The motivation for the present work is to investigate particle-laden turbulent flows using accurate numerical simulations. In the present work, the carrier phase is modeled using direct numerical simulations (DNS) and the particles are tracked in a Lagrangian sense. Investigations of both one-way and two-way coupled particulate flows in homogeneous isotropic turbulence have been carried out. The phenomenon of interest in one-way coupled simulations is preferential accumulation, which refers to the tendency of heavy particles in isotropic turbulence to collect in regions of high strain and low vorticity. Several measures and mechanisms of accumulation have been reported in the literature often showing conflicting scaling with particle and fluid parameters. In the present study, accumulation has been quantified using several indicators to give a unified picture. The present work addresses the scaling of preferential accumulation with Reynolds number and suggests that while the spacing between particle clusters does exhibit a dependence on Reynolds number, the structure of particle clusters as viewed by individual particles shows little dependence on Reynolds number. The effect of adding a gravitational settling force on the particles has also been explored. While the gravity force tends to homogenize the particle distribution at low Stokes numbers, at high Stokes numbers it tends to arrange the originally random distribution into streaks in the direction of gravity. The ability of the Lorentz force to limit preferential accumulation has been the focus of the next part of the study. Charges are placed on particles to produce an electric field when the particles are inhomogeneously distributed. The electric field and thereby the Lorentz force tend to homogenize the particle distribution. It is interesting to note that the particle distribution attains a stationary state determined by the total amount of charge contained in the domain. It is demonstrated that in the presence of gravity, less amount of charge is required to homogenise particle distribution. Good agreement is observed for simulations of settling charged particles with experimental work. The modification of carrier phase turbulence by particles is studied formono-sized particles. The non-uniform modification of the fluid energy spectrum by particles has been demonstrated. It is seen that there is an increase in energy at high wave numbers for microparticles (St k < 1), whereas for high Stokes number particles, energy is damped at all scales. The effect of incorporating two way coupling on particle distribution has also been reported. It is noted that increasing mass loading leads to attenuation of accumulation at low Stokes numbers while the effect is reversed at higher Stokes numbers.

The subject of `irrigation performance assessment' has grown in importance since the early 1970s. This has been as a result of the increasing realization that irrigation schemes around the world, particularly those in developing countries, do not live up to their expectations. There has therefore been an increasing interest in probing into the operations of existing irrigation schemes in order to understand their strengths and weaknesses, and to developing methodologies and indicators for performance assessment, with a view to improving their performance and water use efficiency. This study presents a conceptual methodology and performance indicators for evaluating the performance of medium scale irrigation schemes in Africa with joint participation between smallholder farmers and an irrigation agency. The proposed methodology provides a logical sequence of the main processes involved in irrigation performance assessment with emphasis on the 'whole system' or 'farming system' approach. Performance indicators have been proposed which relate to the inputs, processes of transformation, and outputs, which is a marked variation from existing approaches which focus only on the evaluation of outputs. The indicators describe qualitatively and quantitatively the level of attainment of the objectives of an irrigation scheme, or parts thereof. The methodology and concepts outlined in the first part of this work are applied to study the operation and performance of the Wurno Irrigation Scheme, Nigeria, a typical formal medium scale jointly managed irrigation scheme in sub-Saharan Africa. The results of the case study show the performance of the Scheme to be unsatisfactory. This raises questions regarding the views of international lending agencies and governments of developing countries who are looking to smaller, as opposed to large, scale irrigation schemes as the way forward. The study argues that the critical issue is not that of size per se, but the linkages between the primary characteristics of the physical design of the irrigation infrastructure, and the structure of the organizational and institutional arrangements for the operation and management of the scheme.

Downwind yacht sails are subjected to fluid structure interaction effects which can slightly change the initial design shape, with a direct impact on the overall performances. The turbulent flow acting on downwind sails is separated for the larger part of the device, with large vortices and recirculating regions. The sail is made of a thin fabric, the deformation of which is affected by wrinkling, which produces out-of-plane oscillations of the surface of the fabric, and locally changes the stress/strain distribution. Because of the interactions of these fluid and structural phenomena, the detailed analysis of downwind sails requires sophisticated approaches able to capture the structural deformations, the generation of the wrinkles and the unsteady fluid structure interactions. This is not achieved in conventional sail analysis, the state of the art of which consist, for the most advanced applications, in steady fluid structure analysis adopting membrane structural elements, which are unable to reproduce the wrinkling. The turbulent flow is here analysed with a Reynolds Averaged Navier Stokes method implemented in the finite volume solver OpenFOAM, and case studies are presented regarding the detailed description of the flow/wrinkle interactions, as well as the flow generation on full 3D sail-type devices. This approach is a good compromise between accuracy and computational expense, allowing the investigation of unsteady fluid structure interactions. The work presented here in fact primarily concentrates on the structural response and its influence on the fluid flow rather than the analysis of the fine details of an isolated unsteady flow. Shell finite elements of the Mixed Interpolation Tensorial Components (MITC) family are used for simulating the fabric. The use of these sophisticated Finite Elements allows for capturing the greater detail of the structural behaviour and the generation of the wrinkles. Comparisons are presented between the results obtained with the shells and the membrane finite elements, traditionally adopted for the structural analysis of fabrics. The performances of the method are demonstrated with simplified validation test cases and applications are shown for realistic 3D devices. Unsteady fluid structure interaction analysis is performed using the Arbitrary Lagrangian Eulerian (ALE) framework, providing a conservative environment. Validation test cases are compared with reference solutions and the inflation of a sail-type device is analysed. The flow development is accurately captured, and the presence of wrinkles on the cross-flow determine a substantial decrease of the lift and an increase in the drag. Inducing unsteadiness in the flow produces a general increase of the performances of the device. Using shell elements the wrinkling can be directly reproduced, while using membrane models require additional wrinkling models. The prediction performances of the MITC shells are substantially higher than those of the Constant Strain Triangles (CST) membranes, traditionally adopted for simulating the sail fabric. Unsteady fluid structure interaction analysis are validated against reference solutions with good agreement. When applying the method to yacht-sail type geometries, results are coherent and consistent with the sailing practise.

The effects of system rotation and passive wall compliance on hydrodynamic stability is investigated. Rotating channel flow is studied where a Coriolis force instability mechanism produces streamwise rolls at modest Reynolds numbers and rotation rates. The linear stability of mean flow states consisting of a combination of plane Poiseuille and Couette flows is considered using spectral Chebyshev collocation with a staggered grid. A Newton algorithm is implemented in three-dimensional parameter space to calculate minimum points of the neutral surfaces. Weakly nonlinear behaviour of the rolls is studied using a Ginzburg-Landau formulation and accurate numerical values for the equation coefficients indicate supercritical instability. Effects of external pressure gradient and three-dimensionality on boundary layer stability over compliant walls is examined. In these cases an inflexion point in the boundary layer profile promotes a powerful inviscid instability mechanism. Two-dimensional profiles, including a Falkner-Skan representation, are considered in inviscid and viscous analyses with plate-spring and viscoelastic compliant wall models. Walls which are rendered stable with respect to hydroelastic instabilities are shown to reduce maximum spatial growth rates by up to 60%. This work is extended to consider the three-dimensional boundary layer over a rotating disc where inviscid (Type 1) and viscous (Type 2) instabilities can coexist. A single layer viscoelastic wall model coupled to a sixth order system of fluid equations, which accounts for Coriolis and streamline curvature effects, is solved by a spectral Chebyshev tau technique. The Type 1 stationary instability is found to be significantly stabilised, whilst the effect on the Type 2 mode is complex but can be destabilising. For travelling-wave modes, across a band of positive frequencies, evidence of modal coalescence between the Type 1 and 2 instabilities leading to absolute instability is presented. This would constitute a major route to transition and appears to be caused by large values of viscous stress work at the wall/flow interface.

abstract: Analytical solution of the pressure field for water uptake through a composite root, coupled with fully saturated soil is derived by using the slender body approximation. It is shown that in general, the resistance of the root and soil are not additive. This result can play a very important role in modelling water uptake through plant roots and determination of hydraulic resistances of plant roots. Optimum plant root structure that minimizes a single root’s hydraulic resistance is also studied in this work with the constraint of prescribed root volume. Hydraulic resistances under the slender body approximation and without such a limitation are considered. It is found that for large stele-to-cortex permeability ratio, there exists an optimum root length-to-base-radius ratio that minimizes the hydraulic resistance. A remarkable feature of the optimum root structure is that the optimum dimensionless stele conductivity depends only on a single geometrical parameter, the stele-to-root base-radius ratio. Once the stele-to-root base-radius ratio and the stele-to-cortex permeability ratio are given, the optimum root length-to-radius ratio can be found. While these findings remain to be verified by experiments for real plant roots, they offer theoretical guidance for the design of bio-inspired structures that minimizes hydraulic resistance for fluid production from porous media. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2016

Fire has been a major cause of ship's accidents throughout maritime history. It is by far the most serious threat to life and the environment as passenger ships get larger and more sophisticated. It is also impossible to protect a passenger vessel against all hazards. Despite the fact that a passenger ship contains potential fire hazards in the engine room space, accommodation zone and electrical systems, etc, the single most important fire hazard onboard a ship may be the man himself, either unintentionally or intentionally. 'Fire safety on passenger vessel' has continued to be the focus of attention on passenger ships. The work described in this thesis is concerned with the application of Formal Fire Safety Assessment to passenger ships. The traditional way of conducting a Formal Safety Assessment (FSA) employs typical fire safety analysis methods that require a certain amount of data. Most fire accident data available for passenger vessels is associated with a high degree of uncertainty and considered to be unreliable. As such, the research carried out in this thesis is directed at the development of novel fire safety analysis methods to address this problem. This thesis proposed several subjective fire safety analysis methods for passenger vessels within the FSA methodology. Also, it concentrates on developing an advanced approach for passenger ships. A few novel safety analysis and synthesis methodologies are presented to integrate fire safety assessment with decision-making techniques so that fire safety can be taken into account from the concept design /operation stages of passenger ships. This is to ensure a more controlled development process permitting decisions regarding design and operation to be made based on fire safety assessment. Finally, this thesis is concluded by summarising the results of this research project and the areas where further effort is required to improve the developed methodologies.

The study of applying soft computing techniques, such as evolutionary computation and simulation, to the deployment of intelligent autonomous vehicles (IAVs) in container terminals is the focus of this thesis. IAVs are a new type of intelligent vehicles designed for transportation of containers in container terminals. This thesis for the first time investigates how IAVs can be effectively accommodated in container terminals and how much the performance of container terminals can be improved when IAVs are being used. In an attempt to answer the above research questions, the thesis makes the following contributions: First, the thesis studies the fleet sizing problem in container terminals, an important design problem in container terminals. The contributions include proposing a novel evolutionary algorithm (with superior results to the state-of-the-art CPLEX solver), combining the proposed evolutionary algorithm with Monte Carlo simulation to take into account uncertainties, validating results of the uncertain case with a high fidelity simulation, proposing different robustness measures, comparing different robust solutions and proposing a dynamic sampling technique to improve the performance of the proposed evolutionary algorithm. Second, the thesis studies the impact of IAVs on container terminals’ performance and total cost, which are very important criteria in port equipment. The contributions include developing simulation models using realistic data (it is for the first time that the impact of IAVs on containers terminals is investigated using simulation models) and applying a cost model to the results of the simulation to estimate and compare the total cost of the case study with IAVs against existing trucks. Third, the thesis proposes a new framework for the simulations of container terminals. The contributions include developing a flexible simulation framework, providing a user library for users to create 3D simulation models using drag-and-drop features, and allowing users to easily incorporate their optimisation algorithms into their simulations.

A large number of benefits achieved through the successful implementation of Six Sigma programmes in different industries have been documented. However, very little research has been conducted on their applications in the shipping sector, especially in the Onshore Service Functions (OSFs) of shipping companies. Literature shows that heavy human involvement in the service industries such as shipping leads to a high volume of uncertainties which are difficult to be correctly and effectively measured or managed by simply using the traditional data analysis and statistical methods in Six Sigma. The aim of this study is to develop new quantitative analytical methodologies to enable the application and implementation of Six Sigma to improve the service quality of OSFs in shipping companies. Intensive investigations on the feasibility and effectiveness of the developed new methods and models through case studies in world leading container ship lines and shipping management companies have been carried out to ensure the achievement of the aim. This study firstly reviews the evolvement of quality control and some typical methods in the area, the development of Six Sigma, its tools and current applications, especially in the service industries. It is followed by a new framework of the Six Sigma implementation in the OSFs of shipping companies which is supported by a few real process excellence projects carried out in a world-leading ship line. In the process of the framework development, various issues and challenges appear largely due to the existence of uncertainties in data such as ambiguity and incompleteness caused by extensive subjective judgements. Advanced methods and models are developed to tackle the above challenges as well as complement the traditional Six Sigma tools so that the new Six Sigma methodologies can be confidently applied in situations where uncertainties in data exist at different levels. A new fuzzy Technique for Order Preference by Similarity to an Ideal Solution ii(TOPSIS) method is developed by combining the traditional TOPSIS, fuzzy numbers and interval approximation sets to facilitate the effective selection of Six Sigma projects and achieve the optimal use of resources towards the company objectives. A revised Failure Mode and Effects Analysis (FMEA) model is proposed in the “Analyse” step in Six Sigma to improve the capability of classical FMEA in failure identification in service industries. The new FMEA model uses the Analytical Hierarchy Process (AHP) and Fuzzy Bayesian Reasoning (FBR) approaches to increase the accuracy of failure identification while not compromising the easiness and visibility of the Risk Priority Number (RPN) method. Decision Making Trial and Evaluation Laboratory (DEMATEL) and Analytical Network Process (ANP) methods are incorporated with Fuzzy logic and Evidential Reasoning (ER), for the very first time to generate a Key Performance Indicators (KPIs) management method where the weights of indicators are rationally assigned by considering the interdependency among the indicators. Incomplete and fuzzy evaluations of the KPIs are synthesised in a rational way to achieve a compatible and comparable result. It is concluded that the newly developed Six Sigma framework together with its supporting quantitative analytical models has made significant contribution to facilitate the quality control and process improvement in shipping companies. It has been strongly evidenced by the success of the applications of the new models in real cases. The financial gains and continuous benefits produced in the investigated shipping companies have attracted a wider range of interests from different service industries. It is therefore believed that this work will have a high potential to be tailored for a wide range of applications across sectors and industries when the uncertainties in data exceed the ability that the classical Six Sigma tools and methods possess.

This thesis aims to develop a new framework of container port/terminal performance measurement, modelling and analysis. There is a need for a new performance measurement framework not only to meet the need of port stakeholders, but also to develop diagnostic tools capable of supporting decision-making in complex port/terminal operations in an uncertain environment. This study follows the related questions of ‘what to measure’, ‘how to measure’ and ‘how to control and improve’ container port performance. In this regard, this study proposes the development of a systematic approach to address the multi-stakeholder dimension in port performance measurement. This was achieved by integrating a multi-stakeholder dimension in a port performance measurement framework which takes into account the corresponding port performance indicators (PPIs). To this end, this study identified six dimensions of crucial interests in major (container) ports investigating stakeholders’ goals and objectives, and discussed them with port stakeholders. The six dimensions defined in this study cover the range of port activities to cope with new evolutionary changes, to measure and communicate their impacts on society, economy and environment and to be consistent with their goals. Then, through a literature review and an analysis of industrial practices the associated PPIs were selected. The semi-structured interviews were applied to assess the suitability of the potential indicators and to test the feasibility of the selected indicators. The multi-stakeholder dimension involves both quantitative and qualitative PPIs in order to reflect complexity of port/terminal business environments. This study develops two hybrid port performance measurement models: PPIs independency model and PPIs interdependency model. In the first port performance measurement model, a hybrid approach of the Analytic Hierarchy Process (AHP) and Fuzzy Logic based Evidential Reasoning (FER) for solving multiple criteria decision making (MCDM) problems is applied to address the challenges in port performance measurement. AHP is applied for a part of the FER to evaluate the relative importance of the selected PPIs. FER is applied for dealing with uncertainties presented in the evaluations of the selected PPIs as well as aggregation of the evaluations of PPIs and their importance. An analysis of 12 container terminals in South Korea is conducted to validate the proposed method. The second approach, a new conceptual PPI interdependency model, is developed using a hybrid approach of a Fuzzy Logic based Evidential Reasoning (FER), a Decision Making Trial and Evaluation Laboratory (DEMATEL) and an Analytic Network Process (ANP). These methods are combined to deal with the inherent data uncertainties and the interdependencies among the port performance indicators (PPIs). Its novelty lies in its capability of dealing with interdependency among the performance measures as well as accommodating both qualitative and quantitative evaluations on the measures simultaneously. An analysis of 4 major container ports in South Korea is conducted to demonstrate the feasibility of the proposed method. The empirical investigations are conducted by taking the perspectives from different port stakeholders. For instance, the quantitative data (i.e. cargo and vessel operations and financial data) are collected directly from terminal operating companies and information systems/databases managed by port authorities, government and credit rating agencies. The qualitative PPIs are collected using questionnaires from three groups of terminal operators, users (i.e. shipping lines, shippers, logistics service providers and freight forwarders) and administrators (i.e. port authority and government) to assess their own associated PPIs to measure each container port/terminal performance. The empirical results indicate that the hybrid approach attempting to use quantitative modelling for dealing with the uncertainties and interdependency problems can be successfully fulfilled. The framework and its supporting method suggest an effective performance measurement tool and offer a diagnostic instrument to ports/terminals to satisfy the port stakeholders in a flexible manner. Finally, this thesis proposes a decision making framework for prioritising and selecting port performance improvement strategies. It can be achieved by the concepts of benchmarking-best practices using the analytic hierarchy process (AHP) incorporating a fuzzy order preference by similarity to ideal solution (FTOPSIS) method. Based on the results obtained from the two performance approaches, the leading performer (i.e. Busan New Port) and the poor performer (i.e. Busan North Port) are analysed as real cases to demonstrate the feasibility of the proposed methodology. The results yielded by the framework present the ranking of strategy options in terms of their preference to different terminal operating companies (TOCs), which enables decision makers to find optimal solutions to improving performance under their own dynamic business environments.

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