Flow around a pile-cap of bridge is three-dimensional and complicated. When the influence of pile group and bridge pier is ignored, the current forces on the pile-cap are significantly affected by aspect ratio AR, free surface and free end. Experiments were conducted to investigate the drag force, transverse force, vertical force and flow field of a square cylinder with AR ranging from 0.033 to 1 and

Based on the basic principles of thermodynamics and fluid mechanics, the temperature and pressure model of natural gas hydrate hydraulic lifting pipeline, the hydrate decomposition mass transfer model and the mathematical model of pipeline multiphase flow are established. The relationship between the back pressure of the pipeline outlet, the decomposition surface and the depth of the seawater was analyzed

The study deals with the scattering of obliquely incident gravity waves by a horizontal floating flexible porous plate in the water of finite depth having a variable bottom bed. The problem when a vertical rigid wall is placed in the downstream of the plate is also considered. The problem is analyzed under the assumptions of small amplitude water wave theory and structural responses. The undulated

Hull forms of high-performance sailing dinghies are very interesting for yacht designers. After a long period in which the attention has been focused on one-design boats, in recent years a few exciting restricted classes such as International Moth, International 14′, 18’ Skiff and Class A catamaran become recognized in several countries and led to interesting advances in high-performance yacht design

In this work, the effects of low-cycle fatigue loading and stiffener height on crack propagation regularities of stiffened plates are investigated. The tests are conducted on 14 cracked stiffened plate specimens using an MTS322 fatigue tester. Videos showing the crack propagation are recorded using two electron microscopes, and the data form which are used to plot the a-N curves. The accumulative mean

Wave loading of offshore structures such as oil rigs and wind turbines are governing for the design of these structures. Since the environmental conditions may change during the lifetime, it is of great interest to evaluate the loads which the structure is exposed to at its current state. Since direct measurements of the loads are often not feasible, operators must rely on indirect methods like vibrations

Fluid structure interaction (FSI) problems are often encountered in ocean science and technology. In this present, an implicit immersed boundary (IB) method combined with Lattice Boltzmann Method (LBM) and finite element method (FEM) is presented for the strong-coupled simulations of fluid structure interaction. Velocity field is solved rapidly by lattice Boltzmann-BGK equations without external force

A numerical investigation was conducted to examine the effect of injection velocity of a pair of air jets positioned at the two shoulders of a circular cylinder on the vortex shedding at a low Reynolds number Re = 100. Not only the momentum but also the air flow are injected into the cylinder boundary layer by the air jets, yielding the gas-liquid two-phase fluid in the wake. The ejected air pushes

In this study, buckling analysis of cracked plates is performed by using peridynamics. A peridynamic Mindlin plate formulation is used and the numerical implementation is done using commercial finite element software, ANSYS. Critical buckling load is obtained by utilizing ANSYS Eigenvalue Buckling Analysis feature. Peridynamic results are compared against numerical and experimental results and a good

Axial dynamics of risers is one of challenges in offshore oil and gas engineering. Axial hydrodynamic loads on a riser system are often ignored in traditional analysis methods. To accurately analyze the axial dynamic response of risers, an improved axial dynamic analysis method of risers is proposed based on finite element method and data-driven models. Finite element method is introduced to analyze

Vortex-induced vibration (VIV) responses of the cylinders with the bionic surfaces inspired by giant cactus are numerically studied, and the range of Reynolds number is 8.0 × 103 < Re < 5.6 × 104. The dynamic response of the structure adopts Newmark-beta method. The effects of the height ratios (Ks/D, Ks is the height of the bionic structure) on VIV suppression are discussed in detail, and five different

Flow through and around fishing net cages is an important issue in aquaculture. A three-dimensional multi-relaxation time (MRT) lattice Boltzmann model was used to simulate the flow field around a plane net in a constant current. The model was validated with experimental data. The results show that this numerical model is applicable to and reliable for the investigation of the flow field around a fishing

A ventilated cavity model ship is investigated in a calm water towing tank under a moderate Froude number range. The gas ventilation rate required for cavity from early formation to complete coverage is explored, as well as the cavity morphology, closure modes, shedding features, and cavity growth characteristics. Several flow patterns of the cavity are classified, i.e., discrete foamy flow and initial

Bio-inspired oscillatory foil propulsion has the ability to traverse various propulsive modes by dynamically changing the foil’s heave and pitch kinematics. This research characterizes the propulsion properties and wake dynamics of a symmetric oscillating foil, specifically targeting the high Reynolds number operation of small to medium surface vessels whose propulsive specifications have a broad range

This paper presents numerical investigations of the flow-induced vibration of an elastically mounted elliptical cylinder with different aspect ratios. The cylinder is constrained to vibrate only in the cross-flow direction, with the major axis being perpendicular to the uniform flow. The Reynolds number, based on the free stream velocity and the major axis width, is fixed as 100. The aspect ratio (AR)

Based on the bionics study of trailing-edge serrations of certain birds, a vortex-induced vibration (VIV) suppression device for marine risers was developed, with double bird-wing-shaped streamers. A water flow simulation experiment was performed on a bare cylinder model as well as cylinder models with different trailing edge profiles and varying streamer lengths, and the model wake flow field was

The work studies the ship structural corrosion degradation allowance, analysing several sets of corrosion thickness measurements collected from operating tankers. The corrosion degradation process is modelled by a time-dependent exponential function with parameters adjusted to real corrosion thickness measurement data. Corrosion margins of redundant ship structures with severe consequences of failure

Balance measurements performed by testing sub-scaled ship models determine the global forces and moments acting on the ship, which allows knowing the power required for the ship's movement and provides insight to be applied in the design of the control systems used to steer the ship and to avoid instabilities while sailing. The ship superstructure may produce large separated regions and high air wake

The present paper reports an experimental investigation in order to understand the characteristic evolution of a chain-type floating system with increasing number of modules up to five. Semi-submersible modules are fabricated, connected by hinges and constrained by elastic mooring lines for experimental tests in a wave flume. The module responses of floating structures in various configurations are

The wall pressure caused by underwater explosion is always a key problem in the anti-explosion design of naval ships. Notably, the accurate wall pressure caused by underwater explosion bubble is one of the most difficult parts due to the significant nonlinear deformation of the bubble. In present study, the dynamics of an underwater explosion bubble near a rigid wall are captured by high-speed camera

In this article, Gaussian mixture models are used to estimate the probability density function of wave elevation in the context of the second-order random wave theory. Two approaches are used to construct the Gaussian mixture probability distribution. One is the moment estimate in which the unknown parameters are determined by matching the moments of Gaussian mixture model with those of the real wave

Sloshing of liquid in partially filled tanks under high excitation amplitude is always a complicated phenomenon for shallow water condition. This complication arises due to nonlinear behaviour of liquid free-surface motion when the excitation amplitude is sufficiently large. Due to nonlinearity, the sloshing resonant frequency also gets affected and so the performance of several devices developed based

In the present study, the effect of collar on temporal scour depth variation at the base of a collar-protected circular pier was investigated. Experimental results revealed that a collar performs efficiently by reducing the rate of temporal scour depth variation around the pier. The efficiency of a collar, for different diameters and elevations, has been studied through flume experiments under clear-water

The performance of a submerged cylindrical point absorbing wave energy converter was explored under the addition of different nonlinear stiffness (bistable) conditions. The limitations of previous studies were addressed by incorporating higher-fidelity modelling. Devices employing bistability in other energy harvesting applications, have improved the amount of power generated. For wave energy converters

An array of pressure sensors can be used to correct the drift in inertial navigation systems for underwater vehicles (UVs) in absence of other navigation support systems such as acoustic positioning, GPS and Doppler velocity measurements. To date, multiple pressure sensor arrays have been designed, proposed, and tested to prove the concept. However, it has not been researched the inclusion of non-linearities

Predictions of Significant wave height (Hs) of oceans is highly required in advance for coastal and ocean engineering applications. Therefore, this study aims to precisely predict the ocean wave height via developing a novel hybrid algorithm. Wavelet, Particle Swarm Optimization (PSO), and Extreme Learning Machine (ELM) methods were used and integrated to design the wavelet-PSO-ELM (WPSO-ELM) model

This paper investigates the low frequency (LF) surge motion of a semi-submersible platform in storm sea states without current, where the influence of viscous drag forces on the LF surge motions is focused. Four hydrodynamic models including one potential flow panel model and three panel and Morison's hybrid models were established. LF surge motion was calculated in time domain using AQWA. Five sea

In order to obtain a larger VIV response and harvest energy more efficiently in wider flow velocity ranges in long-distance transport pipelines, the effects of the elastic modulus of material, mass ratio and cross-sectional shapes (circular cylinder, squa-cir prism, cir-squa prism) of flow-around structure on the VIV performance are numerically investigated in this paper. URANS equations with k-ω SST

Fin stabilizers have been widely used to reduce the roll motion of ships at medium-high velocities. However, the anti-rolling efficiency of the traditional fin declines rapidly as the speed of the ship decreases. To enable more efficient use of fin stabilizers across the whole speed range, dynamics of fins at zero-low velocity were derived. Then, the proposed model was verified by experiment and the

To ensure the dimensional accuracy of fillet welded structures of a cantilever beam, triangle reinforcement plate stiffeners (TRPs) are employed to prevent welding distortion. However, this increases the weight of a structure. In this study, an efficient finite element (FE) computation was used to solve the afore mentioned engineering problem. The inherent deformations of typical welded joints in a

In ports and waterways, the impacts of external navigational factors may lead to serious incidents due to limited space for ship maneuvering. Using nautical traffic models, these incidents can be predicted in advance. In current studies of nautical traffic models, the impacts of wind and current on ship behavior are seldom considered when modeling the ship behavior in a port area. The numerical maneuvering

Wave-induced instantaneous liquefaction is crucial to evaluating the stability of offshore foundations. For the instantaneous liquefaction, most previous studies treated the seabed as an invariant poro-elastic medium and hence led to nonphysical tensile stress in the non-cohesive liquefied zone. In this study, a penalty-like dynamic permeability model is proposed, based on the experimental evidences

Response-conditioning wave techniques are a rational way to link wave excitation environments with return-period extreme loading responses. By retaining the wave excitation which leads to a design response, these techniques can also define extreme combined loading scenarios. For complex or novel hull forms, combined loading may be relevant for evaluating structural reliability or adequacy. But using

A coupling algorithm is developed to accelerate the boundary element method for both open water and unsteady calculations. It is realized in the way that the full wake alignment is conducted using the vortex lattice lifting line method with discrete wake sheet. Techniques to convert wake sheets of lifting line to those for boundary element method are described. Numerical simulations for open water

This article investigates two effects of seal friction of hydropneumatic Passive Heave Compensator (PHC) during offshore drilling for contact and non-contact operations. The first is the attenuation rate variation of the transmitted heave movement in function of the amplitude of the platform motion. The second is the Compensator-Induced Vibration (CIV), which induces longitudinal oscillations of frequencies

The nonlinear oscillations of the floating structures anchored by cables are studied in three dimensions. The floating structure is anchored by four symmetric mooring lines and the mooring lines are fixed on the seafloor at the other ends. The stiffness matrix of 3D cable element has been established and applied to analyze the dynamics of the 3D floating structures anchored by cables. The complex compatibility

A wave energy converter (WEC) needs an active control strategy to maximise efficiency in a wide range of operating conditions. Many control strategies require knowledge of the wave excitation force, a quantity which cannot be measured in operation. In this study, two methods based upon Kalman filters are tested with an experimental 1:25th scale multiple degree-of-freedom WEC. A stochastic and a periodic

This paper investigates large amplitude sloshing in a prismatic tank with or without a baffle by a Cartesian grid based three-dimensional (3D) multiphase flow model. In this model, an improved ghost cell method with a unified reconstruction scheme is developed to enforce boundary conditions on the slope walls of the tank. Arbitrary shape tanks and internal structures can be treated on the Cartesian

The ship manoeuvrability in actual seas with both wind and waves, especially in adverse weather conditions, for a full-scale tanker with different maximum available power of the engine is studied. It is directly evaluated based on the result of a free-running model test (FRMT) under a course-keeping manoeuvre in long-crested and short-crested irregular waves of Beaufort scale force (BF) 7–10. The FRMT

Scale models are normally designed as alternatives to true ship structures in ultimate strength experiments. In this paper, a series of true ship hull girders of a 10,000 TEU container ship under different scale combinations of geometric length and plate thickness are modeled and analyzed to investigate the scaling characteristics of hull girders’ ultimate strength and collapse behaviors, aiming at

A steady-state Actuator force model using the RANS equations is developed to calculate the power production and the flow through arrays of tidal or river Darrieus turbines. It uses detailed three dimensional force distributions depending on the position on the turbine, obtained beforehand by a set of blade-resolved URANS simulations of the turbine. New power coefficient and force coefficient laws depending

The conventional extrapolation of ship resistance from model tests to full scale presumes that the coefficient of wave-making resistance (Cw) depends on the Froude number only. This leads to the assumption that Cw of a ship is identical to Cw of its scaled model. However, this assumption is challenged in shallow water due to viscous effects, which are represented by the Reynolds number (Re). In this

The heave plate is widely used in the field of marine engineering because of its advantage of increasing damping and added mass. In this paper, the fractal theory is applied to the structure design of the heave plate and a fractal plate has been proposed. With the technology of dynamic mesh and user defined functions (UDF) in Fluent, numerical simulations on forced oscillation of different heave plates

With the increasing development and utilization of offshore oil and gas resources, seabed instability around pipelines subjected to combined ocean wave and current loadings and protection of the pipelines are becoming increasingly important. As a general practice, it is recommended to use trenching in shallow water region for the protection of submarine pipelines from the danger caused by storm waves

Large-diameter monopiles are the most commonly used foundation to support offshore wind turbines. Early designs usually adopted pile diameters (D) between 4 and 6 m, which is recently extended to 8 m and will target 10 m in the future. It is increasingly evident that the existing design method (i.e., API's p-y model) can significantly under-predict the lateral stiffness and capacity of large-diameter

Two or more structures arranged side by side with narrow gaps may be suffered from large-amplitude free-surface oscillations, which could cause green water on the deck and lead to dramatic increase of hydrodynamic loading acting on structures. Here, transient resonant motions of the free surface inside a narrow gap between two fixed boxes triggered by focused transient wave groups with various focused

To understand the influence of complex hydrodynamic loads on tidal turbines, laboratory testing is necessary as a first approach. Previous laboratory work undertaken gave an indication that the use of speed control strategies may disguise the associated loading range that a turbine may be subjected to when this is operated with a variable speed control strategy. However, the preceding work was undertaken

The power captured by a wave energy converter (WEC) can be greatly increased through the use of a well-conceived wave-by-wave control strategy. Optimal strategies including Model Predictive Control (MPC) rely on a dynamic model of the WEC and prediction of the wave excitation force several seconds into the future. Both the modelling and prediction processes are subject to errors. This study investigates

Nowadays, remotely operated vehicle (ROV) is an integral part of the marine industry. In this study, the hydrodynamic performance of a specific model of ROV is evaluated by numerical and experimental simulations in different Reynolds numbers ranging from 39291 to 157163 and various angles of attack from 0° to 45°. Moreover, two rectangular cubic models with fillet and sharp edges are modeled for comparative

The present study investigates the mechanism of the after-runner surge on the coast of the Gulf of Tonkin, Vietnam, due to Typhoon Kalmaegi 2014 landfalling at Quang Ninh province using a coupled model of surge, wave and tide forced by asymmetric and symmetric wind and pressure fields. It is found that the after-runner surge is mainly caused by tailwinds of the typhoon, generating the maximum surge

The coupled tide-surge and wave model was established for the coast of Taiwan and applied to simulate the storm surge during typhoon events. To prove the capability and availability of the coupled model, the model was calibrated and validated with measured water levels, atmospheric pressures, wind speeds, wave heights, and wave periods at different gauge stations under different historical typhoon

An increasing number of ships are being equipped with sensors and devices for monitoring of operational behavior, and the amount and access to operational data is gradually increasing. Due to various reasons described in this paper, the operational data may contain erroneous data points that are critical to assess prior to performing data analysis or building mathematical and statistical models. In

Flow past a circular cylinder fitted with a rear rigid wavy plate at a low Reynolds number of Re = 150 is first numerically studied in this work. The effects of the plate length and the surface undulation on the hydrodynamic forces and vortex shedding behavior of the circular cylinder are examined. The mean drag coefficient and the fluctuation of lift coefficient are reduced up to 27.5% and 54.9%,

In this work, numerical simulations of steady-state resonant wave system have been conducted by high-order spectral method (HOS) to study its evolution mechanism in deep water. Convergent high-order series solutions of steady-state resonant waves are first obtained by homotopy analysis method (HAM). Theoretical solutions together with disturbances of different orders of magnitude are then served as

A new finite element model of the variable-length underwater cable with geometrically nonlinear motion is presented in this paper.This model accounts for the effects of axial load, shear, bending, and torsion completely.First, a set of nonlinear, time-varying differential equations is derived from the theorem of linear and angular momentum, and its weak formulation is obtained by the principle of D’Alembert–Lagrange

Accurate prediction of the burst pressure of a pipeline is critical for pipeline design and safe operation. It is usually achieved by using analytical and empirical formulae derived from theoretical, numerical and experimental methods. This study was carried out to develop a new methodology to predict the burst pressure for API 5L X grade flawless pipelines. The newly proposed methodology has been

Existing physical model test data indicate that negative-deadrise planing surfaces may be capable of producing greater lift and lift-to-drag ratios than positive-deadrise planing surfaces. However, there is a lack of systematic experiments in which deadrise is varied with all other parameters are fixed. In this study, computational fluid dynamics software STAR-CCM+ is applied to simulate fixed-attitude

A full time-domain two-dimensional (2-D) numerical model was established for the coupled dynamic analysis of submerged floating tunnel (SFT) structures. For hydrodynamic loads, a second-order time-domain potential flow numerical model was developed and a higher-order boundary element method (HOBEM) was applied to discretize the body boundary and the free surface boundary. The elastic rod theory was

We assess the capability of fast wave models to deterministically predict nonlinear ocean surface waves from non-uniformly distributed data such as sampled from an optical ocean sensor. Linear and weakly nonlinear prediction algorithms are applied to long-crested irregular waves based on a set of laboratory experiments and corresponding numerical simulations. An array of wave gauges is used for data