Environmental contours of significant wave height and wave period are established for 10, 25 and 100 year-return periods by different approaches. The environmental contours are first derived by Direct sampling and by the Inverse First Order Reliability method (IFORM) using the Rosenblatt transformation. Then, the importance sampling technique is applied at different locations along the environmental

Temporal and spatial vortex shedding evolution for flow around a circular cylinder near a plane boundary is investigated using three-dimensional direct numerical simulation, with a parameter space of boundary layer thickness-to-diameter δ/D = 0–1.4, gap-to-diameter G/D = 0.4 and Re = 350. For each δ/D, three consecutive wake stages are divided with time based on the dominated flow structures – mode

The base shear and moment may play important roles in behaviors of offshore monopiles, and traditional p-y curves cannot model the base forces. In this study, a new semi-analytical model for monopile is proposed, from which base forces and displacements can all be obtained simultaneously. Green's functions for poro-visco-elastic soil and Timoshenko beam are used. Full bond between pile and soil is

The effects of a high-speed frigate model passing close to a moored container model alongside a closed quay are experimentally and numerically investigated with a focus on ship-generated waves, transient ship motions, and hydrodynamic forces acting on the moored ship. Scaled model experiments are conducted to investigate the hydrodynamic interactions between the passing ship-generated waves and the

Parametric spectrum models describing a frequency spectrum of ocean surface waves (e.g., Pierson-Moskowitz and JONSWAP (Joint North Sea Wave Project) spectrum) as a function of the significant wave height and peak period (Tp) have been used to estimate the energy period (Te) using a relation, Te=CTp, when the frequency wave spectrum is not available. This approach, however, introduces uncertainties

The importance of the transverse viscous loads, in a modular maneuvering model, is investigated. A method to estimate steady sectional drag coefficients is first presented. A 2D+t approach, which accounts for forward-speed effects, is also presented. The time-varying drag coefficients, in the 2D+t method, are estimated with three methods: two simplified methods using results from the literature directly

A long-standing problem in maritime operations and ocean development projects has been the prediction of instantaneous wave energy. Wave measurements collected using an array of freely drifting arrays of Surface Wave Instrument Float with Tracking (SWIFT) buoys are used to test methods for phase-resolved wave prediction in a wide range of observed sea states. Using a linear inverse model in directionally-rich

The effect of extreme wind speeds in applications for design is of great interest in a variety of fields such as meteorology and coastal engineering. In these fields a common problem is the scarcity of long datasets. To overcome this limitation, a common approach is to utilize the entire available dataset using the Peak-Over-Threshold (POT) approach. In small samples there may be a limited number of

Restrictions on greenhouse gas emissions and the existence of developing countries has diversified ship routes and ship types, making the ship operation more complex. Many types of simulation methods have come up in the last decade due to the enforcement of the energy efficiency design index. However, few studies that validated their simulations with actual data. This study performs the optimal ship

Being one of the most commonly used offshore operations, offshore lifting operations become increasingly challenging due to the gradually growing size and weight of payloads. The research on automatic control in lifting operations, e.g., anti-swing control and heave compensation, only considers simple-shaped payloads, such as lumped-mass rigid points. However, the sizes and orientations of many structures

Improved design methods for laterally loaded monopile foundation are crucial for the offshore wind turbine (OWT) sector, as established approaches no longer apply to such a pile foundation characterized by a relatively small length-to-diameter ratio. Numerical modeling is the primary approach to improve and validate design methods for monopiles and a central part of it is the soil constitutive model

The surface morphology of the ballast tank has changed due to years of exposure to seawater corrosion. Hence, the severity of pitting corrosion and the random shapes of corrosion pits may affect the remaining life of the ballast tank. Therefore, this paper presents the difference in surface morphologies of corroded ballast tank and its correlation to the geometry of corrosion pits. These morphologies

The hydrodynamic characteristics of a blended wheel-track amphibious truck were studied via model towed tests and numerical simulations. First the mathematical model was set up and the process of launching and coming ashore was researched by theoretical analysis. The effect of tracks on assisting driving the truck on land was also studied. Second the influence of buoyancy boxes and bow plate on resistance

The bucket foundation is considered as a promising alternative to conventional foundations for offshore wind turbines (OWTs) due to its cost-effectiveness and high-reliability. The behavior of bucket foundation under static loading has been extensively investigated, while its long-term performance induced by the cyclic loading under the surrounding soil influence lack of study. This study aims to investigate

The Sea of Marmara is a typical example of enclosed seas and an inland sea bounded by land-masses in four directions, and it links the Black Sea and the Mediterranean via the Bosphorus and the Dardanelles straits. Moreover, The sea of Marmara has strategic importance with possessing marine structures such as various types of terminals, cruise terminals, and marinas, and also providing a strong economic

The use of deflectors as augmentation devices to improve the power performance of a 3-bladed conventional Savonius turbine has been investigated by analyzing the deflectors’ effects on self-starting capability and power performance at various deflector angles. Two deflector plates positioned at the upstream of the turbine were tested inside a closed-circuit wind tunnel at an air flow speed of 7.0 m/s

The accurate prediction of ship trajectory has great significance in maritime transportation. Among all the prediction methods, multi-step prediction has received increasing attention because it can predict both time and position information in the future period. However, the existing methods are either complex or have low prediction accuracy. In order to overcome the limitations, a physical hypothesis

The present paper investigates the significance of gyroscopic effects on responses of floating offshore wind turbines (FOWTs). A 17-degree-of-freedom (DOF) FOWT model is rigorously developed using the Euler-Lagrange approach. Based on rational approximation of the radiation loads, an extended state-space formulation is then established for the coupled mechanical-hydrodynamic-controller system, enabling

This paper investigates the tracking control of the autonomous surface vessels (ASVs) with the time-varying disturbances. While the echo state network (ESN) accounts for the unknown dynamics in the model, a model-based event-triggered control (MBETC) scheme is presented by using the compound learning technique, which combines the learning of the ESN and the estimation of the compound disturbance. Different

A new control strategy based on adaptive second order sliding mode approach is applied to a floating wind turbine system in the above rated region. This adaptive controller is well adapted to a highly nonlinear system as floating wind turbine, and can be easily implemented with very reduced knowledge of modeling. The proposed controller partially based on multi-blade coordinates transformation combines

The interaction of oblique water waves with a land-fixed Oscillating Water Column (OWC) type wave energy converter is examined. Two-dimensional linear wave theory is used to formulate the mathematical problem. The matched eigenfunction expansion method (EEM) using dual series relations and the Boundary Element Method (BEM) with quadratic elements are utilized to solve the associated boundary value

A modified Box-Cox transformed Rayleigh (MBR) distribution for the wave crests is presented in this paper. The basic idea contains two steps: firstly, non-Gaussian elevations are transformed into Gaussian elevations by a modified Box-Cox transformation. Afterwards the crests of the transformed elevations are described by the Rayleigh distribution. Comparison between the MBR and Tayfun distributions

Wave breaking occurs when waves reach a critical level of amplitude, which results in releasing a significant amount of energy. Predicting the wave heights, locations and other characteristics of breaking waves in shallow water is an important area of research. The breaking wave height, which is the most important characteristic, depends on various parameters such as deepwater wavelength, breaking

Ship drag and self-propulsion simulations of a twin-screw high-speed displacement vessel were performed using the unsteady Reynolds-averaged Navier–Stokes (RANS) method. The sliding mesh and overset mesh methods were applied concurrently to simulate the coupling of the propeller rotation and the ship motion. The effects of the propeller shaft brackets on the drag, propulsion performance, wake field

The prediction of ocean currents is essential for the path planning and control of Autonomous Underwater Vehicles. Regional physics-based forecast models provide valid predictions but are too computationally expensive for real-time prediction necessary for AUV navigation. While vehicle sensors can measure the spatial evolution of currents, temporal prediction remains an open problem as existing data-driven

During the installation of marine flexible pipelines, components, such as flexible risers, umbilicals, and cables, subject to wave motion and ship yaw can cause torque on such pipelines. In addition, marine flexible pipelines are subjected to low tension at the touch down zone (TDZ), which could result in the torsion instability phenomenon of flexible pipeline in the TDZ, thus forming a loop. Moreover

The issue of bubble sweep-down is of great importance within the field of marine research, as the phenomenon greatly affects the measurement accuracy of research vessels. To explore the characteristics of bubble sweep-down, an experimental study into this phenomenon in relation to research vessels was carried out. With the help of particle image velocimetry technology, the microbubble trajectory on

Nile River is considered as an auspicious area; in particular along with Upper Egypt, to produce electrical energy from the water current which called hydrokinetic energy. This sort of renewable energy is admitted deeply as a unique and uncommon solution for the electric power demand in the remote areas on the rivers’ sides. The hydrokinetic energy of the river stream can be extracted by a submerged

Frequent water level fluctuation such as wave is one of the significant differences that distinguish subsea tunnels from land tunnels. For a better understanding of the influence of the dynamic wave loading, this study develops a new set of analytical solutions for the wave-induced hydraulic response on the subsea shield tunnels. The proposed analytical solutions are verified with numerical simulation

Lazy wave risers can mitigate the kinematic coupling between floating structure and riser touchdown zone (TDZ), so as to improve its fatigue life. However, due to the introduction of buoyancy blocks, nonlinear dynamic response and fatigue damage prediction will be more complicated. In this paper, a concept of “multiple lazy wave riser”, namely, deepwater lazy wave riser configuration based on multiple

The flexible pipe industry has been confronted with the potential threat of armour wires lateral buckling for over two decades. Cyclic bending is recognized to play a significant role in the lateral buckling mechanism since it facilitates the armour wire sliding against the frictional resistance. If a flexible pipe is exposed to axial compression larger than the critical load for a certain period,

To promote energy extraction efficiency, an active deformation method to implant an elastic airbag at the leading edge of flapping wings is proposed in this study. The charging and discharging processes of the airbag are accomplished by sinusoidally adjusting the local deformation angle. We investigated numerically the effect of both the reduced frequency f∗ and the local deformation amplitude α on

Saltwater intrusions occur widely in tidal river channels, significantly changing the vertical distribution of mainstream velocity and density (salinity). They are vital to the hydrodynamic conditions of lateral withdrawal. In this study, a 3-D numerical model was constructed and validated through experimental tests, and the hydrodynamic characteristics of lateral withdrawal under saltwater intrusion

The diffraction problem of a concentric truncated cylinder system with a porous ring plate fixed inside is studied in the framework of linear potential theory. The system consists of a porous exterior cylinder and an impermeable interior cylinder, which are connected by an impermeable top and bottom plate, and a porous ring plate arranged below the free surface. Darcy’s law is applied to the porous

A numerical method for solving 3D unsteady potential flow problem of ship advancing in waves is proposed. The flow field is divided into inner and outer domain by an artificial matching surface. The inner domain includes ship-wetted surface, matching surface and free surface inside. The free-surface condition is formulated by perturbation about the double-body flow (DB model) or uniform incoming flow

The Delft Twist 11 Hydrofoil is a common test case for investigating the interaction between turbulence and cavitation modelling in computational fluid dynamics. Despite repeated investigations, results reported for the lift and drag coefficient are accompanied by significant uncertainties, both in experimental and numerical studies. When using scale-resolving approaches, it is known that turbulent

Ocean engineers are often tasked with developing innovative, low-cost floating offshore wind turbines as the industry moves toward deeper waters to access regions with higher offshore wind potential. One example is the hanging-mass concept, in which a suspended counterweight stabilizes a positively buoyant floater; a hybrid design that combines a spar's performance with the maneuverability of a semi-submersible

In the case of tidal turbine arrays, the spatial evolution pattern of turbine wakes affects the power performance of other turbines and the hydrodynamic environment of adjacent turbines. However, the evolution mechanism is unclear, particularly in terms of wake energy restoration process. Therefore, we investigated the wake spatial evolution mechanism of a tidal current turbine experimentally. The

The ultimate strength of stiffened plates subjected to combined biaxial compression and lateral loads has not been widely investigated yet by experiments. In this study, both experimental and numerical analyses were performed to study the ultimate strength and collapse behaviors of stiffened plates under the combined biaxial compression and lateral loads. And the experimental set-up provides reference

A well-planned dive trajectory is the key for the trans-media maneuver and flight control of morphing unmanned aerial-underwater vehicles (MUAUVs). The main focus of this paper is the application of a watch-based multi-objective grey wolf optimizer (MOGWO) to dive trajectory optimization problems. A multi-objective trajectory optimization model considering the change of sweep angle and static moment

This paper focuses on the elastic buckling of cross-ply composite closed cylindrical shell subjected to hydrostatic pressure. The analytical model for buckling of composite cylindrical shell is derived by using the First Order Shear Deformation Theory (FOSDT) and considering the pressure stiffness. Several types of shells including thin, thick, long, and short shells are investigated. Two composite

This paper reviews the state-of-the-art research progress of large-scale model at-sea measurements in relation to ship resistance, propulsion, manoeuvrability, seakeeping and structural loads. Physical experiments have long been an indispensable tool in the research of ship hydrodynamics and structural loads. To date, a substantial number of experiments including tank model tests and full-scale measurements

Elevated pile caps are always located close to the still-water level, where breaking waves can induce great impact loads and threaten the structural stability of bridges. This paper focuses on the interaction between breaking waves and an elevated pile cap with a rectangular cross-section. An elevated cap specimen under three breaking wave conditions was employed in the experimental program. The breaking

Examined the spatial and temporal changes in the wave spectra using waves measured in the coastal area at two locations for three years. Long-term variability is examined with ERA5 reanalysis data. The annual average wave spectra have a significant wave height (Hs) of ~1m at both locations. During the Asian monsoon (June–September), the highest wave spectra resulted in Hs of 5.1m. Frequently, the wave

The oscillating water column is the most widely used wave energy converting technology for onshore applications. In the previous studies, the performances of the chamber and the turbine were investigated separately, or some substitutions were employed to induce the damping effects. In this study, an OWC model employing the cubic chamber and the impulse turbine is studied experimentally in a wave flume

A coupled control volume (CV) and arbitrary Lagrangian–Eulerian (ALE) model was developed to analyse the section geometry of a flexible bag of an air cushion vehicle (ACV) subjected to slamming loads. The model was validated using benchmark tests. The effects of the initial velocity, Young's modulus of the flexible bag, ballast weight, in addition to bag-to-cushion pressure ratio on the section geometry

Due to the substantial volume of materials used in the structural members of jacket platforms, weight optimization is of critical importance. A Genetic Algorithm is a powerful tool that allows for consideration of many parameters in the optimum design of platforms simultaneously, a feature hardly found in ordinary circumstances. Regarding the cyclic loads derived from waves, fatigue is one of the most

Hydropneumatic Passive Heave Compensator (PHC) for offshore drilling may exhibit undesirable effects due to nonlinearities of the friction seal, causing the so called Compensator-Induced Vibration (CIV) phenomenon, which induces longitudinal oscillations of frequencies higher than the heave motion. In this paper, a control system is proposed to attenuate the heave motion and to mitigate the CIV and

Cutter Suction Dredgers (CSDs) are a special type of ships designed for construction and maintenance projects of ocean and offshore engineering. During the dredging operation, CSDs can excavate nearly all kinds of soil on the sea bed, and then the dredged materials with coarse particles need to be sucked up by a slurry pump and transported to a disposal area through a long-distance pipeline. In order

The hydrodynamics of an offshore stationary platform consisting of four cylindrical Oscillating Water Column (OWC) Wave Energy Converters (WECs) are considered in this paper. Based on the potential flow theory, a second-order Higher-Order Boundary Element Method (HOBEM) model is developed to simulate the wave interaction with the multi-OWC platform in time domain. Laboratory tests of a carefully instrumented

This paper presents a dynamic overset mesh based two-dimensional Numerical Wave Tank (NWT) model to study the water entry of a wedge into water waves in the process of offshore lowering. The NWT model is developed by integrating an incompressible multiphase flow solver on the dynamic overset mesh and a wave generation library in OpenFOAM. Numerical results of water entry of a symmetric/asymmetric wedge

Floating protective barriers provide essential protection to critical governmental, commercial, and private assets that are vulnerable to water-borne intrusion, such as liquefied natural gas terminals, tankers, etc. These barriers require additional evaluation in the case of their deployment at significant water depth in offshore environments. The seaworthiness of the Triton® barrier design developed

The classical problem of time-harmonic diffraction and radiation of free-surface flows due to wave–body interaction is revisited based on the Fourier–Kochin theory for zero forward speed. The key idea of the Fourier–Kochin theory is reversing the order of the two fundamental tasks of the Green function based direct solutions of free-surface flows, i.e., evaluation of the Green function and its gradient

The liquid impact induced by slamming in the membrane-type tank is an important issue for the design of Floating Liquefied Natural Gas (FLNG) facilities. The free surface entrapping air may easily happen under shallow-water condition in the tank, which could result in structural local failure. Studying the effect of entrapped air on slamming load is essential to understand the air-free surface-elastic

The damage detection of mooring lines is critical to safe operations because the stability of offshore floating platforms depends on the integrity of such lines. However, existing mooring line damage detection techniques are considerably limited because they cannot be implemented constantly. To resolve this inadequacy, this paper proposes a deep-learning-based approach that can detect underwater mooring

The seakeeping performance of a damaged ship is highly correlated to the wave incident direction. Therefore, predicting the motion responses of a damaged ship under various incoming waves is important. In this study, the seakeeping performance of a DTMB 5415 model is investigated by focusing on its roll motion under beam wave condition. The model performance under an incident wave angle (α) of 180°

The existing studies have been primarily focused on the lateral behavior of large-diameter stubby pile or small-diameter slender pile in sand, with little attention paid to large-diameter slender pile. This study presents a unique series of centrifuge tests on monotonic and cyclic lateral behavior of heavily instrumented large-diameter slender piles in medium dense sand. Two typical length to diameter

In dredging, high pressure water jets are commonly applied to assist the mobilization of soil. This work considers the excavation of cohesive soil. The key objective is to predict the development of the cavity in the soil as a function of the undrained shear strength, translation velocity and hydrodynamic pressure of a single nozzle. A generic computational fluid dynamics (CFD) model has been developed