A synthetic method of dynamic test for identifying hydrodynamic coefficients (HCs) of an ocean vehicle has been proposed. The methodology consists of simulating various planar motion mechanism (PMM) tests simultaneously in a single numerical analysis. As a technical method, a stationary numerical domain has been used. Therefore, non-inertial forms of the fluid flow governing equations have been solved

Resonant wave-induced vibrations of a ship hull girder, known as “springing”, is an important issue when addressing fatigue aging of the steel structure. To compute resonant wave-induced vibrations, fluid-structure interactions and associated structural and hydrodynamic properties need to be addressed. This paper introduces a time-domain numerical method that predicts higher-order springing taking

A small seepage could cause significant changes to the hydrodynamic gradient and further enhance the sediment incipient motion and scour. However, most previous studies either ignored the influence of seepage or only considered the upward seepage in the prediction of sediment incipient motion. In this paper, a modified Shields number considering the two-dimensional seepage was derived. The analytical

The economical design of rubble mound structures namely breakwaters can be facilitated by means of an accurate simulation of interactions between the porous media and the passing currents and waves, to assure the safe economical design of these structures. Unlike most of the previous studies, the present study dealt with the development of a more realistic simulation by simultaneous consideration of

Carbon steel pipe lined with a thin layer of a corrosion resistant alloy is an economical product used in offshore pipelines that carry corrosive hydrocarbons. The liner and carrier pipe are mechanically expanded together so that on unloading they end up in interference contact. The contact pressure that develops is essential for keeping the composite pipeline intact under bending and axial loads experienced

At present, the research on the cavity formed by spudcan penetration is based on two-dimensional axisymmetric analysis of circular spudcans, and it is doubtful whether the results could be applicable to rectangular spudcans. In this paper, centrifuge experiments and finite element analysis are combined to study the penetration process of large scale rectangular spudcans in the clay with undrained shear

Multi-purpose floating platforms are emerging as a promising concept in ocean engineering applications, thanks to their capability of ensuring system integration, cost reduction and modularization. However, their increasing complexity requires the development of numerical tools, which need to be validated experimentally through adequate physical models. New challenges hence arise, since the subsystems

Moonpools as a device for reducing pitch motion is investigated experimentally, numerically and by an approximate theory. A two-dimensional study is carried out of a rectangular body with two moonpools. Forced heave and pitch motion, as well as freely floating body in regular waves are studied. The body geometry is varied; two drafts and five different moonpool inlet configurations are considered;

Spar, tension leg platform, and semi-submersibles use heave plates to reduce heave response by increasing heave damping and added mass. Conventional practice is to use a linear damping ratio, which is typically obtained from free heave decay tests or Computational Fluid Dynamics (CFD) simulations. However, with the addition of heave plates, the system damping becomes nonlinear. Understanding such nonlinear

This paper establishes a two-dimensional mathematical model of a continuous floating bridge with heave plates under linear monochromatic waves. Based on linear potential flow theory, the fluid domain is divided into two regions. The analytical equations for the rigid floating bridge considering the heave plate effect are derived from the boundary conditions. The wave force, added mass and damping coefficient

An improved adaptive integral line-of-sight guidance law and path following control system for Unmanned Surface Vehicles (USVs) with uncertainties is proposed in this paper. The dynamic equations of the tracking errors are established in the Serret-Frenet coordinate system with the consideration of the time-varying ocean currents. In order to eliminate tracking errors, three adaptive variables are

A series of numerical simulations of wave run-up on four-cylinder array is performed at different spacing ratios 1.5 ≤ L/D ≤ 4.25, where L is the center-to-center distance between the adjacent cylinders and D is the cylinder diameter. The effects of spacing ratio and wave steepness on the wave run up ratio and wave force on the four cylinders are investigated. The results show that with variation of

Stick-slip torsional vibration raising from bit-formation contact is a catastrophic dynamic phenomenon occurring in deep-water oil and gas drilling systems. The torsional vibrations can result in premature fatigue failure of drilling equipment and reduce drilling efficiency. Thus, studying the dynamics of the system is a vital key to identify the roots of the vibration and establish appropriate mitigation

Representation of the marine environment is key for reliable coastal hydrodynamic models. This study investigates the implications of common depth-averaged model configuration choices in sufficiently characterising seabed geometry and roughness. In particular, applications requiring a high level of accuracy and/or exhibiting complex flow conditions may call for greater detail in marine environment

Dynamic characteristics of seabed soil under seismic load arevery important for the overall stability of the offshore wind turbine foundation. In this study, the horizontal bearing capacity and its corresponding soil deformation around the large-diameter monopile, where withstandsa transient high frequency seismic load, are simulated using a numerical method. During the numerical analysis in this paper

Flexible pipes play an important role in the transportation of oil and gas from the seabed to floating production units. They are also employed to inject water or gas into offshore wells. In deep-sea oil and gas extraction, flexible pipes must be able to withstand very high tensile and hydrostatic pressures. In this paper, an equivalent method is used to represent the complex carcass layer and the

In this study, unlike most previous investigations have limited to the regular wave conditions or combined wave and current conditions, a numerical model for seabed response around a pipeline in a trenched layer due to random waves is established. Three different wave spectra including the JONSWAP spectrum, Bretchneider–Mitsuyasu spectrum and Pierson–Moscowitz spectrum are considered in the present

This paper deals with a new combined concept consisting of an oscillating water column (OWC) device and an offshore wind turbine for the multi-purpose utilization of offshore renewable energy resources. The wind turbine is supported by a monopile foundation, and the attached OWC is coaxial with the foundation. Within the chamber, the exterior shell of the OWC and the monopile foundation are connected

In this paper an approach-angle-based three-dimensional path-following control scheme has been proposed for underactuated Autonomous Underwater Vehicle (AUV) which experiences unknown actuator saturation and environmental disturbance. First, the path-following error dynamic model is derived based on the principle of relative motion which was followed by the design of approach-angle-based guidance law

The improvement of robust skills for early defect recognition for fixed marine structures is crucial to avoid the possible catastrophe caused by structural degradation. This paper presents an approach for defect recognition based on vibration measurements that is capable of detecting the defect to individual members of offshore jacket platforms, when limited, spatially incomplete modal datum is available

Using linear water wave theory, we consider the wave radiation (both heave and sway) by a sphere submerged in a three-layer fluid consisting of a layer of finite depth bounded above by a fresh water of finite depth with free surface and below by an infinite layer of water of greater density. The sphere is submerged in either of the three-layers. Each problem is reduced to an infinite system of linear

The impact of biofouling is investigated on the accuracy of the records of a wave buoy moored in shallow water. The effects of biofouling on the vertical and horizontal motions of the buoy are analyzed through check factors. Regarding the heave motion, the most critical frequencies of the power spectrum are identified, and selected to run CFD simulations to further evaluate the hydrodynamic impact

The unmanned wave glider (UWG) comprises an underwater glider and surface float connected by an umbilical cord. It is a highly adaptable marine vehicle with the advantages of low cost, low power consumption, and long endurance. At present, research on UWG filtering is still immature and not fully utilized. This paper proposes a variable-structure filtering method based on the double-body coupled yaw

This work presents an optimization study for designing a shrouded turbine diffuser. The goal of the study was to obtain the geometry of the hydrofoil shaped diffuser which maximizes the hydraulic power of a turbine with a given set of constraints. The optimization process has been based on an automatic cycle of geometry modification, meshing and CFD analysis of the flow field, including a loaded diffuser

This study presents an effective solution to evaluate the dynamic impedances of scoured monopiles for offshore wind turbines in a wide excitation frequency range, which can properly account for both the effects of the scour-hole dimensions as well as of the soil stress histories, and the evaluation of these complex-valued impedance functions can be later used to take into account the soil-structure

As fish farms move from nearshore region to open sea, understanding the hydrodynamic force on net structures in extreme waves plays a significant role in the design of offshore aquaculture structures. In this study, a series of experiments on different types of net panels in extreme waves were conducted in a wave flume. The dispersive focusing method with the constant steepness spectrum was adopted

Shorelines around the world are of great importance because of their role in people's lives. Therefore, understanding its behavior seems to be vital. Shoreline changes and its realignments are highly nonlinear and finding a method in such a way that it could model its patterns would be very useful. ANN's are popular methods, as they have been applied to numerous problems. In this study, recurrent ANNs

This paper considers the attitude control problem of a new class of aerial and underwater vehicles with quadrotor structures. A novel single-input FUZZY P+ID attitude controller is proposed to improve the trans-media performance of the aerial and underwater vehicle. The proposed FUZZY P+ID controller has a unique feature to deal with the nonlinear uncertainties using a set of fuzzy rules from experts

Faced with the difficulty in finding and locating leakage points of submarine pipelines timely as well as the high cost of pipeline routine inspection, a scheme using autonomous underwater vehicle (AUV) equipped with multibeam echo sounder (MBES) and forward looking sonar (FLS) for automatic inspection of submarine pipelines was developed. In the process of inspection, the AUV maintains autonomous

The submerged deep-water longline aquaculture facility is known as a typical, flexible multi-degree-of-freedom offshore structure. Effects of layout concepts of the dropper weight, the upper buoy pattern and the incident wave angle on longline aquaculture systems have been studied by means of numerical modellings and conducting scaled model experiments. The results have showed that the dropper weight

The seakeeping behavior of a vessel in multi-directional wave differs significantly from that in uni-directional wave. Given that a vessel operates in multi-directional or short-crested waves during its whole service period, it is important to have a better understanding of the influence of wave directionality on ship seakeeping performance. In this study, CFD method is used to simulate ship motions

Accurate determinations of sediment settling velocity (ws), eddy diffusivity (Ds), and pick-up rate p(t) from available field data are vital for engineering calculations or numerical simulations of coastal processes. Existing methods to determine these parameters are normally based on the assumption of a steady equilibrium that ignores the “phase lag” and “amplitude damping” effects of a diffusing

We investigate the effects of a brace-viscous damper system on the dynamic response of offshore platforms. To do this, offshore jacket platforms with various distributions and three different configurations of brace-viscous damper systems - toggle, chevron, and diagonal configurations - and a wide range of brace stiffness are numerically modelled under the loading of irregular waves in ANSYS software

In this study, the surface wave interactions with submerged horizontal viscoelastic sheets of varying rheological properties are investigated both experimentally and analytically. In the experiments, we adopt the novel development in preparing finite length viscoelastic sheets with different rheological properties using oil-doped polydimethylsiloxane (PDMS) materials reported earlier in Sree et al

The shear behavior of sand-steel interface plays an important role in the performance of steel pipe piles that support marine structures. In this study, the effects of surface roughness (from rough surface to smooth surface) and mean particle size on mobilized sand-steel interface friction were investigated by direct shear tests. Three types of calcareous sand with different particle sizes and three

It is now more than half a century since the development of the renowned and well-established strip theory of Salvesen–Tuck–Faltinsen (STF), Salvesen et al.(1970). One of the existing, and widely used, methods for calculating the wave drift force (zero-speed case), or added resistance (forward-speed case), within this strip theory, is a near-field formulation which was developed by Salvesen himself

This paper presents a power take-off concept for the Moored, Multi-float and Multi-Mode Wave Energy Converter, (M4 WEC), based on oil hydraulic technology. The study shows the importance of having low max-to-mean mechanical power ratios, preliminary to the design of the oil-hydraulic power take-off. It explores the characteristics of the M4 WEC in order to achieve these lower power ratios and shows

Because of the limited and unreliable communication topology in complex marine environment, the formation control of marine vehicles under switching topology is investigated in this paper, whereas the most previous works for marine formation focused on the fixed communication topology. In order to simplify the formation control design, a novel distributed guidance system, rather than the traditional

Conventionally, allowable mean overtopping discharge is used as a design criterion for coastal structures. The mean overtopping discharge needs to be limited to ensure structural stability as well as the safety of people, vehicles, and properties behind the structure. Nowadays, limits for the maximum individual overtopping volumes are also specified in the design manuals, which requires the study of

Labeling the observations collected from the deep manned submersible is time-consuming and difficult, and traditional water leakage detection method is supervised. The online and unsupervised water leakage detection methods are necessary but barely researched. In this paper, a multisensor fusion method based on the sparse representation is proposed, and the unsupervised Bayesian-based online diagnostic

Ventilated partial cavity (VPC) is a drag reduction method with great potential for marine vehicles. In applications of VPC ships or yachts, the cavity usually undergoes flow non-uniformity and perturbations induced by hull and pitching motions. This study presents the experimental and numerical investigation on effects of flow non-uniformity and additional pressure gradient on the VPC caused by lateral

Submarine high-temperature and/or high-pressure (HT/HP) pipelines used to transport oil and gas in different areas of the world are susceptible to global buckling. If the pipelines are simply laid on the seabed, buckling will likely occur in the horizontal plane, while if buried in a trench, buckling will probably arise in the vertical direction. The latter buckling mode may lead to catastrophic pipeline

Ships and offshore structures are exposed to various cyclic loads such as winds, waves and currents in their lifetime. These loads can result in fatigue failures at hot spots, and to prevent such failures, accurate estimates of the fatigue life of hot spots should be performed in the design stage. The cycle distribution indicative of the probability distribution of cycles is an important factor in

Ship tracking from maritime visual sensing data (namely maritime surveillance videos) provides various kinematic maritime traffic information, which significantly benefits remote maritime traffic controlling and management, off-site law enforcement, etc. But, it is difficult to extract distinct ship visual features when the target ship is sheltered by the neighboring ship in the maritime images (or

We propose a control method that changes the geometry of a fishing net into an arbitrary geometry. To control the net geometry, an automatic control system was constructed by integrating the data assimilation method into a fishing net dynamics simulation. This study focused on the function of the data assimilation method to estimate the unknown parameter needed to control the net geometry. By applying

The knowledge of drag characteristic and flow field around knotless and knotted cruciform patterns is very important for the design of successful netting structures. The effects of ratio between sphere (knot) and cylinder (twine) diameters (D/d) on the surrounding fluid flow and drag of cruciform structures with various attack angles was numerically investigated based on k-ω shear stress turbulent

Waves and currents interact, with the resulting combination largely determining the loading on offshore structures and devices. Despite this, currents are often ignored and wave buoy data is processed without consideration of the current or the wave-current interaction. This data is subsequently used in design, yet sea state power, steepness, and directionality may have significant errors. Here we

Flow-induced motions (FIM) can cause fatigue damage to the mooring and riser systems of deepwater offshore structures, especially for cylindrical platforms, such as Tension Leg Platform(TLP). Previous experimental and numerical studies have showed conservative FIM prediction compared to the field measurements, due to many significant factors such as the Reynolds number, the nonuniformity of the incident

The Gate Rudder is a recently introduced twin rudder system whose major advantages stem from its energy-saving properties. The two foil-shaped blades of the rudder, placed aside of the propeller, act as a partial duct in the wake of the hull producing additional thrust. However, since the rudder is a primary safety device on any vessel, investigating the manoeuvrability performance of the Gate Rudder

In this paper the effects of maneuvering motion on the hydro–acoustic performance of a marine propeller in behind–hull configuration is investigated. Velocities induced by ship motions markedly modify the inflow to the propeller and hence noise sources and emission can be different with respect to the rectilinear motion, that traditionally is exclusively considered during the design process. This problem

Since the underwater impurity and cavitation could have a significant impact on the aerodynamic performance of tidal turbine blade airfoil, it is necessary to consider both roughness and cavitation in the process of optimization design. In the present study, a novel multi-objective evolution algorithm based on NSGA‐II is proposed for the design of tidal turbine blade airfoil, to overcome the adverse

This study has established a nonlinear flow-induced vibration (FIV) model of tubing string by using the micro-element method and energy method with the Hamiltonian variational principle, in order to address the vibration failure problem of the tubing string induced by high-speed fluid flow in the tubing of high temperature and high pressure (HPHT) oil&gas well. This model considered factors such as

Spudcan is the foundation of the jack-up unit, and the depression on the seabed left by previous spudcan penetration and extraction was called the footprint. Footprint-spudcan interaction is one of the causal sources of jack-up unit accidents. The depression creates a localized eccentric loading and bending moment on the spudcan and platform legs that invariably cause the tilting of the platform. This

Although solitary wave generation using a piston-type wavemaker has been common, the method cannot be applied to all wave tanks because many of them have been or will be equipped with plunger-type wavemakers. How to use a plunger to generate solitary waves as good as those generated by a piston is an unsolved but practically significant problem. Herein, a theoretical method is proposed. New formulae

The integrated navigation system based on multi-sensor data fusion could effectively improve the navigation accuracy for Autonomous Underwater Vehicle (AUV). Various navigation equipment and sensors have different error characteristics. Current research does not take a specific processor based on their error characteristics, causing the optimal estimation is hard to realize in engineering applications

Several Emission Control Areas (ECAs) have been established to limit sulfur emissions from ships, thus influencing ship voyage planning. In this study, we used a mixed integer nonlinear programming model (MINLP) to reschedule ports-of-call sequences, ship route, speed, and bunkering strategy to minimize total sailing costs, defined as the sum of bunkering costs, time costs, and carbon emissions costs

This paper presents a complete numerical framework for modelling open ocean aquaculture structures in waves and current using Computational Fluid Dynamics (CFD). A structural dynamics model is incorporated to account for the motions and deformations of the net. It is based on the lumped mass method, a non-linear material law and implicit time step advancing. The presence of the porous net is considered

A new Fully Nonlinear Potential Flow (FNPF) numerical model has been developed for the simulation of nonlinear water wave problems. At each time step, the mixed boundary value problem for the flow field is spatially discretised by Finite Volume Method (FVM) and the kinematic and dynamic free surface boundary conditions are defined in a semi-Eulerian-Lagrangian form, which are used to update the wave

In this study, the application of surface roughness on model and full scale marine propellers in order to mitigate tip vortex cavitation is evaluated. To model the turbulence, SST k−ω model along with a curvature correction is employed to simulate the flow on an appropriate grid resolution for tip vortex propagation, at least 32 cells per vortex diameter according to our previous guidelines. The effect

The design of support structures requires precise knowledge about the effect of support tower on turbine performance, loads and its fatigue character. Therefore, a tidal current turbine mounted on an elastic tubular monopile support tower is simulated in coupled Fluid Structure Interaction (FSI) simulations using ANSYS Workbench. The performance and behavior of turbine loads for an elastic tower is