On the dynamics of flexible risers and suspended pipes

This thesis describes a theoretical and numerical study of the static and dynamic behaviour of flexible pipes and risers. Although the effects of conventional loadings due to self-weight, current, waves and surface vessel excitation are included, this work is specifically aimed at identifying the effects of internal and external fluid pressures as well as both constant density and alternating gas-fluid internal flows on the static and dynamic behaviour of risers. Particular emphasis is placed on research and development of advanced numerical analysis methods for solving the non-linear riser equations in the frequency and time domains. Theoretically calculated responses have been compared with results of model tests carried out at Heriot-Watt University and University College London and with theoretical predictions from alternative formulations. Modified forms of the governing equations for flexible risers have been derived from first principles to include the effects of internal and external hydrostatic pressures and a steady internal flow. It is rigorously shown that the conventional derivation of effective tension using a buoyancy analogy is equivalent to that obtained through exact integration of fluid pressures over the curved surface of the riser pipe. It is also demonstrated that the effect of a steady internal flow is analogous to that of hydrostatic pressure and may be included in the governing equations through the effective tension term. The riser governing equations have been solved using a finite element analysis program written specifically for flexible risers and similar pipe geometries. The static analysis of the riser is carried out using an iterative approach that can accommodate general loading conditions using an incremental shifting procedure. Modifications to the standard non-linear static analysis techniques have been proposed and are shown to provide a more accurate representation of the deformation dependence of loading whilst retaining the non-linear influence of tensile forces on pipe geometry. Dynamic analyses have been carried out using both frequency and time domain techniques. The frequency domain approach is a regular wave analysis based on a combined wave and current linearisation whilst the time domain analysis uses the Newmark method and can accommodate regular and irregular sea states as well as geometric non-linearities. Results of this numerical work have been verified by comparison with model tests and analysis results from several sources. Model tests carried out at Heriot-Watt University at 1:50th. scale have been used to verify global predictions for riser responses and tensile forces. Specially designed model tests at University College London have been used to confirm the validity of predicted riser responses to internal flow. Comparisons have also been made with the analysis results of parallel research works. Case studies of typical North Sea flexible risers are presented. The analytical and numerical work demonstrates that it is essential to include the effects of internal and external hydrostatic pressures and internal flow for accurate prediction of the overall response of a flexible riser. In particular, internal flow composed of alternating gas-liquid phases (slug flow) is shown to induce large oscillations in riser tensions at frequencies defined by the flow parameters. These oscillations are comparable to those induced by wave action and have a significant impact on the fatigue life of flexible risers

Modeling and Simulation in Engineering

This book provides an open platform to establish and share knowledge developed by scholars, scientists, and engineers from all over the world, about various applications of the modeling and simulation in the design process of products, in various engineering fields. The book consists of 12 chapters arranged in two sections (3D Modeling and Virtual Prototyping), reflecting the multidimensionality of applications related to modeling and simulation. Some of the most recent modeling and simulation techniques, as well as some of the most accurate and sophisticated software in treating complex systems, are applied. All the original contributions in this book are jointed by the basic principle of a successful modeling and simulation process: as complex as necessary, and as simple as possible. The idea is to manipulate the simplifying assumptions in a way that reduces the complexity of the model (in order to make a real-time simulation), but without altering the precision of the results

Mathematical Modeling and Simulation in Mechanics and Dynamic Systems

The present book contains the 16 papers accepted and published in the Special Issue “Mathematical Modeling and Simulation in Mechanics and Dynamic Systems” of the MDPI “Mathematics” journal, which cover a wide range of topics connected to the theory and applications of Modeling and Simulation of Dynamic Systems in different field. These topics include, among others, methods to model and simulate mechanical system in real engineering. It is hopped that the book will find interest and be useful for those working in the area of Modeling and Simulation of the Dynamic Systems, as well as for those with the proper mathematical background and willing to become familiar with recent advances in Dynamic Systems, which has nowadays entered almost all sectors of human life and activity

Generalized averaged Gaussian quadrature and applications

A simple numerical method for constructing the optimal generalized averaged Gaussian quadrature formulas will be presented. These formulas exist in many cases in which real positive GaussKronrod formulas do not exist, and can be used as an adequate alternative in order to estimate the error of a Gaussian rule. We also investigate the conditions under which the optimal averaged Gaussian quadrature formulas and their truncated variants are internal

MS FT-2-2 7 Orthogonal polynomials and quadrature: Theory, computation, and applications

Quadrature rules find many applications in science and engineering. Their analysis is a classical area of applied mathematics and continues to attract considerable attention. This seminar brings together speakers with expertise in a large variety of quadrature rules. It is the aim of the seminar to provide an overview of recent developments in the analysis of quadrature rules. The computation of error estimates and novel applications also are described

Microwave resonant sensors

Microwave resonant sensors use the spectral characterisation of a resonator to make high sensitivity measurements of material electromagnetic properties at GHz frequencies. They have been applied to a wide range of industrial and scientific measurements, and used to study a diversity of physical phenomena. Recently, a number of challenging dynamic applications have been developed that require very high speed and high performance, such as kinetic inductance detectors and scanning microwave microscopes. Others, such as sensors for miniaturised fluidic systems and non-invasive blood glucose sensors, also require low system cost and small footprint. This thesis investigates new and improved techniques for implementing microwave resonant sensor systems, aiming to enhance their suitability for such demanding tasks. This was achieved through several original contributions: new insights into coupling, dynamics, and statistical properties of sensors; a hardware implementation of a realtime multitone readout system; and the development of efficient signal processing algorithms for the extraction of sensor measurements from resonator response data. The performance of this improved sensor system was verified through a number of novel measurements, achieving a higher sampling rate than the best available technology yet with equivalent accuracy and precision. At the same time, these experiments revealed unforeseen applications in liquid metrology and precision microwave heating of miniature flow systems.EThOS - Electronic Theses Online ServiceGBUnited Kingdo