Detailed experimental investigation has been conducted to provide a detailed insight into the heat transfer and aerodynamic behavior of a separation zone that is generated as a result of boundary layer development along the suction surface of a highly loaded low pressure turbine (LPT) blade. The research experimentally investigates the individual and combined effects of periodic unsteady wake flows and freestream turbulence intensity (Tu) on heat transfer and aerodynamic behavior of the separation zone. Heat transfer experiments were carried out at Reynolds number of 110,000, 150,000, and 250,00 based on the suction surface length and the cascade exit velocity. Aerodynamic experiments were performed at Re = 110,000 and 150,000. For the above Re-numbers, the experimental matrix includes Tus of 1.9%, 3.0%, 8.0%,13.0% and three different unsteady wake frequencies with the steady inlet flow as the reference configuration. Detailed heat transfer and boundary layer measurements are performed with particular attention paid to the heat transfer and aerodynamic behavior of the separation zone at different Tus at steady and periodic unsteady flow conditions. The objectives of the research are (a) to quantify the effect of Tu on the aero-thermal behavior of the separation bubble at steady inlet flow condition, (b) to investigate the combined effects of Tu and the unsteady wake flow on the aero-thermal behavior of the separation bubble, and (c) to provide a complete set of heat transfer and aerodynamic data for numerical simulation that incorporates Navier-Stokes and energy equations. The analysis of the experimental data reveals details of boundary layer separation dynamics which is essential for understanding the physics of the separation phenomenon under periodic unsteady wake flow and different Reynolds number and Tu. To provide a complete picture of the transition process and separation dynamics, extensive intermittency analysis was conducted. Ensemble averaged maximum and minimum intermittency functions were determined leading to the relative intermittency function. In addition, the detailed intermittency analysis reveals that the relative intermittency factor follows a Gaussian distribution confirming the universal character of the relative intermittency function.

O objetivo deste estudo foi comparar à resistência à fratura de três técnicas de colagem usadas para restaurar dentes fraturados hígidos e com tratamento endodôntico associado ou não a colocação de pino de fibra de vidro. Noventa incisivos humanos foram aleatoriamente divididos em três grupos de 30 dentes cada. No grupo A, os dentes não foram tratados endodonticamente, enquanto os dentes dos grupos B e C foram submetidos ao tratamento endodôntico, seguido de restauração da câmara pulpar com resina composta. Todos os dentes foram fraturados por uma carga axial aplicada na superfície vestibular para obter fragmentos dentais. Os dentes de cada grupo foram novamente subdivididos em três subgrupos: colagem simples [CS], chanfro vestibular [CV] e chanfro circunferencial [CC]). Antes da colagem dos fragmentos, pinos de fibra de vidro foram colocados nos dentes do grupo C. Todos os fragmentos dos dentes (grupos A, B e C) foram colados utilizando um cimento de dupla ativação (Duo- Link, Bisco Inc). No grupo CS, nenhum preparo adicional foi realizado após colagem, porém no restante dos dentes realizou-se uma canaleta vestibular (grupo CV) ou uma canaleta circunferencial ao redor da linha de colagem (CC) com aproximadamente 1,0 mm de profundidade. As canaletas foram restauradas com resina composta microhíbrida. Por fim, os espécimes foram submetidos a mesma carga axial no mesmo ponto pré-determinado. A resistência à fratura após o procedimento restaurador foi expressa em porcentagem de resistência do dente íntegro. Os dados foram submetidos a uma análise de variância de dois fatores (Grupo vs. Técnica de colagem) e teste de Tukey (?=0,05). Somente o fator principal Técnica de colagem foi estatisticamente significante (p<0,05). Nenhuma das técnicas de colagem empregadas conseguiu restabelecer a resistência à fratura do dente hígido. A confecção de uma canaleta vestibular e circunferencial proporcionaram uma recuperação de resistência similar (p>0,05) entre si e superior ao alcançado pela técnica de colagem simples (p<0,05). Concluiu-se que o uso de pino de fibra de vidro não é essencial para reforço da estrutura dental antes da colagem de fragmentos de dentes tratados endodonticamente. As técnicas de chanfro vestibular e chanfro circunferencial devem ser preferidas ao se realizar a colagem de fragmentos devido a maior recuperação da resistência do dente hígido em relação a técnica de colagem simples. / The aim of this study was to compare the fracture strength of three techniques used to reattach tooth fragments in sound and endodontically-treated fractured teeth either associated or not with fiber post placement. Ninety human lower incisors were randomly divided into three groups of 30 teeth each. In group A teeth were not subjected to endodontic treatment; while teeth from groups B and C were endodontically treated and the pulp chamber restored with a composite resin. All teeth were fractured by an axial load applied to the buccal area in order to obtain tooth fragments. Teeth from each group were divided again into three subgroups: bonded only [BO], buccal chamfer [BC] and circumferential chamfer [CC]). Before the re-attachment procedures, fiber posts were placed in teeth from group C. All teeth (groups A, B and C) had the fragments re-attached using a dual cure resin luting cement (Duo-Link, Bisco Inc., Itasca, IL). In the BO group, no additional preparation was made. Teeth from groups BC and CC groups had a 1.0 mm-depth chamfer placed in the fracture line either on buccal surface [group BC] or along the buccal and lingual surfaces [group CC]. Increments of microhybid composite resin were used in subgroups BC and CC to restore the chamfer. The specimens were loaded until fracture in the same pre-determined area. The force required to detach each fragment was recorded and a percentage of fracture strength recovery calculated for each tooth. The data was subjected to a two-way analysis of variance (Group vs. Re-attachment technique) and Tukey\'s test (?=0.05). Only the main factor Re-attachment technique was statistically significant (p<0.05). None of the techniques used for teeth re-attachment restored the fracture strength of the intact teeth. The placement of buccal and circumferential chamfer yielded statistically similar (p>0.05) fracture strength recovery, which was superior to the bonded only technique (p<0.05). The use of fiber post is not mandatory for the reinforcement of the tooth structure before reattachment of fragments in endodontically-treated teeth. When bonding a fractured fragment, the buccal or circumferential re-attachment techniques should be preferable in comparison with the simple re-attachment without any additional preparation.

O objetivo deste estudo foi comparar à resistência à fratura de três técnicas de colagem usadas para restaurar dentes fraturados hígidos e com tratamento endodôntico associado ou não a colocação de pino de fibra de vidro. Noventa incisivos humanos foram aleatoriamente divididos em três grupos de 30 dentes cada. No grupo A, os dentes não foram tratados endodonticamente, enquanto os dentes dos grupos B e C foram submetidos ao tratamento endodôntico, seguido de restauração da câmara pulpar com resina composta. Todos os dentes foram fraturados por uma carga axial aplicada na superfície vestibular para obter fragmentos dentais. Os dentes de cada grupo foram novamente subdivididos em três subgrupos: colagem simples [CS], chanfro vestibular [CV] e chanfro circunferencial [CC]). Antes da colagem dos fragmentos, pinos de fibra de vidro foram colocados nos dentes do grupo C. Todos os fragmentos dos dentes (grupos A, B e C) foram colados utilizando um cimento de dupla ativação (Duo- Link, Bisco Inc). No grupo CS, nenhum preparo adicional foi realizado após colagem, porém no restante dos dentes realizou-se uma canaleta vestibular (grupo CV) ou uma canaleta circunferencial ao redor da linha de colagem (CC) com aproximadamente 1,0 mm de profundidade. As canaletas foram restauradas com resina composta microhíbrida. Por fim, os espécimes foram submetidos a mesma carga axial no mesmo ponto pré-determinado. A resistência à fratura após o procedimento restaurador foi expressa em porcentagem de resistência do dente íntegro. Os dados foram submetidos a uma análise de variância de dois fatores (Grupo vs. Técnica de colagem) e teste de Tukey (?=0,05). Somente o fator principal Técnica de colagem foi estatisticamente significante (p<0,05). Nenhuma das técnicas de colagem empregadas conseguiu restabelecer a resistência à fratura do dente hígido. A confecção de uma canaleta vestibular e circunferencial proporcionaram uma recuperação de resistência similar (p>0,05) entre si e superior ao alcançado pela técnica de colagem simples (p<0,05). Concluiu-se que o uso de pino de fibra de vidro não é essencial para reforço da estrutura dental antes da colagem de fragmentos de dentes tratados endodonticamente. As técnicas de chanfro vestibular e chanfro circunferencial devem ser preferidas ao se realizar a colagem de fragmentos devido a maior recuperação da resistência do dente hígido em relação a técnica de colagem simples. / The aim of this study was to compare the fracture strength of three techniques used to reattach tooth fragments in sound and endodontically-treated fractured teeth either associated or not with fiber post placement. Ninety human lower incisors were randomly divided into three groups of 30 teeth each. In group A teeth were not subjected to endodontic treatment; while teeth from groups B and C were endodontically treated and the pulp chamber restored with a composite resin. All teeth were fractured by an axial load applied to the buccal area in order to obtain tooth fragments. Teeth from each group were divided again into three subgroups: bonded only [BO], buccal chamfer [BC] and circumferential chamfer [CC]). Before the re-attachment procedures, fiber posts were placed in teeth from group C. All teeth (groups A, B and C) had the fragments re-attached using a dual cure resin luting cement (Duo-Link, Bisco Inc., Itasca, IL). In the BO group, no additional preparation was made. Teeth from groups BC and CC groups had a 1.0 mm-depth chamfer placed in the fracture line either on buccal surface [group BC] or along the buccal and lingual surfaces [group CC]. Increments of microhybid composite resin were used in subgroups BC and CC to restore the chamfer. The specimens were loaded until fracture in the same pre-determined area. The force required to detach each fragment was recorded and a percentage of fracture strength recovery calculated for each tooth. The data was subjected to a two-way analysis of variance (Group vs. Re-attachment technique) and Tukey\'s test (?=0.05). Only the main factor Re-attachment technique was statistically significant (p<0.05). None of the techniques used for teeth re-attachment restored the fracture strength of the intact teeth. The placement of buccal and circumferential chamfer yielded statistically similar (p>0.05) fracture strength recovery, which was superior to the bonded only technique (p<0.05). The use of fiber post is not mandatory for the reinforcement of the tooth structure before reattachment of fragments in endodontically-treated teeth. When bonding a fractured fragment, the buccal or circumferential re-attachment techniques should be preferable in comparison with the simple re-attachment without any additional preparation.

The separation and reattachment of the suction surface boundary layer in a low pressure turbine is characterized using large-eddy simulation at Re=68,000 based on freestream velocity and suction surface length. A high pass filtered Smagorinsky model is used for modeling the sub-grid scales. The onset of time mean separation is at s=so = 0:61 and reattachment at s=so = 0:81, extending over 20% of the suction surface. The boundary layer is convectively unstable with a maximum reverse flow velocity of about 13% of freestream. The breakdown to turbulence occurs over a very short distance of suction surface which is followed by reattachment. Detailed investigations into the structure and kinematics of the bubble and turbulence statistics are presented. The vortex shed from the bubble, convects downstream and interacts with the trailing edge vortices increasing the turbulence intensity. On the suction side, dominant hairpin structures near the transitional and turbulent flow regime are observed. These hairpin vortices are carried by the freestream even downstream of the trailing edge of the blade with a possibility of reaching the next stage. Longitudinal streaks that evolve from the breakdown of hairpin vortices formed near the leading edge are observed on the pressure surface.

No description available.

A robotically-controlled actuation system has been developed and built to perform active open-loop flow control experiments on transitional and turbulent backward-facing step flows in water. Control of the reattaching shear layer used hydraulic suction-and-blowing actuation emanating from 128 individual ports along the separation edge of the step. Each ports perturbation was periodic in time, but individually controlled to produce either spanwise-invariant (2D) or spanwise-varying (3D) spatial actuation profiles. An image processing system and special aqueous tuft were developed to measure the length of the recirculation bubble. Multiple images of a tuft array were time-averaged to do so. In general, 3D forcing was no more effective in reducing bubble length than 2D forcing. However, greater local spanwise reductions in reattachment length were observed for some cases of spanwise-varying forcing. Backlit dye was used to track the evolution of vorticity in the flow in video and still images.

No description available.

No description available.

No description available.