Early-stage design assessment of loads such as vertical bending moments can be a critical quantity of interest for design exploration. Traditionally, classification societies’ rules are used to calculate such loads. However, relying solely on these rules for designing new vessels may be insufficient, and conducting direct analyses of a large number of designs to support design exploration is computationally infeasible. Currently, key factors such as wave-induced loads are typically evaluated only in later design stages, where a limited number of promising designs are under consideration. This research explores the potential of harnessing multi-fidelity models for early-stage predictions of wave-induced loads, with a specific focus on wave-induced vertical bending moments. As an initial step in this direction, the vertical bending moment analysis was simplified to consider responses in a regular sea state, where the wavelength matches the vessel’s length. The assessed multi-fidelity models include the application of both linear and nonlinear Gaussian processes and compositional kernels to improve predictions of wave-induced loads, specifically focusing on wave-induced vertical bending moments. The case study focuses on the early-stage exploration of the AXE frigates. Multi-fidelity models were constructed using both frequency- and time-domain methods to evaluate the vertical bending moments experienced by the hull. Finally, a critical reflection is provided on how traditional early-stage design processes can be enhanced by integrating multi-fidelity models.

Submarine power cables (SPCs) are subjected to complex mechanical loadings during service, including tension, bending, torsion, and their combinations. However, systematic studies on the behavior of SPCs – particularly multi-core configurations – under such combined environmental loadings remain limited. This lack of comprehensive analysis hampers a full understanding of their mechanical responses and consequently restricts the design and development of these critical structures. Building upon our previously validated Representative Unit Cell (RUC) model for local mechanical analysis under pure tension and pure bending, this paper extends the investigation to a three-core SPC under a range of combined load cases. In addition, full-scale models are developed to study the torsional response in greater detail. The findings of this study provide valuable guidance for cable engineers, offering new insights into the internal interactions within SPCs and supporting more robust cable design.

As the wind industry expands into remoter and deeper areas of the open sea with abundant wind energy, environmental loadings become harsher. This increases the requirements for submarine power cables (SPCs), which serve as the ‘lifeline’ for transporting electricity. Consequently, a more advanced design based on a thorough understanding of this structure is needed. However, the complex configuration and intensive contact issues within SPCs limit our understanding and make them black boxes for cable engineers. To gain more insights, methods for performing local mechanical analysis of SPCs are necessary. Despite this need, a comprehensive review of existing methods for local mechanical analysis of SPC is still lacking. Therefore, it is essential to review the available methods and provide guidelines for utilizing and developing these methods.

Solid oxide fuel cell systems are considered for the power plant of ships, because of their high efficiency, low pollutant emissions, and fuel flexibility. This research compares the volume, mass, fuel consumption, and emissions of different hybrid power plants for cruise ships using solid oxide fuel cells, fuelled with marine gas oil and liquefied natural gas. A component sizing model allocates the installed power over the selected power plant components and determines their size and weight. The components and energy management strategy are simulated with a cruise ship for five years of operation. A simple method is implemented to estimate the degradation and its effect on component operation. The combined component sizing and time-domain model highlights the importance of dynamic simulation for battery sizing. The results show that using solid oxide fuel cells for the auxiliary consumers can reduce greenhouse gas emissions by 21% and pollutants by 38% to 46% with only 17.5% installed power, which has limited consequences for the cost and size of the power plant. With 31% installed power, the ship can operate in low-emission zones while reducing greenhouse gas emissions by 33% and pollutants by 60% to 70%. Performing all cruise operations requires 51% installed fuel cell power and reduces greenhouse gas emissions by 49% and pollutants by 94% to 96%. In conclusion, the study affirms that solid oxide fuel cell systems, with proper sizing and energy management, can be used to reduce shipping emissions and reach IMO's 30% GHG emission reduction target for 2030.

The complex interplay of numerous helical components within submarine power cables (SPCs), especially those with significant contact issues due to initial residual stress, complicates their modelling and limits our understanding of these structures. In this paper we proposed an effective modelling method designed for the local mechanical analysis of SPCs under bending. The method was developed based on three key aspects: (1) constructing appropriate finite elements to reduce the number of elements required; (2) employing contact damping to address the effects of initial residual stress at contact interfaces; and (3) applying periodic boundary conditions on a repeated unit cell (RUC) to reduce the model size. The accuracy of this method was validated through extensive testing on both single-core and three-core SPC samples, and its efficiency was confirmed by comparing these results with those obtained from traditional full-scale models. Following validation, the model was employed to illustrate the local mechanical behaviours of SPCs under bending, both at the overall level and at the component level. This model serves as a powerful tool for cable engineers, offering deeper insights into the internal interplays of SPCs. All relevant codes developed in this paper are freely available at https://pan-fang.github.io/Codes/.

Submarine power cables in offshore wind farm operate within a complex multiphysics environment. Despite being designed to be both flexible and robust though, their mechanical characteristics are susceptible to variations of thermal field. Bending studies of submarine power cables present challenges rooted in geometry complexity, component contact, and material non-linearity, compounded by the intricate stick–slip mechanism. The difficulty is further intensified when incorporating the thermal impact on material and contact properties. This paper presents a three-dimensional Representative Volume Element (RVE) model for predicting the nonlinear bending stiffness of three-core submarine power cables. The RVE model, developed with constant curvature and periodic boundary conditions, incorporates dashpots to address the stick–slip challenges associated with cable bending. This modeling approach minimizes the required cable length for bending analysis, significantly reducing computational costs. Validation against the bending test of a three-core cable at room temperature, alongside comparison with a 3D full-scale finite element (FE) model, demonstrates the efficiency and accuracy of the proposed RVE approach. Furthermore, the study explores the thermal effect on cable bending, highlighting the capabilities of the proposed RVE model in facilitating thermal–mechanical coupled flexural analysis of submarine power cables. This research contributes to advancing understanding and optimization of submarine power cable design for offshore applications.

The complex structure and material property of a cable, particularly the stick-slip issue among its components pose the challenge for the bending analysis of submarine power cables. The calculation time and convergence problem of a full model makes the simulation unpractical during the design phase. This paper takes advantage of the peculiar structural property of helical components inside a cable, proposing a computational homogenization approach for analyzing the cable behavior under bending from global and local perspectives. This method assumes a macro model that is based on the theory of periodic beamlike structure, and a short-size micro model that is solved through a detailed finite element study. Results demonstrate the efficiency and capability of the proposed model that considers the structure nonlinearity and contact condition of a multi-layer cable with helical wires.

This paper introduces a novel analytical approach aimed at predicting the growth of surface cracks in metallic pipes reinforced with Fibre-Reinforced Polymers (FRPs) subjected to cyclic bending and/or tension loads. The primary objective of this study is to develop a comprehensive analytical model that accounts for multiple factors influencing crack growth, namely stress reduction, crack-bridging effect, stiffness degradation, and fatigue damage of the FRP-to-metal interface simultaneously. By considering these simultaneous effects, our proposed approach enables accurate evaluations of the stress intensity factors (SIFs) at both the surface point and the deepest point of a surface crack. To facilitate practical implementation, we have developed an in-house program that automates crack growth rate and residual fatigue life predictions. The proposed analytical method has been validated through a series of comparisons with experimental data and finite element results, demonstrating its accuracy in estimating fatigue lives. The key novelties of this research lie in the holistic consideration of multiple dominating and influencing factors, the achievement of precise SIF evaluations, and the development of an automated prediction tool for practical applications. Overall, our findings confirm the suitability of the proposed analytical approach for predicting crack growth and provide valuable insights for guiding the design of FRP reinforcement in surface-cracked metallic pipes. This work contributes to advancing the understanding of crack growth behaviour in FRP-reinforced metallic pipes and opens new possibilities for the safe and efficient design of such structures.

Predicting the bending behaviours of a submarine power cable (SPC) is always a tough task due to its complex geometry and inner layer contact, not to mention the stick–slip mechanism. A full-scale finite element model is cumbersome during the early design stage and a more efficient model for practical use is required. Therefore, in this paper, a repeated unit cell (RUC) technique-based FE model is developed, which simplifies the bending analysis of SPCs using a short-length representative cell with periodic conditions. The verification of this RUC model is conducted from cable and component levels, respectively. The cable overall response is validated by the curvature-moment relationships from our cable bending tests regarding four cable samples whose material properties are obtained through a set of material tests. As for the component level, the behaviours of particular components are studied and compared with the results from a full-scale numerical model. Discrepancy is observed between the RUC model and the test, which can be explained by the distinctions of boundary conditions between these two methods. The proposed Cable-RUC model has been found robust and computationally efficient for studying SPCs under bending.

Analysis of ship propulsion system performance is often performed using detailed hydrodynamic models to assess load changes, which are subsequently compared to static engine limits, or by detailed engine models that are rarely integrated with sufficiently detailed propulsion models for load change estimation. To investigate the dynamic engine (overloading) behaviour and ship propulsion performance under various heavy operating conditions, a Mean Value First Principle Parametric (MVFPP) engine model is integrated into a ship propulsion system model in this paper. An upgraded thermodynamic-based MVFPP model for two-stroke marine diesel engines is presented, in particular a newly developed MVFPP gas exchange model. Based on the integrated propulsion system model of a benchmark ocean-going chemical tanker, the engine dynamic behaviour during ship acceleration, deceleration and crash stop has been investigated. Results show that, during dynamic processes, the engine could be thermally overloaded even if the engine power trajectory is inside the static engine operating envelope. The paper contributes to finding proper indicators for thermal overloading of modern two-stroke marine diesel engines. It is demonstrated that when matching the engine with the propeller and designing the ship propulsion control system, not only the static engine operating envelope, but also the dynamic engine behaviour should be considered.