The forces and moments on a UUV hull undergoing unsteady sway motions are analyzed using both traditional methods which integrate the pressure and shear stress at the wall, and hydrodynamic impulse based methods which analyze the vortical structure of the flow around the body. Computational fluid dynamics simulations have been conducted of a body with a slenderness ratio of 8.5, at a Reynolds number

In this paper, a turning circle based trajectory planning method (TCBTPM) is proposed to conduct trajectory planning of an underactuated autonomous underwater vehicle (AUV) for mobile docking mission. Firstly, the six degrees of freedom kinematics and dynamics model of underactuated AUV is acquired. Following this, the simulation of horizontal turning circle trial is studied and the overview of mobile

This paper presents a comparative study of wave-induced motion responses and the added resistance of a ship. Four representative types of ships are adopted as test models: LNG carrier, tanker, containership, and bulk carrier. Two experimental techniques—captive and free-running model tests—are conducted under regular head and oblique wave conditions to create benchmark data. Several numerical computation

Experimental study on the local scour around tandem square porous piles in steady current has been carried out in the live-bed flow condition. The influence of the porosity (P) of both front and rear piles in the tandem configuration (P = 0–38.5 %) and the gap ratios (G/D = 2–12) are quantified based on the measurement of the development of the local scour, time scale, three-dimensional scour profiles

Recent progresses in the target tracking technology have changed current unmanned systems into a realistic substitute to the conventional tracking systems. In this paper, existing algorithms on target tracking for both aerial and underwater application scenario are classified based on the active and passive modes of target tracking. These algorithms are analysed and compared in the form of mode, tracking

In the multi-objective optimization discipline (MOD), simultaneous optimization with four or more objectives is referred to as many-objective optimization. Compared with the two-objective and three-objective optimization, many-objective optimization brings a series of new challenges, such as the deterioration of the global search ability of an optimization algorithm, the difficulty of the visualization

In this present work, an in-house solver MPSDEM-SJTU is developed based on the improved Moving Particle Semi-implicit (MPS) method and Discrete Element Method (DEM). The MPS method is used to simulate the movement of the fluid while a more precise bond model, which includes the rolling contact model, is employed to analyse the dynamic responses of structures. Based on the boundary condition of MPS

The single barge floatover method faces great challenges when it comes to the gigantic topsides and the substructures lack of sufficient slots. The twin-barge floatover system with large capacities and great flexibilities for various topsides and substructures would be a promising alternative for fixed and floating platforms. This study experimentally investigates the dynamic responses of the floatover

The wave-body interaction of resonant oscillating wave energy converters (WECs) is complex and nonlinear. Rapid development of WECs needs a reliable simulation tool for analysis and design procedure with the ability to capture the instantaneous nonlinear behavior. This paper presents a methodology to study the behavior of a flap-type WEC utilizing hybrid physical and numerical simulation. Dynamic characteristics

The net position and the spreading performance are crucial for hydrodynamic performances of Antarctic krill trawl, which determine its fishing efficiency. In this paper, the hydrodynamic performance of an Antarctic krill trawl system (including trawler, cable, otter board and trawl) was studied by means of numerical simulation combined with full-scale measurement at sea. The numerical model was established

This paper focuses on recent innovations in the methods used for external remote subsea pipeline inspection. An unmanned method is revealed, in which an Autonomous Underwater Vehicle (AUV), paired with an Unmanned Surface Vessel (USV) was utilised to complete inspections. Results are presented from a recent project, in which existing hardware and software were integrated and combined with automated

Marine Autonomous Systems (MAS) operating at sea beyond visual line of sight need to be self-reliant, as any malfunction could lead to loss or pose a risk to other sea users. In the absence of fully automated on-board control and fault detection tools, MAS are piloted and monitored by experts, resulting in high operational costs and limiting the scale of observational fleets that can be deployed simultaneously

The design and engineering of ships and platforms that operate in the ocean environment requires understanding of a nonlinear dynamical system that responds according to complex interaction with a wide range of sea and wind conditions. Time domain observation of nonlinear marine dynamics with either experiments or high-fidelity numerical simulation tools is costly due to the random nature of the ocean

The equilibrium stage of the scour caused by the wave effect around the marine piles was investigated experimentally for both slender and large piles. Unlike the experimental studies in the literature, some of the experiments were carried out under clear water scour condition, since the coarse bed material was used in the present study. While the effective parameter on scour for slender piles is only

Tuning of vessel models in real-time based on vessel measurements and weather information is of great interest in order to increase the safety and efficiency of marine operations. Vessel motion signals usually contain high-frequency noise. For an unbiased model tuning algorithm, it is essential to filter the noisy signals in order to identify the power of the wave-induced first-order vessel response

Experimental tests on corroded tubular TT-joints with and without Carbon fiber reinforced polymer (CFRP) reinforcement were conducted. The failure process, load-displacement curves, and observed failure modes of the tested specimens under axial brace compression were obtained and discussed. Experimental results indicate that the bearing capacity and stiffness of the corroded tubular TT-joints strengthened

This research provides a thorough investigation on aspects of the structural integrity of composite blades for a range of operating conditions using fluid-structure interaction analysis based on Computational Fluid dynamics (CFD) and Finite Element Method (FEM). Both shell elements and layered solid elements were used in the finite element model. The strength was assessed against Tsai-Wu, Hashin, and

In this paper, vortex-induced vibrations (VIV) of deepwater risers including the VIV-induced tension fluctuations were simulated using a time domain VIV model. Data from a large-scale riser experiment was applied for correlation studies. As a first step, a new combination of in-line and cross-flow synchronization models with empirical parameters was proposed for better in-line response prediction.

The raft-type wave energy converter (WEC), consisting of several hinged rafts and hydraulic power take-off (PTO) systems, captures wave power in a line absorber manner, whose scattered and radiated wave pattern is different from that of a point absorber. This paper focuses on the latching control of a raft-type WEC consisting of two rafts and a hydraulic PTO system. To reduce the complexity of finding

An important part of establishing a prediction model for maritime search and rescue and oil spill drift is to quantify the uncertainty in particle motion simulation. A regional Sub-grid velocity model based on drifting buoy data is proposed to simulate the unsolved velocity which is composed of turbulence and advection simulation errors (TASE) in the ocean model. Contrary to most of the traditional

Splitter plates have been recognized as useful passive devices to reduce drag, mitigate flow-induced vibration, and enhance heat transfer efficiency of a circular cylinder. However, undesired torsional flow-induced vibrations due to splitter plate attachment require further investigation. This paper numerically studies the flow-induced torsional vibrations of an elastically mounted circular cylinder

Reinforced thermoplastic pipes (RTP) are widely used in the offshore oil and gas production industry for their excellent flexibility, corrosion resistance and internal pressure resistance. RTPs inevitably experience extreme environmental loads including internal pressure and tensile load in the procedures of installation and operation, which influence the structural integrity and safety. Therefore

The stability of floating platforms is closely related to the sea states, fairlead positions, and center of mass (CM) of the platform. To investigate the influences of these interference factors, numerical modeling of a spar platform with four mooring cables is performed using an in-house MATLAB code. To analyze the influences of the nonlinear hydrodynamic forces of cables, cable dynamics are considered

A composite buffer has been designed to reduce the impact load of high-speed water entry projectile. Rigid Polyurethane (PU) foams of different densities have been used to make the damper of the buffer. A series of compression tests for PU foam specimens are implemented to obtain the stress-strain curves under different loading speeds. The constitutive model used in the simulation for PU foam has been

Different spacing cases (L/B = 2–6) are numerically examined to identify the spacing effect on the two-degree-of-freedom vortex-induced vibration (VIV) of two tandem square cylinders at Re = 150. According to the various vibration responses, force characteristics and flow patterns, spacing cases can be divided into three different situations. At a small spacing (L/B = 2, 2.5), the upstream cylinder

In this study, an Association Rule Bayesian Networks (ARBN) method is established to investigate the impacts of external factors (i.e. environmental factors and ship factors) on human errors. The Bayesian networks have been structured by mining association rules from historical collision accident records. In addition, unlike other related studies that have introduced subjective data (i.e. expert knowledge)

In this paper, we propose an automatic route design method based on simple recurrent unit (SRU) and automatic identification system (AIS) data. Laplacian eigen maps and Gaussian kernel functions are used to compress the AIS data and extract the turning points of all ships. Fuzzy adaptive density-based spatial clustering of applications with noise (FA-DBSCAN) technique is used to cluster the turning

The number of construction offshore wind turbines (OWTs) is gradually increasing with high clean energy demand and low technology costs. During their service life, a large number of ships will inevitably collide with OWTs, which results in collapse load acting on the OWT foundation. This paper proposes a novel fender for the OWT exposed to extreme collision using the fractal structure, as the first

This paper reported on the free-surface wave behavior in a rectangular open-channel, induced by sluice-gate maneuvers. The numerical solver was based on the (2/4)-dissipative scheme being used for the numerical discretization of the one-dimensional Extended St-Venant model embedding the Boussinesq add-on term. The numerical solver was firstly validated against experimental data and alternative numerical

This paper proposes a control architecture of autonomous underwater vehicle (AUV) for coverage mission in irregular region (CMIR) with an improved task planner. The CMIR control architecture is structured in four layers: perception layer, reactive layer, decision making layer and execution layer. To improve the task planner in decision making layer of control architecture, we adopted convex partitioning

In tramp shipping, a preliminary route is required for voyage planning at the pre-fixture stage (before a chartering contract is agreed). Such routes are conventionally designated by using pilot charts or software considering long-term statistical weather. However, it has been experienced by tramp operators that such route solutions often poorly estimated sailing distances for long journeys and thereby

Arctic platforms have sloped surfaces near waterline to reduce the ice impact on the structure by ice failure in bending. In this paper, authors developed a computer program which can solve the dynamic interactions between moored floating platforms and drifting level ice in time domain. To model the fracture of level ice, the discrete element method with the parallel bonding model is employed. The

This study investigated the dynamic behaviour of a spar-type offshore floating wind turbine (OFWT) analysed under various wave loads by conducting an experiment campaign. Both the characteristic of the spar platform itself and the spar with realistic moorings have been investigated. A particular focus of the study was the motions of the mooring lines, which were measured at a series of discrete points

Ice-breaking processes of an icebreaker are complex and many numerical models are proposed to predict the ice-breaking performance. Under the same polar conditions, different prediction models may derive different ice-breaking performances. Hence, it is necessary to analyze the influences of different prediction models and their corresponding input factors on the ice-breaking performance. However,

This paper applies the method of statistical quadratization to investigate the first and second-order responses of a floating offshore wind turbine platform due to forces from a catenary mooring system, and wave–current coupled interaction. The hydrodynamics are based on the generalized Morison’s equation, while the catenary mooring system is based on a quasi-static approach. The method of statistical

As in many other sectors, accidents that lead to deaths, injuries, environmental pollution, or material damage occur in the maritime sector. Maritime transportation operations, which constitute the backbone of the maritime industry, involve serious risks by nature. Although many safety measures are implemented to eliminate these risks or reduce them to acceptable levels, the number of accidents that

Underwater gliders (UGs) have attracted great attention for their low cost, long range, high endurance, and broad applications in oceanography. However, few studies have been conducted to research motion performances of UGs. In this study, to understand the effects of ocean currents on the motion performances of UGs, a dynamic model of UGs considering ocean currents was established. Based on the dynamic

When jack-up platforms are deployed for long-term services such as those functioning as production units, the consolidation settlement of spudcan footings is an issue of particular concern. Unpredicted and thus unprepared settlement may do harm to the serviceability and safety of jack-up rigs. Through centrifuge experiment and large deformation finite element calculation, this paper first illustrates

The increasingly diverse mission requirements result in challenges to the rapid design and functional diversification of underwater vehicles (UVs). The genealogical design of UVs shape is one of the key steps to deal with these challenges. In the present work, based on the hydrodynamic characteristics with different shape features of UVs, the hull shape genealogy including the spherical/spheroidal

Risk modeling of marine accidents involves many technical and environmental safety factors which cannot be predicted in advance. The aim of this paper is to determine a safety criterion via risk assessment of marine accidents for a certain sea area. The risk is assessed with a combination of two approaches: one is based on a Markov model and MCMC simulation, and the other on three risk factors. On

In this paper, an improved meshless artificial viscosity (AV) method is proposed and combined with the local radial point interpolation method (LRPIM) and the MacCormack method to establish a newly-developed meshless numerical model, which can efficiently and accurately solve wet-dry moving interfaces problems of shallow water flow. As an important model describing shallow water flow, the two-dimensional

A modified ACER method (MACER) is proposed to study the short-term extreme mooring tension in experimental and numerical results, and an adaptive Markov Chain Monte Carlo (MCMC) algorithm based on Bayesian inference is proposed to fit the parameters of the MACER function. To study the feasibility of the MACER and ACER methods, two typical cases are considered. One case is the taut mooring line of a

By using the latest generation atmospheric reanalysis dataset (ERA5) from the European Centre for Medium-Range Weather Forecast, a numerical wave simulation system based on SWAN model for the western shelf of the Yellow Sea (YS) is established. A thorough calibration is conducted in order to satisfy both modeling accuracy and computational efficiency. Technique for Order Preference by Similarity to

Wave-induced response of a closed floating fish cage consisting of a vertical circular cylinder with an external toroidal floater is studied theoretically and experimentally. A main purpose was to investigate how the internal sloshing would influence the global response of the cage, the interior wave elevation and also the mean drift loads. An ocean basin laboratory was used in order to minimize tank

Deepwater anchors, typically the suction embedded plate anchor (SEPLA) and the OMNI-Max anchor, would encounter the phenomenon of embedment loss after initial penetration, which remarkably reduces the pullout capacity and affects the subsequent behavior of the anchor. Therefore, the maximum embedment loss (MEL) becomes a key index for design and engineering practice. Based on the mechanical mechanism

The air wake generated behind a frigate superstructure is a very complex and unsteady three-dimensional flow characterized by highly turbulent flow structures with great velocity gradients that result in flow separation over the flight deck where helicopter operations take a significant role. Naturally, this turbulent flow should be removed or, at least, reduced as maximum as possible to avoid accidents

With high flexibility and low damping, offshore wind turbines (OWTs) are prone to external vibrations such as wind, wave and earthquake, either attacked individually or as combined loading cases. This study proposes a semi-active variable-stiffness tuned mass damper (VSTMD) with magnetorheological elastomer (MRE) materials to mitigate undesired dynamic responses of OWT. A jacket supported OWT with

The pre-swirl stator (PSS), as a type of energy-saving device, has garnered increasing attention due to efforts aimed at global energy-saving and emission reduction. Owing to the influence of the stern profile, the wake field at the stern is complex, and the installation of such energy-saving appendages further increases its complexity. To explore the flow mechanism of a ship's wake field and the working

Optimizing the configuration of risers is a challenging task. It requires numerous nonlinear dynamic finite element analyses to evaluate each candidate configuration regarding its structural behavior. In such an optimization procedure, the computational time is commonly dominated by the structural analysis step. Therefore, reducing the number of simulations required to find feasible candidates is paramount

The dynamic response of a two-rotor wind turbine mounted on a spar-type floating platform is studied. The response is compared against the baseline OC3 single-rotor design. Structural design shows how the two-rotor design may lead to a mass saving of about 26% with respect to an equivalent single-rotor configuration. Simulations predict significant platform yaw response of the two-rotor floating wind

The effects of combined external pressure and cyclic bending on the pipe buckling mechanism are investigated by experiments and finite element analysis. Ten experiments are conducted and it is found that the loading paths of external pressure and cyclic bending have a great influence on the buckling pressure of thick-walled pipes. The loading path of pressure followed by cyclic bending (p→ck) is more

Model towing experiments of a bottom trawl net with hyper-lift trawl door were conducted to investigate the effect of the bottom sediment (concrete, sand, gravel, and rock) on the warp tension of the overall trawl system. The towing speed was from 50 cm/s to 70 cm/s and the ratio of warp length relative to the water depth was within the range of 4–6. Through the signal analysis of time-series warp

Accurate wave forecasts are essential for the safe and efficient maritime operations and, in particular, the maintenance of offshore wind farms. Here, machine learning and remote monitoring from satellites are integrated to provide uniquely detailed predictions of significant wave height (SWH). C-Band Synthetic Aperture Radar images from European Space Agency Sentinel-1 satellites were combined with

The ocean waves in the North Atlantic Ocean are internationally recognized to represent a wave climate suitable for the design of merchant ships. However, the accumulated knowledge from the past indicates that the encountered sea states are less severe than the Standard Wave Data recommended by the International Association of Classification Society. In this study, we propose a statistical model representing

The realistic three-phase water entry of a free-fall cylinder is investigated in this paper using an efficient lattice Boltzmann method (LBM) with automatic interface capturing capability implemented in an in-house FORTRAN 90 code. The numerical method takes advantage of automatic interface capturing, using a real equation of state (EOS), and considering the surface tension and gas phase compared to

To investigate the bubble sweep-down phenomenon of a scientific research ship from the perspective of its flow mechanism, the flow-field characteristics of the bow were measured in a towing-tank environment. First, the silk-thread method was used to visualise the streamline characteristics of the bow. Next, the flow field of the bow was measured using multiple two-section 2-dimensional computed tomography

Wave Energy Converter (WEC) development needs a thorough dynamic characterization of the device and tuning the design properties to harness the maximum power. This paper addresses this need by using experimentally validated numerical simulation for an array of flap-type WEC mounted on a surface of a breakwater as a coherent approach in sustainable coastal protection. The developed numerical model is

This study experimentally investigates the development and decay of bound energy fractions due to positive and negative interactions (b2p and b2n, respectively) applying bispectral analysis. It was revealed that the Ursell number is the most successful parameter to estimate the variation patterns of b2p and b2n. The experimental waves included 27 waves with three offshore wave heights, three periods

Accurate prediction of loads on containers and their pertinent securing systems is important for efficient handling and transportation of the containers as well as for optimization of the applied securing systems. Container stacks react nonlinearly to the excitation forces. This paper presents a nonlinear finite element method developed to predict the structural response of containers and their associated

The prediction of extreme ship responses continues to be an important and longstanding topic in ship hydrodynamics with a significant focus on developing probabilistic methods based on simple descriptions of the hydrodynamics that mainly provide qualitative observations. While simple nonlinear hydrodynamic formulations provide insight into extreme events, their underlying assumptions can prevent accurate