Ship Speed Research Articles

Research on AIS Signal Frequency Statistics based on SpringBoot+Vue

With the rapid development of global industry, AIS (automatic identification system) has become an important tool for ship management and safety monitoring. In order to better display the frequency distribution of AIS signals, this paper graphically displays the data in the AIS signals, allowing users to fully understand the data in the AIS signals, including ship type distribution, speed range, and signal frequencies in different areas. It uses Kafka and Flink technology to receive, clean and analyze the sent data, and finally stores it in MySQL and Redis data. It reads the data through Spring Boot + MyBatis, and uses Vue + Echarts chart tool and AutoNavi Map API for display and analysis. To gain an in-depth understanding of its importance and application prospects in the field of epidemics.

Vertical diffusion of bubbles injected beneath a flat-bottomed ship for frictional drag reduction

There has been concern about the short effective distance of frictional drag reduction achieved by air lubrication, but recent model ship experiments have shown over 30 m longer than our expectation. Also, the reduction ratio can be improved through the artificial generation of void waves appearing beneath the hull. These topics relate to the spatiotemporal bubble distribution and an understanding of them requires clarification of the distribution. In this study, optical probes were used to measure the distributions of bubble states beneath a 20-m long flat-bottomed ship towed with 6–8 m/s. The measurements explained the long effective distance of drag reduction and the process of void wave generation and development. The drag reduction ratio was about 7–25% and mainly depended on the void fraction within 10 mm of the hull. The vertical distribution of the void fraction remained unchanged over long downstream distances. The development of void waves was affected by the streamwise velocity difference between bubble clusters near the hull. The velocity was determined by the number density of the bubbles, decreasing to the half of ship speed until reaching a certain number density, 100 per meter in our experiments, and then becoming constant at higher density.

A Bayesian network-based model for risk modeling and scenario deduction of collision accidents of inland intelligent ships

Safety is an important premise and foundation for the operation of intelligent ships. This paper introduces a novel scenario analysis framework that employs disaster system theory to produce more comprehensive results for identifying scenario elements and calculating collision risks for inland intelligent ships. The framework is utilized to investigate the collision accident risk evolution mechanism. This process is incorporated into Bayesian Network (BN) modeling for ship collisions on inland rivers. By comparing the change in occurrence probability and consequence severity of risk factors for inland ship collision accidents with and without selected intelligent technologies, the collision risk of intelligent ships is quantified. The results indicate that the application of intelligent technologies, such as ship speed optimization and situational awareness, can reduce the occurrence probability of collision accidents and mitigate the severity of their consequences. Moreover, it has been discovered that such intelligent technologies have a greater impact on accidents with severe consequences than those with minor consequences. This research provides a framework for the preliminary safety evaluation of inland intelligent ships. It is of great significance to accelerate the improvement of navigational risk prevention and response-ability of inland intelligent ships in the future.

Robust adaptive output feedback for the formation control of heterogeneous ships based on a nonlinear extended state observer

This study considers the formation control problem of heterogeneous ships with unknown time-varying disturbances, dynamic uncertainties, and unmeasurable speeds, a robust adaptive output feedback formation control scheme for the heterogeneous ships based on nonlinear extended state observer is developed. In order to solve the heterogeneous ships formation control problem with leader-following structure, transforming the formation control problem into a class of ship trajectory tracking problem by improving the design of the virtual ship. Firstly, a nonlinear extended state observer is designed for estimating ship speeds due to technical limitations and external disturbances. Then, combining the adaptive neural networks with disturbances adaptive law to deal with the unknown time-varying disturbances and dynamic uncertainties. Meanwhile, the second-order tracking differentiator is designed to calculate the derivative of the virtual control law, which has higher precision comparing to the first-order filter. Stability theory is proved that all the signal of closed-loop control system are uniformly ultimately bounded, and the tracking errors can converge into arbitrary small neighborhoods around zero. Finally, comparative simulations were performed to demonstrate the effectiveness of the proposed controller.

Impact of Port Shallowness (Clearance under the Ship’s Keel) on Shipping Safety, Energy Consumption and Sustainability of Green Ports

In a majority of ports, a ship’s speed is limited for reasons of navigational safety. At the same time, captains and port pilots choose the speed of the ship, but it cannot be higher than the speed allowed in the port. Therefore, the speed of the ship also depends on the experience of the masters and harbor pilots and the sailing conditions in specific situations. Choosing the optimal speed of the ship in the port, considering the hydrodynamic effect of shallow water and the controllability of the ship, can help reduce fuel consumption and ship emissions, which is important for the development of a sustainable port. In all cases, the safety of the shipping is the highest priority. The main objectives of this article are determining the optimal speed of ships in ports with low clearance under a ship’s hull, ensuring navigational safety, reducing fuel consumption and emissions, and creating a sustainable port. This article presents the methodology for calculating the optimal ship speed as the minimum controllable speed, fuel consumption and emission reduction, as well as its implications for sustainable and green maritime transport and port development. The methodology presented has been tested on real ships and using a calibrated simulator, navigating through port channels and port water’s restricted conditions.

A new method for predicting the maximum wave height of ship-generated onshore slopes in restricted channel

The ship-generated wave causes erosive damage to the slopes of inland waterways and confined waters such as the coastal zone. This critical issue is essentially associated with the navigational safety and sustainable development of coastlines, so it is vital to predicting the maximum wave height of the ship-generated wave (Hm) in the coastline of confined waters. The prediction equations of prior research works are mostly based on measured data and multiple regression analysis; however, this paper aims to propose a novel methodology to predict the maximum wave height of ship-generated waves in confined waters. The maximum wave height caused by a self-propelled ship under various conditions with confined water is measured by employing a water flume. Furthermore, the relationships of functions in the prediction model equation are appropriately derived by dimensional analysis, and the prediction equation model is then solved via the particle swarm optimization algorithm (PSOA). The experimental results reveal that the maximum wave height of the ship-generated wave is seriously affected by the water depth of the channel (hc), the navigation speed of the ship (Vc), and the distance from the forecast point to the navigation line of the ship (Sc). In addition, the maximum wave height grows and then lessens, which touches its peak point in the region close to Frh = 1. The dimensionless analysis indicates that the large wave height of the ship-generated wave can be expressed as a function of the channel depth (hc), ship speed (Vc), and the distance from the measurement point to the ship’s navigation line (Sc) as; HmSc=1Frh2f(gScVc 2). Subsequently, the specific prediction equation is determined by a regression model according to the measured data under various working conditions. By adopting the model expression equation, namely, HmFrh2Sc=k1(gScVc 2)k2, the coefficients k1 and k2 are evaluated via the PSOA, and the relationship between the water depth of the channel and the coefficients is suitably outlined to obtain the maximum wave height prediction model equations for ship-generated waves.

Numerical analysis on the seakeeping performances of a full-scale container ship hull using strip theory

The race of taking more cargo on a ship has increased the size of ships as well as other aspects, such as their capacity and structural complexity, which affect the stability of ships. For naval architects and academics, accurately predicting seakeeping performances is difficult. In order to address this, the seakeeping performance of a container ship hall built by Korea Research Institute for Ships and Ocean Engineering (KRISO), i.e., KRISO container ship hall (KCS) is described in this research utilizing a numerical method. Maxsurf software based on strip theory was used to determine the results, where the containership hull was considered and input motions were applied with appropriate boundary conditions. Later, the ship's heading and speed were changed to see the effect of the seakeeping performance of the container ship. The current study is concentrated on systematic comparative research on the investigation of the ship's pitch, heave, and roll movements in irregular waves. It has been found that rolling motion was the highest at 22 kn at the 60° heading angle, potentially affecting ship stability. The significant amplitude analysis indicates that the roll motion is the largest at 60° of wave direction. The pitch motion response and the heave motion are near for each heading angle when the wave frequency exceeds 0.5 and 1 rad/s, respectively. The calculation findings show that seakeeping performance is directly related to ship direction and speed. Furthermore, threatening heading angles during sailing are classified, which could also help in enhancing ship stability.

Effectiveness of Crew Boat Hull Form on Manouvering Performance

The condition of the crew boat is good hull shape with good operational conditions when maneuvering. In this case, the condition of the waveform at sea will have a significant impact on the ship’s motion. To provide the optimal type of hull, it was developed by conducting several simulations on the ship’s motion. Several simulation conditions were carried out, including analyses of ship speed, the shape of the waves formed, and ship maneuvering. At the simulation stage, several types of hulls were carried out, including the single U-hull, the single V-hull, the trimaran, and the catamaran. The simulation limits the length of the ship but not the width of the ship because the conditions in the multi-hull require sufficient space for its width, so that it can be ascertained that it provides effective and efficient results for the selection of the shape of the hull. The simulation analysis carried out provides a recommendation that the single V hull model gives good results compared to other types of hull selection for crew boat hulls.

Convex modelling for ship speed optimisation

Optimising the ship speed depending on the forecast oceanic and atmospheric conditions is an effective operational measure to reduce both fuel consumption and carbon dioxide emissions. In the literature, this optimal control problem (OCP) has been formulated using different types of mathematical models and solved using various optimisation methods. In this paper, we use convex functions to reformulate the models and cast the OCP as a convex optimisation problem. This type of problem can be solved very efficiently and yields the globally optimal solution. As a first step, we assume that the environmental conditions do not vary with time and only depend on the distance along the route. For this case, we show that the convex reformulation of the OCP is accurate and the computation time to solve it is low. Second, we introduce an iterative method to solve the problem under time-varying conditions, drawing inspiration from the literature on hybrid electric vehicles. Whilst this method converges quickly, it does not converge to the global optimum, which was calculated using dynamic programming. We present an artificial scenario to explain why convergence to the global optimum is not guaranteed. Finally, we discuss the implications of our findings for potential future research on this topic.

Influence of propeller fouling on propulsion performance of an actual ship: a long-term analysis focusing on the power for keeping propeller’s rotation of a controllable pitch propeller

This study focuses on the shaft power at the neutral angle of a controllable pitch propeller to analyze the change in the required power due to propeller fouling. It is named and defined as a power for keeping propeller’s rotation (RP) because a propeller does not generate the net thrust to push the hull but dissipates the power to keep its constant speed. Statistical analysis was conducted using a decade of the observed data from a research vessel. This study assumed that the change in RP can be considered as an indicator showing the state of propeller fouling. In addition, the state of fouling on the hull can be estimated indirectly based on RP because the data correlated the shaft power under several operating conditions with RP on the same voyage. The fouling state was classified into three conditions based on RP. The comparison of shaft power at the same ship speed between the clean condition and the serious fouled condition showed that the shaft power was increased by 35% on average due to fouling. When the ship navigates under 10 knots, propeller fouling has a larger impact on the increase in shaft power than hull fouling.

Producing electricity on board a ship in motion or stationary using photovoltaic panels

A very important pillar for the world economy is the transport sector. Nowadays, about 80% of freight transport has been done by sea. Besides the recognized economic efficiency, ships are, unfortunately, an important sources of marine environment pollution. It is well known that the IMO is permanently concerned in maritime safety and many measures have been shown to be successful in reducing ship-sourced pollution. But it is not enough, new solutions must be found, and the answer can come from the direction of green energies (electricity produced from renewable sources). On board ships can be used as renewable energy sources wind energy or solar energy. Solar energy is easier to use because photovoltaic panels can be mounted on board the ship to produce electricity (however, provided that the photovoltaic panels do not increase the ship's forward resistance or reduce its manoeuvrability). Studies have shown that offshore wind energy is much more efficient than a ship-mounted wind turbine because an on-board wind turbine greatly reduces a ship's speed and manoeuvrability. The authors of the paper proposed to study the production of electrical energy obtained with the help of photovoltaic panels on board a ship in motion and stationary. The ship marched in the Mediterranean Sea for two months.

Risk analysis of bridge ship collision based on AIS data model and nonlinear finite element

Abstract To solve the problem of calculating the probability of ship collision in ship bridge collision risk assessment, the impact parameters of ship collision are obtained based on the automatic identification system (AIS) data to solve the problem that the existing methods do not consider the actual navigable ship information in a specific bridge navigation area. Based on AIS data, the dynamics of sailing ships are analyzed, parameters such as ship position, speed, and yaw angle, are obtained, ship traffic flow is analyzed, and the geometric probability in the actual ship traffic flow specification model is modified. The results before and after correction were compared and analyzed. The results show that the maximum transverse displacement of the anti-collision device is about 1.5 s under all working conditions, indicating that the collision force drops continuously from this moment to 0 in the collision force time history. In the process of collision, the anti-collision device absorbs part of the collision energy through its own deformation. Under the premise of a certain initial kinetic energy, the deformation caused by the collision energy absorption after fortification will be reduced. The anti-collision device has local permanent deformation under the impact of 5,000 t ship, but no damage and failure, and will not cause water entry and subsidence. It proves that the constructed fishery ship collision risk assessment model and the developed fishery ship safety management and evaluation system are reliable and the prediction results are credible, which can provide scientific methods for the safety management and evaluation of fishery vessels. For the bridge area with complicated ship navigation conditions, it is necessary to use the actual navigable ship information obtained based on AIS data to estimate the distribution of ships in the bridge area to improve the accuracy of the calculation results.

Study on the Resistance of a Large Pure Car Truck Carrier with Bulbous Bow and Transom Stern

The resistance of a large Pure Car Truck Carrier (PCTC) with a bulbous bow and a transom stern is evaluated in the present paper. Several cases at nine different ship speeds in calm water are simulated and results are compared with the experimental measurements. The maximum relative error is 0.93% at a Froude number (Fr) of 0.209. The total resistance coefficient of the ship in calm water shows a parabolic trend with increasing Fr, and it reaches a minimum value at Fr = 0.1794. Furthermore, the cases of the ship in regular waves with six different wavelengths and three wave heights are simulated. It is observed that the total resistance exhibits a quadratic relationship with the wavelength when the wave height is fixed. The wave-making resistance increases with the increase in wave height at any fixed wavelength, and it reaches a maximum value when the wave-length is 1.2 times the ship length (Lpp). Additionally, we also investigated the resistance in three different sea states at four different speeds. When the significant wave height of irregular waves is the same as regular waves, the wave-making resistance under irregular waves is much smaller than that of the regular waves. All of these results indicate that the bulbous bow and transom stern can reduce the wave-making and residuary resistances, which can provide a useful reference for the subsequent design and manufacturing of related ships.

A graphical collision alert system of power-driven ship in sight situations considering geometric encounter situations

This paper proposes a power-driven ship collision alert model considering geometric encounter situations in sight situations by collecting the natural environment, ship static and dynamitic information. The kernel of the proposed method is to introduce a ship geometric encounter model to determine the ship encounter situation and to identify the influencing factors, including ship position, ship speed and ship heading, by considering ship-ship collision situations. These factors, together with ship static parameters and natural environment, are treated as input variables to derive the collision risk through a fuzzy inference system. The merit of developed model is that the relative bearing, collision distances and relative course are intuitively described by graphical user interface, which can assist the crew well understand the decision of machine and can be applied to human-machine collaboration for intelligent ship (e.g. remotely control ship). Moreover, from further analysis, the nearest point and the actions taken at the nearest point provide a useful alert for collision risk. From these analyses, the proposed model can be used to improve ship handling and reduce the probability of collision during ship encounters.

Seakeeping Behaviour of a Flettner Rotors-Propelled Catamaran in Beam Waves

This paper deals with the seakeeping of a catamaran propelled by Flettner rotors. The case study is an energy ship. The prediction of the roll motion of such a ship is of particular interest since she will mostly sail in beam seas. We used a numerical model based on the boundary element method to deal with the interactions of the ship with waves. It is supplemented by a model for the aerodynamic damping effect due to the rotors, the gyroscopic effects from the rotors and by the ITTC correction for roll damping. In the present study, it has been assumed that the Flettner rotors can be modelled as a distribution of elementary airfoils whose lift and drag depend on the local apparent wind speed. Interaction effects between the rotors and between the hull and rotors have been neglected. Regular waves have been investigated. For the considered case study, it is found that the Flettner rotors can have a small destabilizing effect or a small stabilizing effect on the ship motion depending on the ship speed and the rotors’ rotational speed.

Modelling of the water on deck problem for an offshore supply vessel running in regular astern waves

The motion of trapped water on the weather deck of an offshore supply vessel running in regular astern seas is modelled using shallow water equations. The inflow and outflow through the weather deck openings and over the bulwarks are modelled using boundary conditions in the flow domain. The hyperbolic flow equations are numerically solved using a higher-order finite volume method. The prescribed motion data for the weather deck is obtained directly from systematic model experiments. Simulated results of the deck water motion are compared against monitored data from the experiments, recorded using a system of pressure sensors and cameras placed on the weather deck. Additionally, the moment caused by the motion of the trapped water and its variation with the ship speed are investigated.

Joint optimization of ship speed and trim based on machine learning method under consideration of load

The maritime sector has diligently endeavored to mitigate fuel consumption to curtail emissions and expenditures within the sustainable development framework. To comprehensively analyze ships’ fuel consumption, considering the combined influence of multiple factors, we develop an integrated optimization approach encompassing speed, trim, and speed–trim adjustments under different loading conditions. Firstly, we employ the fuel consumption prediction models established before, conduct a detailed analysis of the ship’s route in distinct segments, and formulate optimization models by scrutinizing the ship’s actual voyage. Secondly, we conducted single-parameter optimization for speed and trim to achieve the minimum fuel consumption for the entire route. We also implemented a joint optimization approach for simultaneously optimizing speed and trim to enhance fuel efficiency further. Lastly, we applied a smoothing method to the model’s prediction results to solve the step problem; and compared the optimization results before and after smoothing to assess the approach’s effectiveness. The results show that the joint optimization in the ballast condition yielded fuel consumption savings of 12.30% and 11.70% before and after smoothing, respectively; The fuel savings achieved under full load conditions were 10.18% and 9.47%. Demonstrate that joint optimization can overcome the limitations of single parameter optimization and enhance the fuel-saving rate.

A Novel Ship Speed and Heading Estimation Approach Using Radar Sequential Images

This paper proposes an approach to estimate ship dynamic features (i.e., speed and heading) using radar sequential images, which can be used to assess the ship-ship collision risk in vessel traffic service (VTS) center. The proposed approach estimates the ship speed and heading in three steps, including ship detection, tracking, and data fusion. First, the ship target, together with its center coordinate, is detected by introducing the background subtraction detector in each radar image. Second, the ship position in one frame is mapped to the consecutive frame, and ship trajectory distribution is established using the Kalman filter and Hungarian algorithms. Third, fuzzy logic is introduced to fuse data from radar and AIS. Specifically, input variables include two parameters, which are the ship speed/heading difference in consecutive frames using radar and AIS, respectively. The variance of ship speed distribution is 1.30 at 10s sampling frequency, and the variance of ship heading distribution is 26.53, the experimental results indicate that the proposed approach can accurately estimate ship speed and heading in the radar sequential images of the Yangtze River. The strength of the proposed approach is its capability to estimate the ship speed and heading quantitatively from radar sequential images, which is interactive and interpretable for VTS operators.

Assessment of ship speed, operational carbon intensity indicator penalty and charterer profit of time charter ships

The operational carbon intensity indicator (CII) proposed by the International Maritime Organization (IMO) has been officially implemented on January 1, 2023. As an important way of ship operation, applicable time charter ships are subject to the CII regulation. How to properly deal with the CII regulation is a challenge for the shipowner and charterer of time charter ships. Speed reduction is an effective measure to reduce carbon emissions and carbon intensity of ships. This study establishes a speed model including CII penalty for time charter ships. Results show that speed reductions of a time charter ship of 10 %, 20 % and 30 % reduce carbon emissions by 27.1 %, 48.8 % and 65.7 % and carbon intensity by 19 %, 36 % and 51 %, respectively. Speed reduction leads to reductions of carbon emissions, carbon intensity and CII penalty, with greater reductions for larger ships. Under the optimal charterer profit, the speed of a time charter ship increases with the rise of freight rate and reduces with the decrease of freight rate. When the fluctuation range of freight rate is the same, the larger the ship type is, the smaller the speed adjustment range is. For the same ship type, when its freight rate decreases, it is suggested that the charterer reduces speed; otherwise, it is suggested that the charterer increases speed. For different ship types, if the shipping market is booming, the charterer should charter more large ships; otherwise, the charterer can choose more small ships.

Physics-informed machine learning models for ship speed prediction

This paper proposes a novel physics-informed machine learning method to build grey-box model (GBM) predicting ship speed for ocean crossing ships. In this method, the expected ship speed in calm water is first modeled by the physics-informed neural networks (PINNs) based on speed-power model tests. Then the eXtreme Gradient Boosting (XGBoost) machine learning algorithm is integrated to estimate ship speed reduction under actual weather conditions. The proposed GBM has been compared against the traditional black-box model (BBM) using performance monitoring data from two ships. The results show that when the amount of data is sufficient for modeling, the GBM can increase the accuracy of speed prediction by about 30%. When data volume is limited, the GBM can also significantly improve the prediction results. Finally, the GBM is validated by checking its implementation for the ETA predictions of cross-Pacific or North Atlantic voyages. The highest cumulative error of sailing time estimated by the GBM is 5 h among all the study cases.