Proceedings of the Institution of Mechanical Engineers,Part M: Journal of Engineering for the Maritime Environment

The term elastomer is a curtailment of two words, which are elastic and polymers. Accordingly, elastomers are polymer materials with elasticity. The significant challenges hindering the development of materials for naval applications, similar to other engineering sectors, include achieving a competitive light elastomeric structure. Marine structures are susceptible to various damage responses due to various loads throughout their service life. Being flexible, elastomer has a low modulus of elasticity, exhibits higher values of failure strain and yield strength. In these regards, elastomers are attractive materials for applications that require elasticity because they offer substantial advantages compared to traditional materials. However, the low fire resistance of these elastomeric materials jeopardizes their use in some critical applications. As a result, elastomeric blends and composites containing flame retardant (FR) additives are commonly used. On the other hand, elastomers possess (i) high strength-to-weight ratio, (ii) excellent impact properties, (iii) low infrared, magnetic, and radar signatures, (iv) excellent durability, and (v) high resilience to extreme loads. Hence, the scope of this study focuses on review and awareness regarding the feasibility of marine applications of elastomers/elastomeric composites, their current scientific and technological drawbacks, and future outlooks or prospects to support several applications in the marine industry.

A significant proportion of global carbon dioxide emissions are attributed to ocean-sailing ships and shipping emissions are predicted to double in less than 30 years. This paper investigates the benefit of using weather ship routing optimisation, assessing the ship emissions for minimum distance routes and optimised routes. The present contribution merges the estimation of shipping pollutants and their mitigation through weather routing optimisation; two lines of research widely analysed separately but seldom discussed together. A previously developed open software of weather ship routing is used to obtain the minimum cost (i.e. optimised route) in terms of sailing time, using high-resolution wave forecasting. The assessment of fuel consumption and ship emissions calculations were inspired by the STEAM2 bottom-up approach, in conjunction with the estimation of the power increase needed to overcome speed decrement due to waves. Several scenarios covering the Western Mediterranean Short Sea Shipping routes (from 24 to 600 nautical miles and using a real Ro-Pax vessel) are compared in terms of emissions between the minimum distance route and the optimum. The ship routing optimisation reveals a reduction up to 30% of ship emissions during severe storms on longer routes. Nevertheless, all the cases studied show emissions mitigation when ship routing optimisation is used. The expected increase of extreme weather events, in terms of frequency, intensity and duration due to climate change, suggests a gradual gain of implementing weather ship routing optimisation in all types of routes, regardless of the distance.

It is known that trade by ship is a cheaper way than airway, land, and rail trade. One of the most important reasons for this is that ships use heavy fuel oil (HFO), which is cheap but also poor quality fuel. This HFO used in ships needs to be cleaned with machines called separators (purifiers). Therefore, the separator is one of the vital auxiliary machines on the ship. A satisfactory separation should be done in order to get rid of the effects such as water in the fuel, sludge formation, pump ability, mixing of different grades in the tanks, abrasion, and corrosion, which are the most important risks in the burning of fuel oil. Many problems are encountered while trying to make good separation. Therefore, in this article, 20 important problems that are frequently encountered in ship HFO separators are evaluated with the best-worst method (BWM) by consulting marine experts. Results show that dirty separator discs (also fractured or broken), wrong gravity disc choice (or bad interface position), and unsatisfactory bowl work are the most important problems among 20 critical and frequent separator problems. Problems and results are very important in terms of smooth ship machinery operations and we think that this study will close this gap in the literature by ordering and identifying problems and also solution recommendations.

This work aims to understand the variations in the oscillatory seepage force on a buried pipe in the presence of a floating structure under the influence of long-crested waves. The study is based on numerical investigation carried out using Finite Element Analysis wherein the water wave is modelled using potential flow theory and the soil modelling in accordance with Biot’s consolidation equations. The investigation is carried out in the frequency domain considering a range of wave, soil and floating body parameters. At first, the sensitivity of wave and soil parameters on the development of vertical seepage force on a buried pipe is studied. Then a floating body is introduced to the fluid domain and the wave scattering effects on the seabed pressures and seepage forces on the buried pipe are investigated. The numerical results reveal that in the case of barge or floating-fixed breakwater, the increase in vertical seepage forces on the buried pipe is about two-fold in intermediate water depths (π/8 < kh < π/2). The increase in the susceptibility to instantaneous and residual liquefaction of soil above the buried pipe due to the presence of a floating body is also addressed.

This study presents a simulation-based optimization procedure of a high-speed vessel. The presented procedure is applied on benchmark form Model 5365, a 1/8.25 scale model of the transom-stern, high-speed research vessel, R/V Athena. The procedure integrates parametric model generation, viscous numeric resistance analysis, and genetic algorithm evaluation. CAESES, a unique simulation-based design platform, is used to collect the process under one roof and handle the process automatically. The fully-parametric form is constructed by means of main characteristic curves, control curves, and various parameters to achieve quick-variation of hull forms. The numeric resistance analysis are performed via viscous flow solver and the calm-water total resistance force is defined as the optimization objective. The NSGA-II algorithm is used for evaluation of analysis results and regeneration of form variants, to achieve total resistance minimization. The optimization results show that the optimized hull form has lower resistance than Model 5365 form; a form variant with 2.02% total resistance reduction was obtained.

The exciting force generated by the violent sloshing of the fluid in the tank will damage the tank structure and even affect the attitude stability of a vehicle. Hence, this study constructs a numerical model and horizontal excitation experimental platform. Taking the porous baffle in the tank of a specific type of tanker as an example, the current study analyses the impact pressure response law at different frequencies. On the basis of vortex dynamics, this work explores the evolution mechanism of the vortex flow structure under different excitation amplitudes and frequencies. The exploration reveals the law of dimensionless vortex intensity and energy change. In addition, the relationship between vortex intensity and wall pressure is determined. Studies have shown that the non-linear violent sloshing causes the resonance frequency of the tank to deviate from the natural frequency. When the excitation amplitude intensifies, the range and strength of the vortex structure and the distance from the vortex core to the baffle increase. In such circumstance, the accumulation and dissipation of energy are more evident. In addition, when the excitation frequency is closer to the resonance frequency, the distance between the vortex core and the baffle widens. Moreover, the energy intensity around the baffle increases as the frequency increases. The time history of wall pressure P and vortex intensity Q shows a certain regularity, and the ratio of P_max to Q_max decreases with the increase of the excitation frequency.

The present paper focuses on the simulation of vortex-induced vibration (VIV) of a rigid, smooth circular cylinder with elastic supports subject to a cross-flow at the subcritical regime of Reynolds number, 30,000<Re<80,000. The circular cylinder is allowed to move in one degree-of-freedom (DOF), heave. Unsteady Reynolds-averaged Navier-Stokes (URANS) equations are solved with Menter’s k — ω based Shear Stress Transport based Scale-Adaptive Simulation, SAS-SST, turbulence model, and two-equation transition transport γ — θ model. The transport equations are discretized using the Finite Volume Method (FVM). The numerical amplitude and frequency ratio is compared against the experiments conducted in the Marine Renewable Energy Laboratory (MRELab) at the University of Michigan. The angle in which the computed lift leads the displacement in VIV is compared against experimental results reported by Cornell-ONR Water Channel as well. The existence of the initial, upper, and lower VIV response branches is demonstrated. Wake vortex pattern mode has been studied in the different branches of VIV. The time records of the added mass force coefficient and the vortex force coefficient are obtained. Then, the time-averaged phase angle of the vortex and added mass force coefficients are compared against the experimental results. Lastly, the time records of the phase angle in different branches of VIV are shown and analyzed.

In this paper, a predictive control scheme for dynamic collision avoidance and formation trajectory tracking of autonomous surface vessels (ASVs) was designed. First, a trajectory-tracking nonlinear controller for ASVs was developed in the framework of model predictive control (MPC). Next, to realize leader-follower formation control, a graph topology approach was proposed to maintain a balanced distance between the leader and followers. Then, a set of nonlinear dynamic collision avoidance constraints based on the time to closest point of approach (TCPA) and distance to closest point of approach (DCPA) models was applied as control constraints. Specifically, the ship collision risk index (CRI) was proposed as a collision avoidance constraint for the controller. Simulation studies with various collision avoidance scenarios and predictive horizons were conducted using the dynamic CyberShip II model. The simulation results demonstrate the effectiveness of the proposed codesign scheme for formation tracking control and dynamic collision avoidance. Additionally, the simulation results show that the calculation time of the system was greatly reduced when using a trigger function, with an average calculation time of approximately 0.251 s.

This is the third part of water entry hydro-elastic analysis of clamped sandwich plates with lattice core (CSPLC). In the first and second parts analysis, the engineering prediction model is built to estimate the dynamic responses of CSPLC. To discuss the responses of CSPLC in more detail, the objective of the present work is to investigate the hydro-elastic responses of rectangular, clamped sandwich plates with lattice core (CSPLC) subjected to water entry via combined a novel semi-analytical approach and multi-physical numerical simulation. In the theoretical approach, the hydro-elastic characteristics are quantified by coupling a hydrodynamic water entry model with a first shear displacement model of elasticity for CSPLC. The fluid-structure interaction (FSI) effects of water entry are taken into account by dividing the total impact pressure into the rigid water entry pressure and the interacting pressure. To capture the precise responses of CSPLC, both the global displacement field and the local displacement field are considered in the analytical model. The dynamic governing equations are derived from the energy variation principle and solved by employing the modal approach. Furthermore, the 3D FSI finite element simulation is carried out to get the detailed hydro-elastic characteristics of CSPLC. This engineering semi-analytical model is found to yield accurate results for dynamic responses and offers significant savings in computational cost compared to the FSI simulations. As a comparative study, for a same geometrical stiffened panel, the FSI impact pressure and structural deflection are also given respectively.

With the continuous development of the marine economy and the inland river transport, traditional vessels supervision methods have the shortcomings of short supervision range, small supervision scope, and high cost, which make it difficult to meet the requirements of modern maritime supervision. This paper proposes a novel maritime emergency search system based on unmanned aerial vehicle (UAV) and its landing platform. The system takes the base station with the cruise UAV, as the base point. Subsequently, TDMA system networking technology and wireless bridge communication technology are used to set up a local area network. Then, the improved three-dimensional raster processing is used to search the target waters. After that, several algorithms such as area optimization based on image filtering are applied to classify, integrate, and fit the waters. In addition, the base station distribution scheme and the emergency equipment intelligent management system software are designed to achieve more efficient and convenient management of the system. The system realizes unmanned, visualized, and normalized monitoring and management of the target waters through the coupling of UAV, aerial protection base stations and control terminals, and provides more detailed and accurate information for the development of search and rescue work.

Under the impacts of waves and other marine environment, the jacket offshore platform has an obvious vibration and generates lots of energy. Meanwhile, the platform may suffer fatigue damage. The vibration energy harvesting of a jacket offshore platform under random waves with a nonlinear energy sink (NES) was investigated, and a NES-Energy harvester (NES-EH) was then designed by combining an electromagnetic linear generator with the NES. Moreover, the dynamic model of the NES-EH-offshore platform was built, and the electromagnetic damping and stiffness of the energy harvester were optimized by analyzing the energy capture efficiency and root mean square reduction of the platform displacement. The effects of NES nonlinear stiffness and damping, peak period and effective wave height of irregular waves on the capture power and width of the NES-EH were also analyzed. The results show that nonlinear stiffness and damping of the NES impact the energy capturing efficiency of the NES-EH; the smaller the damping and nonlinear stiffness, the higher the power captured by electromagnetic damping in the NES-EH. Compared with NES, the NES-EH system has a better effect on the vibration control of the platform and can better capture considerable vibration energy.

Based on the evaluation criteria of the impact of different types of reclamation design on the natural environment of coastal waters, the environmental fluid dynamics model was used to simulate the seawater environment in 13 scenarios from three aspects: the shape of the artificial island, the size of inner lake outlet and the layout of the artificial island. The hydrodynamic force and water exchange capacity of these islands were quantitatively compared, and the effects of different artificial islands on the Marine environment were summarized. The planning morphology design guidelines are summarized in four aspects: (1) reduce the serrated steep slope shoreline, avoid forming semi-closed water, and increase the simple and smooth shoreline; (2) reduce the width of the lake mouth to increase the length of the lake; (3) choose a simple alignment parallel to the shore; (4) the design mainly focuses on the morphology of shoreline, followed by consideration of the lake mouth and artificial island arrangement.

This study investigates the trajectory-tracking problem of fully actuated unmanned surface vessels (USVs). A three-degree-of-freedom (3-DOF) dynamic model was used with three control variables: surge force, sway force, and yaw moment, where the model uncertainties, environmental disturbances, and actuator saturation were also considered. An improved nonlinear model predictive control (NMPC) method was investigated to improve the control performance in the trajectory tracking of USVs, and a nonlinear optimization problem based on the finite horizon was developed to minimize the divergence between the actual and the reference states. Moreover, a nonlinear disturbance observer (NDOB) was employed to estimate the environmental disturbance, which could enhance the robustness of the controller. Furthermore, an event-triggered mechanism was also employed to reduce the computational frequency of NMPC. Simulations of slide mode control, NMPC, and improved NMPC were performed in the trajectory-tracking control. Besides, the simulation results verified the effectiveness and robustness of the proposed improved NMPC-NDOB scheme.

The liquified natural gas (LNG) is currently considered an attractive marine fuel in the short- to medium-terms that can lead to the reduction of the shipping industry carbon emissions. LNG fuelled ocean-going ships have been designed by employing either low-pressure or high-pressure fuel systems. This study aims at enhancing the safety of a high-pressure fuel gas supply system (FGSS) designed for ocean-going LNG fuelled vessels. A model-based safety analysis is performed by employing the MADe™ software. The functional model of the baseline design of the investigated system is developed and subsequently employed to carry out the Failure Modes, Effects and Criticality Analysis (FMECA), as well as the quantitative Fault Tree Analysis (FTA). FMECA provided the risk priority number (RPN) for the identified system failure scenarios, the analysis of which leads to the identification of the FGSS critical components. The FTA results, which include the probabilities of the selected top events and appropriate importance metrics, are used for the FMECA results verification. This study results demonstrate that the FGSS critical components include the process valves responsible for supplying either LNG or natural gas to the gas treatment system and consumers respectively, as well as the pressure feedback controllers. Recommendations for design alterations pertain to the addition of pressure sensors and redundancy of the identified critical system components. The derived results demonstrate that impact of these design alterations on the calculated safety metrics are quite considerable, thus enhancing the safety of the baseline design. This study contributes to the safety analysis of FGGS and supports decisions for the designer and operator of LNG fuelled ships.

Floating offshore wind is an emerging technology that holds considerable potential to utilise areas deeper than 60 m for sustainable energy generation. As the floating offshore wind turbine industry continues to develop and grow, the capabilities of established port facilities need to be assessed as to their ability to support the expanding construction and installation requirements. This article assesses current infrastructure requirements and projected changes to port facilities that may be required to support the floating offshore wind industry. Understanding the infrastructure needs will help to identify the port-related requirements. Floating offshore wind turbines can be installed further out to sea and in deeper waters than traditional fixed offshore wind arrays, meaning they can take advantage of stronger winds and additional sea locations. Separate ports are required for substructure construction and fit-out of the turbines and maintenance. Large areas are required, about twice the plan area of the structure, for the laydown of mooring equipment, inter array cables, turbine blades and nacelles. The capabilities of established port facilities to support floating wind farms can be assessed by evaluation of size of substructures, height of wind turbine with regards to the cranes for fitting of blades, distance to offshore site and offshore installation vessel characteristics. Spar, barge, TLP and semisubmersible types have been deployed as demonstration units. Pre commercial units have been installed off the coasts of Portugal and the east coast of Scotland. This article reviews and defines the port and shipyard requirements for floating offshore wind turbines. It will support decision-makers to guide port infrastructure investments and project developers in their site selections. There up to 15 port functions that need to be considered, for construction, assembly and support of offshore activities. These could be fulfilled by one or a combination of different ports.

In order to reduce the flow resistance on the surface of ships, the skin with quasi-periodic elastic supports is designed based on the flexible skin drag reduction technology inspired by dolphin skin. In this paper, the stability characteristic equation of fluid-structure coupling system is established based on small perturbation theory and solved by MATLAB. The results indicate that the skin with quasi-periodic elastic supports has the ability of maintaining stability of turbulent boundary layer when the structural parameters are reasonable. In addition, the drag reduction performance of the skin with quasi-periodic elastic supports is studied by immersion boundary method. The analysis results demonstrate that the skin with quasi-periodic elastic supports can show better drag reduction performance than the skin with periodic elastic supports when the structural parameters q and the support spacing L are rationally set. In a certain speed range, the relative drag reduction rate is up to 72.16%. These optimal distribution parameter data of the skin under certain speed conditions obtained in this paper provide a reference for the practical application and intelligent optimization design of the skin with quasi-periodic elastic supports.

The typical negative effects of prolonged slow steaming operations are investigated in this study. The scope of the research is to examine the effects of the carbon deposit formation on piston rings (lack of sealing function), exhaust boiler (reduction in the heat recovery capacity), turbocharger (lack of scavenging capacity), and injector, due to the prolonged slow steaming operation. It is necessary to identify the holistic adverse effects of the low-load operation on the main engine performance and subsequent components. The study shows that the negative consequences of a long-term slow steaming operation cause noteworthy efficiency degradation in marine diesel engines. The paper aims to clarify the barriers to the efficient operation of marine diesel engines via raising awareness of proper and planned maintenance for sustainable slow steaming. The degradation rates affect the total operational efficiency, CO₂ emissions, and fuel consumption. The study results show that the fuel consumption increases by 1.9%, 2.1%, and 1.9% of daily consumption and the corresponding CO₂ emission increments are 4.36, 4.29, and 3.48 kg CO₂ per nautical mile sailing of the container ship at specified speeds at 65%, 55%, and 45% engine loads, respectively. The efficiency variation leads significant amount of emission increment, while up to 50% decrement will enter into force by April 2022 for container ships. The study gives valuable insight into the increase in CO₂ emissions and fuel after long-term slow steaming for the near future with the stricter emission limits. The results provide considerable information about the deterioration effect on the whole energy system and help to estimate potential efficiency levels for marine diesel engines.

In this study, it was aimed to obtain an accurate extrapolation method to compute lift and drag forces of high-speed vessels at full-scale by using CFD (Computational Fluid Dynamics) based GEOSIM (GEOmetrically SIMilar) method which is valid for both fully planing and semi-planing regimes. Athena R/V 5365 bare hull form with a skeg which is a semi-displacement type of high-speed vessel was selected with a model family for hydrodynamic analyses under captive and free to sinkage/trim conditions. Total drag and lift forces have been computed for a generated GEOSIM family of this form at three different model scales and full-scale for Fr = 0.8 by an unsteady RANS (Reynolds Averaged Navier–Stokes) solver. k–ε turbulence model was used to simulate the turbulent flow around the hulls, and both DFBI (Dynamic Fluid Body Interaction) and overset mesh technique were carried out to model the heave and pitch motions under free to sinkage/trim condition. The computational results of the model family were used to get “drag-lift ratio curve” for Athena hull at a fixed Fr number and so the corresponding results at full scale were predicted by extrapolating those of model scales in the form of a non-dimensional ratios of drag-lift forces. Then the extrapolated full-scale results calculated by modified GEOSIM method were compared with those of full-scale CFD and obtained by Froude extrapolation technique. The modified GEOSIM method has been found to be successful to compute the main forces (lift and drag) acting on high-speed vessels as a single coefficient at full scale. The method also works accurately both under fully and semi-planing conditions.

Reliability has become a greater concern in shipboard systems due to increasing amount of technology level, system complexity, and multiple design demands. Enhancement of the shipboard system’s reliability ensures safe and continuous operation onboard a ship. To enhance the reliability of the shipboard system, it is essential to identify each individual component’s reliability. Within this scope, the onerous task of reliability allocation analysis enhances the reliability of shipboard systems through the optimization of component-based designs, construction, and operations. This study proposes a hybrid reliability allocation methodology based on a hierarchical structure with the integration of an analytic hierarchy process (AHP), data envelopment analysis (DEA), and feasibility of objectives (FOO) methods. The proposed methodology provides reliability allocation analyses for systems with any number of components. The study also examines the usefulness of the adaptation of AHP-DEA into reliability allocation analysis. To demonstrate the applicability of the proposed methodology, a case study on the steering gear system is presented.