-column interior connections were constructed and tested to failure. Two variables were investigated; the flexural reinforcement ratio when high strength concrete (HSC) is used and the type of GFRP shear reinforcement (headed studs and corrugated bars) when normal strength concrete (NSC) is used. All specimens were tested under concentric shear force and unbalanced bending moment with a constant moment-to-shear ratio. Increasing the reinforcement ratio increased punching capacity and post-cracking stiffness for HSC connections. Both types of shear reinforcement increased the punching capacity and deflection of NSC connections. Test results were compared with the predictions of the available fibre-reinforced polymer (FRP) design provisions in North American codes.

Vortex Generators (VGs) are flow control devices commonly applied in wind turbine blades, among other applications. A significant advance in the design of wind turbine blades would be the integration of vortex generators in the aerofoil optimisation process. Currently, aerofoil optimisation relies on either computational fluid dynamics or viscous-inviscid solvers ( for instance XFOIL, RFOIL.). However, the latter tools lack a formulation for the effect of VGs. The purpose of this thesis is to get a step closer towards aerofoil optimisation process including VGs. A lag dissipation integral boundary-layer formulation is considered. Stereoscopic particle image velocimetry measurement and numerical simulation based on Menter's two-equation k-omega SST turbulence of counter-rotating VG configuration on a flat plate in turbulent flow regime is studied. Vortex Generator Induced Flow, VGIF exhibit quasi-uniform effect after twelve times the boundary layer thickness downstream of the device. An approach to modifying the effective slip velocity parameter to incorporate VGIF is proposed. Recommendations for direct wall shear stress and comprehensive drag measurements for VG induced flow are argued to validate the claim., Aerospace Engineering, Wind Energy

Vortex Generators (VGs) are flow control devices commonly applied in wind turbine blades, among other applications. A significant advance in the design of wind turbine blades would be the integration of vortex generators in the aerofoil optimisation process. Currently, aerofoil optimisation relies on either computational fluid dynamics or viscous-inviscid solvers ( for instance XFOIL, RFOIL.). However, the latter tools lack a formulation for the effect of VGs. The purpose of this thesis is to get a step closer towards aerofoil optimisation process including VGs. A lag dissipation integral boundary-layer formulation is considered. Stereoscopic particle image velocimetry measurement and numerical simulation based on Menter's two-equation k-omega SST turbulence of counter-rotating VG configuration on a flat plate in turbulent flow regime is studied. Vortex Generator Induced Flow, VGIF exhibit quasi-uniform effect after twelve times the boundary layer thickness downstream of the device. An approach to modifying the effective slip velocity parameter to incorporate VGIF is proposed. Recommendations for direct wall shear stress and comprehensive drag measurements for VG induced flow are argued to validate the claim., Aerospace Engineering, Wind Energy

Breakdown process of the Klebanoff mode and origin of turbulence are experimentally investigated in detail. An acoustic excitation using a 2D roughness attached on the wall are used for T-S wave generation. Piezo-ceramic actuators are used to introduce the Klebanoff mode fluctuation. It is found that another shear layer, in which the spike phenomenon takes place and the turbulence starts, exists between the Lambda structures aligned in rows. The spreading of the turbulence along the shear layer induced by the Lambda structures is newly found., JAXA Special Publication, 宇宙航空研究開発機構特別資料

In this work, the measured modulated integral boundary layer (IBL) characteristics of low-profile vortex generators (VGs) are used to validate new developments in a viscousinviscid interaction code which is modified to incorporate the effect of the passive mixing devices. The motivations are laid out and sample validation data is presented within this abstract., Aerodynamics, Wind Energy & Propulsion, Aerospace Engineering

In this work, the measured modulated integral boundary layer (IBL) characteristics of low-profile vortex generators (VGs) are used to validate new developments in a viscousinviscid interaction code which is modified to incorporate the effect of the passive mixing devices. The motivations are laid out and sample validation data is presented within this abstract., Aerodynamics, Wind Energy & Propulsion, Aerospace Engineering

In this thesis direct numerical simulation is used to investigate the possibility to delay the transition from a laminar to a turbulent flow in boundary layer flows. Furthermore, modal analysis techniques are used to identify the coherent structures in wind turbine wake. Among different transition scenarios, the classical transition scenario is considered where the laminar-turbulent transition occursdue to Tollmien-Schlichting (TS) waves. These waves are convectively unstable and when triggered inside the boundary layer, they grow exponentially inamplitude as they are advected downstream of the domain. The aim is to suppressthese waves using flow control strategies based on a row of spatially localised sensors and actuators distributed near the wall inside the boundary layer. To avoid the high dimensionality arising from discretisation of the Navier–Stokes equations, a reduced order model (ROM) based on the Eigensystem Realisation Algorithm(ERA) is obtained and based on that a linear controller is designed. To manip-ulate the flow, a plasma actuator is modelled and implementedas an externalforcing. To account for the restrictions of the plasma actuators, several strategies are proposed and tested within the LQG framework. We studied also the design of a faster controller based on decentralised approach and compared the performance to a more expensive centralised controller. The outcomes revea lsuccessful performance in mitigating the energy of the disturbances inside the boundary layer and suppressing the TS waves. To extract coherent features of the wind turbine wakes, modal decomposition techniques are employed. In this method a large dynamical system is reduced to a fewer number of degrees of freedom. Two decomposition techniques are employed, namely proper orthogonal decomposition and dynamic mode decomposition. In the former, the flow is decomposed into a set of orthogonal structures which are ranked according to their energy contents in a hierarchical manner., QC 20140526

The use of fibre reinforced polymer (FRP) composites as an alternate to steel has proved to be an effective solution to the corrosion problem. However, FRP bars have low axial and transverse stiffness compared to steel bars which results in a lower shear capacity of FRP reinforced concrete (RC) elements compared to steel-RC elements. Flat plate systems are commonly used to take advantages of the absence of beams. They, however, are susceptible to punching shear failure where the column suddenly punches through the slab. An experimental program was conducted to investigate the punching shear behaviour of slab-column edge connections. Nine isolated full-scale slab-column edge connections were constructed and tested to failure. One connection was reinforced with steel flexural reinforcement, six with GFRP flexural reinforcement and two with GFRP flexural and shear reinforcement. The parameters investigated were the flexural reinforcement type and ratio, the moment-to-shear ratio and the shear reinforcement spacing.

In this thesis direct numerical simulation is used to investigate the possibility to delay the transition from a laminar to a turbulent flow in boundary layer flows. Furthermore, modal analysis techniques are used to identify the coherent structures in wind turbine wake. Among different transition scenarios, the classical transition scenario is considered where the laminar-turbulent transition occursdue to Tollmien-Schlichting (TS) waves. These waves are convectively unstable and when triggered inside the boundary layer, they grow exponentially inamplitude as they are advected downstream of the domain. The aim is to suppressthese waves using flow control strategies based on a row of spatially localised sensors and actuators distributed near the wall inside the boundary layer. To avoid the high dimensionality arising from discretisation of the Navier–Stokes equations, a reduced order model (ROM) based on the Eigensystem Realisation Algorithm(ERA) is obtained and based on that a linear controller is designed. To manip-ulate the flow, a plasma actuator is modelled and implementedas an externalforcing. To account for the restrictions of the plasma actuators, several strategies are proposed and tested within the LQG framework. We studied also the design of a faster controller based on decentralised approach and compared the performance to a more expensive centralised controller. The outcomes revea lsuccessful performance in mitigating the energy of the disturbances inside the boundary layer and suppressing the TS waves. To extract coherent features of the wind turbine wakes, modal decomposition techniques are employed. In this method a large dynamical system is reduced to a fewer number of degrees of freedom. Two decomposition techniques are employed, namely proper orthogonal decomposition and dynamic mode decomposition. In the former, the flow is decomposed into a set of orthogonal structures which are ranked according to their energy contents in a hierarchical manner., QC 20140526

The use of fibre reinforced polymer (FRP) composites as an alternate to steel has proved to be an effective solution to the corrosion problem. However, FRP bars have low axial and transverse stiffness compared to steel bars which results in a lower shear capacity of FRP reinforced concrete (RC) elements compared to steel-RC elements. Flat plate systems are commonly used to take advantages of the absence of beams. They, however, are susceptible to punching shear failure where the column suddenly punches through the slab. An experimental program was conducted to investigate the punching shear behaviour of slab-column edge connections. Nine isolated full-scale slab-column edge connections were constructed and tested to failure. One connection was reinforced with steel flexural reinforcement, six with GFRP flexural reinforcement and two with GFRP flexural and shear reinforcement. The parameters investigated were the flexural reinforcement type and ratio, the moment-to-shear ratio and the shear reinforcement spacing.

A study on the generation and development of high-amplitude steady streamwise streaks in a flat-plate boundary layer is presented. High-amplitude streamwise streaks are naturally present in many bypass transition scenarios, where they play a fundamental role in the breakdown to turbulence process. On the other hand, recent experiments and numerical simulations have shown that stable laminar streamwise streaks of alternating low and high speed are also capable of stabilizing the growth of Tollmien-Schlichting waves as well as localized disturbances and to delay transition. The larger the streak amplitude is, for a prescribed spanwise periodicity of the streaks, the stronger is the stabilizing mechanism. Previous experiments have shown that streaks of amplitudes up to 12 % of the free stream velocity can be generated by means of cylindrical roughness elements. Here we explore the possibility of generating streaks of much larger amplitude by using a row of miniature vortex generators (MVGs) similar to those used in the past to delay or even prevent boundary layer separation. In particular, we present a boundary layer experiment where streak amplitudes exceeding 30 % have been produced without having any secondary instability acting on them. Furthermore, the associated drag with the streaky base flow is quantified, and it is demonstrated that the streaks can be reinforced by placing a second array of MVGs downstream of the first one. In this way it is possible to make the control more persistent in the downstream direction. It must be pointed out that the use of MVGs opens also the possibility to set up a control method that acts twofold in the sense that both transition and separation are delayed or even prevented., QC 20120803

The global linear stability of the flat-plate boundary-layer flow to three-dimensional disturbances is studied by means of an optimization technique. We consider both the optimal initial condition leading to the largest growth at finite times and the optimal time-periodic forcing leading to the largest asymptotic response. Both optimization problems are solved using a Lagrange multiplier technique, where the objective function is the kinetic energy of the flow perturbations and the constraints involve the linearized Navier-Stokes equations. The approach proposed here is particularly suited to examine convectively unstable flows, where single global eigenmodes of the system do not capture the downstream growth of the disturbances. In addition, the use of matrix-free methods enables us to extend the present framework to any geometrical configuration. The optimal initial condition for spanwise wavelengths of the order of the boundary-layer thickness are finite-length streamwise vortices exploiting the lift-up mechanism to create streaks. For long spanwise wavelengths, it is the Orr mechanism combined with the amplification of oblique wave packets that is responsible for the disturbance growth. This mechanism is dominant for the long computational domain and thus for the relatively high Reynolds number considered here. Three-dimensional localized optimal initial conditions are also computed and the corresponding wave packets examined. For short optimization times, the optimal disturbances consist of streaky structures propagating and elongating in the downstream direction without significant spreading in the lateral direction. For long optimization times, we find the optimal disturbances with the largest energy amplification. These are wave packets of Tollmien-Schlichting waves with low streamwise propagation speed and faster spreading in the spanwise direction. The pseudo-spectrum of the system for real frequencies is also computed with matrix-free methods. The spatial, QC 20100924. Uppdaterad från submitted till published (20100924).

Modeling arrays of passive vortex generators (VGs) pairs located in the fully turbulent boundary layer of a two-dimensional flat plate, generating streamwise counterrotating vortex structures is investigated. Usually, a sound computational fluid dynamics investigation requires an adequate grid with a corresponding large number of grid points around such VGs in order to obtain an accurate solution. This leads to a time-demanding grid generation which often comes along with lots of challenges during the creation. An effective way to get around this time-consuming process is to introduce a way to model these flow separation devices statistically and, by that, to add their statistical physical effects to the governing equations rather than resolving their geometries in the computational grid. Here, a computational tool for statistical VG modeling is presented that makes it possible to simulate and model passive VGs in wall-bounded flows, whereas the need for a local mesh refinement is no longer required. Previous research results of the presented statistical modeling of passive VGs have shown that it is necessary to improve the original statistical VG model in terms of the vortex stress modeling in order to evaluate results not only qualitatively, but also quantitatively. Computational results for spanwise averaged fully resolved three-dimensional VGs, experimental results, as well as two-dimensional original VG model results are evaluated and compared to two improved statistical VG model approaches that are presented here. It is shown that the improved VG models gives better results than the original VG model in terms of the nearfield vortex stresses that are important for the immediate respons of the boundary layer flow on momentum mixing. The impact of the improved VG models on flow separation control could be proven to be stronger and thus, closer to experiments and fully resolved results., QC 20140829

An experimental and computational study has been undertaken to investigate the interaction between a transverse circular sonic jet and a Mach 6.7 cross flow on a sharp-edged flat plate with particular emphasis on the influence of the oncoming boundary layer state on the flowfield characteristics. This was achieved by generating ‘steady’ wedges of turbulent flow in the otherwise laminar oncoming boundary layer. The first component of this investigation involved an experimental investigation of transitional phenomena on a sharp-edged flat plate in a free-piston shock tunnel. Four test conditions were examined spanning a unit Reynolds number range of 3.16- 7.82×106m-1 and a flow enthalpy range of 2.86-3.20MJ/kg. The onset of boundary layer transition and the characteristics of the dynamic structures within the transitional region for these conditions were consistent with previously reported results. The main investigation examined the response of the jet interaction (JI) flowfield in response to ‘mixed’ laminar/turbulent oncoming flow. The test condition used for this work had a unit Reynolds number of 4.86×106m-1 and a flow enthalpy of 3.02MJ/kg. The interaction was generated by nitrogen gas from a circular 3mm diameter sonic nozzle at total jet-to-freestream pressure ratios of between 237 and 412. The upstream separated region was found to be very sensitive to the upstream boundary layer state with simultaneous regions of aminar-like and turbulent-like separation. The shock structures immediately around the expanding plume were relatively insensitive, although some change in shape was noted. Highly variable localised regions of high heat transfer were observed around the injector. The Computational Fluid Dynamic (CFD) study found a previously unexplained coupling between the upstream and downstream vortex structures. It also demonstrated that the forces and moments generated by the jet could be strongly influenced by both the location and width of the boundary layer

The objective of this thesis was to determine the feasibility of using loop heat pipes to dissipate waste heat from power electronics to the skin of a fighter aircraft and examine the performance characteristics of a titanium-water loop heat pipe under stationary and elevated acceleration fields. In the past, it has been found that the boundary condition at the condenser can be a controlling factor in the overall performance of this type of thermal management scheme. Therefore, the heat transfer removed from the aircraft skin has been determined by modeling the wing as a flat plate at zero incidence as a function of the following parameters: airspeed: 0.8

The dynamics and control of two-dimensional disturbances in the spatially evolving boundary layer oil a flat plate are investigated from an input output viewpoint. A set-up of spatially localized inputs (external disturbances and actuators) and Outputs (objective functions and sensors) is introduced for the control design of convectively unstable flow configurations. From the linearized Navier Stokes equations with the inputs and outputs, controllable, observable and balanced modes are extracted using the snapshot method. A balanced reduced-order model (ROM) is constructed and shown to capture the input output behaviour of the linearized Navier Stokes equations. This model is finally used to design H-2-feedback controller to suppress the growth or two-dimensional perturbations inside the boundary layer., QC 20101103 Submitted 2008

Many flow cases in fluid dynamics face undesirable flow separation due torising static pressure on wall boundaries. This occurs e.g. due to geometry as ina highly curved turbine inlet duct or e.g. on flow control surfaces such as wingtrailing edge flaps within a certain angle of attack range. Here, flow controldevices are often used in order to enhance the flow and delay or even totallyeliminate flow separation. Flow control can e.g. be achieved by using passiveor active vortex generators (VG) that enable momentum mixing in such flows.This thesis focusses on passive VGs, represented by VG vanes that are mountedupright on the surface in wall-bounded flows. They typically have an angle ofincidence to the mean flow and, by that, generate vortex structures that in turnallow for the desired momentum mixing in order to prevent flow separation.A statistical VG model approach, developed by KTH Stockholm and FOI,the Swedish Defence Research Agency, has been evaluated computationally.Such a statistical VG model approach removes the need to build fully resolvedthree-dimensional geometries of VGs in a computational fluid dynamics mesh.Usually, the generation of these fully resolved geometries is rather costly interms of preprocessing and computations. By applying this VG model, thecosts reduce to computations without VG effects included. Nevertheless, theVG model needs to be set up in order to define the modelled VG geometry inan easy and fast preprocessing step. The presented model has shown sensitivityfor parameter variations such as the modelled VG geometry and the VG modellocation in wall-bounded zero pressure gradient and adverse pressure gradientflows on a flat plate, in a diffuser, and on an airfoil with its high-lift systemextracted. It could be proven that the VG model qualitatively describes correcttrends and tendencies for these different applications.

Modeling arrays of passive vortex generators (VGs) pairs, mounted in the fully turbulent boundary layer of a flat plate and generating streamwise counterrotating vortex structures is the object of this investigation. Usually, a sound computational fluid dynamics (CFD) investigation requires an adequate grid with a corresponding large number of grid points around such VGs in order to obtain an accurate solution of this flow case. This, in turn, leads to a time-demanding grid generation which often comes along with lots of practical challenges during the creation. An effective way to get around this time-consuming process is to introduce a way to model these flow separation devices statistically and, by that, to add their statistical physical effects to the governing equations rather than resolving their geometries in the computational grid. KTH, the Royal Institute of Technology Stockholm, and FOI, the Swedish Defence Research Agency, have developed a computational tool for statistical VG modeling that makes it possible to simulate and add the additional statistical effects of passive VGs in wall-bounded flows, whereas the need for a local mesh refinement is no longer required. This approach for the modeling of passive VGs turbulent flow separation devices is presented using a two dimensional Navier-Stokes flow solver. Computational results for fully three dimensional resolved VGs as well as experimental results are evaluated and compared to this statistical VG model approach. It is shown that the VG model approach gives very promising results that compare well to results from CFD and experiments. Nevertheless, the influence of the vortex structures on the flow and on the turbulent stresses decays quicker than it is observed in experiments. Further-more, the statistical VG model is evaluated for asymmetric diffuser flow and compared to experimental data with as well as without VGs. It is shown that the VG model is capable of predicting the influence of the VGs on dec, QC 20140926

Many flow cases in fluid dynamics face undesirable flow separation due torising static pressure on wall boundaries. This occurs e.g. due to geometry as ina highly curved turbine inlet duct or e.g. on flow control surfaces such as wingtrailing edge flaps within a certain angle of attack range. Here, flow controldevices are often used in order to enhance the flow and delay or even totallyeliminate flow separation. Flow control can e.g. be achieved by using passiveor active vortex generators (VG) that enable momentum mixing in such flows.This thesis focusses on passive VGs, represented by VG vanes that are mountedupright on the surface in wall-bounded flows. They typically have an angle ofincidence to the mean flow and, by that, generate vortex structures that in turnallow for the desired momentum mixing in order to prevent flow separation.A statistical VG model approach, developed by KTH Stockholm and FOI,the Swedish Defence Research Agency, has been evaluated computationally.Such a statistical VG model approach removes the need to build fully resolvedthree-dimensional geometries of VGs in a computational fluid dynamics mesh.Usually, the generation of these fully resolved geometries is rather costly interms of preprocessing and computations. By applying this VG model, thecosts reduce to computations without VG effects included. Nevertheless, theVG model needs to be set up in order to define the modelled VG geometry inan easy and fast preprocessing step. The presented model has shown sensitivityfor parameter variations such as the modelled VG geometry and the VG modellocation in wall-bounded zero pressure gradient and adverse pressure gradientflows on a flat plate, in a diffuser, and on an airfoil with its high-lift systemextracted. It could be proven that the VG model qualitatively describes correcttrends and tendencies for these different applications.

Many flow cases in fluid dynamics face undesirable flow separation due torising static pressure on wall boundaries. This occurs e.g. due to geometry as ina highly curved turbine inlet duct or e.g. on flow control surfaces such as wingtrailing edge flaps within a certain angle of attack range. Here, flow controldevices are often used in order to enhance the flow and delay or even totallyeliminate flow separation. Flow control can e.g. be achieved by using passiveor active vortex generators (VG) that enable momentum mixing in such flows.This thesis focusses on passive VGs, represented by VG vanes that are mountedupright on the surface in wall-bounded flows. They typically have an angle ofincidence to the mean flow and, by that, generate vortex structures that in turnallow for the desired momentum mixing in order to prevent flow separation.A statistical VG model approach, developed by KTH Stockholm and FOI,the Swedish Defence Research Agency, has been evaluated computationally.Such a statistical VG model approach removes the need to build fully resolvedthree-dimensional geometries of VGs in a computational fluid dynamics mesh.Usually, the generation of these fully resolved geometries is rather costly interms of preprocessing and computations. By applying this VG model, thecosts reduce to computations without VG effects included. Nevertheless, theVG model needs to be set up in order to define the modelled VG geometry inan easy and fast preprocessing step. The presented model has shown sensitivityfor parameter variations such as the modelled VG geometry and the VG modellocation in wall-bounded zero pressure gradient and adverse pressure gradientflows on a flat plate, in a diffuser, and on an airfoil with its high-lift systemextracted. It could be proven that the VG model qualitatively describes correcttrends and tendencies for these different applications.

Many flow cases in fluid dynamics face undesirable flow separation due torising static pressure on wall boundaries. This occurs e.g. due to geometry as ina highly curved turbine inlet duct or e.g. on flow control surfaces such as wingtrailing edge flaps within a certain angle of attack range. Here, flow controldevices are often used in order to enhance the flow and delay or even totallyeliminate flow separation. Flow control can e.g. be achieved by using passiveor active vortex generators (VG) that enable momentum mixing in such flows.This thesis focusses on passive VGs, represented by VG vanes that are mountedupright on the surface in wall-bounded flows. They typically have an angle ofincidence to the mean flow and, by that, generate vortex structures that in turnallow for the desired momentum mixing in order to prevent flow separation.A statistical VG model approach, developed by KTH Stockholm and FOI,the Swedish Defence Research Agency, has been evaluated computationally.Such a statistical VG model approach removes the need to build fully resolvedthree-dimensional geometries of VGs in a computational fluid dynamics mesh.Usually, the generation of these fully resolved geometries is rather costly interms of preprocessing and computations. By applying this VG model, thecosts reduce to computations without VG effects included. Nevertheless, theVG model needs to be set up in order to define the modelled VG geometry inan easy and fast preprocessing step. The presented model has shown sensitivityfor parameter variations such as the modelled VG geometry and the VG modellocation in wall-bounded zero pressure gradient and adverse pressure gradientflows on a flat plate, in a diffuser, and on an airfoil with its high-lift systemextracted. It could be proven that the VG model qualitatively describes correcttrends and tendencies for these different applications.

Many flow cases in fluid dynamics face undesirable flow separation due torising static pressure on wall boundaries. This occurs e.g. due to geometry as ina highly curved turbine inlet duct or e.g. on flow control surfaces such as wingtrailing edge flaps within a certain angle of attack range. Here, flow controldevices are often used in order to enhance the flow and delay or even totallyeliminate flow separation. Flow control can e.g. be achieved by using passiveor active vortex generators (VG) that enable momentum mixing in such flows.This thesis focusses on passive VGs, represented by VG vanes that are mountedupright on the surface in wall-bounded flows. They typically have an angle ofincidence to the mean flow and, by that, generate vortex structures that in turnallow for the desired momentum mixing in order to prevent flow separation.A statistical VG model approach, developed by KTH Stockholm and FOI,the Swedish Defence Research Agency, has been evaluated computationally.Such a statistical VG model approach removes the need to build fully resolvedthree-dimensional geometries of VGs in a computational fluid dynamics mesh.Usually, the generation of these fully resolved geometries is rather costly interms of preprocessing and computations. By applying this VG model, thecosts reduce to computations without VG effects included. Nevertheless, theVG model needs to be set up in order to define the modelled VG geometry inan easy and fast preprocessing step. The presented model has shown sensitivityfor parameter variations such as the modelled VG geometry and the VG modellocation in wall-bounded zero pressure gradient and adverse pressure gradientflows on a flat plate, in a diffuser, and on an airfoil with its high-lift systemextracted. It could be proven that the VG model qualitatively describes correcttrends and tendencies for these different applications.

The nonlinear transition regime of supersonic boundary layers at low to moderate supersonic Mach numbers (Mach 2-3:5) under wind-tunnel conditions is studied using linear stability theory (LST) and direct numerical simulations (DNS). Two main flow configurations are chosen, a flat-plate boundary layer and a cone boundary layer. Previous investigations of the early nonlinear transition regime have mainly focused on two nonlinear mechanisms, the so-called "oblique breakdown" mechanism and "asymmetric subharmonic resonance". The first mechanism has only been investigated numerically while the second mechanism was first observed in experiments. This dissertation discusses three open questions related to both mechanisms: (i) Can oblique breakdown be identified in old wind-tunnel experiments published in the literature, (ii) what is the most dominant breakdown mechanism for a supersonic boundary layer, oblique breakdown or asymmetric subharmonic resonance, and (iii) does oblique breakdown lead to a fully developed turbulent boundary layer? By adopting the flow conditions and the disturbance generation of a specific experiment from the literature, in which asymmetric subharmonic resonance in a wave train was studied, it was possible to show that oblique breakdown might also have been present in the experiment, although oblique breakdown was not reported by the experimentalists. Hence, this experiment might provide the first experimental evidence of oblique breakdown for a supersonic boundary layer. The second question was addressed by performing DNS of a wave packet. A wave packet is typically used as a model of a broadband disturbance environment. If a nonlinear mechanism is dominant, it should leave strong imprints in the disturbance spectrum of the wave packet. In the DNS of the wave packet, oblique breakdown was visible in the disturbance spectrum while subharmonic resonance played only a minor role. To study the last question, a set of DNS of the entire transition pat

A numerical investigation has been performed as to the feasibility of using spherical indentations in a flat plate for enhancing heat transfer in the laminar regime.An attempt to validate the calculation procedure resulted in a significant difference with previously published results, in which the inlet boundary condition was stated to be the Polhausen distribution. An investigation of the disparity lead to a study of the effects of various boundary conditions on the development of laminar boundary layers on an infinitesimally thin flat plate. In two-dimensions, regions appear in which velocities are greater than the free stream velocity (overshoot), unless the Blasius distribution is used to predict the inlet velocity in both directions. Surprisingly, although regions of overshoot occur when areas upstream and downstream of the plate are included in calculating the flow near the plate, the velocity distribution within the boundary layer is well represented by the Blasius profile for most of the plate. Outside the boundary layer the velocity distribution depends on the position and the length of the plate.Calculations in three dimensions using inlet boundary conditions developed from the two-dimensional study indicate that a single dimple does not enhance heat transfer.

The abdominal KUB (Kidneys, Ureters, and Bladder, also sometimes referred to as "Flat Plate") demonstrates a smooth, large, calcific opacity in the left lower quadrant (see figure 1). An enteric tube is also noted with its tip in stomach; surgical staples are noted peripherally to skull cap. No other abnormalities are present on the KUB. The axial CT of the abdomen localizes the skull cap to the anterior abdominal wall subcutaneous tissue (see figure 2). CT also shows 10 x 6 x 1.5 cm non-enhancing homogeneous low attenuating fluid collection posterior to the skull cap. For providers that have not heard of banking the skull cap in the abdomen, this type of finding can be perplexing. This procedure became common in recent military combat operations; however, the trend may change due to unique infection potential in other continents., Published in Military Medicine Radiology Corner, 2006.

[Formulae and special characters can only be approximated here. Please see the pdf version of the Abstract for an accurate reproduction.] Since the damping functions employed by most of the low-Reynolds-number models are related to the non-dimensional distance y+[ special character – near-wall non-dimensional distance in y direction], which is based on local wall shear stress, these models become invalid for separated flows, because the wall shear stress is zero at the reattachment point. In addition, the pressure-velocity correlation term is neglected in most of these models, although this term is shown in this thesis to be important in the near-wall region for simple flows and large pressure gradient flows. In this thesis, two main efforts are made to improve the k – [special character - dissipation rate] model. First, based on Myong and Kasagi’s (1990) low-Reynolds-number model (hereafter referred to as MK model), a more general damping function [special character - turbulent viscosity damping function in LRN turbulent model] is postulated which only depends on the Reynolds numbers [formula – near-wall turbulence Reynolds number]. Second, a form for the pressure-velocity correlation term is postulated based on the Poisson equation for pressure fluctuations.This modified model predicts the turbulent flow over a flat plate very well. It is found that the inclusion of the pressure-velocity correlation term leads to significant improvement of the prediction of near-wall turbulence kinetic energy. When the model is applied to turbulent flow over a backward-facing step, it produces better predictions than the traditional k – [special character - dissipation rate] model, FLUENT’s two-layer model and the MK model. Again, the pressure-velocity correlation term improves the turbulence kinetic energy prediction in the separated region over that of other models investigated here.The studies of numerical methods concerning computational domain size and grid spacing reveal tha

The effects of coolant-to-mainstream density ratio (D.R.) and mass flux (blowing) ratio (Mb) on flat plate heat transfer were investigated in a shock tube. The round-nosed plate has a single row of holes inclined 35 deg downstream with two-diameter lateral spacing and hole length of three diameters. Mixing helium with air in the shock tube produced a D.R. range of 1.2 to 2.1. The parameters studied approach those of film-cooled turbine components. For an Mb range of 0.4 to 3 and 10% mainstream turbulence, heat flux was measured with thin-film heat flux gauges located 4 to 30 hole diameters downstream of the cooling holes using an electrical analog. Various flow conditions were produced over the flat plate. The 'steady' portion of turbulent flow heat transfer data compared within 20% of the theoretical flat plate solution. Ratios of heat flux with cooling to heat flux without cooling versus M. and D.R. were determined. Analysis of the results showed film cooling heat transfer is correlated by coolant-to-mainstream velocity ratio. Effectiveness of cooling was reduced by the high mainstream turbulence.

An analytic investigation is made of the aerodynamic coefficients of various bodies located in a free-molecule-flow field These bodies are the following: flat plate, cylinder, sphere, and cone. Calculations are performed using values of molecular speed ratio (ratio of stream speed to most probable molecular speed) ranging from 0 to 20. The aerodynamic coefficients of a cone are calculated for angles of attack ranging from 0 degrees to 60 degrees. The semivertex angles of the cones investigated vary from 2.5 degrees to 30 degrees.

A problem encountered in the flow of atmospheric winds over the earth surface is that of cold air over a warm boundary. The study is a part of a long range program directed toward understanding such flows. An exploratory set of measurements in the boundary layer over a heated, smooth, flat plate are reported. The boundary wall was maintained at approximately 85F and the free stream air temperature was approximately 40F. The free stream velocity was 20 feet per second. Measurements of the mean temperature, density and velocity distributions are given in both tabular and graphic data. Data on the fluctuating temperature, longitudinal velocity and velocitytemperature correlation are also presented. The data were taken as an exploratory study to first determine the magnitude of the mean and turbulent terms in the boundary layer. Secondly, the present experiment indicated the problems to be overcome in measuring the thermal boundary layer. The report is intended as a data report on the measurements. (Author)

The use of liquid crystal thermography is discussed as a technique for visualizing the disturbance field created on a surface from which a jet is injected into a crossing flow. The study is part of an ongoing investigation of the perfor­mance of jet steering systems such as ship bow thrusters. An experimental apparatus was designed and built to provide a heated surface coated with liquid crystals. For a range of jet-to-crossflow velocity ratios, the temperature field on the flat plate was visually represented. The technique allowed continual visual observation of the cooling effects of the jet as jet velocity increased. It also showed the cooling pattern similarities that exist at the same velocity ratios for different crossflow velocities. Strong visual similarities were shown to exist between the temperature distribution on the flat plate as depicted by the liquid crystals and the theoret­ical surface velocity field around a jet modeled as a symmet­rical foil near the point of injection and a vortex sheet in the plumes., http://archive.org/details/liquidcrystalmap1094520584, Lieutenant, United States Navy, Approved for public release; distribution is unlimited.

This study was an attempt to map the density field in a fin-flat plate junction three-dimensionally using holographic interferometry. This investigation has extended the density studies by Matulka [12, 13] and Jagota [3, 4] to include, for the first time, interferometric fringe information obtained through a transparent model in supersonic flow. The fringe information was then inverted by a FORTRAN computer program to produce a plot of the density field around the model. The feasibility of the method was demonstrated. The factors which are thought to have limited the success of the experiment include vibration of the model, fluctuations of the tunnel flow and the fact that the model was somewhat too large in relation to the size of the wind tunnel test section. Schlieren photography was used to look through and around the model and to verify that the same flow was established as was reported by Thomas [23, 24] and Winkelmam [26, 27] . The data reduction of holographic inter ferograms was, for the first time, accomplished using photographic enlargements. This technique is considered to be much easier and more accurate than the one used in the previous investigations. However, the data reduction step, because of the time and labor involved, is considered to be the rate controlling process of the whole analysis., http://archive.org/details/holographicinter1094516171, Lieutenant, United States Navy, Approved for public release; distribution is unlimited.