Experimental aeroacoustic research was conducted on a wind turbine specific airfoil at low Reynolds numbers. The goal of this thesis was to study trailing edge noise generation from the airfoil and investigate correlations between the noise and the flow field. Before experiments were performed the current wind tunnel had to be modified in order to make it more suitable for aeroacoustic tests. Sound absorbing foam was added to the inside of the tunnel to lower the background noise levels and turbulence reduction screens were added which lowered the turbulence. An S822 airfoil was chosen because it is designed for low Reynolds flows attainable in the wind tunnel which are on the order of 104. Smoke wire flow visualization was used to gain insight into the airfoil wake development and oil film flow visualization was used to qualitatively assess the boundary layer development. Laser Doppler anemometry (LDA) was used to measure two components of velocity at high data rates in the airfoil wake. Wake profiles were measured in addition to single point measurements to determine the velocity spectrum. A microphone was mounted inside the test section in order to measure the trailing edge noise. Initial plans included measuring the trailing edge noise with a microphone array capable of quantifying and locating noise sources. Although an array was built and beamforming code was written it was only used in preliminary monopole source tests. Oil film results showed the behaviour of the boundary layer to be consistent with previous low Reynolds number experiments. LDA results revealed sharp peaks in the velocity spectra at 1100 Hz from U0 = 15–24 m/s, and 3100 and 3800 Hz, from U0 = 25–35 m/s, which were inconsistent with vortex shedding results of previous researchers. Also present were a series of broad peaks in the spectra that increase from 1200–1700 Hz in the U0 = 25–35 m/s range. The shedding frequency from the smoke wire flow visualization was calculated to be 1250 Hz at U0 = 26 m/s. These sharp peaks were also present in the acoustic spectrum. It was reasoned that these peaks are due to wind tunnel resonance which is a common occurrence in hard wall wind tunnels. In particular the tone at 1100 Hz is due to a standing wave with a wavelength equal to half the tunnel width. The shedding frequency from the smoke wire flow visualization was calculated to be 1100 Hz at U0 = 20 m/s. These tones exhibited a “ladder-like” relationship with freestream velocity, another aspect indicative of wind tunnel resonance. It was reasoned that the wind tunnel resonance was forcing the shedding frequency of the airfoil in the U0 = 15–24 m/s range, and in the U0 = 25–35 m/s range, the shedding frequency corresponded to the broad peaks in the LDA spectra.

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 150-155).

Electromagnetic acoustic transducers (EMATs) are increasingly used in industries due to their attractive features of being non-contact, cost-effective and the fact that a variety of wave modes can be generated, etc. There are two major EMATs coupling mechanisms: the Lorentz force mechanism for conductive materials and the magnetostriction mechanism for ferromagnetic materials; EMATs operated on Lorentz force mechanism are the focus of this study. This work aims to investigate novel efficient modelling techniques for EMATs, in order to gain further knowledge and understanding of EMATs wave pattern, how design parameters affect its wave pattern and based on above propose and optimise novel sensor structures. In this study, two novel modelling methods were proposed: one is the method combining the analytical method for EM simulation and the finite-difference time-domain (FDTD) method for US simulation for studying the Rayleigh waves' properties on the vertical plane of the material; the other one is the method utilizing a wholly analytical model to explore the directivity of surface waves. Both simulations models have been validated experimentally. The wholly analytical model generates the radiation pattern of surface waves, which lays a solid foundation for the optimum design of such sensors. The beam directivity of surface waves was investigated experimentally, and results showed the length of wires has a significant effect on the beam directivity of Rayleigh waves. A novel configuration of EMATs, variable-length meander-line-coil (VLMLC), was proposed and designed. The beam directivity of surface waves generated by such novel EMATs were analytically investigated. Experiments were conducted to validate such novel EMATs models, and results indicated that such EMATs are capable of supressing side lobes, and therefore resulting in a more concentrated surface waves in the desired direction. Further, another two novel configuration of EMATs, the four-directional meander-line-coil (FDMLC) and the six-directional meander-line-coil (SDMLC), were proposed and designed; results showed these EMATs are capable of generating Rayleigh waves in multiple directions and at the same time suppressing side lobes.

Este trabalho tem por objetivo avaliar a capacidade de detecção e dimensionamento de descontinuidades internas em juntas soldadas dissimilares e cladeadas com a utilização da inspeção por ultrassom através da técnica de Phased Array. Este estudo se justifica pela possibilidade da aplicação desses materiais nas atividades de exploração de petróleo no campo offshore com a utilização de dutos rígidos de aço carbono com revestimento interno de Inconel. As juntas circunferenciais foram soldadas com material austenítico e foram realizados ensaios com juntas sem a realização do amanteigamento do bisel e com corpos de provas que receberam camadas de amanteigamento que tem a finalidade de aumentar a resistência à corrosão-fadiga da junta circunferencial. A tubulação soldada tinha como material de base um aço ferrítico API 5L X-52 com revestimento interno de Inconel 625. As descontinuidades foram inseridas nos passes de raiz fabricadas com o processo de soldagem TIG, nos passes de enchimento através do processo por eletrodos revestidos e na região da raiz através do processo de eletroerosão com a finalidade de simular uma falta de fusão na raiz. Para as inspeções foram adotados as varreduras setorial e linear com duas posições do cabeçote em relação à linha de centro da solda. Estas foram realizadas com o intuito de avaliar a capacidade de detecção e dimensionamento das descontinuidades através da utilização de ondas transversais com freqüência de 5 MHz e assim analisar os resultados encontrados para poder viabilizar a aplicação desta técnica como ferramenta de inspeção nestes equipamentos. Análises metalográficas serviram para realizar o dimensionamento real das descontinuidades e caracterizar a micrografia do metal de base, zona afetada pelo calor e metal de solda para poder correlacioná-los com os resultados encontrados nas inspeções por Phased Array. Assim com os resultados encontrados foi possível demonstrar a possibilidade de aplicação da técnica de Phased Array na inspeção das juntas dissimilares e cladeadas. / This work aims to evaluate the detection capability and sizing of internal discontinuities in dissimilar welded and claded joints with the use of Phased Array ultrasonic inspection technique. This study was performed due to the possibility of the application of those materials in the activities of exploration of petroleum in the offshore field with the use of rigid risers of carbon steel with internal covering of Inconel. The girths joints were welded with material austenitic and testing were accomplished with joints without the realization of the buttering of the bevel and with specimens that received layers of buttering that has the purpose of increasing the resistance to the corrosion-fatigue of the girth joint. The welded piping had as base material a ferritic steel API 5L X-52 with internal overlay of Inconel 625. The discontinuities were inserted in the root pass manufactured with the welding process TIG, in the filler pass through the process by covered electrodes and in the area of the root through the electric discharge machining process with the purpose of simulating a lack of fusion in the root. For the inspections the sectorial and linear sweepings were adopted with two positions of the transducer in relation to the line of center of the weld. This was performed with the intention of evaluating the detection capacity and sizing of discontinuities through the use of shear waves frequently of 5 MHz and like this to analyze the results found to make possible the application of this technique as inspection tool in these equipments. Metallographic analyses were to accomplish the real sizing of the discontinuities and to characterize the micrograph of the base metal, affected area for the heat and weld metal to correlate them with the results found in the inspections by Phased Array. Like this with the found results it was possible to demonstrate the possibility of application of Phased Array technique in the inspection of the dissimilar and claded joints.

A operação segura e eficiente em unidades de produção de petróleo e gás depende do desempenho de seus dispositivos, componentes e estruturas. Dutos rígidos são importantes componentes utilizados na indústria offshore, comumente empregados como flowlines e risers. Durante a vida em serviço destes componentes, eles sofrem tensões axiais cíclicas associadas a sua movimentação, ao processo de extração de petróleo e ao vórtice das marés. O aço inoxidável superduplex surgiu na última década como um material alternativo para ambientes quimicamente agressivos, mas quando catodicamente protegidos contra a corrosão, esses aços são vulneráveis a fragilização por hidrogênio. Este trabalho tem como objetivo, através da técnica de Ensaio Não Destrutivo de ultrassom phased array, monitorar o crescimento de defeitos internos e externos criados intencionalmente próximos à raiz e ao reforço da solda de um tubo de aço superduplex (UNS S32750) de 6´´ submetido a fadiga tração-tração e fragilização induzida por hidrogênio devido à proteção catódica. As inspeções foram realizadas periodicamente com varreduras de 30 a 75° ao longo da circunferência da solda, por um transdutor linear 1-D de 16 elementos e 5MHz acoplado a uma sapata de 36°. Os resultados obtidos foram utilizados para alimentar análises de integridade estrutural, obtenção da curva da/dN x ΔK. / Safe and efficient operation in oil and gas production units depends on the performance of your devices, components and structures. Rigid pipelines are important components in the offshore industry, common used as flowlines and risers. During a life in service of components, they suffer cyclical axial stresses associated with their movement, by the oil extraction process and tidal vortex. Super duplex stainless steel has emerged in the last decade as an alternative material for chemically aggressive environments, but when cathodically protected against corrosion, it is vulnerable to hydrogen embrittlement. This work aims to, through the ultrasonic non-destructive testing by phased array monitor the growth of internal and external defects created intentionally close to the root and reinforcement of the weld of a superduplex steel tube (UNS S32750) with diameter of 6" submitted to tensile-traction fatigue and hydrogen-induced embrittlement due to cathodic protection. The inspections were performed periodically with 30 to 75° scans along the circumference of the weld, by a linear transducer of 1-D, 16-element and 5MHz coupled to a wedge of 36°. The obtained results were used to feed structural integrity analyzes, obtaining the curve of da/dN x ΔK.

Componentes metálicos em operação podem estar sujeitos a diversas condições de operação deletérias. Visando avaliar os riscos de operação para evitar falhas, a análise de integridade estrutural é uma ferramenta amplamente aplicada e requer constante evolução. Por utilizar dados de ensaios não destrutivos, essa ferramenta requer cada vez mais precisão, para aprimorar seus resultados e reduzir ao máximo as falhas de componentes em operação. Por apresentar menor tempo de inspeção e maior probabilidade de detecção, o Phased Array surge como alternativa às técnicas convencionais de ultrassom. Dentre as técnicas de Phased Array, o Total Focusing Method (TFM) apresenta um dos resultados mais promissores, apresentando grande vantagem sobre técnicas convencionais de ultrassom e de Phased Array devido a sua melhor precisão e fácil interpretação dos resultados. Neste trabalho, o TFM foi aplicado em diversos blocos contendo descontinuidades usinadas, as quais simulam diferentes tipos de defeitos. O foco do TFM foi gerar blocos em três dimensões (3D) dos defeitos, facilitando a interpretação dos resultados, além da possibilidade da inserção desses blocos em softwares de análise de integridade estrutural, melhorando a precisão dos resultados. O TFM foi aplicado através do tratamento de dados de um sensor linear de Phased Array, com frequência de 5 MHz e com 64 elementos ativos. Nesse trabalho, foram desenvolvidas e aplicadas novas etapas no algoritmo do TFM para melhorar a precisão dos resultados, como a compensação da perda de energia e o half-skip. As etapas adicionais aplicadas ao algoritmo do TFM geraram bons resultados para entalhe e furos usinados nos blocos de aço carbono. Além dos blocos com defeitos usinados, foi realizada a inspeção de um bloco de aço inoxidável austenítico soldado. Para o bloco soldado, os resultados não foram satisfatórios, não sendo possível detectar defeitos existentes. Após a aplicação do TFM, foi simulado o deslocamento do sensor ao longo da peça, gerando diversas imagens 2D, as quais foram conectadas via isosuperfícies, gerando sólidos 3D dos defeitos presentes em cada bloco. Por fim, esses blocos foram exportados para um software CAD, apresentando excelente correspondência. / Metallic components in operation can be submitted to several harming operation conditions. Aiming to evaluate the operational risks to avoid failure, the structural integrity analysis is a widely applied tool and requires constant evolution. As it uses non-destructive testing data, this tool requires increasingly precision, to enhance its results and reduce the majority of the operating components failures. Because of the shorter inspection time and greater probability of detection, Phased Array is an alternative to conventional ultrasonic techniques. Among the techniques of Phased Array, the Total Focusing Method (TFM) presents one of the most promising results, offering great advantage over conventional ultrasonic and Phased Array techniques due to its better precision and easy interpretation of results. In this work, the TFM was applied to many blocks, which contain machined discontinuities simulating several defects. The objective of applying the TFM was to generate three-dimensional (3D) blocks, turning the interpretation of the results easier and giving the possibility to insert these blocks into a structural integrity analysis software, enhancing the results precision. The TFM algorithm was applied through treatment of data from a 5 MHz linear Phased Array sensor with 64 active elements. In this work, it were developed and applied new steps in the TFM algorithm, as energy loss compensation and half-skip interaction, to improve its precision. The additional steps applied to the TFM algorithm achieved great results for notch and holes machined in carbon steel blocks. In addition to the blocks with machined defects, a welded austenitic stainless steel block was inspected. For the welded block, the results were not satisfactory and it was not possible to detect the present defects. After the application of the TFM, the displacement of the transducer along the block was simulated, generating several 2D images, which were connected via isosurfaces, generating 3D solids corresponding to the defects present in each block. To conclude, these blocks were exported to a CAD software, presenting excellent matching.

Este trabalho tem por objetivo avaliar a capacidade de detecção e dimensionamento de descontinuidades internas em juntas soldadas dissimilares e cladeadas com a utilização da inspeção por ultrassom através da técnica de Phased Array. Este estudo se justifica pela possibilidade da aplicação desses materiais nas atividades de exploração de petróleo no campo offshore com a utilização de dutos rígidos de aço carbono com revestimento interno de Inconel. As juntas circunferenciais foram soldadas com material austenítico e foram realizados ensaios com juntas sem a realização do amanteigamento do bisel e com corpos de provas que receberam camadas de amanteigamento que tem a finalidade de aumentar a resistência à corrosão-fadiga da junta circunferencial. A tubulação soldada tinha como material de base um aço ferrítico API 5L X-52 com revestimento interno de Inconel 625. As descontinuidades foram inseridas nos passes de raiz fabricadas com o processo de soldagem TIG, nos passes de enchimento através do processo por eletrodos revestidos e na região da raiz através do processo de eletroerosão com a finalidade de simular uma falta de fusão na raiz. Para as inspeções foram adotados as varreduras setorial e linear com duas posições do cabeçote em relação à linha de centro da solda. Estas foram realizadas com o intuito de avaliar a capacidade de detecção e dimensionamento das descontinuidades através da utilização de ondas transversais com freqüência de 5 MHz e assim analisar os resultados encontrados para poder viabilizar a aplicação desta técnica como ferramenta de inspeção nestes equipamentos. Análises metalográficas serviram para realizar o dimensionamento real das descontinuidades e caracterizar a micrografia do metal de base, zona afetada pelo calor e metal de solda para poder correlacioná-los com os resultados encontrados nas inspeções por Phased Array. Assim com os resultados encontrados foi possível demonstrar a possibilidade de aplicação da técnica de Phased Array na inspeção das juntas dissimilares e cladeadas. / This work aims to evaluate the detection capability and sizing of internal discontinuities in dissimilar welded and claded joints with the use of Phased Array ultrasonic inspection technique. This study was performed due to the possibility of the application of those materials in the activities of exploration of petroleum in the offshore field with the use of rigid risers of carbon steel with internal covering of Inconel. The girths joints were welded with material austenitic and testing were accomplished with joints without the realization of the buttering of the bevel and with specimens that received layers of buttering that has the purpose of increasing the resistance to the corrosion-fatigue of the girth joint. The welded piping had as base material a ferritic steel API 5L X-52 with internal overlay of Inconel 625. The discontinuities were inserted in the root pass manufactured with the welding process TIG, in the filler pass through the process by covered electrodes and in the area of the root through the electric discharge machining process with the purpose of simulating a lack of fusion in the root. For the inspections the sectorial and linear sweepings were adopted with two positions of the transducer in relation to the line of center of the weld. This was performed with the intention of evaluating the detection capacity and sizing of discontinuities through the use of shear waves frequently of 5 MHz and like this to analyze the results found to make possible the application of this technique as inspection tool in these equipments. Metallographic analyses were to accomplish the real sizing of the discontinuities and to characterize the micrograph of the base metal, affected area for the heat and weld metal to correlate them with the results found in the inspections by Phased Array. Like this with the found results it was possible to demonstrate the possibility of application of Phased Array technique in the inspection of the dissimilar and claded joints.

abstract: The objective of this work is to design a low-profile compact Terahertz (THz) imaging system that can be installed in portable devices, unmanned aerial vehicles (UAVs), or CubeSats. Taking advantage of the rotational motion of these platforms, one can use linear antennas, such as leaky-wave antennas or linear phased arrays, to achieve fast image acquisition using simple RF front-end topologies. The proposed system relies on a novel image reconstructing technique that uses the principles of computerized tomography (Fourier-slice theorem). It can be implemented using a rotating antenna that produces a highly astigmatic fan-beam. In this work, the imaging system is composed of a linear phased antenna array with a highly directive beam pattern in the E-plane allowing for high spatial resolution imaging. However, the pattern is almost omnidirectional in the H-plane and extends beyond the required field-of-view (FOV). This is a major drawback as the scattered signals from any interferer outside the FOV will still be received by the imaging aperture and cause distortion in the reconstructed image. Also, fan beams exhibit significant distortion (curvature) when tilted at large angles, thus introducing errors in the final image due to its failure to achieve the assumed reconstructing algorithm. Therefore, a new design is proposed to alleviate these disadvantages. A 14×64 elements non-uniform array with an optimal flat-top pattern is designed with an iterative process using linear perturbation of a close starting pattern until the desired pattern is acquired. The principal advantage of this design is that it restricts the radiated/received power into the required FOV. As a result, a significant enhancement in the quality of images is achieved especially in the mitigation of the effect of any interferer outside the FOV. In this report, these two designs are presented and compared in terms of their imaging efficiency along with a series of numerical results verifying the proof of concept. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2018

A operação segura e eficiente em unidades de produção de petróleo e gás depende do desempenho de seus dispositivos, componentes e estruturas. Dutos rígidos são importantes componentes utilizados na indústria offshore, comumente empregados como flowlines e risers. Durante a vida em serviço destes componentes, eles sofrem tensões axiais cíclicas associadas a sua movimentação, ao processo de extração de petróleo e ao vórtice das marés. O aço inoxidável superduplex surgiu na última década como um material alternativo para ambientes quimicamente agressivos, mas quando catodicamente protegidos contra a corrosão, esses aços são vulneráveis a fragilização por hidrogênio. Este trabalho tem como objetivo, através da técnica de Ensaio Não Destrutivo de ultrassom phased array, monitorar o crescimento de defeitos internos e externos criados intencionalmente próximos à raiz e ao reforço da solda de um tubo de aço superduplex (UNS S32750) de 6´´ submetido a fadiga tração-tração e fragilização induzida por hidrogênio devido à proteção catódica. As inspeções foram realizadas periodicamente com varreduras de 30 a 75° ao longo da circunferência da solda, por um transdutor linear 1-D de 16 elementos e 5MHz acoplado a uma sapata de 36°. Os resultados obtidos foram utilizados para alimentar análises de integridade estrutural, obtenção da curva da/dN x ΔK. / Safe and efficient operation in oil and gas production units depends on the performance of your devices, components and structures. Rigid pipelines are important components in the offshore industry, common used as flowlines and risers. During a life in service of components, they suffer cyclical axial stresses associated with their movement, by the oil extraction process and tidal vortex. Super duplex stainless steel has emerged in the last decade as an alternative material for chemically aggressive environments, but when cathodically protected against corrosion, it is vulnerable to hydrogen embrittlement. This work aims to, through the ultrasonic non-destructive testing by phased array monitor the growth of internal and external defects created intentionally close to the root and reinforcement of the weld of a superduplex steel tube (UNS S32750) with diameter of 6" submitted to tensile-traction fatigue and hydrogen-induced embrittlement due to cathodic protection. The inspections were performed periodically with 30 to 75° scans along the circumference of the weld, by a linear transducer of 1-D, 16-element and 5MHz coupled to a wedge of 36°. The obtained results were used to feed structural integrity analyzes, obtaining the curve of da/dN x ΔK.

Componentes metálicos em operação podem estar sujeitos a diversas condições de operação deletérias. Visando avaliar os riscos de operação para evitar falhas, a análise de integridade estrutural é uma ferramenta amplamente aplicada e requer constante evolução. Por utilizar dados de ensaios não destrutivos, essa ferramenta requer cada vez mais precisão, para aprimorar seus resultados e reduzir ao máximo as falhas de componentes em operação. Por apresentar menor tempo de inspeção e maior probabilidade de detecção, o Phased Array surge como alternativa às técnicas convencionais de ultrassom. Dentre as técnicas de Phased Array, o Total Focusing Method (TFM) apresenta um dos resultados mais promissores, apresentando grande vantagem sobre técnicas convencionais de ultrassom e de Phased Array devido a sua melhor precisão e fácil interpretação dos resultados. Neste trabalho, o TFM foi aplicado em diversos blocos contendo descontinuidades usinadas, as quais simulam diferentes tipos de defeitos. O foco do TFM foi gerar blocos em três dimensões (3D) dos defeitos, facilitando a interpretação dos resultados, além da possibilidade da inserção desses blocos em softwares de análise de integridade estrutural, melhorando a precisão dos resultados. O TFM foi aplicado através do tratamento de dados de um sensor linear de Phased Array, com frequência de 5 MHz e com 64 elementos ativos. Nesse trabalho, foram desenvolvidas e aplicadas novas etapas no algoritmo do TFM para melhorar a precisão dos resultados, como a compensação da perda de energia e o half-skip. As etapas adicionais aplicadas ao algoritmo do TFM geraram bons resultados para entalhe e furos usinados nos blocos de aço carbono. Além dos blocos com defeitos usinados, foi realizada a inspeção de um bloco de aço inoxidável austenítico soldado. Para o bloco soldado, os resultados não foram satisfatórios, não sendo possível detectar defeitos existentes. Após a aplicação do TFM, foi simulado o deslocamento do sensor ao longo da peça, gerando diversas imagens 2D, as quais foram conectadas via isosuperfícies, gerando sólidos 3D dos defeitos presentes em cada bloco. Por fim, esses blocos foram exportados para um software CAD, apresentando excelente correspondência. / Metallic components in operation can be submitted to several harming operation conditions. Aiming to evaluate the operational risks to avoid failure, the structural integrity analysis is a widely applied tool and requires constant evolution. As it uses non-destructive testing data, this tool requires increasingly precision, to enhance its results and reduce the majority of the operating components failures. Because of the shorter inspection time and greater probability of detection, Phased Array is an alternative to conventional ultrasonic techniques. Among the techniques of Phased Array, the Total Focusing Method (TFM) presents one of the most promising results, offering great advantage over conventional ultrasonic and Phased Array techniques due to its better precision and easy interpretation of results. In this work, the TFM was applied to many blocks, which contain machined discontinuities simulating several defects. The objective of applying the TFM was to generate three-dimensional (3D) blocks, turning the interpretation of the results easier and giving the possibility to insert these blocks into a structural integrity analysis software, enhancing the results precision. The TFM algorithm was applied through treatment of data from a 5 MHz linear Phased Array sensor with 64 active elements. In this work, it were developed and applied new steps in the TFM algorithm, as energy loss compensation and half-skip interaction, to improve its precision. The additional steps applied to the TFM algorithm achieved great results for notch and holes machined in carbon steel blocks. In addition to the blocks with machined defects, a welded austenitic stainless steel block was inspected. For the welded block, the results were not satisfactory and it was not possible to detect the present defects. After the application of the TFM, the displacement of the transducer along the block was simulated, generating several 2D images, which were connected via isosurfaces, generating 3D solids corresponding to the defects present in each block. To conclude, these blocks were exported to a CAD software, presenting excellent matching.