With the significant development of computer hardware, many advanced numerical techniques have been proposed to investigate complex hydrodynamic problems. This article aims to provide a detailed review of moving particle semi-implicit (MPS) techniques and their application in ocean and coastal engineering. The achievements of the MPS method in stability and accuracy, boundary conditions, and acceleration techniques are discussed. The applications of the MPS method, which are classified into two main categories, namely, multiphase flows and fluid-structure interactions, are introduced. Finally, the prospects and conclusions are highlighted. The MPS method has the potential to solve practical problems.

Water-lubrication bearings are critical components in ship operation. However, studies on their maintenance and failure detection are highly limited. The use of sensors to continually monitor the working operation of bearings is a potential approach to solve this problem, which is collectively called intelligent bearings. In this literature review, the recent progress of electrical resistance strain gauges, Fiber Bragg grating, triboelectric nanogenerators, piezoelectric nanogenerators, and thermoelectric sensors for in-situ monitoring is summarized. Future research and design concepts on intelligent water-lubrication bearings are also comprehensively discussed. The findings show that the accident risks, lubrication condition, and remaining life of water-lubricated bearings can be evaluated with the surface temperature, coefficient of friction, and wear volume monitoring. The research work on intelligent water-lubricated bearings is committed to promoting the development of green, electrified, and intelligent technologies for ship propulsion systems, which have important theoretical significance and application value.

This paper presents experimental results on configuration hydrodynamics. Three models are used in the model tests, which are typical of hard, round, and soft chines. Although specific values are different, the influence patterns are similar in the three ship models. A set of different outrigger positions is investigated in calm water and regular waves. A variety of interesting phenomena are observed, among which the splash resistance is the dominant component for a trimaran at high speeds (with Froude number Fr > 0.6). If two small outriggers are placed inside Kelvin’s wave systems of the main hull, a strong splash appears, resulting in a significant resistance increase. Moreover, short and long waves cannot be neglected, for they may excite the motions of much smaller outriggers. This condition leads to non-vanishing heaving at high-frequency and non-normalized pitches at low frequencies. Based on the tests, three spectra of optimum configurations for resistance, longitudinal motions, and transverse motions are presented. These results reveal the optimum configurations of a trimaran hull in terms of hydrodynamic performance, thus providing a very powerful tool for optimum design of trimaran ships.

In this paper, the effect of water and air fluids on the behavior of a planing catamaran in calm water was studied separately in calm water by using experimental and numerical methods. Experiments were conducted in a towing tank over the Froude number range of 0.49–2.9 with two degrees of freedom. The model vessel displacement of 5.3 kg was implemented in experimental tests. Craft behavior was evaluated at the displacements of 5.3, 4.6, and 4 kg by using the numerical method. The numerical simulation results for the hull’s resistance force were validated with similar experimental data. The fluid volume model was applied to simulate two-phase flow. The SST k-ω turbulence model was used to investigate the effect of turbulence on the catamaran. The results showed that in the planing mode, the contribution of air to pressure resistance increased by 55%, 40%, and 60% at the mentioned displacements, whereas the contribution of air to friction resistance was less than 15% on average. The contribution of the air to the total lift force at the abovementioned displacements exceeded 70%, 60%, and 50% in the planing mode but was less than 10% in the displacement mode. At the displacements of 5.3 and 4 kg, the area under the effect of maximum pressure moved around the center of gravity and caused porpoising longitudinal instability at the Froude numbers of 2.9 and 2.4, respectively. However, at the displacement of 4.6 kg, this effect did not occur, and the vessel maintained its stability.

Recently, computational fluid dynamics (CFD) approaches have been effectively used by researchers to calculate the resistance characteristics of ships that have rough outer surfaces. These approaches are mainly based on modifying wall functions using experimentally pre-determined roughness functions. Although several recent studies have shown that CFD can be an effective tool to calculate resistance components of ships for different roughness conditions, most of these studies were performed using the same ship geometry (KRISO Container Ship). Thus, the effect of ship geometry on the resistance characteristics of rough hull surfaces is worth investigating. In this study, viscous resistance components of four different ships are calculated for different roughness conditions. First, flat plate simulations are performed using a previous experimental study for comparison purposes. Then, the viscous resistance components of three-dimensional hulls are calculated. All simulations are performed using two different turbulence models to investigate the effect of the turbulence model on the results. An examination of the distributions of the local skin friction coefficients of the DTMB 5415 and Series 60 showed that the plumpness of the bow form has a significant effect on the increase in frictional resistance with increasing roughness. Another significant finding of the study is that viscous pressure resistance is directly affected by the surface roughness. For all geometries, viscous pressure resistances showed a significant increase for highly rough surfaces.

This paper presents analytical and numerical results of vapor bubble dynamics and acoustics in a variable pressure field. First, a classical model problem of bubble collapse due to sudden pressure increase is introduced. In this problem, the Rayleigh—Plesset equation is treated considering gas content, surface tension, and viscosity, displaying possible multiple expansion—compression cycles. Second, a similar investigation is conducted for the case when the bubble originates near the rounded leading edge of a thin and slightly curved foil at a small angle of attack. Mathematically the flow field around the foil is constructed using the method of matched asymptotic expansions. The outer flow past the hydrofoil is described by linear (small perturbations) theory, which furnishes closed-form solutions for any analytical foil. By stretching local coordinates inversely proportionally to the radius of curvature of the rounded leading edge, the inner flow problem is derived as that past a semi-infinite osculating parabola for any analytical foil with a rounded leading edge. Assuming that the pressure outside the bubble at any moment of time is equal to that at the corresponding point of the streamline, the dynamics problem of a vapor bubble is reduced to solving the Rayleigh-Plesset equation for the spherical bubble evolution in a time-dependent pressure field. For the case of bubble collapse in an adverse pressure field, the spectral parameters of the induced acoustic pressure impulses are determined similarly to equivalent triangular ones. The present analysis can be extended to 3D flows around wings and screw propellers. In this case, the outer expansion of the solution corresponds to a linear lifting surface theory, and the local inner flow remains quasi-2D in the planes normal to the planform contour of the leading edge of the wing (or screw propeller blade). Note that a typical bubble contraction time, ending up with its collapse, is very small compared to typical time of any variation in the flow. Therefore, the approach can also be applied to unsteady flow problems.

In this work, the deformation of free interface during water entry and exit of a circular cylinder is investigated numerically by using the two-dimensional (2D) immersed boundary-multiphase lattice Boltzmann flux solver (IB-MLBFS). The fluid domain is discretized by finite volume discretization, and the flux on the grid interface is evaluated by lattice Boltzmann equations. Both the implicit velocity correction and the surface flux correction are implemented by using the immersed boundary-method to consider the fluid-structure interaction and the contact interface between the multiphase fluids and the structure. First, the water entry of a circular cylinder is simulated and the results are compared with the experiment, which considered the length-diameter ratio of the circular cylinder. The reliability of 2D simulation is verified and the deformation of the free interface is well investigated. Afterward, the water exit of a circular cylinder with constant velocity is simulated, which is less researched. In addition, the results show the advantage of present IB-MLBFS to some extent. Finally, the water exit and re-entry of a circular cylinder are presented, and the results present the complex deformation of the free interface and the dynamic response of the moving structure. Based on the numerical results, the free interface of the multiphase fluids is well captured, and the contact interface on the boundary of the moving structure is accurately presented by the IB-MLBFS.

Nonlinear time-domain simulations are often used to predict the structural response at the design stage to ensure the acceptable operation and/or survival of floating structures under extreme conditions. An environmental contour (EC) is commonly employed to identify critical sea states that serve as the input for numerical simulations to assess the safety and performance of marine structures. In many studies, marginal and conditional distributions are defined to construct bivariate joint probability distributions for variables, such as significant wave height and zero-crossing period. Then, ECs can be constructed using the inverse first-order reliability method (IFORM). This study adopts alternative models to describe the generalized dependence structure between environmental variables using copulas and discusses the Nataf transformation as a special case. ECs are constructed using measured wave data from moored buoys. Derived design loads are applied on a semisubmersible platform to assess possible differences. In addition, a linear interpolation scheme is utilized to establish a parametric model using short-term extreme tension distribution parameters and wave data, and the long-term tension response is estimated using Monte Carlo simulation. A 3D IFORM-based approach, in which the short-term extreme response that is ignored in the EC approach is used as the third variable, is proposed to help establish accurate design loads with increased accuracy. Results offer a clear illustration of the extreme responses of floating structures based on different models.

This paper aims to reduce the wind resistance of the self-designed offshore tourism platform by optimizing its superstructure, and a transparent shape design is finally suggested. A numerical simulation was performed to calculate the wind load on the platform to test the effect of wind resistance reduction. Two original scale models (sealed and transparent) were established in accordance with the design requirements. The numerical simulation uses the FLUENT software combined with the built-in self-compiled user-defined function (UDF). The stochastic wind was also applied on the basis of the Davenport wind spectrum. The detached eddy simulation (DES) model was used to solve the NS equation. Numerical simulation results show that the wind resistance reduction for the transparent shape model is subtle in the horizontal direction but can effectively reduce the drag force and moment in the vertical direction. Moreover, the force variation of the transparent shape model under different wind attack angles decreases, which reduces the wind load fluctuations.

Goal based and limit state design is nowadays a well-established approach in many engineering fields. Ship construction rules started introducing such concepts since early 2000. However, classification societies’ rules do not provide hints on how to verify limit states and to determine the structural layout of submerged thin-walled stiffened cylinders, whose most prominent examples are submarines. Rather, they generally offer guidance and prescriptive formulations to assess shell plating and stiffening members. Such marine structures are studied, designed and built up to carry payloads below the sea surface. In the concept-design stage, the maximum operating depth is the governing hull scantling parameter. Main dimensions are determined based on the analysis of operational requirements. This study proposes a practical concept-design approach for conceptual submarine design, aimed at obtaining hull structures that maximize the payload capacity in terms of available internal volume by suitably adjusting structural layout and stiffening members’ scantling, duly accounting for robustness and construction constraints as well as practical fabrication issues. The proposed scantling process highlights that there is no need of complex algorithms if sound engineering judgment is applied in setting down rationally the hull scantling problem. A systematic approach based on a computer-coded procedure developed on purpose was effectively implemented and satisfactorily applied in design practice.

This paper presents a new type of double-helical rotor wave energy converter (WEC), which consists of two isolated sets of helical rotor structures (inner and outer). This device can generate electricity by using the rising and falling energy of a wave. The rotors are simulated and optimized by Fluent. Each rotor’s blades are simulated and analyzed, which are separately changed in terms of helix angle, shape, and thickness. The simulation result shows that, for both inner and outer helical rotors, the energy harvesting efficiency is the highest when the blade helix angle is 45°. Triangular blades have better hydrodynamic performance than square and circular blades. The energy harvesting efficiency of 15 mm thick blades is higher than that of 75 mm thick blades.

This paper proposes a risk assessment model considering danger zone, capsizing time, and evaluation time factors (DCEFM) to quantify the emergency risk of ship inflow and calculate the degree of different factors to the emergency risk of water inflow. The DCEFM model divides the water inflow risk factors into danger zone, capsizing time, and evacuation time factors. The danger zone, capsizing time, and evacuation factors are calculated on the basis of damage stability probability, the numerical simulation of water inflow, and personnel evacuation simulation, respectively. The risk of a capsizing scenario is quantified by risk loss. The functional relationship between the location of the danger zone and the probability of damage, the information of breach and the water inflow time, the inclination angle and the evacuation time, and the contribution of different factors to the risk model of ship water inflow are obtained. Results of the DCEFM show that the longitudinal position of the damaged zone and the area of the breach have the greatest impact on the risk. A simple local watertight plate adjustment in the high-risk area can improve the safety of the ship.

Shoreline change analysis frequently begins with feature identification through visual interpretation (proxy-based shoreline) or the intersection of a specific tidal zone (datum-based shoreline). Using proxy-based shoreline information, this study quantifies the distance between proxy-based and datum-based shoreline data, which is defined as the proxy-datum bias. The study was conducted at meso-tidal beaches in Kuala Nerus, Terengganu, Malaysia, with morphodynamic responses to northeast and southwest monsoons. The high-water line (HWL) shoreline (proxy-based) was determined using ortho-rectified aerial images captured by an unmanned aerial vehicle (UAV). By contrast, the mean high-water (MHW) shoreline (datum-based) was determined using measured beach profiles adjusted with the Peninsular Malaysia Geodetic Vertical Datum (DTGSM). The theoretical proxy-datum bias was approximated using the best estimate (median) for the beach slope, wave height, and wave period from the estimated total water level (TWL) model. Based on the study, the recorded horizontal proxy-datum bias for the research area was up to 32 m. This study also discovered that the theoretical assumption of the proxy-datum bias based on the TWL model yields values comparable to those of the measurements, with a narrower distinction in bias for steeper beach slopes than the obtained results. The determined proxy-datum bias value can benefit future shoreline change studies as it could be incorporated to either proxy-based shorelines by shifting the shoreline seaward or to datum-based shorelines by shifting the shoreline landward in order of the bias value. The seasonal monsoon’s effect on beach profiles should be considered when calculating bias values and conducting potential shoreline change rate studies.

This study aims to analyse and forecast the significance of input process parameters to obtain a better ENi-P-TiO₂ coated surface using artificial neural networks (ANN). By varying the four process parameters with the Taguchi L9 design, forty-five numbers of AH36 steel specimens are coated with ENi-P-TiO₂ composites, and their microhardness values are determined. The ANN model was formulated using the input and output data obtained the 45 specimens. The optimal design was developed based on mean squared error (MSE) and R² values. The experimentally measured values were compared with their predicted values to determine the ANN model’s predictability. The efficiency of the ANN model is evaluated with an R² value of 0.959 and an MSE value of 34.563 4. The authors have concluded that the developed model is suitable for designing and predicting ENi-P-TiO₂ composite coatings to avoid extensive experimentation with economic production. Scanning Electron Microscope (SEM) and X-ray diffraction analysis (XRD) are also utilised to compare the base metal and optimal coated surface.

Underwater data collection is an importance part in the process of network monitoring, network management and intrusion detection. However, the limited-energy of nodes is a major challenge to collect underwater data. The solution of this problem are not only in the hands of network topology but in the hands of path of autonomous underwater vehicle (AUV). With the problem in hand, an energy-efficient data collection scheme is designed for mobile underwater network. Especially, the data collection scheme is divided into two phases, i.e., routing algorithm design for sensor nodes and path planing for AUV. With consideration of limited-energy and network robustness, Q-learning based dynamic routing algorithm is designed in the first phase to optimize the routing selection of nodes, through which a potential-game based optimal rigid graph method is proposed to balance the trade-off between the energy consumption and the network robustness. With the collected data, Q-learning based path planning strategy is proposed for AUV in the second phase to find the desired path to gather the data from data collector, then a mode-free tracking controller is developed to track the desired path accurately. Finally, the performance analysis and simulation results reveal that the proposed approach can guarantee energy-efficient and improve network stability.

Development of man-packable, versatile marine surface vehicle with ability to rescue a drowning victim and also capable of carrying mission specific sensor is explored. Design thinking methodology is implemented by using existing equipment/platform with the addition of external attachment to make it a functional product. Iterative prototyping process with extensive testing to achieve user-centric solution. Individual prototypes and their possible sub-configurations with their integration and characteristics are studied and compared with numerical model, inferences obtained are utilised to improve for the next iteration. A novel hinge-clamp assembly enables this marine surface vehicle to operate in the event of an overturn, this phenomenon is further studied with the aid of a mathematical model (Pendulum in a fluid). This research project aims to demonstrate a multi-role unmanned surface vehicle.

This paper studies a deconvolved Chebyshev beamforming (Dcv-Che-BF) method. Compared with other deconvolution beamforming methods, Dcv-Che-BF can preset sidelobe levels according to the actual situation, which can achieve higher resolution performance. However, the performance of Dcv-Che-BF was not necessarily better with a lower preset sidelobe level in the presence of noise. Instead, it was much better when the preset side lobe level matched the signal to noise ratio of the signal. The performance of the Dcv-Che-BF method with different preset sidelobe levels was analyzed using simulation. The Dcv-Che-BF method achieved a lower sidelobe level and better resolution capability when the preset sidelobe level was slightly greater than the noise background level. To validate the feasibility and performance of the proposed method, computer simulations and sea trials were analyzed. The results show that the Dcv-Che-BF method is a robust high-resolution beamforming method that can achieve a narrow mainlobe and low sidelobe.

The exhaust volute is a device that can change the exhaust direction of the ship’s gas turbine to reduce the flow loss of the high-temperature and high-speed turbine exhaust gas in the box-type exhaust volute, thereby improving its power output performance. This paper first investigates the internal flow field characteristics of the exhaust volute via numerical simulation and reveals the main source of the internal resistance loss of the volute. On the premise of not affecting the installation size of the volute and matching it with other components in the cabin, the design scheme of volute bottom shunt and volute chamfer are then optimized in accordance with the flow characteristics inside the volute. Numerical simulation results show that the partial flow structure at the bottom of the volute can effectively improve the low-velocity region and the vortex flow at the bottom of the volute, and the chamfered angle scheme can control the regular expansion and compression of the airflow. When the volute adopts the appropriate chamfer angle and the bottom split-flow structure, the total pressure loss can be reduced by 19.6%, and the static pressure recovery coefficient can be increased by 42.05%.