Equipment repair and intervention in subsea oil and gas fields are expensive, mainly due to vessel mobilization time, retrieval, repair, and replacement costs. The loss of revenue due to downtime could also be significant and the producer could face penalties in not meeting contractual commitments. These costs are part of the life cycle cost, which must be considered at the design stage. Estimating

The microbial induced carbonate precipitation (MICP) technique has been increasingly employed for ground improvement and fracture sealing, as well as for erosion mitigation and stabilization of sandy slopes. However, there is a lack of an effective assessment method to estimate the erosion resistance of biocemented sandy slope under wave actions. In this study, a series of bench-scale flume erosion

In high precision underwater acoustic positioning, the ray tracing algorithm is often used to reduce the acoustic ray error. However, it is generally assumed that precision of the acoustic ray with low elevation angle is the same to that with high elevation angle. In the context of the ray tracing algorithm, with the Snell acoustic equation we derive a relationship between the ray tracing error and

Multi-mode wave energy converters are able to generate power from multiple degrees-of-freedom, typically delivering increased power absorption from ocean waves compared to devices operating in heave or surge only. However, the control of such systems is complex due to strong coupling between different degrees-of-freedom. This study aims to understand the effect of both linear and nonlinear pitch-surge

In this paper a new procedure for detection and quantification of the main features of ship models bubbly wake is presented. The method is based on light scattering characteristics of laser beams passing through the wake of ship models. An optical light scattering model is developed and validated in a series of steady bubbly flow tests in a water tank, with time-invariant mean multiphase flow properties

The performance of different forcing datasets for trajectory prediction in the South China Sea and the sensitivity of prediction accuracy from selected datasets and model-based methods have been studied using Lagrangian models. Seven global ocean forecast or reanalysis forcing datasets including three current forcing datasets (CMEMS, CMEMS-R, and GlobCurrent), three wind forcing datasets (NCEP, ERA5

This study presents the problem of tracking control for underactuated autonomous marine vehicle in condition to uncertainty dynamic and unavailable velocity. A robust controller for tracking control is designed by employing backstepping method, multi-layer neural network, and adaptive control technique. Moreover, the all error variables are guaranteed time-varying bounded based on Lyapunov synthesis

The present paper provides a model updating application study concerning the jacket substructure of an offshore wind turbine. The updating is resolved in a sensitivity-based parameter estimation setting, where a cost function expressing the discrepancy between experimentally obtained modal parameters and model-predicted ones is minimized. The modal parameters of the physical system are estimated through

The radiated noise induced by the unsteady propeller forces is an important part of the vessel's total acoustic radiation. Therefore, understanding the role of propeller-shafting system in force transmission characteristics is necessary investigate the underwater vibro-acoustic responses of a vessel. This study compared the contribution of hull and propeller-shafting system to the radiated sound power

The degree of bending (DoB) characterizes the member through-the-thickness stress distribution which has a profound effect on the fatigue behavior of tubular joints commonly found in steel offshore structures and the determination of DoB values is essential for improving the accuracy of fatigue life estimation. Multi-planar joints are an intrinsic feature of offshore tubular structures and the multi-planarity

The installation process of caisson foundations causes the seabed soil heaving as well as the soil strength remoulding. This paper investigates these two effects by examining the installation process of caissons through large deformation finite element analysis. The short-term undrained bearing capacity of caisson foundations in clay after installation, which is a critical engineering scenario because

An analytical solution of a new composite breakwater consisting of a moored submerged flexible porous membrane and a submerged ruble mound below the membrane is presented. The semi-analytical solution is obtained based on the velocity potential decompositions where the consideration of a dispersion relation with complex wave numbers is not required. The convergence of the series solution is demonstrated

Since the construction of the Deepwater Navigation Channel Project in Yangtze River Estuary 1998, it is extremely imperative to clarify the sediment dynamics in Yangtze River Estuary to reduce deposition risks in the channel. However, the sediment deposition mechanism has not been well understood. Therefore, four mechanisms of sediment deposition in Yangtze River Estuary were simulated and another

This paper proposes a novel fixed-time output feedback sliding mode tracking control of marine surface vessels (MSVs) under unknown external disturbances, unmeasurable velocities, unmodelled dynamics and actuator faults (AF). A fixed-time extended state observer (FXESO) is proposed to observe unknown lumped disturbances. Considering the FXESO, a novel fixed-time velocity-free fault-tolerant control

In this paper, the drag forces on a rigid segment of a twin-tube submerged floating tunnel (SFT) under various Re number and submergence are experimentally investigated with a simplified rigidly connected tandem twin-cylinder model towed in a tank. The effects of the spacing distance between two cylinders and vortex-induced vibration (VIV) on the drag forces are investigated through stationary and

The paper presents the numerical studies of seakeeping behavior for a high-speed catamaran with stern flap advancing in long crest head wave. Both model-scale and full-scale simulations have been carried out in sea state 6 using unsteady Reynolds-averaged Navier-Stokes (URANS) solver. Uncertainty analyses were performed to verify the accuracy of the numerical solver. Model tests were conducted for

Experiments with wave groups are carried out to investigate 3D wave resonance in the gap between two fixed parallel elongated boxes with square corners. The gap responses are re-created in a numerical wave tank using computational fluid dynamics (CFD) with reasonable accuracy. Based on the CFD results with high temporal and spatial resolution, the free-surface behaviour, internal flow velocity and

In this paper, the slamming pressure and load characteristics of a trimaran cross-section under various conditions were investigated by CFD (Computational Fluid Dynamics) simulations. The computation model was first validated against experimental results. After that, the simulation of different types of motion, i.e. free fall with different mass and entry velocity, entry with constant velocity and

In this study, the hydrodynamic performance of a reverse podded propulsor under azimuthing conditions is evaluated. The shear stress transfer (SST) k-omega turbulence model and sliding mesh technique are adopted for this evaluation, and the commercially available software, STAR-CCM+ is used for the numerical simulation. An extensive convergence study was performed with respect to time step and grid

A biplane-type hyper-lift trawl door is newly designed to achieve stable handling while maneuvering, deploying, and stowing with excellent hydrodynamic performances for both bottom and midwater trawling. Flume-tank experiments were carried out to investigate the effect of the aspect ratio (λ, defined as the span b divided by chord c) on the hydrodynamic characteristics of the biplane-type hyper-lift

h Hydrofoil vessels, which greatly take the advantage of the dynamic lifting force during the cruising, are amongst the watercrafts that can significantly benefit from the application of the winglets. These benefits can be decreasing the lift off speed of the vessel, increasing its maximum speed or reducing the drag force acting on the hydrofoils and hence contributing to fuel saving. This study aims

The complex flow field interference between the front and rear propellers will affect the efficiency of the tandem propeller. To reduce or utilize this kind of interference and improve efficiency, inspired by the excellent aerodynamic performance (lift-drag ratio) of the plane with canard-configuration wings, an exploratory numerical study has been carried out to investigate the hydrodynamic performance

This paper presents a formation reconfiguration method for multiple unmanned surface vehicles (MUSVs) executing target interception missions. In its essence, the objective can be described as follows: given a target at a given position and a set of USVs, maneuver the USVs from their initial positions towards the target so that they end forming a “protective barrier” in the vicinity of the target. In

Head-on collision of two internal solitary waves (ISWs) in a two-layer inviscid fluid with fully nonlinear free-surface (FS) condition is investigated numerically in this paper. The collision process of and nonlinear interaction of internal solitary waves is studied based on nonlinear potential flow theory and a series of numerical simulations are conducted using a multi-domain boundary element method

This paper presents a method for the rational processing of ship voyage data for improved ship operation. The proposed approach is based on a physical modeling method, in which the ship resistance-propeller-engine model is first developed by using available ship information and basic hydrodynamics. For the analysis of operational scenarios in realistic environmental conditions, seaway data are retrieved

Wave glider is a revolutionary ocean surface autonomous vehicle, which has the ability to convert surface wave motion into forward propulsion. Theoretically, the endurance of the wave glider is unlimited because of the consistent wave energy resources in ocean. Therefore, it has a broad application prospect in ocean survey and observation. However, due to the characteristics of low speed, underactuation

Suction caisson foundations are increasingly considered as a foundation solution for offshore wind farm development in China. This paper outlines the design considerations for developing a suction caisson supported jacket solution for an offshore wind farm in Southern China. Geotechnical analyses for four major aspects, ultimate limit state (ULS), serviceability limit state (SLS), fatigue limit state

The surface-piercing propellers (SPPs) are a specific type of supercavitating propellers that have higher efficiencies at high advance speeds. The SPPs operate on a free surface, so due to the ventilation and air suction into the water, the pressure of the suction surface of the blade approaches atmospheric pressure. Given the importance of better understanding this phenomenon, in this research, the

Thermal problems may be encountered in offshore engineering applications, such as pipeline engineering activities and submarine nuclear waste storage. However, few studies have focused on the behaviours of marine sediment involved temperatures, especially under long-term low cyclic loads. In this study, a series of undrained temperature-controlled triaxial tests were carried out to study the thermal

The present paper aims to explore and gain more knowledge about the viscosity effect on a shallowly submerged UV hydrodynamics. For this purpose, the hydrodynamic drift tests are performed on the generic SUBOFF UV geometry using URANS equations with a Reynolds stress turbulence model and Euler equations available in the commercial code STARCCM+. The simulations are conducted for drift angles ranging

Landing large diameter conductor or surface casing strings in deepwater has become a great concern to offshore oil companies, since the dynamic tensile load induced by the heave motion of drillship approaches the capacity of today's landing system. For an accurate prediction of heave induced dynamic tensile load on landing strings and determining the safe margin of deepwater landing operation, a comprehensive

Under cyclic loads, such as wave, earthquake, and traffic load, the direction of the principle stress axis rotates continuously in the soft foundation of embankment dam. However, the research conducted on stress-strain and stiffness characteristics of soft foundation in embankment dam under complex loads considering principal stress rotation was limited. In this paper, the deformation property of natural

Sloshing inside liquid containers may result in carrier instability or structural damage of the tank. To suppress the liquid sloshing in a swaying and rolling rectangular tank, a bottom-hinged and top-tensioned vertical porous membrane baffle at the center of the tank was employed and its performance as an anti-sloshing device was investigated. As a hydroelastic theoretical-analysis tool, a matched

Attitude determination for underwater vehicles in control and navigation applications has been always an important issue. MEMS-based accelerometer and gyroscope data can be usually used to determine the underwater vehicle attitude. However, the gyroscope sensors suffer from bias problem and the accelerometer data is not reliable in the presence of the external acceleration for the attitude determination

Body force propulsion model has been used for ship self-propulsion CFD simulation for a long time due to its higher computational efficiency and less computer source required. This paper presents a new body force method coupled the blade element momentum theory (BEMT) considering the three-dimensional viscous effects with the RANS solvers. In-house code HUST-Ship was used to solve RANS equations with

The main objective is to present alternative algorithms to neural networks when improving sea state forecast by numerical models considering main spectral bulk parameters at a specific location, namely significant wave height, peak wave period and peak wave direction. The two alternatives are random forest and gradient boosting trees. To our knowledge, they have never been used for error prediction

Risks in maritime navigation linked to cyberthreats emerge, and they must be assessed together with the more traditional risks such as grounding or colliding another vessel, as now the latter might be the consequence of a cyberattack. The fields of mobility and transportation data see vulnerabilities of navigation systems jeopardising their normal use, and putting both users and their environment at

Interest in marine renewable energies has grown in recent years, especially in northern European shelf seas where several technological devices have been developed. In this context, numerous investigations focused on accurate predictions of tidal currents and their respective kinetic energy. An empirical estimation of the current velocity is explored in this study, where three different methods are

This paper addresses trajectory tracking control problem for autonomous underwater vehicles (AUVs) using quaternion-based attitude representation. A quaternion based adaptive non-singular terminal sliding mode control scheme is proposed for an AUV subject to ocean current and modelling uncertainty. At first, kinematic equations of the translational and rotational motions are described by unit quaternions

The objective of this study is to investigate the damage characteristics response of the ice sheet and reveal the mechanism of ice-breaking subjected to the underwater explosion. The Arbitrary-Lagrangian–Eulerian (ALE) algorithm for the fluid–structure-interaction issue of the LS-DYNA software was adopted. The efficiency and accuracy of the underwater explosion material and numerical model were studied

Numerical simulations of flow-induced transverse vibration of a near-wall cylinder with small gap to diameter ratios (e/D ≤ 0.5) at Re=200 are performed based on the Navier-Stokes equations using a finite volume method based OpenFOAM codes. Multi-block mesh is used. As the cylinder is very close the wall, remeshing is regularly applied during the body oscillation to avoid over distortion of the grid

In this study, a detailed analysis of hydrodynamic performance of a pumpjet propulsor (PJP) in different oblique inflow angles (β=0⁰, 5⁰, 10⁰, 15⁰, 20⁰, 25⁰, 30⁰, 40⁰) and different rotational speeds (n=3000rpm, 3600rpm, 4200rpm) is investigated numerically. The SST k-ω turbulence model and sliding mesh technology based on the Reynolds Averaged Navier-Stokes (RANS) method are employed. The structured

Crack damage is commonly found in aged hull structure severely affecting the ultimate compressive strength. A numerical study is comprehensively carried out to reveal the ultimate strength reduction behaviors of steel unstiffened cracked plate. The parameters such as crack length, angle and positions as well as the plate aspect and slenderness ratios were taken into account in the FE models. The crack

Wavemaker problem is a fundamental and important issue in the study of marine and coastal engineering. An accurate incident wave field provided by a wavemaker is crucial to explore the problems of wave and wave-structure interaction. Generally, wavemakers start working from a rest state both in physical and numerical tanks. Excessive acceleration induced by sudden motions of wavemaker will result in

The effects of a propulsor on the hydrodynamic forces acting on an autonomous underwater vehicle (AUV) were investigated by towing tank model tests. A mathematical maneuvering model using a whole vehicle model was established, and captive model tests using vertical planar motion mechanism equipment were performed to obtain maneuvering coefficients. The Reynolds number of the full scale test model in

Artificial upwelling is considered as a potential way to increase the phytoplankton productivity. However, one of major obstacles for the large-scale field application of artificial upwelling is the dilution of uplifted nutrient-rich water in density-stratified ocean. In this paper, the hydrodynamic characters, such as trajectory and initial velocity of artificial upwelling, is investigated by using

Pipe-in-pipe (PIP) systems are utilized widely in modern petroleum industry owing to their good insulation effect. In present work, a novel mathematical model for the free vibration of the fluid-conveying cantilevered PIP system considering thermal effect and two-phase flow is proposed. The insulation layer connecting two concentric pipes is simplified as the distributed springs and dampers here. The

The efficiency of a low-reflective caisson built at the Outer Port of Punta Langosteira (A Coruña, Spain), with a front-wall porosity of ≈ 5%, has been numerically investigated by means of OpenFOAM® for different chamber configurations and different sea states. The numerical model is validated with data coming from experimental tests performed on a scaled prototype. First, two different water levels

The shipping industry is the heart of international trading activities and the global economy. Maritime transport contributes to environmental pollution through the emission of greenhouse gases. New mandatory regulations aim at improving the environmental performance of ships by encouraging power reduction and alternative fuels. These requirements drew attention to the estimation of the ship performance

Iron ore fines (IOFs) are indispensable material for industries with over million tons transported annually by sea. The transportation involves serious risk of marine accidents due to cargo liquefaction caused by the loss of shear strength under cyclic loads. In this work, the effect of moisture content on the unsaturated shear strength of the IOFs was analyzed, including the matric suction and the

The critical initial angle of attack that the cylinder can move along the non-circuitous trajectory in water entry is investigated experimentally and numerically. A primary focus is on characterizing the relationship between the initial inclined angle α0 and horizontal velocity u0 in the parameters space of α0∼u0/v0, where u0/v0 is the horizontal velocity u0 to vertical velocity v0 ratio. To build

Evaluating marine system reliability requires considering the interaction of a limit state with the stochastic ocean excitation. Given a range of operational profiles, a relevant question is which sea states lead to the worst-case system responses, considering the effects of short and long-term variability. If the identified subset of operational profiles indeed leads to the worst-case system responses

A nonlinear time-domain numerical model based on a body-exact approach is applied to study the problem of large amplitude motion of a tightly moored submerged sphere. In this model, the exact body condition on the instantaneous wetted body surface is satisfied as well as the linear condition on the still water surface. Numerical simulations were carried out for two wave steepness, each with various

The dynamic characteristics and coupling mechanisms of a bottom fixed offshore wind turbine (OWT) with a pentapod substructure under combined seismic, wind, and wave conditions are analyzed. A passive control method of a tuned mass damper (TMD) is then applied. The influence of the TMD parameters on the control effects of the OWT is investigated, and the feasible parameters for the vibration mitigation

Numerical simulations of the S-175 containership obliquely advancing at constant forward speed in calm water and in regular waves were conducted using a potential flow method. A double-body potential and trailing vortex sheets, which modeled the flow field around the ship obliquely advancing in calm water, yielded transverse forces and yaw moment due to the lift effect. Perturbation potentials describing

The deep-water high-pier bridges that located in active seismicity areas have the potential to be suffered for earthquakes, wave and current action synchronously during construction and service period. In order to investigate the dynamic responses of the whole bridge piers under joint earthquakes, waves and current action. This paper is based on a deep-water high-pier whole bridge as a prototype, pursuant

Focused on cavity dynamics in high Froude number (10

The uniaxial compressive behavior of stiffened plates with pitting corrosion is investigated, with a specific concern about corrosion-caused transition within different failure modes. To control the geometrical parameters and distributions of corrosion pits, ten specimens with mechanically-drilled cylindrical corrosion pits near the weld seams are deliberately prepared and tested. During the test,

In this paper, air cavity and Worthington jet formations due to the entrance of a hydrophilic steel sphere into three different target liquids are studied. The liquids are water, silicone oil and silicone oil film on water. A high-speed camera is used to observe cavity and jet formations, and the resulting data is used to measure important parameters such as jet height, deep-seal time and deep-seal