Ship Speed Research Articles

Voyage scheduling and energy management co-optimization in hydrogen-powered ships

The maritime sector is striving to lessen its dependence on fossil fuels, motivated by both economic factors related to fuel efficiency and the policies established by the International Maritime Organization (IMO). Consequently, there has been a growing focus on developing and deploying all-electric ships (AES) as a more sustainable alternative to conventional fossil fuel-powered vessels. AES presents several advantages over conventional ships, including zero emissions, enhanced energy efficiency, and greater sustainability. However, the implementation of AES also brings new challenges, such as the necessity to manage a hybrid microgrid and optimize voyage scheduling. Hybrid fuel cell (FC)-battery energy storage (BES) technology can significantly contribute to addressing these requirements. To tackle these challenges, this article introduces a comprehensive framework for the optimal planning of hybrid microgrids and voyage scheduling in AES. The framework incorporates multi-objective optimization techniques based on genetic algorithms to achieve a balance between cost and voyage time. The proposed framework is applied to a case study of a ship operating on a fixed route between two ports. The simulation results indicated that the total cost per voyage, associated with the objective function of cost minimization and voyage time reduction, has decreased by 12% and increased by 40%, respectively, when compared to the regular ship speed profile. Additionally, the travel time has been reduced by half an hour and 2 h, respectively, in comparison to the regular ship speed profile. To verify the results, the optimization problem for cost and voyage scheduling is also solved by Mayfly Algorithm (MA) separately. Thus, it can be illustrated the effectiveness of the framework in enhancing energy efficiency and fuel economy while preserving the ship's performance.

Numerical simulations of a ship sailing across pack ice area in forward motion under different drafts

Different from the existing CFD-DEM models in which the ship remains stationary, a CFD-DEM model with the ship in forward motion is proposed in this paper to simulate the process of a ship sailing across pack ice area at a forward speed under different drafts. A high-precision method for generating pack ice area on the undisturbed free surface that can be used in conjunction with the proposed model is introduced. Taking an ice-strengthened Panamax bulker as study object, the available model test results are used to verify the reliability of the proposed model, which shows that the model can effectively evaluate the resistance performance and simulate the ship-ice-water interaction. Based on the verified model, the ice resistances on different parts of the hull are first investigated, which reveals that the ice resistance of the bow is most significant, while those of the midship and stern are negligible. Then, the speed dependence of ice resistance under different drafts is studied. It shows a strong nonlinearity under shallow draft, while the nonlinearity gradually weakens as the draft increases. Finally, the proportions of ice resistance and open-water resistance in the total resistance under different drafts and ship speeds are discussed.

A Dynamic Bayesian Network model for ship navigation risk in the Arctic Northeast Passage

The melting of a significant amount of sea ice has enabled the commercial and normal operation of ships in the Arctic. However, the harsh natural environment, unique geographical location and complex navigational conditions pose a serious challenge to the safety of ships during navigation. Ship besetting in ice and ship-ice collision are identified as the most critical risks, potentially resulting in vessel damage, property loss, environmental harm, and even casualties. This study proposes a dynamic Bayesian network (DBN) model to assess and predict the risk of ship besetting in ice and ship-ice collision in five sea areas along the Arctic Northeast Passage. The proposed method comprehensively considers environmental, ship and human factors and incorporates multi-year (2013–2022) marine meteorological reanalysis data and expert knowledge. The developed model has seven time steps and can be updated based on past, current and future conditions. The results indicate that it can effectively reflect the distribution of ship navigation risks in various sea areas and has the capability to be updated in real-time, serving as a tool for guiding ship operations and navigation decisions. At the same time, this study confirms August and September are the optimal navigation periods for the Northeast Passage, and the East Siberian Sea presenting the highest navigation risk. Ice thickness, ice concentration, navigation experience, professional skills, ship speed and ship class are identified as the primary risk factors in the region.

Joint Ship Scheduling and Speed Optimization for Naval Escort Operations to Ensure Maritime Security

Joint Ship Scheduling and Speed Optimization for Naval Escort Operations to Ensure Maritime Security

Real-time simulation of ship overtake maneuvering at different water depths with a ship motion controller

This study aimed to predict ship trajectories in deep and shallow waters in real-time by properly accounting for the effects of hydrodynamic interactions on ship maneuvering. Ship maneuverability and motion control were investigated under hydrodynamic interactions arising from the effects of water depth, ship speed, and lateral distance between interacting ships on parallel courses. The Maneuvering Modeling Group (MMG) model was used, and the hydrodynamic interaction effect was estimated using an efficient three-dimensional potential-flow code that can run in real time. The influence of water depth on ship maneuverability was analyzed. The ship velocity response to the hydrodynamic interactions and maneuvering motion was simulated during the overtaking process of two ships at a range of water depths, lateral distances, and speeds. The findings suggest that, in shallow waters, changing the heading of the ship becomes more difficult, and the course deviation associated with the overtaking maneuver of two ships also increases. A conventional proportional-integral-derivative (PID) controller was employed for course-keeping. When the ratio of the water depth to ship draft was less than 2.0, the PID controller continued to perform effectively for the overtaking ship. For the overtaken ship, the effectiveness of the controller was diminished owing to the relatively low rudder effect at slow speeds.

The local ship speed reduction effect on black carbon emissions measured at a remote marine station

The local ship speed reduction effect on black carbon emissions measured at a remote marine station

A benchmark study on ship speed prediction models in Arctic conditions: machine learning, process-based and hybrid approaches

Ship speed forecasting in harsh and uncertain ice conditions is a core technology enabling Arctic fleet planning at strategical, tactical, and operational levels of maritime logistics. In this benchmark study, we examine five alternative models that differ by their nature (process-oriented, data-driven, and hybrid approaches) and set of predictors (combinations of AIS and ice parameters). To develop these models, AIS data on YamalMax LNG carriers and ice data from diagnostic charts were merged in a joint dataset covering the period 2017–2022. A detailed description of this dataset is given in the article, including spatiotemporal variability of ice parameters and ship speed. Actual and predicted speeds are compared by five statistical indicators not only in the case of speed estimation at a point, but also when calculating average speed over long-distance route segments. The article analyses the difference in accuracy of speed predictions in various geographical areas of the Arctic and during different seasons. The degree of influence of model parameters is estimated using a SHAP approach. Several conclusions about the architecture of forecasting models and their predictors are drawn as a result.

Influence of sea ice on ship routes and speed along the Arctic Northeast Passage

The accelerated melting of sea ice and the growing influx of ships in the Arctic pose significant challenges to navigational safety and the resilient development of the Arctic routes. This study aims to explore the influence of sea ice on ship routes and speed by analyzing the spatiotemporal correlation of Sea Ice Concentration (SIC), Sea Ice Thickness (SIT), Sea Ice Volume (SIV), and Automatic Identification System (AIS) data along the Northeast Passage (NEP) in 2022. Our findings indicate that during the navigation window period (July–October), 115 ships traversed the NEP. It was observed that ships preferred navigating at speeds ranging from 6kn to 14kn when the SIC was below 10% and the SIT was less than 0.1m. Compared with cargo ships and tankers, the trajectory and speed distributions of other ships show greater differences under the influence of sea ice. Furthermore, our results suggest that the SIV, compared to the SIC and SIT, could better reflect the influence of sea ice on ship navigation. These insights are crucial for developing management strategies in Arctic routes.

Numerical analysis of wave slamming on the David Taylor Model Basin 5415 ship model

This paper employs the user-defined function method to define the boundary and analyzes the effects of various ship speeds, wave parameters, and bow structural loads on deck and hull motion responses. When the ship has a wave slamming phenomenon, the water body's height, its response to the slamming load on the deck and superstructure, and hull motion improve the seakeeping performance of the hull model. Analysis of simulation results reveals that peak slamming loads generally increase with higher speeds and wave heights. As speed increases, results oscillate irregularly, affecting the nonlinearity of the slamming load. Additionally, when the wave slamming occurs, the slamming load near the superstructure of the bow model is relatively small. Finally, the numerical modeling method is used to modify the bow area structure, and the simulation analysis is carried out under different incident waves and speeds. The influence of the drift angle on the superstructure is discussed, and beneficial suggestions are provided for the future studies of waves on deck.

Control method for the ship track and speed in curved channels

Due to natural and external influences in curved channels, ships frequently require adjustments in course and speed, posing challenges for existing control methods. Particularly lacking are speed control methods suitable for curved channel navigation. This study initially developed a three-degree-of-freedom MMG model incorporating external interference. It introduced an OP-PID heading controller merging optimal control strategies with traditional PID, adaptable to both external conditions and ship speed, validated through heading control simulations. The study analysed the ship's speed change process, deriving a mathematical expression for advance distance, and proposed a dichotomy-based speed control method to determine speed change points, addressing differential equations with unknown integrands. To mitigate uncertainty errors like parameter inaccuracies in ship maneuvering models and dynamic environmental disturbances, the study proposed a comprehensive control approach. This approach integrates model predictive control, feedback compensation, segment identification, and an enhanced line-of-sight (LOS) guidance method alongside the OP-PID course controller and dichotomy-based speed control. Simulation experiments in the Dongboliao Channel compared the proposed and existing methods. Results demonstrate the proposed method's capability to handle frequent course and speed adjustments effectively, even under model errors and external interference, showcasing superior track deviation and course control accuracy over existing methods.

Nonlinear Robust Stabilization of Ship Roll by Convex Optimization

For ship roll stabilization, this paper presents a nonlinear robust controller design method using the sum of squares (SOS) technique combined with the dual of Lyapunov's stability theorem. Varying ship speed and initial metacentric height are seen as uncertainties, sea waves are regarded as external disturbance, and then the robust nonlinear controller is also designed based on the suggested method. Simulations are performed by taking container ship model as an example. It is shown that the designed system guarantees robust performance with respect to the uncertainties and disturbance.

Four-quadrant propeller hydrodynamic performance mapping for improving ship motion predictions

On the path toward fully autonomous sea vessels, forecasting a ship’s exact velocity and position during its route plays a crucial role in dynamic positioning, target tracking, and autopilot operations of the unmanned body navigating toward predetermined locations. This paper addresses the prediction of the operational performance of a free-running submarine advancing in a straight route (in surge motion). Along with the forward advancing vessel (straight-ahead motion) the study covers all possible scenarios of ship’s surge, including crash-ahead, crash-back, and astern motions. Conventional maneuvering models cannot handle motions other than forward advancement due to the absence of propeller data in all four quadrants of hydrodynamic performance map. This study proposes an approach for predicting submarine performance in all these surge conditions by utilizing four-quadrant propeller performance and resistance test data. We developed an in-house code, SMot4QP, to simulate ship speed and position in the time domain. We obtained satisfying results for the straight-ahead and crash-ahead motions, while the crash-back and astern maneuvers require further refinement due to propeller wake interaction with the hull. The proposed method is capable of predicting the motions of all types of vessels using the ship’s resistance and four-quadrant propeller test results. Thus, SMot4QP offers a fast and robust alternative to computationally expensive free-running self-propulsion simulations for operational performance prediction in broader naval applications.

Microscopic characteristics and influencing factors of ship emissions based on onboard measurements

The sailing environment has a significant impact on the microscopic characteristics of ship emissions. A portable emission measurement system was used to measure and quantify the emission characteristics of two ships using different energy types in the Yangtze River. The effects of the key influencing factors, waterway environment, operating conditions, and fuel type on ship emissions were investigated. The reasonable control of ship speed, acceleration and engine revolution speed and torque can reduce ship exhaust emissions. The use of liquefied natural gas (LNG) can substantially increase CO emissions. The emission levels of the ship during departure and berthing were higher than that during cruising. As an alternative fuel, LNG may increase CO emissions; hence fuel selection requires careful consideration. This study provides key information for the development of effective emission reduction measures and can facilitate the adaptation of inland waterway shipping to low-carbon policies and the mitigation of the associated environmental impacts.

Underwater radiated noise numerical analysis of polar transport vessels under ship-ice-water-air coupling continuous icebreaking based on the S-ALE algorithm

With the gradual opening of the Arctic channel, the underwater radiated noise induced by the ship-ice collision cannot be ignored. However, the underwater radiated noise induced by ship-ice collision is significantly different from that of ships navigating in open water. To explore the response rule of transient underwater radiation noise induced by ship-ice collision, this paper proposes a simplified numerical analysis method of ship-ice collision-induced transient underwater radiated noise in the full frequency band by combining the explicit dynamic method and acoustic analysis method. The ship-ice-water-air coupled collision analysis method based on the S-ALE algorithm is used to simulate and verify the ice load in the process of ship-ice continuous collision at different speeds. Then, the frequency-domain acoustic analysis method is used to predict the transient underwater radiated noise response in the full frequency band under icebreaking excitation and evaluate it by referring to the steady-state underwater radiated noise standard. The results show that the simplified analysis method can effectively predict the transient underwater radiation noise under icebreaking excitation. Under the icebreaking excitation, the radiation shape is irregularly scattered and the radiation direction is concentrated towards the bottom and bow of the ship with the frequency increase. The influence range of transient underwater radiated noise is mainly within 1000 Hz at different speeds, and the variation in the ship's speed affects the amplitude of the sound power level and the smoothness of the periodic response. The synthesized total sound power levels are 172.56 dB (V = 2.0kn), 174.15 dB (V = 2.5kn), 175.70 dB (V = 3.0kn), and 182.49 dB (V = 4.0kn), respectively. According to the comparison with the evaluation standard, it is found that the transient underwater radiation noise induced by ship icebreaking has a greater impact on marine organisms. It should give more detailed requirements within 10–1000 Hz when using relevant standards to evaluate underwater radiated noise induced by polar icebreaking. This paper can provide a reference for the research of underwater radiated noise induced by ship-ice collision and the formulation of relevant standards.

Towards decarbonization: How EEXI and CII regulations affect container liner fleet deployment

This study examines the effects of two pivotal maritime regulations, namely the Energy Efficiency Existing Ship Index (EEXI) and the Carbon Intensity Indicator (CII), implemented by the IMO starting from 2023, on the container-fleet deployment. A mixed-integer programming model is formulated to optimize the fleet deployment with considering the constraints of the above-mentioned regulations and the goal of minimizing operating costs. The findings reveal that the CII regulation leads to a substantial decrease in both ship speeds and carbon emissions concurrently, although there may be an uptick in the number of deployed ships. Conversely, the EEXI has a minor effect on speeds due to the prevalence of slow steaming. Based on research findings, several policy implications are elucidated for shipowners.

Numerical and Experimental Analysis of Lifting Forces of Fin Stabilizers with Fin–Hull Interaction

A fin stabilizer is one of the most effective and frequently used anti-roll devices for maintaining a ship’s operational safety and passengers’ comfort. However, the discrepancy between theoretical hydrofoil-based predictions and the actual dynamic lift force of fin stabilizers due to fin–hull interactions requires more research attention. This study investigates the effect of fin stabilizers on mitigating roll motion through the performance of extensive computational fluid dynamic (CFD) simulations over a range of fin angles and ship speeds. Model tests were carried out to validate the drag and motion results obtained from numerical analyses. The results show that fin stabilizers significantly reduce the roll motion, with the lift coefficient values influenced by the Reynolds number, leading to differences between the theoretical and Reynolds-averaged Navier–Stokes (RANS) calculations. At a high Froude number (Fr), the actual fin lift is about half of the theoretical value. These findings highlight the requirement of selecting an adequate fin area at the predominant ship speeds and ensuring an effective anti-roll effect with fin–hull interaction. This study provides a significant reference for ship design, as well as stabilization system control and optimization.

Sensitivity analysis of parameters impacting the performance of an energy ship using airborne wind energy

This study assesses the impact of different model parameters on the power performance of energy ship systems using point-mass models, focusing on two operational modes. The first mode involves a kite operating in a pumping mode with adjustable tether lengths, aided by additional propellers for ship propulsion. It utilizes a quasi-steady kite model coupled with ship motion’s drag force and velocity triangles. The second mode features a kite pulling the ship, while underwater hydraulic turbines harness energy from ship velocity. Derived from a sail-based model, calculations deploy the force balance equation in line with ship motion, considering the drag forces of the ship and hydraulic turbines, alongside the propulsive force resulting from the kite’s interaction with the ship. The investigated parameters influencing the power performance include kite surface, ship length, wind speed, the angle between the ship’s motion direction and wind direction, and, for the pumping mode, ship speed. The power production of the propulsion mode is generally lower, with differences of at least 72%, depending on the combination of considered parameters.

Integration of Radar Sequential Images and AIS for Ship Speed and Heading Estimation Under Uncertainty

Integration of Radar Sequential Images and AIS for Ship Speed and Heading Estimation Under Uncertainty

Technical and economical comparison of optimized diesel-electric propulsion systems for a pleasure craft

The article compares between them three diesel-electric propulsion and power generation systems, characterized by a similar overall power but with diesel-generator sets very different in number and power; these systems are developed for the needs of an existing pleasure craft. In addition, each system configuration includes two versions, with diesel-generators operating at constant speed and other at variable one. Once defined the used diesel engines type, the characteristics of the six diesel-electric systems have been defined and optimized, by a genetic algorithm, in both design and off design ship speeds. The main performance, weight and cost of the generated systems, with both constant and variable speed diesel-generators, are compared between them and with the pleasure craft current mechanical propulsion system, for different vessel speeds. The comparison results are presented in graphical and tabular form and extensively commented.

HULL REDESIGN AND ITS EFFECT ON THE RESISTANCE OF MANADO PROTOTYPE SMALL PURSE SEINER

This research aims to determine the effect of redesigning the hull of a small purse seine ship on its motion resistance. The research was carried out using a small purse seine ship prototype in Manado by changing the length-breath-depth ratio based on the main dimensions of the ship, resulting in three new hull designs coded K-0 (prototype), K-1, K-2, and K- 3. Maxsurf modeler and Maxsurf resistance were used to run a simulation set of three loading conditions (light, half, full) and speed (low, medium, high). The research results show that changes in ship hull design affect the resistance and thrust of the ship. There is a difference in resistance between the ship with the redesigned hull and the prototype, where the smallest difference is shown by K-3. In addition to changes in hull design, changes in ship loading conditions, Froude number, and ship speed lead to increases in ship resistance and thrust. Based on the average allowance (sea margin or service margin) in shipping lanes, the need for propulsion power and the number of propulsion power vessels K-0 (prototype) and K-3 are still better than K-1 and K-2. Keywords: purse-seiner, resistance, speed, propulsion