Tidal turbines represent a new frontier for extracting energy from a huge potential of renewable source such as the tides. Despite the technology being mature enough, new solutions aimed at improving the machines efficiency with reduced environmental impact and installation costs are currently under investigation. A novel tidal turbine, characterized by being self-balanced and not requiring structures

The acoustic wave propagating in ocean is severely distorted due to the sound speed profile of sea water and the reflection and absorption of seabed. The FEM/BEM is a preferable method to solve the fluid-structure interactive vibration and sound radiation problem of underwater structure in ocean acoustic environment, since the Green function can be applied in the integral equation. The simple source

The aim of this work is twofold. We analyze a dynamical model for the transversal motion of a vertical riser, which is a long tube used in the petroleum industry for subsea well drilling operations, and in other cases to bring the oil from the bottom to the sea surface. After the analysis, we propose a new numerical approach to solve the resulting system of coupled differential equations. The proposed

Non-planar composite π joints are receiving increasing attention in marine engineering. Efficient two-dimensional (2D) finite element (FE) methods, which can accurately predicted the failure behavior of this kind of joint, are critically meaningful for structural design emphasizing low computational time and easy operation. A material model is developed here, from which the equivalent engineering constants

The hydrodynamic characteristics of cambered otter boards with a camber ratio of 15% and aspect ratios of 0.5, 1.0, 1.5, and 2.0 were investigated through flume tank experiments and CFD analysis for the cases in which the wingtips were blocked or unblocked. In the blocked wingtip case, the maximum lift coefficient, stall angle, and lift slope (α: 0° to 15°) were approximately 1.75, 15°, and 0.115 (deg−1)

An analytical model is proposed to investigate the linear and nonlinear mechanical response of reinforced thermoplastic pipes (RTPs) under axial tension, in which the existing homogenization method, failure criteria and material degradation models are combined to predict the CDM behavior in an iterative and cyclic way. To obtain damage sequences, the homogenization method is modified by a stress correction

The conventional practice of retrieving the whole length of deepwater drilling riser during imminent typhoon is tedious, time-consuming, and has huge risk of untimely evacuation of personnel and facilities for safety. A proposed operational solution is one which has the drilling riser disconnectable near surface while the longer section is left tensioned by buoyancy can (BC) in freestanding mode. This

This study aims to determine long-term spatial variability of wind and wave characteristics over the Sea of Marmara. For this purpose, we produced four different wind and wave datasets for a period of 40 years (1979–2018) using the calibrated and default-setting SWAN models forced with both CFSR and ERA-Interim winds and inter-compared. The performance of these datasets is examined against the wave

The autonomous ship carrying valuable cargoes and passengers in a more effective and cost-saving manner will soon be state of the art technology, which most likely shall be introduced into the public horizon as the remote control mode within the foreseeable future. The highly connected intelligent systems though come at the cost of the increased system vulnerability to cyber-attacks. To smooth this

Accurate modeling of low-frequency (LF) wave loads and responses is important but challenging in the design of spar-type floating offshore wind turbines (FOWTs), especially for shallow and intermediate water depths. A 6 MW spar-type FOWT system designed for a water depth of 100 m is investigated both experimentally and numerically to study the nonlinear hydrodynamics responses in waves. The second-order

In the present work, numerical simulation of structural damage subjected to the near-field underwater explosion is carried out by coupling the SPH and RKPM. The fluid solver is established based on the compressible SPH method, while the dynamic response of the structure is calculated based on the RKPM shell formulation. Since large deformation with contact will occur in the underwater explosion problem

Peregrine breather solution of the nonlinear Schrödinger (NLS) equation can be treated as one of the excellent backbone models for abnormal wave in the ocean. Fully nonlinear numerical simulations performed with the higher-order spectral method reveal that its maximum amplification factor can be larger than the theoretical prediction in the regular background wave and that such breather dynamics has

Oscillating Water Column (OWC) with its mechanism based on converting hydrodynamic energy into pneumatic energy is one of the earliest wave energy converters studied by researchers. While the focus of the previous studies were mainly on hydrodynamic efficiency, this paper addresses free surface fluctuation inside the OWC chamber emphasizing on sloshing phenomenon through irregular wave impingement

Cruise ships have large and long superstructures, which are almost extending the whole ship length with discontinuous characteristics, such as side shell recess and many window openings. The superstructure effectiveness on hull girder longitudinal strength is a complicated but unavoidable issue in ship design stage. This paper has carried out a collapse experiment of steel model with superstructures

Burst pressure prediction of pipelines with interacting defects is essential in the integrity assessment of steel pipelines. A series of evaluation criteria have been proposed to predict the burst pressure. However, the burst pressure is not accurately estimated by the existing evaluation methods for some defect distribution cases, especially for circumferentially aligned defects. In this study, a

Discussers (Hariri-Ardebili and Sattar) address the paper “Seismic assessment of deep water bridges in reservoir considering hydrodynamic effects using endurance time analysis” written by the coauthors of this response. They present the fundamental assumptions on the generation of Endurance Time Excitation Functions (ETEFs) and the derivation of fragility functions by Endurance Time Analysis (ETA)

The airwake behaviour around a ship provides useful information for the safe operation of helicopters on naval ships as well as in helicopter pilot training. This study investigates the impact of ship motions on the airwake behind the superstructure of a naval ship using Detached Eddy Simulation. A full-scale simplified frigate geometry is analysed stationary and in head waves at three different wavelengths

In the present paper, hydrodynamic behavior and bottom wetted surfaces of two-stepped planing hull are investigated by conducting towing tank tests. To this accomplishment, hydrodynamic resistance, reattachment length, trim angle, and bottom wetted surfaces are determined under different geometric variables of the two transverse steps and planing hull speeds. Qualitative investigation is also conducted

This paper proposes a novel neural finite-time formation control algorithm for multiple underactuated surface vessels with actuator faults. In the algorithm, the leader-follower formation problem is formulated as a two-stage tracking problem. First, to address the leader-follower configuration without the information of leader velocity, the virtual vessel is designed to track the reference trajectory

Energy consumption estimation and management of the maritime Unmanned Surface Vehicles (USV) is an important issue to deal with energy minimization techniques such as path planning, tasks scheduling, etc. In this paper, we introduce the energy consumption parameter in USV simulation through three contributions: 1) An analytic USV's energy consumption model is developed based on the three-degrees-of-freedom

The parametric design of a resonant point absorber, equipped with a fully submerged toroidal shape and connected to a permanent magnet linear generator lying on the seabed, is performed to investigate the effectiveness of the new WEC device in terms of power production and cost of energy. After developing a non-linear time-domain model for the heave, surge and pitch motions of the floating buoy and

A design method for pre-swirl stators energy saving devices, using a combined BEM-RANSE approach, is proposed. RANSE calculations, using actuator disks, are employed to provide the required thrust and the effective wake to an unsteady Boundary Element Method through which the rate of revolution of the propeller and its averaged performance in self-propulsion are evaluated. An automatic variation of

Prediction of structural response during water entry is of great significance for the design of naval architecture and aircraft. In order to study fluid-structural interaction (FSI) of flexible wedge during water entry, coupling algorithms based on boundary element method (BEM)/Wagner theory and modal superposition method (MSM) are utilized. The first solution is a numerical method by coupling BEM

It is well known that discrete advection schemes can induce spurious numerical mixing in numerical models. In the present study, an offline method is applied to several idealized lock-exchange simulations and a realistic model simulation of BYECS (Bohai Sea, Yellow Sea, and East China Sea) to estimate the magnitude of numerical mixing. Numerical mixing is defined as the tracer variance dissipation

An evaluation of the stabilizer fin's influence on the flow fields of a waterjet-propelled ship was studied by the Reynolds-Averaged Navier-Stokes (RANS) method. Model- and full-scale simulations of the unsteady multiphase flow were carried out both in the bare hull and the self-propulsion conditions. The reliability of grid arrangement and numerical methods was confirmed by the uncertainty analysis

Steady flow around a square cylinder placed near a plane wall boundary is investigated experimentally in the present work covering the range of Reynolds number of Re = 7.34 × 104–4.12 × 105, gap ratios of G/D = 0–3 with two different freestream turbulent intensity Iu = 1% and 9%. The influence of Reynolds number, gap ratios and turbulent intensity on the hydrodynamic characteristics have been studied

Submarine pipelines, as an important tool for oil and gas transportation, have been distributed in offshore oil and gas fields worldwide. Under extreme waves, a large number of submarine pipelines have been damaged in the past decades. In order to investigate the effect of extreme marine environments on the pipelines, the joint effect of solitary waves and background currents on the pipelines is numerically

To avoid collisions between guide ship and approach ship during the underway replenishment process, it is important to maintain a certain distance between them. Based on trajectory tracking requirements, a control strategy suitable for engineering applications is proposed for an approach ship without velocity measurements. First, considering the effects of wind, waves, currents, hydrodynamic interactions

In this paper, the influence of the damping matrix and mud discharge on the recoil response of deepwater drilling riser after emergency disconnection is studied based on our published study. Mathematically, the deepwater drilling riser is discretized into a mass-spring-damping system with three degrees of freedom (DOF). The governing equation is solved by the principal coordinates analysis method (Method

An articulated intervention autonomous underwater vehicle (AIAUV) is a slender, multi-articulated underwater robot. Accurate trajectory tracking is essential for AIAUV operations. Furthermore, due to hydrodynamic and hydrostatic parameter uncertainties, uncertain thruster characteristics, unknown disturbances, and unmodelled dynamic effects, robustness is crucial. In this paper, we present a super-twisting

This study presents prediction of crack propagation in polycrystalline materials under cyclic loads using Peridynamic (PD) theory. The PD fatigue model utilizes the strain-load cycle (ε-N) data and introduces the “remaining life” of each bond calculated from its cyclic strain, which changes over time. The model also captures the traditional Paris law, which is widely used for computing the fatigue

This discussion is based on the paper by Pang et al. (2020) (hereafter identified as “the original authors” and “the original paper” or “the reference paper”). The original authors employed the endurance time analysis (ETA) and incremental dynamic analysis (IDA) techniques to investigate the probabilistic response of a deep water bridge in a reservoir. They derived multiple fragility curves using both

The load of cavitation collapse is one of the main input loads to the structure subjected to underwater explosion. The cavitation effects near different boundaries are of particular importance in understanding the load mechanisms and designing the protective structures. In present study, a numerical model that couples a Runge Kutta Discontinuous Galerkin method, a finite element method and an isentropic

Thrust, efficiency, induced pressure on hull surface and negative pressure distribution on blade surface of five conventional propellers and twenty-eight tandem propellers were studied comprehensively by numerical method to assess the ability of two different types of propellers in dealing with efficiency, cavitation, vibration and noise problems. The flow field was simulated by solving RANS equations

Structural damage identification is the core problem of structural health monitoring (SHM). The traditional damage detection methods are restricted in the practical applications, due to factors including the complete measured data and modal information required before and after damaged states. Strain damage indexes have attracted wide attention due to their high sensitivity to local damage. This paper

This paper aims at investigating the optimum positions and the required flexural rigidity (γrq) of a single and two longitudinal web stiffeners of unsymmetric plate girders subjected to pure bending by using gradient-based optimization algorithms. The optimization procedure is performed into two steps: The first step is to maximize the bend-buckling coefficient kb generated from eigenvalue buckling

A two-dimensional finite element numerical model was developed to predict local scour around a vibration submarine pipeline in steady current. The numerical model was based on incompressible two-dimensional Navier-Stokes equations with a Shear-Stress Transport (SST) k-ω turbulence model closure. The transportations of suspended load and the bed load were taken into consideration in the present numerical

At present, although there are a large number of studies on the hydroelastic analysis of ship propellers, almost all of them neglect the shaft, thus ignoring the influence of the structural coupling effect between the propeller and the shaft. Therefore, considering this coupling effect, a new hydrodynamic analysis model of propellers is established by using the boundary element method (BEM) coupled

Explicit wave models and expensive sensor equipment capable of predicting and measuring wave parameters often carry a prohibitive computational and financial expense. To counter this, this paper proposes an alternative method for nowcasting coastal zone significant wave heights through the joint use of meteorological and structural data in the training of supervised machine learning models. In testing

Most of the references are automatic mesh generation, but the accuracy of armored umbilical cable (AUC) analysis is not high enough. There is no detailed introduction about high-quality mesh generation method. Therefore, a high quality mesh method (hexahedral mesh generation method) for AUC for deep sea equipment is proposed in this paper. Hexahedral mesh generation method is often used in the analysis

In this paper, the stress concentration factors (SCFs) in tubular T/Y-connections strengthened with fiber reinforced polymer (FRP) under OPB are investigated. For this aim, 263 FE models of T/Y-joints with FRP were generated and analyzed. In the FE models, the contact between the FRP sheets and the members was modeled. By using the generated FE models, the effect of the FRP layers, the brace inclination

wave-driven robot is a flexible multi-body dynamic system driven by ocean waves. Self-propelled performance is an important index of wave-driven robot, which includes propulsion performance, resistance performance and rapidity of wave-driven robot, as well as its ability to capture and utilize ocean wave energy. However, the wave-driven robot belongs to flexible multi-body structure, whose dynamic

This paper investigates the dynamical analysis and control synthesis for fractional-order pitch-roll system of marine vessels under regular waves. Suppression of the effects of roll and pitch motions is critical in improving maneuverability and stability of marine vessels with ensuring the safety of cargo and comfort to sailors. The pitch-roll mode shows complex behaviours such as period-2 motion,

The understanding of the internal gaseous flow of artificially ventilated supercavities is developed using a locally homogenous, multiphase computational fluid dynamics model that is benchmarked using experimental data. The solutions indicate that gas leakage from a ventilated supercavity originates from the gaseous shear layers forming at the gas-water interface. Not only do these observations corroborate

A mathematical model is developed based on the application of permeable and impermeable breakwaters utilizing the mild slope equation (MSE) to analyze the wave amplification in an arbitrary shaped harbor with variable bathymetry. Finite element method (FEM) coupled with analytical approximation is described as Hybrid FEM, which is used to solve the MSE and Helmholtz equation in bounded and unbounded

A series of centrifuge shaking table tests were performed on a new type of foundation, the composite caisson-piles foundation (CCPF) which is recently suggested for the cross-sea bridge or offshore engineering, to investigate its seismic response. The CCPF model with 2 × 2 and 3 × 3 pile groups embedded in homogeneous clayey silt or layered soil consisting of dry sand underlain by clayey silt were

Course keeping control of ships deals with the automation of their trajectories for which a better rudder action is required to control the ship heading to continuously remain at the desired reference despite of environmental disturbances like sea winds and sea waves. For this purpose, this paper proposes Robust Integral Backstepping, Synergetic, and Terminal Synergetic controllers for good course

The present study investigates experimentally and numerically the impact of composite materials on hydro-elastic performances of a hydrofoil experiencing Fluid–Structure Interactions, and focus on the bend–twist coupling phenomenon. Four flexible hydrofoils piercing the free surface, with identical geometry of extruded plan-form, a constant NACA0015 section, are tested in a cantilevered configuration

An active multi-strut assembly is used to attenuate vibration transmission from the shaft to the hull of underwater vehicles induced by the propeller forces. The active assembly with embedded actuators is inserted between the stern bearing and the hull. First, the dynamic model of the shaft-hull system is developed using the Timoshenko beam theory and the FRF (Frequency Response Function)-based synthesis

A real-time two-way coupled atmosphere-wave model in the South China Sea (SCS) has been established based on the atmosphere model WRF and the wave model SWAN in this study. We implement a nested computational grid along the SCS in the SWAN model and utilize the WRF model to provide high-resolution mesoscale wind field and pressure field over the SCS under the influence of typhoons. The numerical simulation

For the new sandglass-type floating body with special shape, this paper mainly analyzes the characteristic of the heave damping and its corresponding components by computational fluid dynamics (CFD) method. Firstly, the convergence and accuracy of the CFD method to simulate the heave motion of sandglass-type floating body were validated along with the experimental data. Secondly, the numerical model

Bubble has significant applications in ocean engineering. Aiming at the difficulty of conducting the underwater explosion bubble experiment with large charge in deep water, this paper adopts a new way to deal with this problem. On the basis of similarity theory, it is found that by considering the scaling relationship of gravitational acceleration, the explosion bubble with small charge in shallow

Monopile towers used for offshore wind turbines are sensitive to Vortex-Induced Vibration (VIV). Here, their structural response to VIV was experimentally investigated with models of a partially and a fully immerged offshore monopile. The partially and fully immersed model cylinders had aspect ratios of 18.75 and 28.13, respectively. They were subject to reduced velocities of up to 9.78 and 5.45, respectively

The present study introduces a framework for predicting nearshore waves using two machine learning techniques of Group Method of Data Handling (GMDH) and Artificial Neural Network (ANN), trained with three global wave datasets of Japan Meteorological Agency (JMA), National Oceanic and Atmospheric Administration (NOAA), and European Centre for Medium-Range Weather Forecasts (ECMWF). Prior to our ultimate

This article proposes a new formalism for the dynamic modeling of a cable towing system, in which both the tugboat and the towed vessel are subject to forces from waves on the sea surface. The continuous flexibility of the cable is approximated by a discrete equivalent, formed by rigid links connected by fictitious elastic joints that allow elevation movements, since the dynamics are restricted to

The increasing demand for efficient, safe, and economic operation of ships has drawn attention to practical maneuvering behaviors for developing autonomous ships. Actual sailing conditions are reproduced to determine the relationship between environmental factors and ship steering records in rough seas. First, we generate realistic ocean environmental fields and analyze actual sea data. Then, we derive

Ships in ocean waves are suffered from cyclic wave loads which can cause fatigue damage to ship structures. Classification societies require owners to carry out fatigue assessment for ship structure for its potential great loss caused by fatigue failure. Currently there are many fatigue assessment methods including simplified method, deterministic method, spectral-based method and time domain method

We consider the estimation of return values in the presence of uncertain extreme value model parameters, using maximum likelihood and other estimation schemes. Estimators for return value, which yield identical values when parameter uncertainty is ignored, give different values when uncertainty is taken into account. Given uncertain shape ξ and scale parameters of a generalised Pareto (GP) distribution