This work details the development of a computational tool that can accurately model strongly-coupled fluid-structure-interaction (FSI) problems, with a particular focus on thin-walled structures undergoing large, geometrically non-linear deformations, which has a major interest in, amongst others, the aerospace and biomedical industries. The first part of this work investigates improving the efficiency with which a stable and robust in-house code, Elemental, models thin structures undergoing dynamic fluid-induced bending deformations. Variations of the existing finite volume formulation as well as linear and higher-order finite element formulations are implemented. The governing equations for the solid domain are formulated in a total Lagrangian or undeformed conguration and large geometrically non-linear deformations are accounted for. The set of equations is solved via a single-step Jacobi iterative scheme which is implemented such as to ensure a matrix-free and robust solution. Second-order accurate temporal discretisation is achieved via dual-timestepping, with both consistent and lumped mass matrices and with a Jacobi pseudo-time iteration method employed for solution purposes. The matrix-free approach makes the scheme particularly well-suited for distributed memory parallel hardware architectures. Three key outcomes, not well documented in literature, are highlighted: the issue of shear locking or sensitivity to element aspect ratio, which is a common problem with the linear Q4 finite element formulation when subjected to bending, is evaluated on the finite volume formulations; a rigorous comparison of finite element vs. finite volume methods on geometrically non-linear structures is done; a higher-order finite volume solid mechanics procedure is developed and evaluated. The second part of this work is concerned with fluid-structure interaction (FSI) modelling. It considers the implementation and coupling of a higher order finite element structural solver with the existing finite volume fluid-flow solver in Elemental. To the author’s knowledge, this is the first instance in which a strongly-coupled hybrid finite element–finite volume FSI formulation is developed. The coupling between the fluid and structural components with non-matching nodes is rigorously assessed. A new partitioned fluid-solid interface coupling methodology is also developed, which ensures stable partitioned solution for strongly-coupled problems without any additional computational overhead. The solver is parallelised for distributed memory parallel hardware architectures. The developed technology is successfully validated through rigorous temporal and mesh independent studies of representative two-dimensional strongly-coupled large-displacement FSI test problems for which analytical or benchmark solutions exist. / Dissertation (MEng)--University of Pretoria, 2012. / Mechanical and Aeronautical Engineering / unrestricted

Please read the abstract (Summary) in the 00front part of this document / Dissertation (M Eng (Mechanical Engineering))--University of Pretoria, 2006. / Mechanical and Aeronautical Engineering / unrestricted

Dans le cadre d’une collaboration avec la société PHYTOREM, nous avons élaboré un prototype de distribution autorégulé afin d’épandre des Eaux Usées après un simple dégrillage et via la Phytorémédiation (dépollution par les plantes).La première approche du projet de thèse a été de comprendre les comportements rhéologiques des effluents, mis à disposition par Phytorem, et mécaniques du matériau élastomère de type EPDM. Nous avons exposé les différentes façons de retrouver leurs propriétés rhéologiques et mécaniques par le biais de divers tests de rhéométrie, concernant les effluents, et de traction uni-, bi- et équibi-axiale, pour la partie matériau. Ceci nous a permis d’obtenir d’une part, la viscosité de nos effluents, et d’autre part, la loi de comportement la mieux adaptée à notre matériau.La deuxième et dernière approche porte sur les interactions entre un fluide et une membrane hyperélastique ayant pour fonction de réguler un écoulement. Le comportement de la membrane contrainte par la pression a été simulé sous Abaqus. Ces résultats ont permis de modéliser l’écoulement (code CFD commercial) lorsque la membrane est déformée et de déterminer numériquement la loi débit/pression du dispositif. Ces développements numériques s’appuient sur la méthode des éléments finis et un couplage partitionné simple en une étape pour une première approche entre le fluide, la membrane et la structure. Les modèles numériques sont validés expérimentalement. Ces travaux participent à l’élaboration d’un prototype de distributeur auto-régulé. / In collaboration with PHYTOREM, we have developed a prototype of self-regulated drip emitter to spread the Wastewater after a simple screening using phytoremediation (remediation by plants).The first approach of the thesis project was to understand the rheological behaviour of waste provided by PHYTOREM, and mechanical properties behaviour of EPDM elastomer type. We have explained the different ways to find their rheological and mechanical properties through various rheometry tests on waste, and tension uni-, biand equibi-axiale, for the material part. This allowed us to obtain first, the viscosity of our waste, and secondly, the behaviour law of best suited to our material.The second and final approach focuses on the interactions between a fluid and a hyperelastic membrane whose function is to regulate flow. The membrane behaviour under pressure stress was simulated using Abaqus. These results were used to model the flow (commercial CFD) when the membrane is distorted and to determine numerically its flow versus pressure law. These developments are relying on numerical finite element method and partitionned into a single coupling step for a first approach between fluid, membrane and structure. The numerical models are validated experimentally. This work contributes to the development of a prototype of self-regulated drip emitter.

This master thesis is focused on usage of monitoring pulse wave propagation in aortic system in a field of diagnostic abdominal aortic aneurysm (AAA). There is a description of cardio-vascular system and its pathology in a form of AAA. A summarization of temporary diagnostic method was created and some new methods were proposed. This new methods presume monitoring of pulse wave propagation. Fluid structure interaction (FSI) analyses of pulse wave propagation were performed on simplified models of geometry which representing specific sections of aorta. The goal of these analyses was to prove usage of FSI method in a future development of proposed diagnostic methods.

The purpose of this study was to develop a robust fluid-structure-interaction (FSI) technology that can accurately model non-linear flutter responses for sub- and transonic fluid flow. The Euler equation set governs the fluid domain, which was spatially discretised by a vertex-centred edge-based finite volume method. A dual-timestepping method was employed for the purpose of temporal discretisation. Three upwind schemes were compared in terms of accuracy, efficiency and robustness, viz. Roe, HLLC (Harten-Lax-Van Leer with contact) and AUSM+-up Advection Up-stream Splitting Method). For this purpose, a second order unstructured MUSCL (Monotonic Upstream-centred Scheme for Conservation Laws) scheme, with van Albada limiter, was employed. The non-linear solid domain was resolved by a quadratic modal reduced order model (ROM), which was compared to a semi-analytical and linear modal ROM. The ROM equations were solved by a fourth order Runge-Kutta method. The fluid and solid were strongly coupled in a partitioned fashion with the information being passed at solver sub-iteration level. The developed FSI technology was verified and validated by applying it to test cases found in literature. It was demonstrated that accurate results may be obtained, with the HLLC upwind scheme offering the best balance between accuracy and robustness. Further, the quadratic ROM offered significantly improved accuracy when compared to the linear method. / Dissertation (MEng)--University of Pretoria, 2011. / Mechanical and Aeronautical Engineering / unrestricted

Elementos de materiais flexíveis são empregados em diversas aplicações na engenharia, como por exemplo, em pás de turbinas eólicas. O comportamento do escoamento é afetado pela alteração na forma da estrutura. Muitas vezes, seu movimento e deformação são induzidos pelas próprias forças fluidodinâmicas. O trabalho apresenta o estudo de escoamentos externos envolvendo a interação fluido-estrutura, com o interesse voltado ao comportamento de pás de turbinas eólicas. Simulações numéricas são realizadas com o intuito de avaliar o efeito que a deformação da estrutura, devido à resposta elástica às forças oriundas do escoamento, tem nas próprias forças fluidodinâmicas. A plataforma ANSYS Workbench é utilizada, combinando o software ANSYS CFX para a análise do fluido e o ANSYS Mechanical para a análise da estrutura. Como validação do método, o escoamento laminar sobre um cilindro apoiado elasticamente é estudado e comparado com dados da literatura. O caso escolhido para o presente trabalho é o de um escoamento turbulento sobre um elemento de pá, fixo em uma das suas extremidades e livre na outra. A geometria da pá é retangular com o perfil NACA 0012 e o modelo de turbulência utilizado é o k-ω SST. Os resultados demonstram a influência significativa que a deformação da estrutura tem nas forças fluidodinâmicas de sustentação e arrasto e concordam com a literatura existente. / Elements of flexible materials are employed in several engineering applications, for instance, in wind turbine blades. The flow behavior is affected by any change in the shape of the structure. Often, its displacement and deformation are induced by the fluid-dynamic forces themselves. This paper presents the study of an external flow using fluid-structure interaction (FSI), focused on the behavior of wind turbine blades. Numerical simulations are performed in order to evaluate the effect that the deformation of the structure, caused by the elastic response to the flow forces, has on the fluid-dynamic forces themselves. The ANSYS Workbench platform is used, combining the software ANSYS CFX for the fluid analysis and ANSYS Mechanical for the structural analysis. As a form of validation of this method, the laminar flow over an elastically mounted cylinder is studied and compared with literature data. The chosen case for this work is a turbulent flow over a 3D blade element, fixed at one end and free at the other. The blade geometry is rectangular with the NACA 0012 profile and the turbulence model used is the k-ω SST. The results demonstrate the significant influence that the deformation of the structure has on the fluid-dynamic lift and drag forces, leading to an agreement with the existing literature.

Elementos de materiais flexíveis são empregados em diversas aplicações na engenharia, como por exemplo, em pás de turbinas eólicas. O comportamento do escoamento é afetado pela alteração na forma da estrutura. Muitas vezes, seu movimento e deformação são induzidos pelas próprias forças fluidodinâmicas. O trabalho apresenta o estudo de escoamentos externos envolvendo a interação fluido-estrutura, com o interesse voltado ao comportamento de pás de turbinas eólicas. Simulações numéricas são realizadas com o intuito de avaliar o efeito que a deformação da estrutura, devido à resposta elástica às forças oriundas do escoamento, tem nas próprias forças fluidodinâmicas. A plataforma ANSYS Workbench é utilizada, combinando o software ANSYS CFX para a análise do fluido e o ANSYS Mechanical para a análise da estrutura. Como validação do método, o escoamento laminar sobre um cilindro apoiado elasticamente é estudado e comparado com dados da literatura. O caso escolhido para o presente trabalho é o de um escoamento turbulento sobre um elemento de pá, fixo em uma das suas extremidades e livre na outra. A geometria da pá é retangular com o perfil NACA 0012 e o modelo de turbulência utilizado é o k-ω SST. Os resultados demonstram a influência significativa que a deformação da estrutura tem nas forças fluidodinâmicas de sustentação e arrasto e concordam com a literatura existente. / Elements of flexible materials are employed in several engineering applications, for instance, in wind turbine blades. The flow behavior is affected by any change in the shape of the structure. Often, its displacement and deformation are induced by the fluid-dynamic forces themselves. This paper presents the study of an external flow using fluid-structure interaction (FSI), focused on the behavior of wind turbine blades. Numerical simulations are performed in order to evaluate the effect that the deformation of the structure, caused by the elastic response to the flow forces, has on the fluid-dynamic forces themselves. The ANSYS Workbench platform is used, combining the software ANSYS CFX for the fluid analysis and ANSYS Mechanical for the structural analysis. As a form of validation of this method, the laminar flow over an elastically mounted cylinder is studied and compared with literature data. The chosen case for this work is a turbulent flow over a 3D blade element, fixed at one end and free at the other. The blade geometry is rectangular with the NACA 0012 profile and the turbulence model used is the k-ω SST. The results demonstrate the significant influence that the deformation of the structure has on the fluid-dynamic lift and drag forces, leading to an agreement with the existing literature.

Elementos de materiais flexíveis são empregados em diversas aplicações na engenharia, como por exemplo, em pás de turbinas eólicas. O comportamento do escoamento é afetado pela alteração na forma da estrutura. Muitas vezes, seu movimento e deformação são induzidos pelas próprias forças fluidodinâmicas. O trabalho apresenta o estudo de escoamentos externos envolvendo a interação fluido-estrutura, com o interesse voltado ao comportamento de pás de turbinas eólicas. Simulações numéricas são realizadas com o intuito de avaliar o efeito que a deformação da estrutura, devido à resposta elástica às forças oriundas do escoamento, tem nas próprias forças fluidodinâmicas. A plataforma ANSYS Workbench é utilizada, combinando o software ANSYS CFX para a análise do fluido e o ANSYS Mechanical para a análise da estrutura. Como validação do método, o escoamento laminar sobre um cilindro apoiado elasticamente é estudado e comparado com dados da literatura. O caso escolhido para o presente trabalho é o de um escoamento turbulento sobre um elemento de pá, fixo em uma das suas extremidades e livre na outra. A geometria da pá é retangular com o perfil NACA 0012 e o modelo de turbulência utilizado é o k-ω SST. Os resultados demonstram a influência significativa que a deformação da estrutura tem nas forças fluidodinâmicas de sustentação e arrasto e concordam com a literatura existente. / Elements of flexible materials are employed in several engineering applications, for instance, in wind turbine blades. The flow behavior is affected by any change in the shape of the structure. Often, its displacement and deformation are induced by the fluid-dynamic forces themselves. This paper presents the study of an external flow using fluid-structure interaction (FSI), focused on the behavior of wind turbine blades. Numerical simulations are performed in order to evaluate the effect that the deformation of the structure, caused by the elastic response to the flow forces, has on the fluid-dynamic forces themselves. The ANSYS Workbench platform is used, combining the software ANSYS CFX for the fluid analysis and ANSYS Mechanical for the structural analysis. As a form of validation of this method, the laminar flow over an elastically mounted cylinder is studied and compared with literature data. The chosen case for this work is a turbulent flow over a 3D blade element, fixed at one end and free at the other. The blade geometry is rectangular with the NACA 0012 profile and the turbulence model used is the k-ω SST. The results demonstrate the significant influence that the deformation of the structure has on the fluid-dynamic lift and drag forces, leading to an agreement with the existing literature.

<p dir="ltr">Precise measurement of the flowrate is crucial for both process control and energy consumption evaluation. The main aim of this work is to develop a methodology to calibrate mechanical flowmeters, designed to measure high viscosity fluids, in water. In order to accomplish this, a series of computational fluid dynamics (CFD) analysis are carried out to determine how the motion of the mechanical component varies with different flow rates of water and high viscosity fluids. This data is recorded and analyzed to develop calibration curves that relate the motion of the mechanical component the flow rates. From the calibration curves, it can be determined the required water flow rate to achieve the equivalent motion of the mechanical component in a specified viscosity. This method provides an efficient and cost-effective calibration process because it eliminates the need for calibrating using heated engine oil to achieve the fluid viscosity of the flow meter is designed. Flowmeter sensitivity analysis was also performed and it was observed that the motion of the mechanical component curves converges as the size of the flowmeter increases suggesting that the effect of viscosity on flowmeter sensitivity decreases as the size of the flowmeter is increased, likely due to reduced resistance to flow and smaller pressure drops. </p><p dir="ltr">The Kanbara Reactor ladle is a commonly used method in the steelmaking industry for hot-metal desulfurization pre-treatment. The impeller's configuration is pivotal to the reactor's performance, yet its precise function remains partially understood. This study introduces a 3-dimensional Volume-of-Fluid (VOF) model integrated with the sliding mesh technique, investigating the influence of five different impeller speeds. After Validating the model through experimental data, this numerical model is applied to investigate the typical developmental phenomena and the consequences of impeller speed variations on fluid flow characteristics, interface profile, and vortex core depth. The findings reveal that the rotational impeller induces a double-recirculation flow pattern in the axial direction due to the centrifugal discharging flow. With increasing impeller rotation speed, the vortex core depth also rises, emphasizing the substantial impact of impeller speed on vortex core depth.</p>

In this thesis, a loosely coupled Fluid-Structure Interaction (FSI) analysis method is developed for the solution of steady state missile/rocket aeroelastic problems. FLUENT is used as the Computational Fluid Dynamics (CFD) tool to solve Euler equations whereas ANSYS is used as the Computational Structural Dynamics (CSD) tool to solve linear structural problem. The use of two different solvers requires exchanging data between fluid and structure domains at each iteration step. Kriging interpolation method is employed for the data transfer between non-coincident fluid and structure grids. For mesh deformation FLUENT&rsquo / s built-in spring based smoothing approach is utilized. The study is mainly divided into two parts. In the first part static aeroelastic analysis for AGARD 445.6 wing is conducted and the results are compared with the reference studies. Deformation and pressure coefficient results are compared with reference both of which are in good agreement. In the second part, to investigate possible effects of aeroelasticity on rocket and missile configurations, static aeroelastic analysis for a canard controlled generic slender missile which is similar to a conventional 2.75&rdquo / rocket geometry is conducted and results of the analysis for elastic missile are compared with the rigid case. It is seen that the lift force produced by canards and tails lessen due to deformations, stability characteristics of the missile decreases significantly and center of pressure location changes due to the deformations in the control surfaces.