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The effect of different insulation scenarios on the transient characteristic of oil-gas-water multiphase flow in deepwater catenary risers is investigated. A systematic study of risers with the pipe-in-pipe configurations and different insulation materials and with an external insulation material is presented. The impact of insulation techniques on multiphase up-flow crude in the riser is clarified and the phenomena based on the fundamentals of multiphase flow and heat transfer is discussed. Numerical transient analyses are conducted to simulate the system shut-in conditions. The effects of insulation scenarios on the temperature pressure and liquid holdup responses during the system cool down conditions are investigated. The results of this study enhance the understanding of multiphase flow transient behaviour in insulated deepwater pipeline-riser systems. Data tables graphs and diagrams appear on pages 6 to 10.

This paper concerns a detailed large-scale experimental study of wave loading on offshore platform decks. A series of model tests with wave loading on different types of deck elements has been performed in the large wave channel (GWK) at Forschungszentrum Kuste in Hannover Germany. During the tests the following parameters have been measured: wave elevations deck element inundation's wave kinematics profile and wave forces on the individual deck elements. The model test results are analysed to provide hydrodynamic load coefficients to a wave-in-deck load programme based on the concept of change of fluid momentum. The results will also be used to verify a CFD code based on the Volume of Fluid method.

For truss SPAR platforms damping plates are used to increase the added mass and viscous drag in the heave direction. This paper aims to investigate experimentally the hydrodynamic forces on heave plates with different opening sizes. Model scale experiments were carried out on three 40 by 40cm flat plates to investigate the effects of oscillation amplitude and opening size on the hydrodynamic forces acting on the plates whilst undergoing forced heave motion. Three different methods of data processing were investigated namely directly processing unfiltered data to obtain the hydrodynamic coefficients filtering the data before evaluating the coefficients and fitting the filtered data to a sine curve before evaluating the coefficients. The most accurate method was then selected and used to evaluate the experiment results. The coefficient values obtained were compared with the published data available. The effects of various variables such as opening size KC number and frequency of oscillation on the hydrodynamic coefficients were also studied. Relative magnitudes of the drag and inertia components of the overall hydrodynamic load are compared.

A vessel manoeuvring on an inland waterway is restricted by the riverbanks and the river's winding course as well as by the riverbed and the water depth. The size and velocity of inland vessels is growing rapidly and this affects the development and maintenance of inland waterways. Numerical simulations are suited to analyse numerous case studies of ship's motions under different random conditions in advance. This should lead to an improvement in the necessary expertise to minimise the risk for vessels as well as for the environment. Results of numerical and experimental analysis of ship motions are presented with consideration of river current and water depth. Mathematical models for the determining the influence of variable current environments on the manoeuvring behaviour are presented and validated by model tests. Some applications of the mathematical model are also presented. Theories and experiments are shown to have good agreement.

Intensive research into multi-hulls for both naval and commercial applications involves hydrodynamic and sea-keeping analyses; however little research on loads building and structures has been developed. Multi-hulls for small and medium-size have been realised for naval applications. Now researchers and designers are analysing small- and medium-sized multi-hulls for commercial and tourist applications on short routes and larger multi-hulls carrying containers on trans-oceanic routes. In recent years displacement hulls for intermediate Froude Numbers Fn < 0.6 have been studied. Among the solutions tested multi-hulls both symmetric (catamarans and trimarans) and asymmetric (staggered catamarans) seem to be quite interesting. The small amount of available experimental data for staggered catamaran in particular led to a research program using a towing tank to evaluate the relation between the total resistance of the ship the stagger of demi-hulls and displacement. A study is presented considering the hypotheses on which the design formulas of the classification societies are based for the determination of the transverse global loads for catamarans. Simplified methods are proposed for calculating loads and loads effects on a catamaran staggered fast ferry. The method

The Local Collision Efficiency (LCE) is a key parameter for ice accretion simulation since it describes the distribution of droplet impingements on the surface of an object. In this paper a numerical procedure is introduced to calculate airflow and water droplet trajectories which were used to evaluate the LCE in the newly developed ice code. Also the validity of several approaches and approximations for determining LCE in the context of atmospheric icing is studied. This paper also examines the influence of the droplet spectrum on the collision efficiency.

This work evaluates data from the offshore wind farm Bockstigen in order to study the effect of directional spreading of waves and wind wave misalignment on the response of the structure. The development of offshore wind energy has led to wind farms at sites with water depths ranging from approximately 6 to 30 m. The change of location from land to sea changes the design requirements of wind energy converters. In addition to wind loads the wave load on the structure has to be taken into account. Since a wind turbine is highly damped in the inline direction as compared to the crosswise direction the effect of directional spreading of waves on the response is studied. Depending on the dynamics of the structure the crosswise force could give a larger response than the corresponding inline force. In this study the influence of the directional spreading of the waves on the response is not clear however the effect of wind and wave misalignment is clear.

This paper responds to the recommendations of the House of Lords Select Committee Report on Safety Aspects of Ship Design and Technology and outlines the Government's view on the applicability of the safety case concept to the shipping industry internationally. It is divided into two parts. Part I contains the chapters "Shipping and the Safety Case Concept (Government Response to Recommendations 12.1, 12.2 (iv) and 12.2 (v)); and End Notes to Shipping and the Safety Case Concept. Part II covers Government Response to Other Recommendations (Recommendations 12.2.(i)-(iii), 12.2(vi)-12.4))

In 1973 the US Army Corps of Engineers published a pamphlet called Help Yourself. This pamphlet described erosion problems on the Great Lakes and showed alternate methods of shore protection (principally structures). However new knowledge and experience have made the old pamphlet obsolete. Lakebed erosion on cohesive shores is now recognised as a threat to virtually all types of shore protection structures. Freeze-thaw action on armor stone is now recognised as a common cause of structural failure on stone structures across the world's northern temperate zone. New advice on shore protection for Great Lakes property owners and contractors is presented that is contained in a draft replacement booklet. The booklet contains a new primary message and fresh insights from a group of experts convened in August 2000. The new recommended approaches to coastal risks of erosion and flooding are in the following order of choice: adaptation restoration moderation and armoring (a choice of last resort). These approaches follow those taken in the Corps of Engineers' new Coastal Engineering Manual.

A validation of the current prediction tool of ship's manoeuvrability at the early design stage has been conducted on three hull forms with differing course stability and on hulls which have the same principal particulars but different stern frame lines. Kijima's mathematical model now used widely by shipbuilders is chosen for the predictions. The prediction method is described. The validation study on the prediction model is looked at. A sensitivity study on simulation parameters is performed and discussed. An attempt is made to improve the prediction accuracy based on the sensitivity study.

The results of a theoretical and experimental investigation on the coefficient of pressure distribution on steps under hydraulic jump conditions in sloping basins are presented. The results show the coefficient is a function of the initial Froude number the step height ratio the slope of the channel bed and the type of jump. The developed equations are used to study the effect of various parameters on the coefficient. It is concluded that negative pressure may occur on a negative step. Consequently dynamic pressure fluctuations on the faces of the steps should be measured to locate any negative zones and to verify the occurrence of cavitation.

In recent decades many liquefaction phenomena have been reported which are due to earthquakes in reclaimed deposits that contain fines. When the deposits liquefy structures built on these deposits are seriously damaged. A full understanding of the effect of fines on the liquefaction characteristics is necessary for selecting the most suitable and reliable remediation. A series of undrained cyclic torsional shear loading tests was carried out on sandy soils with non-plastic fines to investigate the effect of fines properties on the liquefaction characteristics. The features of the cyclic failure modes of sandy soils with non-plastic fines at different initial densities are presented and the effects of both fines properties and initial relative density of the soil on the liquefaction strength and the development rates of both pore water pressure and shear strain during cyclic loading are discussed. The liquefaction strength is shown to decrease slightly with increasing non-plastic fines content in sandy soils and the rates of development of both pore water pressure and shear strain during cyclic loading increase with increasing non-plastic fines content and initial relative density of the soil.

In heavy storms, the waves and ship motions can become so large that water flows onto the deck of the ship. This is generally known as 'green water loading'. On ship-type offshore structures green water loading can result in risk for the ship, its crew and its sensitive equipment. Therefore, it should be taken into account in the design of such structures. The main objective of this study was to develop methods for the evaluation of green water on ship-type offshore structures based on a clear description of the green water physics. Contents cover the physics of green water on the bow, systematic model testing, non-linear relative wave motions at the bow, water flow onto and on the bow deck, green water impact loading, green water from the side and stern, review and application of the method, numerical prediction of green water, and conclusions and recommendations of the study.

In this paper the effect of inspection updating on fatigue reliability of offshore structures is investigated. In particular the effect of inspection on the reliability of both inspected and un-inspected joints is assessed dependent upon the correlation of properties of different joints. The effect of repeated inspections and inspection sample size on fatigue reliability is also investigated. The influence of inspection of certain joints on the reliability of a series system is studied and the effect of system-based updating policy on fatigue reliability is investigated. It is found that the system reliability is significantly affected by the inspection updating policy.

On 25 August 1994 fire broke out in the main engine room of MV Sally Star a ro-ro passenger ferry. The fire was caused by the failure of a bolted lange joint on the low pressure fuel system of No 4 main engine allowing flammable fuel oil vapour to come into contact with part of the engine exhaust system. Recommendations include matters concerning the early warning of oil fuel vapour leakage in machinery spaces and more stringent requirements for low pressure fuel systems of medium speed diesel engines

The second-order mean wave drift loads on multiply-connected semi-submersibles are studied in this paper. The calculations are done on three Very Large Floating Structures (VLFS) which are formed by connecting three five and seven identical semi-submersible modules. For the 5 module VLFS the first-order responses are also compared with the published results. To reduce the computational effort the symmetry properties of the modules are utilized. The mean wave drift loads are obtained for a number of incoming wave directions. Different types of connectors are used to understand the effect of connector stiffness on the drift loads. It is shown that the mean wave drift loads on connected multiple semisubmersible modules are generally small compared with box- or mat-type very large floating structures. It is also found that due to the small water plane surface of the semisubmersible-type VLFS the effect of the interaction of the neighboring modules on the drift loads is small.

The effect of swell on air-sea interaction phenomena is controversial. The problem is important not only as dynamical processes at air-sea boundary but also for practical application such as wave forecasting. On the basis of recent studies contributions of swell to sea surface phenomena are discussed. It is shown that the attenuation of wind waves by swell depends not only on swell steepness but also on the ratio of the frequency of the swell to the spectral peak frequency of wind waves. It is also shown that the measured growth rate of swell in a wind area agrees well with the empirical formula of Hsiao and Shemdin (1983) in a region of small inverse wave age while it approaches the empirical formula of Mitsuyasu and Honda (1982) in a region of large inverse wave age. Finally the increase of surface drift current by opposing swell using the result of recent study on Langmuir circulation (Mizuno 2002) is briefly discussed.

As offshore activities move to deeper scenarios pipelines and risers used to connect sea-floor wells to platforms can also be susceptible to collapse due to the ambient external pressure. Internal corrosion in pipelines is often caused by water sediment or chemical contaminants present in the multi-phase flow. This normally occurs at the bottom of the pipe and at low points in the pipeline where sediment and water can settle out of the product being transported therefore creating narrow and long defects. The effect of corrosion defects on the collapse pressure of offshore pipelines was studied through combined small-scale experiments and nonlinear numerical analyses based on the finite element method. After calibrated in view of the experimental results the model was used to determine the collapse pressure as a function of material and geometric parameters of different pipes and defects. An extensive parametric study using 2D and 3D numerical models was carried out encompassing different defect geometries and their interaction with pipe ovalisation. These results are reported. They are subsequently used to develop a simple procedure for estimating the collapse pressure of pipes with narrow defects.

The application of the RANS solver FINFLO to the hydrodynamic design of podded propulsors for high-speed operation is described. In particular a Ropax and a cargo ship are used as candidates for speeds of 35-38 knots. For such high speeds the hydrodynamic design of the propeller with its housing is critical due to the danger of cavitation on both propeller blades and supporting strut. The optimisation process of the propeller housing is dealt with using RANS solver FINFLO. Even though RANS solvers are analysis tools as opposed to design ones they can be used iteratively for design purposes. The right choice of the computational grid together with the computational model make it possible to test alternative geometries in a relatively short time. A non-symmetric strut is designed to delay cavitation inception keeping at the same time low drag and low lateral forces on the strut. A remarkable reduction of low-pressure areas is observed on the strut surfaces for a tailor-made design as compared to a conventional symmetric strut. Several pod configurations have also been analysed. Their hydrodynamic merit is evaluated on the basis on RANS results.

Estimation of wave pressures on vertical impermeable caissons and seawall is needed to determine the dimensions and appropriate material selection of the structure. Reduction of extreme wave loadings (pressures) by constructing an offshore breakwater on seaward side of these structures is investigated. A series of physical model tests were carried out in a wave flume to examine the performance of the defence structure (offshore breakwater) in reducing the wave pressures on the seawall/caisson. Quasi-static nature of the wave pressures was observed due to piling-up of fluid mass behind the breakwater. The influence of the pool length on reduction of pressures on seawall/caisson is also investigated for regular waves.