O aumento das ocorrências de VIM em plataformas flutuantes do tipo \"spar\" e monocoluna serviu de motivação para a investigação dos fundamentos do fenômeno de VIV em cilindros com baixa razão de aspecto e pequena razão de massa. Tal investigação também foi motivada pela necessidade de se preencher lacunas de conhecimento a respeito deste assunto, articularmente por conta da escassa disponibilidade de resultados acerca do VIV em cilindros curtos, bem como pela ausência de modelo fluido que justifique os comportamentos dinâmicos conhecidos. Para o entendimento pretendido, três grupos de experimentos com cilindros dotados de razão de aspecto na faixa 0,1 <= L/D <= 2,0 foram realizados em um canal de água circulante na Escola Politécnica da Universidade de São Paulo, sendo: o primeiro grupo focado nos cilindros curtos estacionários; o segundo nos cilindros curtos de baixa razão de massa, 1,00 <= m* <= 4,36, e dois graus de liberdade; e o grupo final interessado no VIV em cilindros flutuantes, ou seja, razão de massa unitária e seis graus de liberdade. De uma maneira geral, a partir dos resultados aqui obtidos e das comparações com os resultados respectivamente encontrados na literatura, conclui-se que o VIV em cilindros curtos somente acontece se L/D > 0,2. Além de original, a determinação deste valor crítico também identificou outras três regiões com comportamentos fluido-dinâmicos distintos, cada qual marcada por especificidades quanto aos impactos nas amplitudes, frequências e coeficientes de força. Assim sendo, para cilindros com L/D > 2,0 a esteira de von Kármán foi a principal responsável pelas forças sustentação; fato não identificado para os cilindros com 0,5 < L/D < 2,0, onde esta mesma esteira sofreu forte contaminação das estruturas partindo da extremidade livre, principalmente aquelas com vorticidade predominante no plano vertical. Para os cilindros na faixa de 0,2 < L/D <= 0,5, apenas estas últimas estruturas foram responsáveis pelas oscilações de VIV. Finalmente, buscando compreender a origem das forças oscilatórias em cilindros com baixíssima razão de aspecto, \"end-plates\" foram aplicadas e confirmaram que o fenômeno de VIV nestes casos está relacionado à liberação de vórtices junto à extremidade livre, o que indica uma solução interessante para a mitigação do VIM de plataformas. / The increase of VIM occurrences on spar and monocolumn platforms was the motivation to study the vortex-induced vibrations of cylinders with low aspect ratio and small mass ratio under a fundamental perspective. The present work was also motivated by the small number of works in the literature dealing with VIV of cylinders with low aspect ratio, as well as by the scarce concerns about the flow models around this cylinders, which justify the dynamic behaviors observed. Aiming to better understand this problem, three groups of experiments with cylinders of 0.1 <= L/D <= 2.0 were carried out in a recirculating water channel at Escola Politécnica of University of São Paulo, as follow: firstly, the flow around stationary cylinders; secondly, VIV of cylinders with two degrees-of-freedom and 1.00 <= m* <= 4.36. finally, VIV of floating cylinder, thus six degrees-of-freedom. The works concluded that VIV occurs only for cylinders with L/D > 0.2. Besides of being original, this result was also related to the observation of three regions of aspect ratio, each of them with different behaviors of the motion amplitudes, frequency ratios and force coefficients. For cylinders with L/D > 2.0, the von Kármán wake was the mainly responsible for the oscillatory lift forces. On the other hand, the von Kármán wake was contaminated by the effects coming from the free end of cylinders with 0.5 < L/D < 2.0, mainly by the vortex structures with vorticity in the vertical plane. And for cylinders with 0.2 < L/D <=0.5, the vortex structures at the free end were predominant, thus the only one responsible for the oscillatory lift forces. Finally, in order to understand the source for oscillatory lift forces on cylinders with very low aspect ratio, end-plates were applied and confirmed that VIV in these cases is related to the vortex-shedding around the free end, which indicates an interesting solution for VIM mitigation of platforms.

A vibração induzida por escoamento é parte intrínseca do transporte de fluidos. Por exemplo, na indústria de petróleo e gás esse fenômeno pode ser encontrado em tubulações, tanto no setor upstream, quando downstream. Essas vibrações são produto das forças geradas pelo escoamento e, portanto, carregam informações sobre sua fenomenologia. No caso de escoamento bifásico em tubo, resultados experimentais indicam forte influência da velocidade da mistura, fração de vazio e padrão de escoamento no comportamento dinâmico da estrutura. Contudo, pouco foi feito na tentativa de obter informações do escoamento a partir da reposta estrutural. Assim, o objetivo do presente estudo é desenvolver métodos para a previsão dos parâmetros do escoamento baseados na resposta de um tubo submetido a escoamento bifásico. Foi conduzido um trabalho experimental da vibração induzida por diversos padrões gás-líquido numa tubulação horizontal (PVC &#216;3/4\'\') duplamente engastada, com água e ar como fluidos de trabalho. A partir de uma abordagem analítica, corroborada com resultados experimentais para escoamento monofásico e bifásico, estabelece-se a existência de uma relação, de natureza quadrática, entre a velocidade de atrito e o desvio padrão da aceleração. Dado que a velocidade de atrito é função do fator de atrito bifásico, um método para a sua previsão é desenvolvido. Ele prevê de maneira precisa os dados coletados; todos eles com erro percentual menor do que 30%. O método foi comparado também com dados experimentais e modelos da literatura, mostrando boa concordância. Além disso, apresenta-se uma relação entre a frequência pico da resposta e a fração de vazio homogênea. No fim, são apresentados: (i) um método de identificação de escoamento pistonado, baseado na superposição dos mecanismos de vibração por turbulência e intermitente, com desempenho mínimo de 81.8%; (ii) um método experimental para determinação da velocidade da mistura (J) e fração de vazio homogênea (&beta;). Os melhores resultados são obtidos para os padrões disperso e pistonado, prevendo adequadamente os parâmetros J e &beta; com erro percentual absoluto médio de 24.1% e 20.65%, respectivamente. / Flow-induced vibration is intrinsic to piping problems. For example, in the oil and gas industry the FIV phenomenon can be found in pipe flow both in upstream and downstream applications. The structural vibration response contains information about the flow phenomenology. In the case of two-phase pipe flow, experimental results show a strong influence of mixture velocity, void fraction and flow pattern on pipe structural dynamics. However, efforts to obtain information of the flow from pipe response have been scanty. The goal of this study is to develop two-phase flow parameters predictive methods based on the structural pipe response. An experimental study of flow-induced vibration was carried out for several flow patterns in a clamp-clamp straight pipe (PVC &#216;3/4\'\'), with air and water as working fluids. From an analytical approach, a quadratic relationship between shear velocity and standard deviation of acceleration is proposed and validated against the experimental data of single and two-phase flow. Since the shear velocity depends on the friction factor, a method to predict two-phase friction factor is presented. The method predicts accurately our experimental data with a mean absolute error up to 30%. Good agreement was also found when it was compared with some models and experimental data from the literature. Furthermore, an expression to correlate peak frequency and homogeneous void fraction as a function of added mass is offered. Finally, we present: (i) a slug flow identification technique based on the superposition of the turbulence and intermittent flow-induced vibration mechanisms, with performance of 81.8% and (ii) an experimental methodology to estimate mixture velocity (J) and homogeneous void fraction (&beta;). The latter method shows better agreement for dispersed and slug flow-patterns, predicting J and &beta; with a mean absolute error of 24.1% e 20.65%, respectively.

Os resultados de uma simulação numérica são apresentados para amplitudes de vibração induzidas por um escoamento transversal num feixe tubular no regime de instabilidade fluidelástica.O feixe tubular considerado tem geometria e características iguais às de uma instalação equivalente descrita na literatura, para a qual estão disponíveis as medições experimentais das amplitudes de vibração no regime de instabilidade elástica.O arranjo tipo triângulo rodado tem uma relação passo/diâmetro de 1,375 e consiste de um tubo móvel cercado por 134 tubos rígidos.A simulação numérica foi efetuada através de um software comercial de CFD (Computational Fluid dynamics).Para a região em torno de cada tubo foi considerada uma malha com dimensões do elemento crescendo geometricamente na direção normal ao tubo com fator de crescimento 1,13 , sendo a dimensão do elemento adjacente ao tubo igual a 0,1% do diâmetro externo do tubo.Na simulação numérica o escoamento foi considerado incompressível, monofásico, turbulento e bidimensional. Os dados do escoamento foram considerados idênticos aos das experiências da instalação descrita na literatura.Os resultados obtidos para as amplitudes pela simulação numérica são comparados com os resultados obtidos experimentalmente na instalação acima citada.Os desvios da maioria dos valores calculados em relação aos valores experimentais estão numa faixa aceitável. Isto mostra que existe a possibilidade de utilização, num futuro próximo, de CFD para análise deste tipo de problemas. / Results from a numerical simulation are reported for amplitudes of cross-flow induced vibrations at the fluid elastic instability regime in a tube bank. The tube bank has identical geometry and characteristics as for an experimental facility described in the literature, for which there are experimental measurements of the amplitudes of vibrations at the fluid elastic instability regime.The rotated triangular array has a pitch ratio of 1.375 and consists of 1 movable tube surrounded by 134 rigid tubes. The numerical simulations were accomplished with a commercial CFD (Computational Fluid Dynamics) software. For the region around each tube, a mesh with elements dimensions growing geometrically normal to the tube was considered, with growing factor 1.13, and the dimension for the element adjacent to the tube wall was set to 0.1% of the tube external diameter. The flow was considered incompressible, monophasic, turbulent and two-dimensional for the numerical simulation. The flow data considered were the same as for the experiments at the facility. The results presented in this paper for the amplitudes obtained by numerical simulation are compared with the experimental results obtained in the above mentioned experimental facility.The differences between the calculated values and the experimental values are acceptable. This show that in the near future there is the possibility to use CFD for these kind of problems.

This research focuses on developing sensors for properties of aerodynamic interest (i.e., flow and pressure) based on low-cost polymeric materials and simple fabrication processes. Such sensors can be fabricated in large arrays, covering the surface of airfoils typically used in unmanned vehicles, allowing for the detection of flow separation. This in turn potentially enables, through the use of closed-loop control, an expansion of the flight envelope of these vehicles. A key advance is compensation for the typically inferior performance of these low cost materials through both careful design as well as new readout methods that reduce drift, namely a readout methodology based on aeroelastic flutter. An all-polymer micromachined piezoresistive flow sensor is fabricated, based on a flexible polyimide substrate and an elastomeric piezoresistive composite material. The flow sensor comprises a cantilever that is extended into the embedding flow; flow-induced stress on the cantilever is sensed through the piezoresistive composite material. Increasing the sensitivity of the sensor is achieved by either utilizing a long single-cantilever beam or using a dual-cantilever beam supporting a flap extending into the flow. In the latter case, the sensor demonstrates increased sensitivity with a reduced cantilever length. The increase in sensitivity helps to reduce sensor drift, which in turn is further reduced by a new measurement method, the vibration amplitude measurement method. In this drift reduction measurement method, the flow-induced vibration amplitude of the sensor structure (i.e., the amplitude of the aeroelastic flutter induced by the flow), instead of the absolute value of cantilever deflection, is measured in order to find the flow rate. Measurement of this relative resistance change instead of the absolute resistance in the piezoresistor rejects common-mode drift and greatly reduces overall drift. Experimental results verify the expected drift reduction. Sensor drift is also reduced when the elastomeric piezoresistive material is replaced by a Pt thin film piezoresistor. Development of pressure sensors based on polymers proceeds by encapsulating a reference cavity within a multilayer polymer structure and forming capacitor plates on the polymeric membranes encapsulating the cavity. Measuring the capacitance change induced by changes in the embedding pressure (which cause changes in the positions of the bounding polymeric membranes) enables calculation of the pressure. The use of polymeric membranes requires understanding the leakage rate of gas into the reference cavity, which is a source of pressure drift. Developing a polymer-based pressure sensor that solves the problem of sensor drift as a result of gas permeation entails the fabrication of a silicon pressure reference cavity embedded in the polymer substrate, which results in a more hermetic and lower drift sensor while preserving the flexibility of the embedding polymer. Both wired and wireless versions of pressure and flow sensors of these types were developed and characterized. Further, the sensors were characterized on airfoils and their performance in a wind tunnel was determined.

Die experimentellen Untersuchungen zur Strömungs-Struktur-Interaktion kommen zu folgenden Ergebnissen. Die als entrainment bezeichnete Verhaltensweise von Fischen kann durch den gezielten Ausgleich von Auftriebs-, Widerstands- und einer erstmals nachgewiesenen Saugkraft und der damit verbundenen Reduzierung der lokomotorischen Energie erklärt werden. Des Weiteren zeigen die Experimente an einer wellenförmig bewegten Oberfläche, dass die Strömung an einem Wellenberg zyklisch zwischen laminarem und turbulentem Regime wechselt und dass diese Oszillation zur Reduzierung des Form- und Gesamtwiderstandes der geschleppten Oberfläche führt. Dünne, flexible Häutchen hairy flaps an der Rückseite eines Zylinders führen zu einer Änderung der Struktur der Wirbelablösung an diesem. Dadurch wird sowohl die auf den Zylinder wirkende Auftriebskraft als auch die Widerstandskraft um bis zu 65% reduziert. Für die Interaktion zwischen der Strömung um zwei hintereinander positionierte elastische Zylinder und ihrer Kinematik konnte die Synchronisierung (lock-in) ihrer Bewegung mit einer verbundenen Zerstörung der Wirbelstraße hinter dem zweiten Zylinder gezeigt werden. / The experimental investigations presented herein explain the behavioural adaptation of fish called entrainment for the first time. The results confirm a balance of lift-, drag- and a suction-force, explaining the reduction of locomotive energy. Furthermore, flow measurements around an undulating membrane affirm an oscillation between laminar and turbulent flow over one period of the motion and that this oscillation decreases the pressure- and drag-force of the towed membrane. Experiments on thin and flexible flaps attached at the lee-side of a cylinder, show that the flaps alter the natural vortex separation cycle in such a way that the vortices do not shed in a staggered side-by-side arrangement but in line in a row with the cylinder wake axis. Thus, flow fluctuations are reduced by 42% in stream-wise - and 35% in transversal direction at best, compared to a reference case without hairy-flaps. Finally, investigations on the flow around and on the kinematics of two flexible cylinders in a tandem arrangement demonstrate a synchronisation of their motion (lock-in), resulting in the destruction of the vortex-street behind the second cylinder.

O aumento das ocorrências de VIM em plataformas flutuantes do tipo \"spar\" e monocoluna serviu de motivação para a investigação dos fundamentos do fenômeno de VIV em cilindros com baixa razão de aspecto e pequena razão de massa. Tal investigação também foi motivada pela necessidade de se preencher lacunas de conhecimento a respeito deste assunto, articularmente por conta da escassa disponibilidade de resultados acerca do VIV em cilindros curtos, bem como pela ausência de modelo fluido que justifique os comportamentos dinâmicos conhecidos. Para o entendimento pretendido, três grupos de experimentos com cilindros dotados de razão de aspecto na faixa 0,1 <= L/D <= 2,0 foram realizados em um canal de água circulante na Escola Politécnica da Universidade de São Paulo, sendo: o primeiro grupo focado nos cilindros curtos estacionários; o segundo nos cilindros curtos de baixa razão de massa, 1,00 <= m* <= 4,36, e dois graus de liberdade; e o grupo final interessado no VIV em cilindros flutuantes, ou seja, razão de massa unitária e seis graus de liberdade. De uma maneira geral, a partir dos resultados aqui obtidos e das comparações com os resultados respectivamente encontrados na literatura, conclui-se que o VIV em cilindros curtos somente acontece se L/D > 0,2. Além de original, a determinação deste valor crítico também identificou outras três regiões com comportamentos fluido-dinâmicos distintos, cada qual marcada por especificidades quanto aos impactos nas amplitudes, frequências e coeficientes de força. Assim sendo, para cilindros com L/D > 2,0 a esteira de von Kármán foi a principal responsável pelas forças sustentação; fato não identificado para os cilindros com 0,5 < L/D < 2,0, onde esta mesma esteira sofreu forte contaminação das estruturas partindo da extremidade livre, principalmente aquelas com vorticidade predominante no plano vertical. Para os cilindros na faixa de 0,2 < L/D <= 0,5, apenas estas últimas estruturas foram responsáveis pelas oscilações de VIV. Finalmente, buscando compreender a origem das forças oscilatórias em cilindros com baixíssima razão de aspecto, \"end-plates\" foram aplicadas e confirmaram que o fenômeno de VIV nestes casos está relacionado à liberação de vórtices junto à extremidade livre, o que indica uma solução interessante para a mitigação do VIM de plataformas. / The increase of VIM occurrences on spar and monocolumn platforms was the motivation to study the vortex-induced vibrations of cylinders with low aspect ratio and small mass ratio under a fundamental perspective. The present work was also motivated by the small number of works in the literature dealing with VIV of cylinders with low aspect ratio, as well as by the scarce concerns about the flow models around this cylinders, which justify the dynamic behaviors observed. Aiming to better understand this problem, three groups of experiments with cylinders of 0.1 <= L/D <= 2.0 were carried out in a recirculating water channel at Escola Politécnica of University of São Paulo, as follow: firstly, the flow around stationary cylinders; secondly, VIV of cylinders with two degrees-of-freedom and 1.00 <= m* <= 4.36. finally, VIV of floating cylinder, thus six degrees-of-freedom. The works concluded that VIV occurs only for cylinders with L/D > 0.2. Besides of being original, this result was also related to the observation of three regions of aspect ratio, each of them with different behaviors of the motion amplitudes, frequency ratios and force coefficients. For cylinders with L/D > 2.0, the von Kármán wake was the mainly responsible for the oscillatory lift forces. On the other hand, the von Kármán wake was contaminated by the effects coming from the free end of cylinders with 0.5 < L/D < 2.0, mainly by the vortex structures with vorticity in the vertical plane. And for cylinders with 0.2 < L/D <=0.5, the vortex structures at the free end were predominant, thus the only one responsible for the oscillatory lift forces. Finally, in order to understand the source for oscillatory lift forces on cylinders with very low aspect ratio, end-plates were applied and confirmed that VIV in these cases is related to the vortex-shedding around the free end, which indicates an interesting solution for VIM mitigation of platforms.

A vibração induzida por escoamento é parte intrínseca do transporte de fluidos. Por exemplo, na indústria de petróleo e gás esse fenômeno pode ser encontrado em tubulações, tanto no setor upstream, quando downstream. Essas vibrações são produto das forças geradas pelo escoamento e, portanto, carregam informações sobre sua fenomenologia. No caso de escoamento bifásico em tubo, resultados experimentais indicam forte influência da velocidade da mistura, fração de vazio e padrão de escoamento no comportamento dinâmico da estrutura. Contudo, pouco foi feito na tentativa de obter informações do escoamento a partir da reposta estrutural. Assim, o objetivo do presente estudo é desenvolver métodos para a previsão dos parâmetros do escoamento baseados na resposta de um tubo submetido a escoamento bifásico. Foi conduzido um trabalho experimental da vibração induzida por diversos padrões gás-líquido numa tubulação horizontal (PVC &#216;3/4\'\') duplamente engastada, com água e ar como fluidos de trabalho. A partir de uma abordagem analítica, corroborada com resultados experimentais para escoamento monofásico e bifásico, estabelece-se a existência de uma relação, de natureza quadrática, entre a velocidade de atrito e o desvio padrão da aceleração. Dado que a velocidade de atrito é função do fator de atrito bifásico, um método para a sua previsão é desenvolvido. Ele prevê de maneira precisa os dados coletados; todos eles com erro percentual menor do que 30%. O método foi comparado também com dados experimentais e modelos da literatura, mostrando boa concordância. Além disso, apresenta-se uma relação entre a frequência pico da resposta e a fração de vazio homogênea. No fim, são apresentados: (i) um método de identificação de escoamento pistonado, baseado na superposição dos mecanismos de vibração por turbulência e intermitente, com desempenho mínimo de 81.8%; (ii) um método experimental para determinação da velocidade da mistura (J) e fração de vazio homogênea (&beta;). Os melhores resultados são obtidos para os padrões disperso e pistonado, prevendo adequadamente os parâmetros J e &beta; com erro percentual absoluto médio de 24.1% e 20.65%, respectivamente. / Flow-induced vibration is intrinsic to piping problems. For example, in the oil and gas industry the FIV phenomenon can be found in pipe flow both in upstream and downstream applications. The structural vibration response contains information about the flow phenomenology. In the case of two-phase pipe flow, experimental results show a strong influence of mixture velocity, void fraction and flow pattern on pipe structural dynamics. However, efforts to obtain information of the flow from pipe response have been scanty. The goal of this study is to develop two-phase flow parameters predictive methods based on the structural pipe response. An experimental study of flow-induced vibration was carried out for several flow patterns in a clamp-clamp straight pipe (PVC &#216;3/4\'\'), with air and water as working fluids. From an analytical approach, a quadratic relationship between shear velocity and standard deviation of acceleration is proposed and validated against the experimental data of single and two-phase flow. Since the shear velocity depends on the friction factor, a method to predict two-phase friction factor is presented. The method predicts accurately our experimental data with a mean absolute error up to 30%. Good agreement was also found when it was compared with some models and experimental data from the literature. Furthermore, an expression to correlate peak frequency and homogeneous void fraction as a function of added mass is offered. Finally, we present: (i) a slug flow identification technique based on the superposition of the turbulence and intermittent flow-induced vibration mechanisms, with performance of 81.8% and (ii) an experimental methodology to estimate mixture velocity (J) and homogeneous void fraction (&beta;). The latter method shows better agreement for dispersed and slug flow-patterns, predicting J and &beta; with a mean absolute error of 24.1% e 20.65%, respectively.

The thesis compares the dynamic response of lightweight footbridge structure. Two finite element models were made. One in Ansys 15.0 software, and another in RFEM 5.05 structural software. The results of the models were compared to each other. The response to dynamic excitation from pedestrians was evaluated in accordance to ČSN EN 1990/A2.

Die experimentellen Untersuchungen zur Strömungs-Struktur-Interaktion kommen zu folgenden Ergebnissen. Die als entrainment bezeichnete Verhaltensweise von Fischen kann durch den gezielten Ausgleich von Auftriebs-, Widerstands- und einer erstmals nachgewiesenen Saugkraft und der damit verbundenen Reduzierung der lokomotorischen Energie erklärt werden. Des Weiteren zeigen die Experimente an einer wellenförmig bewegten Oberfläche, dass die Strömung an einem Wellenberg zyklisch zwischen laminarem und turbulentem Regime wechselt und dass diese Oszillation zur Reduzierung des Form- und Gesamtwiderstandes der geschleppten Oberfläche führt. Dünne, flexible Häutchen hairy flaps an der Rückseite eines Zylinders führen zu einer Änderung der Struktur der Wirbelablösung an diesem. Dadurch wird sowohl die auf den Zylinder wirkende Auftriebskraft als auch die Widerstandskraft um bis zu 65% reduziert. Für die Interaktion zwischen der Strömung um zwei hintereinander positionierte elastische Zylinder und ihrer Kinematik konnte die Synchronisierung (lock-in) ihrer Bewegung mit einer verbundenen Zerstörung der Wirbelstraße hinter dem zweiten Zylinder gezeigt werden.:Zusammenfassung 1 Conclusions 7 1. Einleitung und Zielsetzung 11 2. Messtechnische Grundlagen 17 2.1. Klassische Particle Image Velocimetry 18 2.2. Scanning Particle Image Velocimetry 20 2.3. Mirror Particle Tracking Velocimetry 21 2.4. Druckberechnung 35 3. Hydrodynamisches Modell des entrainments 37 3.1. Stand der Forschung 38 3.2. Experimenteller Aufbau 42 3.3. Ergebnisse 44 3.4. Zusammenfassung 51 4. Undulatorisch bewegte Oberflächen 53 4.1. Stand der Forschung 54 4.2. Mechanisches Modell 57 4.3. Experimenteller Aufbau 61 4.4. Ergebnisse 65 4.5. Zusammenfassung 74 5. Selbstadaptive elastische Klappen - hairy flaps 77 5.1. Stand der Forschung 78 5.2. Experimenteller Aufbau 82 5.3. Ergebnisse 86 5.4. Zusammenfassung 107 6. Umströmung stumpfer elastischer Körper 109 6.1. Stand der Forschung 110 6.2. Experimenteller Aufbau 116 6.3. Ergebnisse 120 6.4. Zusammenfassung 128 7. Ausblick 131 Abbildungsverzeichnis 135 Tabellenverzeichnis 141 Symbolverzeichnis 142 Literaturverzeichnis 146 A. Anhang 155 / The experimental investigations presented herein explain the behavioural adaptation of fish called entrainment for the first time. The results confirm a balance of lift-, drag- and a suction-force, explaining the reduction of locomotive energy. Furthermore, flow measurements around an undulating membrane affirm an oscillation between laminar and turbulent flow over one period of the motion and that this oscillation decreases the pressure- and drag-force of the towed membrane. Experiments on thin and flexible flaps attached at the lee-side of a cylinder, show that the flaps alter the natural vortex separation cycle in such a way that the vortices do not shed in a staggered side-by-side arrangement but in line in a row with the cylinder wake axis. Thus, flow fluctuations are reduced by 42% in stream-wise - and 35% in transversal direction at best, compared to a reference case without hairy-flaps. Finally, investigations on the flow around and on the kinematics of two flexible cylinders in a tandem arrangement demonstrate a synchronisation of their motion (lock-in), resulting in the destruction of the vortex-street behind the second cylinder.:Zusammenfassung 1 Conclusions 7 1. Einleitung und Zielsetzung 11 2. Messtechnische Grundlagen 17 2.1. Klassische Particle Image Velocimetry 18 2.2. Scanning Particle Image Velocimetry 20 2.3. Mirror Particle Tracking Velocimetry 21 2.4. Druckberechnung 35 3. Hydrodynamisches Modell des entrainments 37 3.1. Stand der Forschung 38 3.2. Experimenteller Aufbau 42 3.3. Ergebnisse 44 3.4. Zusammenfassung 51 4. Undulatorisch bewegte Oberflächen 53 4.1. Stand der Forschung 54 4.2. Mechanisches Modell 57 4.3. Experimenteller Aufbau 61 4.4. Ergebnisse 65 4.5. Zusammenfassung 74 5. Selbstadaptive elastische Klappen - hairy flaps 77 5.1. Stand der Forschung 78 5.2. Experimenteller Aufbau 82 5.3. Ergebnisse 86 5.4. Zusammenfassung 107 6. Umströmung stumpfer elastischer Körper 109 6.1. Stand der Forschung 110 6.2. Experimenteller Aufbau 116 6.3. Ergebnisse 120 6.4. Zusammenfassung 128 7. Ausblick 131 Abbildungsverzeichnis 135 Tabellenverzeichnis 141 Symbolverzeichnis 142 Literaturverzeichnis 146 A. Anhang 155

Flow-induced vibration caused by fully developed pipe flow has been recognized, but not fully investigated under turbulent conditions. This thesis focuses on the development of a numerical Fluid-Structure Interaction (FSI) model that will help define the relationship between pipe wall vibration and the physical characteristics of turbulent flow. Commercial FSI software packages are based on Reynolds Averaged Navier-Stokes (RANS) fluid models, which do not compute the instantaneous fluctuations in turbulent flow. This thesis presents an FSI approach based on Large Eddy Simulation (LES) flow models, which do compute the instantaneous fluctuations in turbulent flow. The results based on the LES models indicate that these fluctuations contribute to the pipe vibration. It is shown that there is a near quadratic relationship between the standard deviation of the pressure field on the pipe wall and the flow rate. It is also shown that a strong relationship between pipe vibration and flow rate exists. This research has a direct impact on the geothermal, nuclear, and other fluid transport industries.