In offshore areas, the silty soil seabed can be liquefied under cyclic wave loads, and the liquefied soil fluctuates with the upper water body with the same period. Similar to the movement of water, the fluctuation orbit of liquefied soil particles is elliptical with a horizontal major axis, and the orbit radius gradually decreases with depth. Although some researchers have constructed theories to

For damaged submarine pipelines, interference fit is necessary for the mechanical connector repair. The ovality of pipelines resulting from the fabrication errors is easy to increase the failure risk during the fit process. In order to ensure the construction safety, it is necessary to judge whether the repair process may be affected by the strength damage in advance. Since the interference joint with

This research proposes a new route decision-making strategy, a real-number grid method, that challenges the state-of-the-art method in route decision-making. The key features of the proposed method compared to the conventional route decision making method are implementing a real number grid in the grid generation procedure, global speed optimization in the speed optimization procedure, and a Monte

Upheaval buckling may occur for subsea pipelines laid on the seabed with topographic step imperfection under high temperature. In order to predict the post buckling behaviour of upheaval buckling, a finite element model of ABAQUS is proposed to simulate upheaval buckling for surface laid subsea pipelines with step imperfection. Firstly, a new method to introduce a step imperfection from an originally

Drag anchor has been widely used for offshore mooring system. Prediction of the invisible anchor trajectory during the drag-in installation is still challenging but important for determination of anchor capacity in anchor design and guiding the field installation. Kinematic analysis based on yield envelope method provided an alternative method for anchor trajectory prediction. However, the existing

To investigate the consolidation responses of coastal rheological aquitards to tide-induced groundwater fluctuations, this study adopts a nonlinear 1-D consolidation model considering the rheological properties of the aquitard and non-Darcian flow. In this model, the depth-dependent property of the initial permeability and compressibility of the aquitard are considered using the continuous exponential

Biofouling is the colonization of underwater surfaces by microorganisms, plants, algae or animals and can be divided into soft and hard fouling. Soft fouling is consisted of algae, slime and grasses and typically has a lower impact on the performance of the ship than hard fouling, which has a calcareous structure. Furthermore, hard fouling can be extremely detrimental to the performance of machinery

Regional frequency analysis is applied to North Atlantic Ocean wave data to determine the regions that can be considered homogenous from the point of view of extreme distributions and to obtain the extreme regional frequency distributions able to characterize those regions. The entire information is used on a regional scale to obtain an accurate estimation of the probability of occurrence of extreme

Most of the research done on tidal energy focuses on marine current turbines. Therefore, tidal turbine’s wake is well-documented. The tidal energy converter studied here is based on the fluid-structure interactions that occur between a flexible membrane and an axial flow, resulting in an undulating motion that can be used to harvest energy. This device’s performance had been studied but it is the first

This paper reports the effect of the remoulded soil strength of a footprint on the reinstallation of jack-up rigs near the footprint. The footprint creation is from an earlier spudcan penetration and extraction process in which the soil is remoulded. Dissipation of pore pressures between the footprint creation and jack-up reinstallation causes further consolidation of the soil around the footprint

Several structures as in the case of offshore structures like jetty, flood wall and wind turbines are mostly subjected to uplift loads. Thereby, the safe design for such cases is using piles. In this research a novel recent technique is adopted to improve the uplift capacity of the pile. In this paper, the uplift capacities of single regular piles (without wings) and anchor winged vertical piles installed

In this paper, the hydrodynamic performance of a floating breakwater-Wave Energy Converter (WEC) integrated system was investigated under the framework of the linear potential flow theory, with a focus on the effect of the coastal reflection. The reflection coefficient and capture width ratio were verified using the rule of wave energy flux conservation. The water wave resonances, including the piston-

The stability and integrity of structures under indeterminant external loadings, particularly earthquakes, is a vital issue for the design and safe operation of marine and offshore structures. Over the past decades, many structural control systems, such as viscous-based systems, have been developed and embedded in marine and offshore structures, particularly oil platforms to maintain the stability

Reliable estimations of overtopping rates are necessary for the design of vertical seawalls. Although many studies have been carried out to address this, few have paid attention to vertical seawalls built on coral reefs. In this study, a physical model was constructed with an idealized coral reef topography and vertical seawalls located on the middle or inner reef flat. A steep fore-reef slope in combination

The purpose of this paper is to study the diffraction of second order Stokes waves by four cylinders in a uniform current and mainly focus on the near-trapping phenomenon. A time domain second-order theory is employed to establish the mathematical Smodel by splitting the total potential into the disturbed velocity potential caused by current, the first- or linear and second-order potentials, which

The shape optimization approach of the cambered otter board has been performed by the integration of the neural network model and the multi-objective genetic algorithm (MOGA). Because the excellent performance of an otter board is expressed by great lift and less drag force, in this study the lift and drag coefficients were chosen as objective functions to obtain the optimal otter board. The Bézier

Tripod substructures have been widely used in China for building offshore wind turbines (OWTs); correspondingly, three-planar tubular Y-joints have gained considerable attention, especially in the fatigue design. The out-of-plane bending moment load is a classical load type for steel tubular joints based on the mechanical analysis of the whole structure. This study examines the performance of hot-spot

Recently tetrapod piled jacket (TPJ) foundations are considered as a promising solution for offshore wind turbines in waters with depths ranging from 20 m to 50 m. This paper presents a numerical study into the monotonic lateral loading behaviour of TPJ foundations in medium sand, in terms of overall load-displacement responses of TPJ foundations and internal force within individual corner piles as

This paper presents an algorithm for docking a torpedo-shaped autonomous underwater vehicle (AUV). We propose a new docking assessment algorithm comprising three phases: depth tracking, docking-feasibility region analysis, and docking-success probability evaluation. For depth-tracking analysis, a neural network-generated path is used to satisfy constrained docking conditions of depth and distance.

This paper presents a CFD-RANS investigation of the effect of the skeg hydrodynamics on the manoeuvrability of an Azimuth Stern Drive Escort Tug. This study is devoted to identifying a proper mathematical model to be included in a dynamic manoeuvring simulator. The hydrodynamic problem is therefore decomposed in the hull and skeg components. The hydrodynamic characteristics of the skeg were so explored

Marine structures are typically sensitive to the direction of wind and waves, especially in extreme metocean conditions. The extreme metocean conditions and their associated predicted directions are not easily reachable from traditional design methodologies. In this research, the most probable combinations of different extreme metocean conditions along with their associated direction are predicted

The breaking properties of internal solitary waves (ISWs) flowing over a bottom step were investigated experimentally. The experiments were performed in a two-layer immiscible system to avoid the influence of diffusion and mixing. The flat bottom condition and the bottom step condition had been conducted respectively. The characteristics of incident ISWs, the process of breaking and the subsequent

A semi-analytical method is derived, which enables optimisation of the power absorption of a collection of wave-interacting bodies, subject to a weighted global motion constraint associated with both the controlled and uncontrolled modes of motion. As an illustrative example, the method is then applied to a six degree of freedom solo duck with various modes of motion under direct control. This is in

Pre-deformation design can improve the propulsive efficiency of composite ship propellers under off-design conditions, where propulsive efficiency is related to the geometry of the propeller blade. Material attributes affect the deformation of composite propeller blades, suggesting that these also affect the propulsive efficiency of a pre-deformed composite propeller (PDCP) under off-design conditions

Spudcan foundations for mobile jack-up units are large diameter conical foundations that can penetrate into the seabed to a maximum depth of three times the diameter of the spudcan. As a deeply penetrated foundation, the bearing capacity of a spudcan is highly dependent on the failure mechanism and the strength distribution of the seabed soil, which exhibits strong spatial variability. While many recent

Quantification of the bed shear stress in the swash zone is subject to much uncertainty due to the very shallow water, complex flow structure and the strong unsteadiness in this zone. This study presents a RANS modeling of experimental dam-break flow generated swash processes, giving numerical reproduction of vertical flow structure of swash flows and thus an opportunity to study the magnitude and

Ship navigation safety is a growing concern in maritime transportation and shipping industry. Rescue ship patrol is an important operation for improving navigation safety in the marine environment. This paper proposes a patrol path support framework, which incorporates multiple criteria decision making, geographical information system (GIS), and linear programming, to determine optimal paths for rescue

The global pipeline configuration in installation is mainly governed by static lay effects, which, besides pipeline material properties and geometry, primarily depend on its submerged gravity and horizontal tension provided by the laying vessel. These loads are insensitive to the pipeline deformation and preserve both their values and their directions as the pipeline deforms throughout the whole course

The paper presents an experimental study on the characterization of the effect of surface-wave of different frequencies on spatially-averaged turbulent statistics over a rough bed. The model roughness comprised of periodically positioned, transverse square ribs that extended across the whole width of the channel. The three-dimensional turbulent velocity fluctuations were mapped by an acoustic Doppler

In this paper, the dynamic responses of a Spar-type floating offshore wind turbine (FOWT) are simulated and analyzed under the scenarios with freak wave superimposed a uniform current. The wave-current interaction is considered in the process of freak wave generation. An improved phase modulation algorithm is used to generate the free surface profile of the freak wave. Compared with the deterministic

Rotor-stator interaction of a pump-jet propulsor can induce strong pressure fluctuations and vibrations, which may deteriorate the vibration and acoustic performance and cause damage to the propulsion system at some severe working conditions. In this paper, the role of stator parameters, such as the prewhirl angle, the rotor-stator spacing and the chord length of the stator blades, in the propulsion

Nowadays concrete-filled steel tubes (CFTs) are used in many types of structures. In spite of significant advances, the application of this system has not widely adopted in marine structures. While due to the presence of hydrostatic pressure on the body of the tube, outward buckling, which may be considered as one of the weaknesses of the system, could be delayed. Therefore, theoretical and experimental

Originally discussed in the context of ocean statistics for oil rig platform decks and satellite data, spatiotemporal exceeding probability distributions have recently been thought to explain the failure of second and third-order nonlinear models of distributions at a fixed point in space. To investigate this possibility, we derive a simplified model for the (2+1) exceeding probability distribution

Attitude perception for autonomous underwater vehicles (AUVs) is a challenging task. Most of existing sensor systems are unable to detect the navigation attitude of AUVs while at the same time to identify the attitude geometric parameters. In order to bridge this research gap, a new artificial lateral line sensor (ALLS) system based on a pressure sensor array is proposed to perform pitch motion perception

A rectangular barge consisting of multiple oscillating water columns (OWCs) is considered in this paper, hereinafter referred to as a multi–OWC platform. Each OWC chamber is enclosed by two partially submerged vertical walls and the deck of the platform. An incident wave produces oscillation of the water column in each OWC chamber and hence air is pumped by the internal water surface to flow through

The rapid development of the oscillating water column (OWC) wave energy converter proposes a demand to predict its overall performance accurately. Traditional experimental and numerical studies only employed the orifice or porous media as the power take-off substitutes, causing an inaccurate evaluation of the OWC performance. In this study, an impulse turbine model was used directly in a generic OWC

This article is Part B of a study into the proof-of-concept of a floating breakwater integrated with multiple Oscillating Water Column (OWC) Wave Energy Converters (WEC). The structure is designed for nearshore and offshore applications and the investigation was performed through model scale hydrodynamic experimentation. Part A introduced the concept and the experiments performed, followed by an investigation

There is a large body of research available focusing on how ship hull conditions, including various hull coatings, coating defects, and biofouling, influence the boundary layer, and hence resistance and wake field of a ship. Despite this there seems to be little consensus or established best practice within the ship design community on how to model hull roughness for ship-scale CFD. This study reviews

Motion based wave inference allows the estimation of the directional sea spectrum from the measured motions of a vessel. Solving the resulting inverse problem is challenging as it is often ill-posed; moreover, inaccuracies related to the linearity hypothesis behind estimated platform response functions (RAOs) may result in misleading estimations of the sea states. This work discusses how these inaccuracies

The present study is a new experimental investigation into energy dissipation due to wave breaking. Long-crested wave groups based on JONSWAP spectra are generated in a wave flume to estimate the energy loss from the wave packet due to the occurrence of single breaking events. These events range from gentle spilling to large plunging breakers. The fractional energy losses and breaking strength parameter

Maritime transport is the most energy-effective mode to move large amounts of goods around the world. Hauling cargo via waterway produces an enormous quantity of greenhouse gas emissions. Vessel fuel efficiency directly influences ship emissions by affecting the amount of burnt fuel. Optimizing ships operating in waves rather than in calm water conditions could decrease the fuel consumption of vessels

In this paper, a two-stage risk assessment approach for gas hydrate exploitation is presented. In the first stage, a probabilistic analysis method is used to evaluate the failure probability of submarine landslide due to hydrate exploitation. The excess pore pressure due to hydrate exploitation is evaluated using a proposed maximum excess pore pressure model, which can consider the equilibrium of pressure

The traditional neutral buoyancy underwater vehicle's carrying capacity is limited by space and displacement, making it difficult to meet the increasing demand for mission sensors. In light of this, a new type of negative-buoyancy autonomous underwater vehicle equipped with an autorotating rotor is proposed in this paper. Referring to the principle of air autorotating rotor, the negative-buoyancy autorotating-rotor

Maritime structure integration is widely considered as a potential solution for reducing the high Levelised Cost of Electricity (LCOE) associated with Wave Energy Converter (WEC) technologies. However, the majority of published research has focused on fixed structure integration [1,2], with far fewer investigating the potential for floating structure integration [3]. Expanding on previous works [4

A URANS CFD-based study has been undertaken to investigate scale effect in container ship squat. Initially, CFD studies were carried out for the model scale benchmarking squat cases of a self-propelled DTC container ship. Propulsion of the vessel was modelled by the body-force actuator disc method. Full scale investigations were then undertaken. Validation of the full scale set-up was demonstrated

Pipeline walking induced by heat-up and cool-down cyclic loadings during shutdown and restart cycles is a challenge in the design of relatively short pipelines exposed on seabeds. A major source of uncertainty in the analysis of pipeline walking is the pipe-soil response, which has a significant influence on pipeline walking. To investigate the pipe-soil response during pipeline walking, a set of large-scale

Increase in ship energy efficiency is one of the main goals set by the International Maritime Organization (IMO). In this sense the IMO identified the significance of the control and management of the hull fouling. The weed or grass stage is often seen as the beginning stage of the ship hull fouling, while the effects of soft fouling on the ship resistance and propulsion characteristics as well as

In the present study, the flow around two-dimensional (2D) square and trapezoidal wall- mounted structures in tandem on a horizontal flat wall has been simulated using two-dimensional Reynolds-averaged Navier-Stokes (RANS) equations combined with the standard k−ω SST turbulence model. The Reynolds number (Re) based on the free stream velocity and the height of the structures is set to be 1.19 × 105

A numerical model based on WCSPH method is utilized to simulate wave propagation over a pipeline. A hybrid approach is introduced to absorb outgoing waves based on gradual decrease of fluid velocity in an absorbing layer and using sloping beds simultaneously. The interaction of both regular and irregular waves with pipelines located on porous and impermeable sea-beds has been studied. The effect of

Both the time domain simulations based on potential flow theory and wave tank model tests are used to evaluate the motion responses of a wave energy device. In this work, system identification is applied to obtain the frequency dependent transfer functions (between motions and excitations) from a series of model test runs of a wave energy platform exposed to irregular (random) waves. This is the first

The collision risk in the port area, especially in the anchorage area, increases gradually along with the progressive development of port traffic. This paper proposes a novel anchorage collision risk model in the identification of the collision risk of anchorage. First, the regional collision risk model was improved in order to fit the characteristics of vessels in anchorage. Second, a novel anchorage

Measurements were performed inside and in the wake of a commercial salmon sea cage. The key instrumentation included the following: sea bottom-mounted acoustic Doppler current profilers providing continuous concurrent flow velocity and turbulence information about the water columns; vessel-mounted acoustic current profilers mapping the flow pattern around the wake of the cage in a selected incoming

In this study, a multi-scale approach concept is introduced to estimate OPB (out of plane bending)-induced failure considering time-varying interlink bending stiffness by using both high-fidelity nonlinear-FEM (finite element method)-based local structural analysis and low-fidelity global-system-simulation program so that they can mutually be interfaced during the time-stepping procedure. In addition

In this work, the potential of harvesting energy from ocean salt basins is discussed. These deep ocean depressions which host thick salts deposits whose salinities could be up to 5-10 times higher than normal seawater open an interesting -and so far, unexplored possibility for ocean energy. It is known that upon mixing two solutions of different concentrations spontaneous energy can be released, and

This paper presents the results of physical modelling tests carried out in a geotechnical drum centrifuge to investigate the impact forces of submarine slide at debris flow stage acting on pipelines with various incident angles. The UK kaolin clay was used and normally consolidated clay samples were prepared at 40 g level. For each incident angle condition, the impact velocity was changed from 0.23

In this study, the effectiveness of an oscillating-body WEC with a tuned inerter (TI) proposed by the authors is shown through wave flume testing. The TI mechanism consisting of a tuning spring, a rotational inertial mass, and a viscous damping component is able to increase energy absorption capability by taking advantage of the resonance effect of the rotational mass. This mechanism has been recently

Prediction and optimisation of non-cavitating marine propeller noise at low frequency are important for design of submarine propellers that are required to operate in the non-cavitating condition. The low-frequency discrete- and broadband-spectrum forces of propellers have different generation mechanisms, and thus have not previously been studied within a unified framework. In this work, the strip

The equations of motion of the coupled dynamics of a moored barge and cylinder for deployment/retrieval operations in waves and current are formulated using Kane’s formalism [1] and an approximate analytic evaluation of the first order wave forces. Such systems are commonly used for oceanographic and marine renewable energy applications as well as in offshore oil operations. The purpose is to provide

When characterising local geometry for unsteady water waves, the accurate determination of spatial quantities such as the wavenumber from measured time traces is non-trivial. The present study investigates different methods in order to highlight the discrepancies that arise when estimating the wavenumber from fully nonlinear numerical time traces of the free surface profile. To this extent, the open