This thesis presents the feasibility, advantages and impact on Preliminary Ship Design of an approach to integrate ship configurational design with the modelling and simulation of a range of crewing issues, such as operations and evacuation. Integrating personnel movement simulation into preliminary ship design introduces the assessment of onboard operations at the front-end of the design process, informing the design and enabling improved operability while the design is still amenable to changes. The approach to accomplish this integration is discussed with the aim of informing all parties involved in the design of ships with regard to the main aspects of personnel operability and on board safety. The research was undertaken as part of a three years research project funded by the Engineering and Physical Sciences Research Council (EPSRC) entitled “Guidance on the Design of Ships for Enhanced Escape and Operation”. The project aimed at bringing together the University of Greenwich developed “maritimeEXODUS” personnel movement simulation software and the SURFCON implementation in the PARAMARINE suite of the Design Building Block approach to Preliminary Ship Design, which originated with the UCL Ship Design Research team. The approach and procedural implications of integrating personnel movement simulation into the preliminary ship design process are presented through a series of SURFCON ship design case studies. With the UK Ministry of Defence as the industrial partner to the project, this study on “design for operation” concentrates on naval vessels, which provide excellent examples of complex environments. Design studies, based on the Royal Navy Type 22 Batch III Frigate design, were analysed using PARAMARINE, maritimeEXODUS and bespoke interface software produced by the candidate. Technical aspects of the development of the interface software are discussed from a procedural perspective, focusing on integration and usability issues. The discussion addresses alternative options to visualising the simulation results and how to integrate into a ship design model a minimum level of detail sufficient to conduct simulations able to inform the designer, while retaining the flexibility the design requires in early stages design. The thesis concludes by summarising the opportunities that integrating operational simulation into preliminary ship design opens up for the future practice of ship design, contributing to the debate on the nature of ship design and of Computer Aided Preliminary Ship Design.

The annual rise of hip procedures occurring year upon year is a major concern, especially with revision rates increasing. There is need for improvements for orthopaedic materials to compensate for this problem with higher success rates in the long term. The main failure of current metallic materials used in hip replacement devices is due to wear and the metallic ions being leached out. Cobalt-based alloys are one of the best bearing surface materials used in hip replacement, however, a better understanding of the microstructure and mechanical properties is required to enhance its properties and also the need for new fabrication techniques to be explored to develop materials that can reduce the number of revision surgeries. The most common cobalt based alloy (F75) used in orthopaedics is investigated and a novel route to manufacture the alloy is conducted. Heat treatments via annealing and normalising are analysed. In the annealed alloy up to 1100°C there is an increase in hardness and carbide content. Above this temperature, there is a significant decrease in both properties due to carbide dissolution. XRD analysis identifies the phases present and how they varied with temperature. The production of the F75 alloy via spark plasma sintering has yielded an alloy with carbide free microstructures. The grains are finer than the conventional methods of fabrication (cast and wrought) and the hardness is significantly higher even in the absence of the carbides. The hardness has been attributed to the formation of oxide phases within the microstructure and chromium and molybdenum rich phases that act as solid solution hardeners. The oxide in the microstructure is identified as chromium oxide formed by a redox reaction between cobalt oxide found on the surface of cobalt particles and chromium. Tribological performance has been investigated upon this newly manufactured alloy (SPS alloy) against two commercial medical grade cobalt based alloys (F75 and F1537) used in hip replacement devices. The SPS alloy had higher hardness, which resulted in the lowest wear rate and friction coefficient, with lower amounts of chromium and molybdenum detected from the wear debris compared to the F75 and F1537 alloys. The wear debris size and size distribution generated from the SPS alloy were very small and the shape was more spherical. The element leaching is conducted upon these alloys, with the SPS alloy forming an oxide layer upon the surface that could be beneficial for limiting ion leaching and for tribological performance.

Local blood flow can cause wall shear stress (WSS) patterns which are linked to the formation of aneurysms[1]. A common location for intracranial aneurysms is the anterior communicating artery (ACoA) which connects the anterior cerebral arteries (ACAs) in the circle of Willis (CoW)[2]. The CoW is a ringlike four-to-six junction[3] with potentially highly complex flow patterns[3-5]. In this thesis, we develop a two-dimensional, rigid CoW model, with pulsatile inlet pressure conditions and resistance outlet conditions. The Navier-Stokes equations are solved using the latest finite volume method derivation[6] and some additional mathematics for the pressure condition. A code, based on that of the author's supervisor, is developed to carry out flow simulations. Three simulation set-ups cover a physiological range of flows: symmetric inlet conditions and configuration; internal carotid artery inlet pressure phase difference and symmetric configuration; symmetric inlet conditions and a narrow proximal (A1) section of the left ACA. In the first case, we find asymmetric, weak ACoA flow with vortex patches at each end due to stronger passing ACA streams. This causes areas of raised WSS in the ACA, narrow WSS peaks at the ACoA ends, and low magnitude, oscillating WSS along the ACoA. In the second case, we find that small phase differences lead to significant ACoA flow, oscillating in direction. This results in (potentially low magnitude) oscillating ACoA WSS. Compared with the first case, we see increases in the raised ACA WSS on the upstream ACoA side and considerable increases in the narrow peaks leading to high magnitude WSS and high WSS gradient. In the third case, a one-half normal width left A1 causes a significant right-to-left ACoA flow. Striking consequences include increases in both narrow peaks, from the first case, causing high magnitude WSS and high WSS gradients, and separation inducing disturbances and low magnitude, oscillating WSS.

Blood is a complex fluid comprised of predominantly red blood cells (RBCs) suspended in a continuous, Newtonian phase, the plasma. Blood viscosity is highly dependent on the RBC concentration (haematocrit) and also displays shear thinning properties, as a result of RBC deformation and aggregation at high and low shear rates, respectively. However, these two phenomena also lead to uneven haematocrit distributions, which are exacerbated in microvascular bifurcations. In the present study, multifaceted experiments of human blood, perfused through bifurcating microchannels, are used to further elucidate the relationship between haematocrit, velocity and viscosity. A custom pressure based perfusion system was developed and was coupled with image acquisition for velocity measurement with μPIV and further processing. The acquired data was analysed in order to investigate the flow characteristics of human blood in two different idealised bifurcation geometries. The `cell-depleted layer' (CDL), a region of reduced haematocrit which occurs near the walls of the channel, and the continuous haematocrit distribution were experimentally measured. Analytical and numerical approaches were used to extract further information on the effect of flow rate, flow ratio and the presence of aggregation on microhaemodynamics. In the parent branch of the bifurcation, RBC aggregation was observed to increase the radial migration of RBCs away from the vessel wall. This enhanced the non-uniformity of the haematocrit downstream of the bifurcation and altered the relative velocity between the RBCs and the suspending medium. A skewed distribution of cells was observed downstream of the bifurcation, which resulted in skewed velocity profiles, which were also captured in the analytical and computational approaches. The geometry of the bifurcation was observed to influence the results and RBC aggregation quite significantly modified the haemodynamic characteristics even at high flow rates.

The detection of fatigue cracks at fasteners in the sub layers of multi-layered aircraft structures can be problematic using conventional nondestructive testing methods. In this thesis the sensitivity of low frequency guided ultrasonic waves to detect these defects is studied. Guided ultrasonic waves typically have energy distributed through the thickness of such structures and allow for defect detection in all sub-layers, but have wavelengths larger than commonly used in bulk wave ultrasonic testing. The model aerospace multi-layered structure investigated consists of two aluminium plate strips adhesively bonded using a paste adhesive with a fastener hole. Guided waves were excited by placing piezoelectric (PZT) transducers on the surface of the structure. Experimentally the wave propagation and scattering was measured using a laser interferometer. The wave propagation was studied numerically using Semi-Analytical Finite-Element (SAFE) calculations and 3D Finite Element (FE) simulations. Thickness and width mode shapes of the guided waves were identified from the SAFE simulations. By placing PZT discs across the width of the structure the excited exural wave modes could be controlled to an extent. The thickness mode shapes of these waves are similar to those in a large multi-layered plate structure. 3D FE simulations predict a similar amplitude change due to a defect in these structures. Fatigue crack growth monitoring on tensile specimens was realized, measuring the amplitude at a single point. The measured changes in the amplitude of the ultrasonic signal due to a defect agree well with 3D FE simulations. These investigations found that using low frequency guided ultrasonic waves defects through the thickness of a hidden sub layer can be detected from measurements on the undamaged, accessible layer.

In this thesis, the capability of the electrohydrodynamic atomization (EHDA) process for preparing drug delivery carriers consisting of biodegradable polymeric particles with different sizes and shapes was explored. The first part of the thesis describes a detailed investigation of how the size, morphology and shape of the particles generated can be controlled through the operating parameters; specifically the flow rate, applied voltage and the properties of the solutions. Diameter and shape of the particles were greatly influenced by viscosity and applied voltage. The mean size of the particles changed from 340 nm to 4.4 μm as the viscosity increased from 2.5 mPa s to 11 mPa s. Also, using more concentrated polymer solution (30 wt%) and higher applied voltage (above 14 kV) were found to be ideal for promoting chain entanglement and shape transition from spherical to oblong to a more needle-like shape. Estradiol-loaded micro and nanoparticles were produced with mean sizes ranging from 100 nm to 4.5 μm with an encapsulation efficiency ranging between 65% to 75%. The in vitro drug release profiles of the particles started with an initial short burst phase and followed by a longer period characterised by a lower release rate. Two strategies were developed to tailor these profiles. First, ultrasound was explored as a non-invasive method to stimulate “on demand” drug release from carrier particles. Systematic investigations were carried out to determine the effect of various ultrasound exposure parameters on the release rate in particular output power, duty cycle and exposure time. These three exposure parameters were seen to have a significant enhancing effect upon the drug release rate (up to 14%). The second strategy explored was coating the surface of the particles with chitosan and gelatin. This enabled control and reduction of the prominence ‘burst release’ phase without affecting other parts of the release profile. Coating the particle surface with 1 wt% chitosan solution considerably reduces the initial release by 62%, 60% and 42% for PLGA 2 wt%, 5 wt% and 10 wt%, respectivly in the first 72 hours This work demonstrates a powerful method of generating micro and nano drug-loaded polymeric particles, with modified release behaviour and with control over the initial release.

A recently developed electrohydrodynamic direct-write printing method which can be applied to all types of materials and used to create ordered structures and complex patterns using coarse processing needles is described. Utilising co-axial flow of materials has been successful in enabling encapsulated structures to be generated by this technique. Topography is a crucial physical cue in influencing cellular responses and should be considered when designing biomedical architectures. Electrohydrodynamic printing is used in this work to generate ordered topographies with proven biomaterials. By coupling this method with solvent evaporation techniques, desirable scaffold properties can be achieved. These novel areas will offer much greater control over the forming of a plethora of micro- and nano-scaled structures and is essential for topographic studies (e.g. of living cells), novel particle preparation methods, coatings and direct writing of biomaterials. Few studies have evaluated the early stages of cell attachment and migration on the surface of biomaterials, partly due to a lack of suitable techniques. One of the major aims of this study was to use time-lapse microscopy to evaluate the behaviour of fibroblasts cultured with polycaprolactone microfibers and to assess spatially and temporally, the cell-microfiber interaction over a 24 hours period. Ordered polymeric structures were printed onto glass substrates using electrohydrodynamic printing to produce fine microfibers according to a predetermined architecture. Fibroblast attachment and migration was characterized as a function of distance from microfibers. The use of time-lapse microscopy revealed a gradual decrease in cell attachment as the distance from the structures was increased. The technique also revealed interesting cell behaviour once attached to the structures that would otherwise have been missed with standard microscopy techniques. The findings demonstrate time-lapse microscopy is a useful technique for evaluating early stage cell-biomaterial interaction that is capable of recording important events that might otherwise be overlooked.

Cells sense and generate both internal and external forces. They resist and transmit these forces to the cell interior or to other cells. Moreover a variety of cellular responses are excited and influenced by transducing mechanical stimulations into chemical signals that lead to changes in cellular behaviour. The cytoplasm represents the largest part of the cell by volume and hence its rheology sets the maximum rate at which any cellular shape change can occur. To date, the cytoplasm has generally been modelled as a single-phase viscoelastic material; however, recent experimental evidence suggests that its rheology can be described more effectively using a poroelastic formulation in which the cytoplasm is considered to be a biphasic system constituted of a porous elastic solid meshwork (cytoskeleton, organelles, macromolecules) bathing in an interstitial fluid (cytosol). In this framework, a single parameter, the poroelastic diffusion constant p D , sets cellular rheology scaling as ~ 2 / p D Ex m with E the elastic modulus, x the hydraulic pore size, and m the cytosolic viscosity. Though this poroelastic view of the cell is a conceptually attractive model, direct supporting evidence has been lacking. In this work, such evidence is presented and the concept of a poroelastic cell is validated to explain cellular rheology at physiologically relevant time-scales. In this work, the functional form of stress relaxation in response to rapid application of a localised force by atomic force microscopy microindentation is examined in detail and it is shown that at short time-scales cellular relaxations are poroelastic. Then, p D is measured in cells by fitting experimental stress relaxation curves to the theoretical model. VI Next, using indentation tests in conjunction with osmotic perturbations, the validity of the predicted scaling of p D with pore size is qualitatively verified. Using chemical and genetic perturbations, it is shown that cytoplasmic rheology depends strongly on the integrity of the actin cytoskeleton but not on microtubules or intermediate filaments. Finally, comparison of scaling of viscoelastic and poroelastic models suggests that shorttime scale viscoelasticity might be due to water redistribution within the cytoplasm and a simple scaling relating cytoplasmic viscosity to cellular microstructure is provided.

Fluid flows often consist of multiple bodies either filling most of the flow domain (for instance, porous media) or grouped in localized regions. Flow through localized groups containing many bodies has, hitherto, had little detailed study. The primary objective was to develop and trial new numerical and experimental procedures that make possible detail studies of complex multibody flows. The research investigates flow through a circular array of fixed size and populated by different numbers of equally spaced cylinders, allowing the void fraction (φ) to be varied. The main contribution is a detailed fully-resolved two-dimensional numerical calculation of flow past arrays containing from 1 to 133 cylinders, where the array Reynolds number is 2100. To produce this, a parallel computational code has been written, specifically for a supercomputer, in general object-orientated language using late binding and high performance numerical libraries (PETSc, MKL and ParaMETIS). New diagnostics were applied to understand the array’s influence on the flow through and around the array. A linear model was used to interpret the results. An experimental apparatus was designed to measure and vizualize the flow field and force contributions from an array fixed in a uniform flow. The design concept (including the flume, instrument array and electronics) was tested and optimized using CFD and FEA. The experimental results provide insight into the difference between two- and three-dimensional flow patterns. Case studies and experiments have generated data and graphical images at a level of resolution not previously possible. Three distinct regimes have been identified. For low φ, the interaction between the individual cylinders is weak. For intermediate φ, a shear layer is created and stabilized by the bleed flow through the group, resulting in steady forces on the group. For high φ, strong blocking occurs and the array acts like a solid cylinder.

Efficient maritime navigation through obstructions is still one of the many problems faced by mariners. The increasing traffic densities and average cruise speed of ships also impede the collision avoidance decision making process by reducing the time in which decisions have to be made. It seems logical that the decision making process be computerised and automated as a step towards reducing the risk of collision. Although some studies have focused on this area, the majority did not consider the collision regulations or environmental conditions and many previously proposed methods were idealistic. This study develops a motion planning algorithm that determines an optimal navigation path for ships in close range encounters based on known and predicted traffic and environmental data, with emphasis on the adaptability of the algorithm to optimised for different criteria or missions. The domain of interest is the 5 nautical mile region around own-ship based on the effective range of most modern navigation radars and identification devices. Several computational constraints have been incorporated into the algorithm and categorised based on safety priority. Collision-free and conformity with collision regulations are the primary constraints that have to be satisfied; followed by secondary or optional mission specific constraints e.g. commensurate with environmental conditions or taking the shortest navigation path. Own-ship speed is considered to be a dynamic property and a function of the engine setting, which is a variable modifiable by the optimisation routine. The change in the ship’s momentum as a result of a turning manoeuvre is also included in the model. A modified version of an evolutionary algorithm is adopted to perform the optimisation, where the variables are spatial coordinates and the engine setting at the particular path segment. The navigation path can be optimised for specific criteria by adjusting the weighting on the cost functions that describe the properties of the navigation paths.