Models of cylinders in the oscillatory flow can be found virtually everywhere in the marine industry, such as pump towers experiencing sloshing load in a LNG ship liquid tank. However, compared to the problem of a cylinder in the uniform flow, a cylinder in the oscillatory flow is less studied, let alone multiple cylinders. Therefore, we experimentally and numerically studied two identical circular cylinders oscillating in the still water with either a side-by-side or a tandem configuration for a wide range of Keulegan-Carpenter number and Stokes number β. The experiment result shows that the hydrodynamic performance of an oscillating cylinder pair in the still water is greatly altered due to the interference between the multiple structures with different configurations. In specific, compared to the single-cylinder case, the drag coefficient is greatly enhanced when two cylinders are placed side-by-side at a small gap ratio, while dual cylinders in a tandem configuration obtain a smaller drag coefficient and oscillating lift coefficient. In order to reveal the detailed flow physics that results in significant fluid forces alternations, the detailed flow visualization is provided by the numerical simulation: the small gap between two cylinders in a side-by-side configuration will result in a strong gap jet that enhances the energy dissipation and increase the drag, while due to the flow blocking effect for two cylinders in a tandem configuration, the drag coefficient decreases.

The dynamic response of a jacket-supported offshore wind turbine under coupled wind, wave, and current fields during Hurricane Sandy is the subject of this study. To illustrate the detailed procedure related to the response evaluation of a 5-MW offshore wind turbine with a jacket support structure, we consider a single site where the water depth is 50 m. Loads are computed using two simulation tools, FAST and Abaqus, with partial coupling. Aerodynamic loads on the turbine rotor are first evaluated using a wind turbine model in FAST with a fixed base; then, these rotor aerodynamic loads are applied as point loads at the top of a model of a tower that is supported by a jacket structure in Abaqus. Based on stochastic simulations, we discuss the applicability of the Abaqus jacket modeling and describe the characteristics and comparisons of the aerodynamic and hydrodynamic effects on loads on the jacket members. Details related to the structural model and soil-pile interaction model employed in the analyses are also discussed.

Instabilities of deep-water wave trains subject to initially small perturbations (which then grow exponentially) can lead to extreme waves in offshore regions. The present study focuses on the two-dimensional Benjamin–Feir (or modulational) instability and the three-dimensional crescent (or horseshoe) waves, also known as Class I and Class II instabilities, respectively. Numerical studies on Class I and Class II wave instabilities to date have been limited to models founded on potential flow theory, thus they could only properly investigate the process from initial growth of the perturbations to the initial breaking point. The present study conducts numerical simulations to investigate the generation and development of wave instabilities involving the wave breaking process. A CFD model solving Reynolds-averaged Navier-Stokes (RANS) equations coupled with turbulence closure model in terms of the Reynolds stress model is applied. Wave form evolutions, Fourier amplitudes, and the turbulence beneath the broken waves are investigated.

This paper addresses the applicability of liquid–liquid extraction for separating mineral particles by the difference in oil–water partition coefficient, for the seafloor mineral processing of seafloor massive sulfides (SMSs). Measurements of contact angle of sulfide mineral–aqueous solution–oil systems under high-pressure conditions were performed to evaluate the efficiency of liquid–liquid extraction at high pressures. The results showed that the contact angle stayed around 80–100 deg at the pressure range up to 16 MPa, and the changes in the contact angles were within 5 deg with varying pressure. Extraction experiments were carried out by using particles of an SMS ore, which contained Zinc (Zn), Lead (Pb), and Barium (Ba) in the grade of more than 10 mass% and Copper (Cu) in a small percentage, to evaluate the beneficiation performance of liquid–liquid extraction. In the experiments, extraction conditions such as the dosage of chemical reagents and pH in the aqueous solution were varied to optimize both the recovery and selectivity of Cu, Zn, and Pb in the oil phase and those of Ba in the water phase. The experimental results showed that the optimum condition was 200 g/t dosage—pH 7, where the grade and recovery were ca. 37 mass% and ca. 90 mass%, respectively. The beneficiation performance of liquid–liquid extraction would be comparable with that of flotation, adapted to the processing of other SMS ores.

Ice accretion on marine vessels and offshore structures is a severe hazard in the Polar regions. There are increasing activities related to oil and gas exploration, tourism, cargo transport, and fishing in the Arctic. Ice accretion can cause vessel instability, excess load on marine structures, and represents a safety risk for outdoor working environment and operations. Freezing sea spray is the main contributor to marine icing. For safe operations in cold climates, it is essential to have verified models for the prediction of icing. Sea spray icing forecast models have improved. Empirical and theoretical models providing icing rates based may be useful as guidelines. For predicting the distribution of icing on a surface at the design stage, computational fluid dynamics has to be applied along with a freezing module. State-of-the-art models for numerical simulation of sea spray icing are still not fully capable of modeling complex ship-sea-wind interactions with spray generation and impact of shipped water. Existing models include a good understanding of spray flow effects and freezing. Further development should focus on developing models for dynamic ship-sea-wind interactions, in particular including spray generation, effects of shipped water, and distribution of icing on the vessel surface. More experimental and full-scale data are needed for the development and verification of new and improved models. Models that estimate ice distribution may improve the winterization design process and reduce the effort required for de-icing. Improved methods for de-icing and anti-icing will reduce the impact of sea spray icing and increase safety for marine operations in cold waters.

It is important to predict the pressure loss due to hydraulic transport of large solid particles for the design of subsea mining system. The mixture flow in the lifting pipe is expected to be unsteady in the actual mining system. The authors develop the one-dimensional mathematical model to predict the pressure loss of pulsating mixture flow in a static vertical pipe assuming that the flow in the pipe is fully developed. The experiment on hydraulic transport of solid particles was carried out to obtain the data for the investigation of the effects of flow fluctuation on pressure loss in a static vertical pipe. In the experiment, alumina beads and glass beads were used as solid particles, and the experimental parameters were mixture velocity, solid concentration, pulsating period, and pulsating amplitude. The proposed model was validated by a comparison with experimental data. Furthermore, we calculated the pressure losses due to hydraulic transports of polymetallic sulfide ores and manganese nodules using the proposed model. The calculation results showed that the fluctuating component in pulsating mixture flow should be considered for the design of lifting system and that the homogeneous mixture model could not be applied to the prediction of the pressure loss unless the mixture concentration is low and the pulsating period is short.

Roll motion of a planing hull can be easily triggered at high speeds, causing a significant change in hydrodynamic pressure pattern, which can threaten the stability of the vessel. Modeling and investigating roll motion of a planing vessel may require a strong coupling between motions in vertical and transverse planes. In the present paper, we have used a mathematical model to analyze the roll of a planing hull by coupling surge, heave, pitch, and roll motions using 2D + T theory to study the effects of roll-induced vertical motions on roll coefficients and response. Mathematically computed forces and moments as well as roll dynamic response of the vessel are seen to be in fair quantitative agreement with experimentally measured values of previously published data. Using the 2D + T method, it has been shown that to model the roll of a planing hull at high speeds, we need to consider the effects of heave, pitch, and surge motions. Through our mathematical modeling, it is found that freedom in vertical motions increases time-dependent roll damping and added mass coefficients, especially at early planing speeds. The results of dynamic response simulations suggest that freedom in the vertical plane can decrease the roll response.

The hydrodynamic performance of a novel and efficient concept of a floating oscillating water column device has been investigated. The new concept consists of two chambers. These chambers are positioned on the upstream (fore chamber) and on the downstream (rear chamber) of the incident wave direction. The rear chamber acts mainly similar to a backward bent duct buoy system, while the design of the fore chamber follows conventional types of oscillating water column systems with the harbor plates (bottom plates and side plates) elongated outside of the fore chamber. The primary efficiency of the devised concept has been investigated in the frequency domain. In this context, to solve the corresponding diffraction and radiation problems due to the influence of the air pressure inside the chambers as well as motions of the body, an in-house code has been developed in two-dimensional using the boundary element method based on the linear wave theory. The obtained numerical results show that the introduced concept has advanced hydrodynamic efficiency in a broad range of waves.

The stochastic waves generated by storm landfalls usually determine the design and safety of coastal and offshore structures in typhoon regions. This study developed a parametric wave spectrum model for typhoon-generated stochastic waves that considers the variation in the wave spectrum due to the temporal variation in the typhoon. A field measurement campaign was conducted in nearshore strait water on the east coast of China to measure the wave data for two landfall typhoons: Soudelor and Dujuan. The measured wave data were filtered through a preprocessing framework. The parametric wave spectrum model was then developed based on the measured wave spectra for different stages of the typhoon. The main conclusions include the following: (1) 78% of the measured wave spectra at the example site under a typhoon are double-peaked, and approximately 15% are single-peaked; (2) the parametric model with either the Joint North Sea Wave Project (JONSWAP) or Ochi-Hubble (OH) kernel function is effective in defining the typhoon-generated wave spectra; and (3) the critical parameters of the developed model for typhoon-generated waves are site-specific and depend on the temporal variation of the typhoon.

This paper gives a detailed description of the main hydrodynamic characteristics of different types of green water events occurring on a fixed structure in a series of experiments. High-speed video, at 250 fps, was used to capture the flow details from regular waves produced inside a wave flume. The green water events were classified according to their type and the results of the evaluation from the apparent and effective interaction features. The air cavities in the plunging-dam-break (PDB)-type events were almost spherical for longer waves. PDB with large, elliptical cavities, and hammer-fist (HF)-type events occurred with steeper waves. The highest wave front and bow run-up velocities were found in PDB and HF events, respectively. The size of the cavities in PDB events increases and becomes more elliptical for higher bow run-up velocities. The results of these experiments show that not all events can be treated in the same way as the dam-break (DB)-type events when designing structures or implementing models, as not all interactions with the deck happen when the shipping water crosses the bow edge.

Spray generated by ships traveling in cold oceans often leads to topside icing, which can be dangerous to vessels. Estimation of the spray flux is a first step in predicting icing accumulation. The amount of spray water, the duration of exposure to the spray, and the frequency at which the spray is generated are all important parameters in estimating the spray flux. Most existing spray flux formulae are based on field observations from small fishing vessels. They consider meteorological and oceanographic parameters but neglect the vessel behavior. Ship heave and pitch motions, together with ship speed, determine the frequency of spray events. Thus, the existing formulae are not generally applicable to different sizes and types of vessels. This paper develops simple methods to quantify spray properties in terms that can be applied to vessels of any size or type. Formulae to estimate water content and spray duration are derived based on principles of energy conservation and dimensional analysis. To estimate spray frequency considering ship motions, a theoretical model is proposed. The model inputs are restricted to ship’s principal particulars, operating conditions, and environmental conditions. Wave-induced motions are estimated using semi-empirical analytical expressions. A novel spray threshold is developed to separate deck wetness frequency from spray frequency. Spray flux estimates are validated against full-scale field measurements available in the open literature with reasonable agreement.

Subsea pipelines and umbilicals are used for the transportation of fluids and electrical power between subsea installations and floating production units (FPUs). The installation and maintenance of these systems can be expensive. In a conventional subsea field development, the produced fluids can be transported from the well to a FPU where they can be offloaded to a tanker (surface ship). In the case of carbon dioxide (CO 2 ) injection into the well, the direction of flow is reversed, i.e., CO 2 flows from the tanker to the FPU, down the riser base and through the subsea pipelines to the well. This offloading process is weather-dependent and cannot be performed in severe weather conditions, i.e., strong winds and large waves. This paper presents a novel subsea shuttle tanker system proposed by Equinor ASA designed to be a possible alternative to subsea pipelines, umbilicals, and tanker ships. The subsea shuttle is intended to operate submerged under the sea surface to transport liquid CO 2 from an existing offshore/land facility where CO 2 is captured to a subsea well where the CO 2 is injected into the reservoir. As the shuttle is subsea, it can operate under any type of weather conditions. Even though the subsea shuttle is proposed as a vehicle for liquid CO 2 transport, it can also transport other types of cargo such as hydrocarbons, injection fluids, electrical power, or subsea tools. The paper will discuss the most important design considerations surrounding the subsea shuttle tanker.

The structural design of offshore wind turbines is based on the consideration of coupled dynamic phenomena. Wave loads cause the dynamic oscillation of the monopile, and the dynamic oscillation of the monopile affects the wave loads. The boundary conditions of the gravity-based foundation-monopile-turbine system are mostly affected by the flexural stiffness of the foundation plate, the elastic and creep behavior of the soil, and the inertia (translational and rotational) of the wind turbine mass. The design of the foundation should consider the dynamic response of the soil and the monopile, and the dynamic response of the soil and the monopile is affected by the design parameters of the foundation. The initial conditions of the system yield transient dynamic phenomena. A braking wave at t = 0 causes different dynamic response than the steady-state conditions due to a harmonic wave load. In the present work, an integrated analytical model simulating the above dynamic phenomena is proposed. With the aid of double integral transforms and generalized function properties, a solution of the corresponding differential equations for the monopile-soil-foundation system and the boundary and initial conditions is derived. A parametric study is carried out, and results of the effect of the design parameters and soil properties are presented and discussed.

Oscillating water column (OWC) wave energy converters are one of the most widely researched devices for ocean wave energy harvesting. This study investigates the hydrodynamic performance of a shore-fixed OWC device for different bottom slopes using two numerical approaches, namely, computational fluid dynamics (CFD) and boundary integral equation method (BIEM). In the BIEM method, the boundary value problem is solved in two-dimensional Cartesian coordinates using the linear water wave theory. The CFD model uses a numerical wave tank (NWT) built using the volume of fluid (VOF) method. Numerical computations are carried out for different sloped bottom geometries and front wall drafts to analyze the hydrodynamic efficiency. There is a general agreement between CFD and BIEM results in terms of resonating behavior of the device. It is observed that the front wall draft has a more significant effect, a lower draft leading to a wider frequency band for optimum conversion at high efficiency. While the BIEM-based analysis resulted in improved performance curve for few of the steeper slopes, the CFD study predicted a lower peak efficiency for the same slopes due to the consideration of real fluid characteristics. Detailed performance comparisons are presented using the time histories of free surface elevation, chamber pressure, and streamlines at different time instants within the OWC chamber.

Hovering control of autonomous underwater vehicles (AUVs) via a variable ballast system (VBS) is challenging owing to the difficulty in precisely estimating related hydrodynamic coefficients and vertical disturbance. In this work, a hierarchical control strategy is proposed which comprises an upper layer—the proportional-integral-derivative (PID) type ballast water mass planner generating the desired ballast mass, and a lower layer—the continuous mass flowrate controller adjusting the actual ballast mass. The resulting flowrate algorithm endows the system with local uniform asymptotic stability and robustness to both modeling errors and vertical disturbance. Numerical results verify the feasibility and effectiveness of the proposed hierarchical hovering control strategy.

A very interesting topic in naval architecture is propeller's choice. The engineering team must pay attention to several characteristics of the vessel to properly choose the most effective propeller for that specific application. At the beginning of the Second World War, the diagrams of a well-known propeller, the B-Series propeller, were published. They were tested at the Netherlands Ship Model Basin in Wageningen, and this led to the development of multiple polynomial regression analysis to predict propeller characteristics. Until today this propeller is studied because it possesses satisfactory efficiency and adequate cavitation properties. In addition, its open-water characteristics (K T , K Q , and η 0 ) are easy to obtain. The main goal is to evaluate the usefulness of computational fluid dynamics (CFD) to gather the open-water characteristics, from the design of the propeller on prototype scale, considering cavitation to data analysis and verification and validation of the characteristic curves. A Microsoft Excel tool was developed to draw any B-Series propeller. For this work, the B3.80 was used. CFD results were verified using Richardson Extrapolation and then validated. To this end, the open-water characteristics were used and the numerical results showed a fairly good agreement with the experimental data. The cavitation results were in agreement with the Burrill diagram in most of the cases. The characteristic curves of the cases where cavitation occurred were similar to those shown in the Principles of Naval Architecture (PNA) (Lewis, E. V., 1988, Principles of Naval Architecture, The Society of Naval Architects and Marine Engineers). Other interesting results of this propeller are also shown, e.g., pressure distribution, streamlines.

Flow-induced motions (FIM) are an issue for floating offshore structures, such as multi-column platforms, as the phenomenon can decrease the fatigue life of the mooring, riser, and cable systems. The new concept of floating offshore wind turbines (FOWT) have a multi-column design that may be subjected to FIM. In the past, FIM was studied mainly for Oil & Gas platforms installed in deep waters. However, the FIM phenomenon of FOWT has been insufficiently explored. To rectify this, model tests were performed for the semisubmersible (SS) floating system design developed for the DeepCwind project (Offshore Code Comparison Collaboration Continuation (OC4) phase II). This paper will investigate the presence of FIM and show its importance in the design process of FOWT. Three different incidence angles of the current were tested, namely, 0, 90, and 180 deg. For each heading, 30 reduced velocities were tested, across the range 8000 < Re < 70,000. The results showed amplitudes in the transverse direction of around 70% of the diameter of the platform column, which is similar to those observed for deep-draft (DD) SS with circular columns. Note that these amplitude values are larger for a floater with a circular column, than for a platform with square columns. The results showed that as FIM occurred for this specific FOWT SS, its effect has to be considered in the mooring system and electric cable design.

The negative effect of biofouling on ship resistance has been investigated since the early days of naval architecture. However, for more precise prediction of fuel consumption of ships, understanding the effect of biofouling on ship propulsion performance is also important. In this study, computational fluid dynamics (CFD) simulations for the full-scale performance of KP505 propeller in open water, including the presence of marine biofouling, were conducted. To predict the effect of barnacle fouling on the propeller performance, experimentally obtained roughness functions of barnacle fouling were used in the wall-function of the CFD software. The roughness effect of barnacles of varying sizes and coverages on the propeller open water performance was predicted for advance coefficients ranging from 0.2 to 0.8. From the simulations, drastic effects of barnacle fouling on the propeller open water performance were found. The result suggests that the thrust coefficient decreases while the torque coefficient increases with increasing level of surface fouling, which leads to a reduction of the open water efficiency of the propeller. Using the obtained result, the penalty of propeller fouling on the required shaft power was predicted. Finally, further investigations were made into the roughness effect on the flow characteristics around the propeller and the results were in correspondence with the findings on the propeller open water performance.

During a ship life cycle, one of the most critical phases in terms of safety refers to harbor maneuvers, which take place in restricted and congested waters, leading to higher collision and grounding risks in comparison to open sea navigation. In this scenario, a single accident may stop the harbor's traffic as well as incur in patrimonial damage, environmental pollution, human casualties, and reputation losses. In order to support the vessel's captain during the maneuver, local experienced maritime pilots stay on board coordinating the ship navigation while in restricted waters. Aiming to assess the main factors contributing to human errors in pilot-assisted harbor ship maneuvers, this work proposes a Bayesian network model for human reliability analysis (HRA), supported by a prospective human performance model for quantification. The novelty of this work resides into two aspects: (a) incorporation of harbor specific conditions for maritime navigation HRA, including the performance of ship's crew and maritime pilots and (b) the use of a prospective human performance model as an alternative to expert's opinion for quantification purposes. To illustrate the usage of the proposed methodology, this paper presents an analysis of the route keeping task along waterways, starting from the quantification of human error probabilities (HEP) and including the ranking of the main performance shaping factors that contribute to the HEP.