A review presents the state-of-the-art path-following control systems for maritime autonomous surface ships, where the special focus is placed on the guidance subsystem and control subsystem. The path following control system is one of the basic requirements for autonomous ships since it guarantees that the ship can track the predefined path with small cross-track errors. The path following problem is firstly defined, and the cross-track error dynamics are derived from the kinematic equations of marine surface ships. The classical guidance laws are introduced, and the governing equations are also presented in this paper. A review of the guidance laws and controllers for the maritime autonomous surface ships has been carried out based on relevant journal and conference papers. Several important properties and characteristics, such as control structure, guidance law, control method, stability, environmental disturbance and vessel dynamics, are defined for the comparative analysis. Finally, the summary and a discussion on the most used technologies for the path following control of marine autonomous surface ships are presented and highlighted.

Automatic berthing guidance is an important aspect of automated ship technology to obtain the ship-shore position relationship. The current mainstream measurement methods for ship-shore position relationships are based on radar, multisensor fusion, and visual detection technologies. This paper proposes an automated ship berthing guidance method based on three-dimensional (3D) target measurement and compares it with a single-target recognition method using a binocular camera. An improved deep object pose estimation (DOPE) network is used in this method to predict the pixel coordinates of the two-dimensional (2D) keypoints of the shore target in the image. The pixel coordinates are then converted into 3D coordinates through the camera imaging principle, and an algorithm for calculating the relationship between the ship and the shore is proposed. Experiments were conducted on the improved DOPE network and the actual ship guidance performance to verify the effectiveness of the method. Results show that the proposed method with a monocular camera has high stability and accuracy and can meet the requirements of automatic berthing.

The identification of ship collision risks is an important element in maritime safety and management. The concept of the ship domain has also been studied and developed since it was proposed. Considering the existing trend that the ship domain is increasingly widely used in collision risk-related research, a new domain-oriented collision risk factor, i.e., the current state of domain (CSD), is introduced in this paper, which can effectively reflect the current state and show a certain predictability of collision risk from the perspective of the ship domain. To further prove the rationality of the CSD, a series of different simulations consisting of three typical encounter scenarios were conducted, verifying the superiority of the proposed parameter.

In this paper, after the successful applications to open water propeller performance estimations, the influence of transition sensitive and modified mass transfer models tuned to account for the laminar flow in the prediction of the cavitation inception of marine propulsors is investigated from the point of view of the unsteady functioning and induced pressure pulses. The VP1304 (also known as PPTC) test case, for which dedicated data were collected during several workshops, is considered first. After preliminary analyses using RANS, also Detached Eddy Simulations (DES) are included to better account for the vortex dynamics and its influence on pressure pulses. Similarly to what observed in uniform inflow, results show a better agreement with the available measurements of propeller performances and confirm the reliability of the proposed approaches for unsteady, non-cavitating, model scale propeller predictions. The overall cavitation pattern is improved too by the application of the transition sensitive correction to the mass transfer model, but the complex dynamics of bubble cavitation observed in experiments prevents quantitatively better predictions in terms of thrust/torque breakdown and induced pressure pulses levels regardless the use of RANS or DES methods.

A large eddy simulation of wall-adapting local eddy-viscosity model (LES-WALE) is used to simulate the three-dimensional flow around a circular cylinder with a diameter of 0.25 m from sub-critical to super-critical Reynolds numbers at 1×10⁵, 2.5×10⁵, and 7.2×10⁵, respectively. The present results such as drag crisis, surface pressure distribution, and Strouhal number are in good agreement with the classical experimental data. When entering the critical region, a small plateau was found on the pressure distribution curves, corresponding to the appearance of laminar separation bubbles, and the separation point is delayed and the recirculation bubbles become narrowed and shortened. The tangential velocity of the cylinder surface changes from positive to negative at the separation point. The instantaneous vorticity and time-averaging separation bubbles embody an unstable feature. Within the separation bubble, the pressure varies dramatically with time, but not with position. The surface pressure fluctuates greatly after the laminar separation bubble appears, and it is gradually stabilized until the basic pressure is reached. The process of laminar separation, transition from laminar flow to turbulent flow and turbulent reattachment is also shown. The three-dimensional Q criterion of vortex structure and the two-dimensional spanwise vorticity reveal the phenomenon that the wake structure narrows with the increase of the Reynolds number.

Responses of the very large floating Structures (VLFS) can be mitigated by implementing oscillating water columns (OWCs). This paper explores the fundamental mechanism of present wave interactions with both structures and examines the hydrodynamic performance of VLFS equipped with OWCs (VLFS-OWCs). Under the linear potential flow theory framework, the semi-analytical model of wave interaction with VLFS-OWCs is developed using the eigenfunction matching method. The semi-analytical model is verified using the Haskind relationship and wave energy conservation law. Results show that the system with dual-chamber OWCs has a wider frequency bandwidth in wave power extraction and hydroelastic response mitigation of VLFS. It is worth noting that the presence of Bragg resonance can be trigged due to wave interaction with the chamber walls and the VLFS, which is not beneficial for the wave power extraction performance and the protection of VLFS.

The nonlinear dynamic behaviors of viscoelastic axially functionally graded material (AFG) pipes conveying pulsating internal flow are very complex. And the dynamic behavior will induce the failure of the pipes, and research of vibration and stability of pipes becomes a major concern. Considering that the elastic modulus, density, and coefficient of viscoelastic damping of the pipe material vary along the axial direction, the transverse vibration equation of the viscoelastic AFG pipe conveying pulsating fluid is established based on the Euler-Bernoulli beam theory. The generalized integral transform technique (GITT) is used to transform the governing fourth-order partial differential equation into a nonlinear system of fourth-order ordinary differential equations in time. The time domain diagram, phase portraits, Poincaré map and power spectra diagram at different dimensionless pulsation frequencies, are discussed in detail, showing the characteristics of chaotic, periodic, and quasi-periodic motion. The results show that the distributions of the elastic modulus, density, and coefficient of viscoelastic damping have significant effects on the nonlinear dynamic behavior of the viscoelastic AFG pipes. With the increase of the material property coefficient k, the transition between chaotic, periodic, and quasi-periodic motion occurs, especially in the high-frequency region of the flow pulsation.

The present paper presents the sloshing oscillation behaviour and sloshing force in three different tanks of model scales of 1:86, 1:57 and 1:43. The rectangular tank is mounted on shake table, to study the scale effect of sloshing with sway excited motion. The tests are carried out for the aspect ratio (h_s /l, where h_s liquid depth and l is the length of the tank) of 0.162 5, 0.325, and 0.487 5 which represents 25%, 50% and 75% of liquid fill levels, respectively. Seventeen excitation frequencies ranging from 0.456 6 Hz to 1.975 7 Hz are considered, which covers up to the fifth sloshing mode. The sloshing oscillations occurs in the longitudinal axis when subjected to sway excitations. An experimental setup is designed and devised to measure sloshing force by the concept of ballast mass. The inertia forces are measured by load cells and sloshing oscillation time histories are measured by capacitance probes. It is found that violent sloshing is experienced for 50% filled condition irrespective of scaled tanks, excitation amplitudes and excitation frequencies. The sloshing force is maximum in 1:43 scaled tank than other scaled sloshing tanks irrespective of the excitation frequency and amplitude for 50% fill level. Based on the experimental observations and analysis of results, it is concluded that proportionate volume of water and tank size decides the severity of sloshing in the partially filled tanks.

Ship propulsion performance heavily depends on cavitation, increasing the recent interest in this field to lower ship emissions. Academic research on the effects of cavitation is generally based on the open-water propeller performance but the interactions of the cavitating propeller with the ship hull significantly affect the propulsion performance of the ship. In this study, we first investigate the INSEAN E779A propeller by a RANSE-based CFD in open-water conditions. The numerical implementation and the selected grid after sensitivity analysis partially succeeded in modeling the cavitating flow around the propeller. Satisfactory agreement was observed compared to experimental measurements. Then, using the open-water data as input, the propeller’s performance behind a full-scale ship was calculated under self-propulsion conditions. Despite being an undesired incident, we found a rare condition in which cavitation enhances propulsion efficiency. At σ = 1.5; the propeller rotation rate was lower, while the thrust and torque coefficients were higher.

In this study, we conducted numerical experiments to examine the effects of turbulence parameterization on temporal and spatial variations of suspended sediment dynamics. Then, we applied the numerical model to the Yamen Channel, one of the main eight outfalls in the Pearl River Delta. For the field application, we implemented the k-ε scheme with a reasonable stability function using the continuous deposition formula during the erosion process near the water-sediment interface. We further validated and analyzed the temporal-spatial suspended sediment concentrations (SSCs). The experimental results show that under specified initial and boundary conditions, turbulence parameterization with stability functions can lead to different vertical profiles of the velocity and SSC. The k-ε predicts stronger mixing with a maximum value of approximately twice the k-kl. The k-kl results in smaller SSCs near the surface layer and a larger vertical gradient than the k-ε. In the Yamen Channel, though the turbulent dissipation, turbulent viscosity and turbulence kinetic energy exhibit similar trends, SSCs differ significantly between those at low water and high water due to the tidal asymmetry and settling lag mechanisms. The results can provide significant insights into environmental protection and estuarine management in the Pearl River Delta.

Mooring systems are usually adopted to position floating structures, including mooring lines and anchors, and directly determine the safety of floating structures. Seabed inspection reported that seabed trenches induced by mooring line-soil interaction appear in front of the anchor and reduce the anchor bearing capacity. This work first introduces the research progress of mooring line-soil interaction and seabed trenching simulation. Research about the suction anchor capacity in clay and sand is presented, and the seabed trench influence on anchor capacity is analyzed. For anchor analysis, this study gives a new perspective to analyze anchor installation and bearing capacity, i. e., structure-soil interface characteristic. Some common anchor types are analyzed. Results showed that seabed trench simulation is still needed to acquire trench 3D profiles, in which the mooring line-soil dynamic interaction cannot be ignored. At present, the trench influence is not considered in suction anchor design, making the design dangerous. For the anchor, the interface shear characteristics control the most unfavorable loading conditions. Thus, accurate interface parameters should be obtained for anchor analysis.

Duplex stainless steel was formed through welding wire and arc additive manufacturing (WAAM) using tungsten inert gas. The effects of wire feeding speed (WFS), welding speed (WS), welding current, and their interaction on the weld bead width and height were discussed. Back-propagation (BP) neural network algorithm prediction model was established by taking the bead width and height as the output layer, and the network weight and threshold values were optimized using the particle swarm optimization (PSO) algorithm to obtain the prediction model of bead width and height. The predicted results were verified by experiments. Results show that the weld bead width increases with the increase in WFS and the welding current and decreases with WS. The smaller the WFS, the faster the WS, which is beneficial for the generation of equiaxed crystals. The smaller the welding current, the faster the cooling speed of the metal melt, which is conducive to the formation of dendrites. The interaction among WS, wire feed speed, and welding current has a significant effect on the bead width. The weld bead height is positively correlated with the wire feed speed and negatively correlated with the WS and current. The interaction between the wire feed speed and WS is significant. The optimized WAAM process parameters for duplex stainless steel are a wire feed speed of 200 cm/min, WS of 24 cm/min, and welding current of 160 A. The maximum error of the BP neural network in predicting the weld bead width and height is 7.74%, and the maximum error between the predicted and experimental values of the BP-PSO neural network is 4.27%. This finding indicates that the convergence speed is fast, improving the prediction accuracy.

The efficiency of a tuned liquid damper (TLD) in controlling the dynamic responses of offshore monopile platforms under seismic excitation has been investigated in this paper. Damping is performed by applying a type of reservoir inside a tower, which is designed optimally via seawater and a monopile body. Hydrodynamic forces due to water surface oscillation in the reservoir act as resistant forces against structure vibration and displacement. Using ANSYS finite element (FE) software, a monopile structure with the same dimensions as the samples in the Persian Gulf climate was modeled and then analyzed in this research using the transient time history analysis related to the records of El-Centro, Kobe, and Tabas earthquakes for seismic investigation. The dynamic responses of the monopile platform with and without TLD were compared after the completion of FE results. Findings show that using the mentioned TLDs reduced structure displacement by more than 50% based on the earthquake frequency content.

This study investigates the underwater radiated noise (URN) of a manned submersible support mother ship. To this end, a detailed finite element model of the hull and outflow field is established, and the vibration wet mode of the scientific research ship is calculated. A combination of finite element and boundary element methods is used to analyze the spectral features of ship low-frequency URN. The URN source is comprehensively analyzed, the vibration energy is considered the basic parameter to describe the vibration, and the medium- and high-frequency URN of the ship are calculated using the statistical energy analysis. To obtain the full frequency-band URN of the ship, the risk position of exceeding the standard is determined, and the contribution of each main noise source in the ship to the URN is analyzed. The URN level of the ship is comprehensively measured in the free navigation state. The accuracy of the URN control evaluation model, and the method of the ship are verified.The data support for the ship to apply for the classification society certificate provides a scheme reference for the URN control of other scientific research ship in the future.

The requirement of low radiated noise is increasing for underwater propulsors as the noise significantly affecting the comfort and quietness of ships, submarines, and vessels. To broaden the view of noise characteristics of pump-jet propulsors (PJPs), this paper considers the radiated noise of a pre-swirl stator PJP with the effects of the advance coefficient and rotor rotational speed. Radiated noise is obtained by the “hybrid method” approach, which combines a hydrodynamic solver with a hydroacoustic solver. The turbulence flow is obtained through improved delayed detached eddy simulation (IDDES), which show good agreement with the experiment, including the performance and flow field. The solver precision, permeable surface size, and sampling frequency notably affect the noise calculation. The spectra of thrust fluctuation and radiated noise are characterized by the tonal phenomenon around the blade passing frequency and its harmonics. The spectrum of radiated noise and overall sound pressure level (OSPL) are considerably affected by both the advance coefficient and the rotor rotational speed. Overall, the numerical results and analysis given in this paper should be partly helpful in deepening the understanding of the radiated noise characteristics of PJPs.

Using the underwater acoustic channel (UWA) for information dissemination requires a high data rate. However, some phenomena like refraction, reflection, phase shift, and high attenuation are undesirably apparent when the subject of using UWA is raised. Accordingly, sound communication would be a highly challenging task to be accomplished. Therefore, proposing a model of acoustic underwater communication channels is critical because of the multipath interference originating from the surface and bottom of the ocean. In this contribution, a straightforward geometry channel model for vertical and horizontal marine communications is presented. To do so, transmission loss and channel impulse response are analyzed as a function of transmitter and receiver distance, water depth, and reflection rate. The results of the model proposed in this paper are in very good agreement with those available in the literature. Initial findings indicate that the delay spread of horizontal communication with a 1 000 m range reaches79 ms and 0.3 s for 30 m vertical communication.

With the current revolution in Shipping 4.0, a tremendous amount of data is accumulated during vessel operations. Data quality (DQ) is becoming more and more important for the further digitalization and effective decision-making in shipping industry. In this study, a practical DQ assessment method for raw data in vessel operations is proposed. In this method, specific data categories and data dimensions are developed based on engineering practice and existing literature. Concrete validation rules are then formed, which can be used to properly divide raw datasets. Afterwards, a scoring method is used for the assessment of the data quality. Three levels, namely good, warning and alarm, are adopted to reflect the final data quality. The root causes of bad data quality could be revealed once the internal dependency among rules has been built, which will facilitate the further improvement of DQ in practice. A case study based on the datasets from a Danish shipping company is conducted, where the DQ variation is monitored, assessed and compared. The results indicate that the proposed method is effective to help shipping industry improve the quality of raw data in practice. This innovation research can facilitate shipping industry to set a solid foundation at the early stage of their digitalization journeys.

This paper analyses the issue of accelerated start-up of a marine steam turbine, which is an important problem because the start-up of a steam machine involves the combustion of fuel that is not transformed into useful energy. To find novel technologies that offer improvements in this aspect is essential due to restrictions on reducing ship emissions. Thus, the shorter the start-up time, the better for the environment and economy. High-pressure (HP) part of the turbine originally located on the Queen Elizabeth II unit was analysed. Advanced numerical calculations by thermal fluid-solid-interaction (Thermal FSI) were carried out. A series of simulations were performed for the accelerated start-up with controlled steam injection. A description of the chosen calculation methodology and the results obtained by simulation are included in this paper. The stress occurring during the accelerated start-up are approximately 40 MPa higher than those during the reference start-up. The relative elongations between the rotor and the hull during accelerated start-up reach a maximum value of 0.89 mm (0.83 mm for ultra-fast start-up). Reducing the steam turbine start-up time by 75% results in a 36.7 tons reduction in fuel consumption for start-up, resulting in an annual savings of 5 372 USD. In conclusion, the concept proposed by the authors is safe, less expensive and does not affect the life of the turbine. In addition, results and applications from Siemens prove that additional injection of cooling steam is possible.