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A typical marine drilling riser joint has a main riser pipe in the middle as the load carrying structural member; the auxiliary lines are outside of the main riser pipe and piercing through the synthetic foam module. Whether the auxiliary lines carrying any tension load depends on the float between the auxiliary line's couple housing and the cut-out 'pocket' in the flange has closed or not. The advantage of a load-sharing flange design is the main riser pipe wall thickness reduction. As a result less riser tension is required; hence less deck load. A significant cost can be saved in the drilling vessel construction. For a load sharing marine drilling riser the main riser pipe carrying the full tension load (the first slope) then auxiliary lines sharing the load (the second slope) is well accepted and used in the design. Therefore in the finite element analysis for a load sharing marine drilling riser flange the two-slope theory is followed. However a much more elaborate model reveals that the main riser pipe has a third slope when the auxiliary lines are pressurised. Marine drilling riser using a load sharing flange design as the coupling connector is becoming popular as people venture into the ultra deep water over 10000 ft. The advantage and goal is the reduction in riser pipe wall thickness; hence the riser system weight saving. The float (gap) value between the auxiliary lines' coupling and the flange cut-out pocket is diligently designed in the engineering phase and carefully maintained in the manufacturing phase so that auxiliary lines start sharing the load at the desired tension magnitude.

Dynamic response analysis of ship propulsion systems has become an accepted and proven practice worldwide as part of the ship propulsion system design process. This process entails the use of a simulation model of the hull and integrated propulsion machinery components mated with a model of the propulsion Machinery Control System (MCS) algorithms. From this entire propulsion system model extensive simulation tests are performed to predict the systems steady state operating envelope as well as its transient performance for various drive modes hull displacements and environmental conditions. Tests are also performed to predict the propulsion system's dynamic response for various manoeuvres. The analysis of these simulation results is an integral part of the design process because it allows system performance estimates to be available during the design stage of the ship. The analysis is essential in designing and validating MCS algorithms and contributes substantially to the development of training/test support systems. In essence it provides an understanding of how the propulsion system and propulsion control algorithms will function on the ship before it is built. Sail it before you build it. This paper describes the use of dynamic response analysis in the MCS algorithm development process and includes examples and lessons learned during the application of this process to various marine applications.

Due to the increasing power of electric power and propulsion systems on board warships the magnetic signature generated by these systems has become a significant design aspect because of mine threats. In the conceptual design phase of a ship it is important to have a rough idea of its expected magnetic signature. The aim of this work is to obtain a practical too that predicts these magnetic fields. The aim here is to develop this model for the magnetic signature of a ship generated by the electrical power and propulsion system. An outline of the strategy to achieve this is given as well as the results obtained so far. Firstly it is argued that the Maxwell equations can be reduced to a subset describing the magneto stationary problem. In the paragraph 'basic geometry' a simple configuration is considered that can be seen as a primitive form of the problem at hand. This configuration brings to light the fundamental properties of the modelling problem and can be used as a reference to put the different modelling tasks in perspective. After the outline of the modelling strategy those elements of the modelling that have been completed so far are considered. Finally the results are evaluated and future work is identified.

With increasing fuel prices and the demand to achieve lower emissions gas engines have become a real seller on the engine market. Various new engine types entering the market show that the development in terms of power density and efficiency has not yet come to an end. The piston as a core engine component is directly affected with higher peak firing pressures and higher temperature loads. Thus new ways need to be found to ensure proper functionality at higher demands. Various challenges impact upon the piston design of large bore gas engines. Market and customer demands for increased engine efficiency and stringent exhaust gas legislation need to be met with measures like employment of the Miller Cycle and others. This consequently results in higher peak cylinder pressures. At the same time temperature spots need to be avoided in order to stay away from knocking combustion. All these affect the piston and are essential for gas engines with spark ignition (pre chamber or open chamber) as well as for dual fuel gas engines. In close co-operation with the engine builders MAHLE developed new piston designs addressing the above requirements. Here measures to reduce the maximum piston temperature by approx. 25K through cooling optimization are explained. FEA results of temperature calculations are compared with measured temperatures showing the high capability of the FEA simulation.

A method of marine seafloor classification is proposed which promises to be a useful and simple tool for characterising bottom and sediment types. The distribution of sediment types is surveyed using Datasonics SIS1502 sidescan sonar interfaced to GeoDAS (Geographical Data Acquisition System). The GIS (Geographic Information Systems) software ERmapper is used to classify the digital sidescan image based on colour differences using an unsupervised classification technique. Sediment samples are taken from the study area and are analysed for grain size distribution to verify the use of ERmapper as a classification tool. The imagery clearly reveals different sediment properties. These differences are also distinguished by the unsupervised classification process. An insufficient number of sediment samples is processed to allow for a statistical comparison of sediment grain size distribution and the sidescan image. However the sediment size distribution observed in the samples analysed shows a clear relationship to the sidescan image. This analysis therefore shows that the use of sidescan sonar coupled with GIS software has the potential to be used to remotely characterise sediment types within the coastal zone.

This paper describes the US Navy's program to ensure that compensated fuel-ballast ships comply with oil waste discharge requirements during refuelling and that the operational capability of these vessels is optimised by the reduction-elimination of water hideout. The CFD (computational fluid dynamics) analysis is described together with 1/8-scale physical model experimental efforts to assess the performance of the Arleigh Burke (DDG 51) class of US Navy guided missile destroyer mid-group compensated fuel-ballast tank 5-300-2-F. Results show that baseline configurations can have mass fuel discharge before refuelling is terminated due to non-uniformities in tank filling. The tanks also have a high potential for fuel- water mixing particularly where buoyant jets impinge on the tank top. Various modifications to the tank structure and diffuser piping are assessed. Results show that water hideout and problems with mass fuel discharge can be minimised or eliminated with relatively minor modifications to the structure. Also the potential for fuel-water mixing can be reduced by eliminating buoyant jets. The ultimate objective of this work is to quantify effluent fuel concentrations during refuelling.

Oil platforms seem to sustain damage due to waves more often than standard theories would predict. Ocean waves are dispersive and directionally spread changing size and shape as they propagate. Therefore the maximum crest height over an area in a given length of time will be larger than the maximum crest at a single point. Extreme crest heights are usually calculated from single point statistics but the designer of a platform is really interested in the probability of a wave crest reaching any part of the deck area. Statistics for the maximum crest over an area have been developed using a combination of analytic theory and numerical simulations. A sophisticated theory for the maximum of a multi-dimensional Gaussian process is reviewed. Simulations are used to verify the theory and calibrate simple formulas for engineering use. Next it is shown how the linear crest heights can be corrected up to second order. Then the area inundated by 2D wave crests is calculated by a applying a 2D version of the NewWave method that finds the most probable shape of an extreme wave. These calculations show that although the maximum crest over an area is higher than given by the usual method of calculation the force on a platform from that crest is not necessarily very high and only a small fraction of the deck may be inundated. Finally conclusions are drawn.

New production facilities require accurate metering of produced fluids for optimal reservoir and facilities management. The need for cost and size reduction and the severe effects of high watercut production on accuracy are forcing careful evaluation of multiphase metering methods. A process of custom design of multiphase metering systems from commercially available components is being used selected to optimally perform in accuracy and cost for the production design basis. Software models of conventional and compact separation have been developed which allow comparison in cost and size for equal performance. These models demonstrate that separation can rarely be considered to be perfect and that optimal system design must take realistic incomplete separation of gas and liquid into account. Software and data have been developed for design and implementation of partial separation multiphase metering applicable to surface floating and subsea contexts. These products allow design engineers to input their field conditions and obtain within minutes performance cost and size expectations for hundreds of combinations of separation rate metering and watercut metering for further review.

The problem of classification of underwater targets involves discrimination between mine-like and non-mine-like objects as well as the characterisation of background clutter. To improve the performance of a given classifier usually multiple aspects are fused together in some fashion. In this work an HMM (hidden Markov Model) is used to make the overall decision. This is a very powerful tool for using multiple observations to make a decision as no decision is made until all the evidence is presented. In recent years much attention has been given to the area of automatic speech recognition using MLP (multi-layer perceptron) networks for estimating certain probabilities in the HMM framework. Here several approaches are taken to this MLP-HMM idea and the results are compared. The test results presented are obtained on a wideband acoustic backscattered data set collected using four different objects with one degree of aspect separation for two different bottom (smooth and rough) conditions. The advantages and disadvantages of an HMM scheme in classification of mine-like objects are presented. Several connectionist approaches are discussed and their impact upon the HMM classifier is shown. The idea is to exploit both HMM and MLPs to improve the performance of multi-aspect schemes within the realms of the classification problem. The HMM model is discussed together with the possible training techniques. Various connectionist approaches are explained. The data set used for this paper is described and pre-processing and feature extraction schemes are given. The results of the var87880 Multi-attribute concept design model of search and rescue vessels

With the approach of the 200th anniversary of the Royal Navy's greatest battle off Cape Trafalgar on October 21st 1805, much attention will be given to our most tangible symbol of that most ferocious engagement, Nelson's fully preserved flagship HMS Victory. Much has been written about HMS Victory but it is often simplistic and romanticised or clearly aimed at the technical requirements of the naval historian. In Nelson's Victory: 101 Questions & Answers about HMS Victory, Nelson's Flagship at Trafalgar 1805, Peter Goodwin adopts a fresh approach to explain the workings of the only surviving 'line of battle' ship of the French Revolutionary and Napoleonic Wars. As Victory was engaged in battle during only two per cent of her active service, Peter Goodwin also provides a glimpse into life and work at sea during the other ninety-eight per cent of the time. As technical and historical advisor to the ship in Portsmouth, he is in a unique position to investigate an interpret not only the ship's structure but also the essential aspects of shipboard life: victualling, organisation, discipline, domestic arrangements and medical care. In his role as Keeper and Curator of the ship, the autho

Prediction of VIV (vortex-induced vibrations) is one of the main topics in the design of deepwater risers. The understanding and modelling of the complex fluid-structure interaction requires advanced analysis techniques coupling in a correct manner both structural and fluid dynamics aspects. This study aims to develop optimise and calibrate a numerical code to provide reliable results within a reasonable analysis timeframe and without or very limited need of experimental verification. For this purpose the unsteady RANS (Reynolds Average Navier-Stokes) code Navis is applied to solve a typical riser VIV problem and compute the 3D riser-fluid dynamics interaction. During a preliminary analysis phase the 2D flow past (1) a bare circular cylinder and (2) a straked riser at high Reynolds numbers is simulated (different incidences flow-strake vanes are analysed). Numerical results are validated and calibrated against published test data. The core analysis phase is then focused on the numerical investigation of the unsteady flow over a 3D helical strake. In this phase the 3D flow field turbulent structures and response frequency patterns are analysed. Spectral analysis of data is carried out to identify carrier frequencies deemed to be critical due to the induced vibration of the whole structure and helical strakes efficiency in reducing the riser vibrations is also addressed. Finally comparison between numerical and experimental results shows that the complexity of a 3D model is indeed compensated by a significantly improved accuracy of the obtained results.102069

Coherence time of sound is modeled for a 3250 km section in the Pacific at 75 Hz 0.03 s resolution between a source and receiver both moored high above the ocean floor. The model is based on the temporal evolution of a standard spectrum of internal gravity waves and an accurate approximation for the acoustic wave equation. The probability is 0.6 that the signal-to-noise (s/n) ratio first decreases at times of 13 min or less. Afterward the s/n usually increases reaching a peak near 40 min. This is longer than the experimentally reported coherence time of 12.7 min. The discrepancy could be due to the fact that the experimental value was obtained assuming that movement between the source and receiver could be accounted for using a single Doppler speed correction for each transmission lasting between 10 and 40 min. However accelerations of the source and receiver appear to be too large to use the single Doppler speed correction. Coherence times from the data should be re-analyzed with a variable Doppler scheme to see if they are consistent with the 40 min coherence time predicted from the model.

The behaviour of floating objects such as debris of plants seaweed man-made objects foam etc is determined by surface current. In particular surface convergence results in the concentration of floating objects often along fronts. Surface convergence may also form even without fronts. In this case the area of surface convergence is called 'streak'. Fronts and streaks play an important role in the physical environment of coastal region and the distribution of floating objects may provide useful information about the position and strength of the fronts and streaks. In this study visual observation of floating objects was carried out in The Ariake Sea to establish the relation between fronts and streaks and concentration of floating objects. The Ariake Sea is a partially enclosed bay located in the centre of Kyushu Island Japan. One of the most serious problems was the damage to cultivated seaweed in 2001. Although the main cause of damage was allegedly the reclamation of tidal flat in Isahaya Bay such a connection is still unproved because of the lack of knowledge concerning both the physical and biological environment in the Ariake Sea. Therefore the estimation of water mass distribution and water circulation in the Ariake Sea can have a significant impact on coastal management. The relationship between the distribution of floating objects and water mass distribution in Ariake Sea

Increases in both the use of fertilisers for agriculture and the use of industrial and household detergents have led to increasing concern about the fate of nitrates and phosphates in natural rivers and estuaries and on possible increases in the occurrence of eutrophication problems in estuarine areas. Much of the recent literature has highlighted the importance of understanding the nutrient balance in estuaries in identifying the root causes of eutrophication problems. It is therefore important to investigate the patterns of distribution of nutrients within these lagoons in order that this effect may be better predicted and mitigation measures undertaken. Results of nitrate and phosphate concentrations are shown measured both over individual tidal cycles and over longer-term deployments at Pagham Harbour West Sussex UK. In particular the effects of fresh water-salt water stratification over two tidal cycles are presented. It is shown how obtaining periodic vertical profile measurements during the tidal cycle helps to quantify the flux of nutrients from the tidal limits into the main body of the lagoon. Also of key interest is the interaction between sediment bound nutrients with the surrounding water in which the sediment is suspended during parts of the tidal cycle. Synthesis of these results with existing knowledge about sediment-water-nutrient interactions reveals how it is possible for nutrients to become trapped at the muddy tidal limits of the lagoon.

Research into ship performance in actual seas have been taken up recently. The aim of this research is to estimate ship performance in actual seas and to apply this to the building of a good performance ship. Oceangoing simulation is one of the methods used to estimate a ship's performance in actual seas. In this simulation sea states and ship conditions have to be simulated more exactly and rationally. The nominal loss of ship speed induced by added resistance in waves and other forces acting on ship hull is usually taken into consideration. The deliberate loss of ship speed and course change is often ignored. This study proposes a new oceangoing simulation considering deliberate speed loss and course change. A captain changes ship speed and course for safety in rough seas when the occurrence probability of the critical condition of the ship e.g. deck wetness propeller racing and slamming is higher than the critical probability. The occurrence probability of the critical condition is clarified from ship motions in an encounter sea condition calculated by using the EUT method. The joint probability distribution of ship speed and course can be plotted as a polar diagram in any sea conditions consisting of two different wave directions of wind wave and swell. Using this polar diagram a new method is proposed of oceangoing simulation with ship handling as the ship goes toward the original course as fast as possible. The oceangoing siX36881

Conventional merchant and military applications of diesel and gas turbine marine main propulsion plant are compared the high-power availability of the gas turbine is identified as the main reason for its selection for military ships fast ferries and yachts while the availability high efficiency and relatively low fuel consumption of 2 and 4 stroke diesels determine their choice for the majority of merchant ships. A detailed discussion examines the characteristics and advantages of gas turbines (including savings in weight and space the optimisation of hull form single unit installation competitive life-cycle costs vibration-free operation environmentally friendly) and of diesel engines (notably high efficiencies for low fuel consumption rates). Particular attention is paid to the features of a new combination power plant COGES (Combined Gas Turbine And Steam Turbine Integrated Electric Drive System) developed by General Electric Marine Engines and to be fitted in 6 new Millennium-class cruise vessels on order for Royal Caribbean International (RCI)/Celebrity Cruises - the COGES system is described in comparison with the well established diesel-electric drives usually used for cruise ships - it is anticipated that the high fuel costs of a turbine power plant will be offset by revenue from additional passenger carrying capacity.

High-resolution sea surface temperature (SST) fields are crucial for modelling upper ocean circulation and estimating air-sea fluxes. To meet these critical needs SST products are often constructed by combining measurements from a variety of sources. One such application is described that produces a regional SST product for the Gulf of Maine and results are provided from an ongoing study to validate this product. These SST fields are derived using measurements from the geostationary operational environmental satellite (GOES) and analyses from the real-time global sea surface temperature (RTG_SST) and the ocean surface temperature and ice (OSTIA) systems over the Gulf of Maine region. This algorithm has been implemented into a prototype near-real time production system that since May 2007 has produced SST fields four times per day on a 4km grid. This system also provides daily validation data constructed by collocating estimated SST values with in-situ measurements from buoys. The average bias in the domain from May to August 2007 is found to be 0.02±0.8°C. The system was applied to analyse diurnal variability in the region which revealed significant amplitudes and complex spatial distribution during summer.

A detailed procedure is described for the design of marine screw propellers in combination with stators (also known as fixed guide vanes or pre-post swirl devices). This procedure is based on lifting line theory with selection of the best among generated propulsors using a genetic algorithm procedure. This design procedure involves the realistic representation of the propeller slipstream which is a contracted form of helical vortices. As slipstream deformation is the key parameter in the design of reaction type performance improvement devices the design methodology is applied to a stator device behind the propeller and then the hydrodynamic performance of the combined propulsor is analysed. Design studies for a SWATH Bessel and a conventional ship are carried out to demonstrate the effect of the slipstream contraction as well as the efficiency and gain by the systematic variation of the number of stator blades and the axial distance between the propeller and stator. The use of GA (genetic algorithm) for the optimisation involves a further study in which various combinations are analysed to determine the main design parameters of the propulsor system. The use of the GA optimisation method allows a greater number of design parameters to be explored and provides an efficient methodology for determination of a true global near-optimal solution.

The contribution of non-linearities to tension leg platforms (TLPs) has been investigated. A rigid body with three degrees of freedom was selected to represent a TLP hull that consists of four columns and four pontoons. The tendons were modelled as elastic springs to allow for the variation in axial forces and the effect of setdown. The lateral forces were computed with Morison's equation in the hull's instantaneous position and up to the wave-free surface. The longitudinal forces on the bottom of the columns were computed using diffraction and radiation results for truncated cylinders. The analyses were performed in the time domain and the time histories of the motions and the tendon forces were obtained. A parametric study investigated the effects of wave frequencies and heights water depth and column spacing. Using frequency-dependent wave heights instead of a constant wave height for different wave frequencies or a constant wave frequency for different wave heights produced different relations between the response and the parameters of the applied waves from those previously published. Maintaining a constant axial stiffness in the tendons for any water depth kept the same force level in the tendons.

Phytoplankton form he base of nearly all marine foodwebs. Therefore a detailed study of their abundance structure and function is central for understanding the basics of marine ecology and global elemental cycles. The phytoplankton division Haptophyta is one of the most abundant and geographically widespread components of natural phytoplankton assemblages. The pigment approach is described followed by pigment analytical procedures. These procedures can be used to study distribution abundance and composition of natural phytoplankton populations using a chemotaxonomic approach. Pigment detection in the Haptophyta is overviewed from a historic perspective and new data on their distribution in cultured coccolithophores is given. A study is presented that was carried out with the largest and most diverse haptophyte sample set ever subjected to a comparative study. The methods are described and results presented and discussed. The extraordinary diversity in the pigment composition observed appears closely related to current taxonomy and published phylogeny. HFx (open-ocean and non-littoral coastal environments) is shown to have recovered its previously questioned status as a straightforward marker for haptophyte distribution in offshore habitats. Haploid and diploid lifecycle stages yielded identical pigment compositions. This provides further evidence for an evolutionary origin of pigment content rather than short-term temporal adaptations to environmental conditions.