Ship Speed Research Articles

Numerical Simulation Flow Around the Containership by using CFD Method

Predict accurately resistance of the ship and flow around ship hull form is extremely important as these are input parameters for optimizing ship hull form, designing the ship propulsion system. This paper focuses on the numerical simulation of the flow around the Container Ship Fortune Freighter in calm water condition at different ship speeds by using CFD method. The results of impact of ship speed on components of ship resistance, wave patterns, volume fraction of air, the distribution of pressure, and wall shear stress on the ship's hull surface, as well as the nominal wake field are provided and analysed in this paper.

Numerical prediction for vertical dynamic anti-sinking performance of underwater vehicle

Computational fluid dynamics (CFD) simulations of an underwater vehicle (UV) during self-propulsion and dynamic anti-sinking maneuvers are presented. A generic submarine, Joubert BB2, was selected as the test model, which was modified by the Maritime Research Institute, Netherlands (MARIN). Different recovery maneuvers for improving the anti-sinking ability were performed when the UV bow cabin was broken. The overset mesh method was used to simulate the deflection of the rudder and stern planes, and a body-force propeller represented by an actuator disk incorporating predetermined propulsion properties provided the thrust and torque for self-propulsion. Extra vector forces of inflow water forces and recovery buoyancy forces were proposed to simulate the flooding of a bow cabin and recover buoyancy by emptying the ballast. Numerical simulations were performed for 20 different combinations of vertical anti-sinking maneuvers, including stern control surfaces, increasing ship speed, and emptying the ballast water. The pitch angle and depth characteristics of UV self-propelled motion were analyzed based on the pre-set anti-sinking criterions. The results indicated stern control surfaces combined with accelerating could effectively maintain the UV's depth and pitch angle, and discharge ballast water could always make it surface quickly. We hope that this study will provide ideas for further research on anti-sinking abilities.

Route, speed, and bunkering optimization for LNG-fueled tramp ship with alternative bunkering ports

To reduce emissions, shipping companies are deploying eco-friendly ships, like those powered by LNG or methanol. Unlike traditional fuels, LNG bunkering is available at a limited number of ports. At the same time, tramp or bulk ships have fewer ports of call on their shipping lines, which may necessitate LNG-fueled ships sailing to alternative bunkering ports for refueling. The selection of bunkering ports impacts the operating costs of shipping lines due to differences in fuel prices and geographical locations. Moreover, it must factor in ship speed limits to meet loading and unloading schedules. To optimize the shipping route, speeds, and bunkering plan for LNG-fueled tramp ships, we develop an arc-based mixed-integer linear programming model with the objective of minimizing total operation costs. Subsequently, we propose a leg-based formulation based on the predetermined port call orders. Finally, case studies are conducted to demonstrate the effectiveness and efficiency of the models. Experimental results indicate that the bunkering mode with alternative bunkering ports effectively reduces total operating costs without altering the total voyage time, particularly with substantial differences in fuel prices between ports.

Study on the influence of ship waves on the dynamic response of floating tidal current power generation device

To study the influence of ship traveling waves on the hydrodynamic performance between the carrier platform and the turbine, the computational fluid dynamics method and the DFBI motion module of STAR CCM+ software were adopted. Under the condition of the coupling of the ship traveling wave and wave current generated at different speeds, the overall motion response of the power plant is simulated. What’s more, the influence of different wave conditions on the heave, pitch, and roll of the carrier platform and the energy efficiency of the turbine is analyzed. The results show that the ship speed has little effect on the carrier heave motion, but the maximum value of the carrier pitch motion increases with the increase in the ship speed. The value of turbine energy acquisition efficiency always decreases with decreasing lateral spacing and increases with decreasing speed. This paper has a certain reference value for the engineering application of floating tidal current power generation equipment.

Testing for biofilm release as a function of simulated ship speed using a calibrated water jet device

Biofouling release coatings (BRCs) have received attention for their potential to limit the negative impacts of biofouling on marine shipping. The calibrated water jet (CWJ, patent # US 8,984,958 B1) can be used to study the effectiveness of BRCs as a function of ship speed. Using a balance of force and linear momentum, we examined the theory and application of the CWJ for simulating the effect of ship speed on biofilm release for surfaces fouled under (1) laboratory and (2) natural conditions. Greater fouling release corresponded with an increase in CWJ pressure and, therefore, simulated ship speed for the surfaces coated with HullKote. The effectiveness of the CWJ was further confirmed for biofilm release from glass fouled naturally by submersion in flow-through seawater. A scaling analysis confirms that the results of these small-scale experiments are applicable to larger-scale biofouling release from ship hulls. This study is the first to utilize the pressure of a CWJ to quantify biofouling release as a function of simulated ship speed.

Numerical investigations of the restriction effects on a ship navigating in pack-ice channel

This paper adopts Computational Fluid Dynamics (CFD) method and Discrete Element Method (DEM) to simulate a ship navigating in pack-ice channel considering the effects of channel restriction. First, from the simulations of the ship sailing in open-water channel by CFD, it is found that the effects of channel width on water resistance is more pronounced than the impacts by level-ice thickness. Then, based on the stable and converged flow field obtained by CFD simulations, the CFD-DEM coupling method is applied to reveal the effects of channel width and level ice thickness on ship-ice-water interactions and ice resistances at different ship speeds. The results indicate that as the channel width decreases, the accumulation of pack ice in the areas of bow and midship intensifies. The ice resistances on the bow and midship increase notably, and the lateral ice forces exhibit pronounced asymmetric and random characteristics. In extremely narrow pack-ice channels, lower ship speed results in lager ice resistance and lateral ice force on the ship. In addition, as the level ice thickness decreases, the pack ice is more easily squeezed below the level ice, resulting in the decreases of ice resistance and lateral ice force.

Analysis of turning ability of large tankers with and without bulbous bow in calm sea and waves

The present study introduces an experimental and numerical investigation of the turning ability of two ships with and without a bulbous bow: original and modified KVLCC2 hulls Experiments are performed via free-running model tests in a square basin, and a system-based simulation are performed. The maneuvering coefficients for the system-based solver are obtained via numerical planar motion mechanism (PMM) tests based on CFD computations, and other variables are obtained from reference ships. The effects of ship speed, wave direction, and wavelength are investigated. Results of a calm-water turning test obtained experimentally and numerically agree well. When the ship turns in the presence of incident waves, the overall behavior and evaluation parameters predicted in the simulation are similar to those obtained from experiments. However, the evaluation parameters show scattered values under severe turning-failure conditions. The most significant wave effects are observed in short waves. Additionally, the turning ability is compared between two ships, and slightly different maneuvering capabilities are observed. The time series for two hulls are further compared to investigate the reason for the difference showing the difference in the force and drift angle time series.

Bi-objective ship speed optimization based on machine learning method and discrete optimization idea

With the introduction of increasingly stringent carbon dioxide (CO2) emission regulations in the shipping industry, shipping companies face significant pressure to reduce emissions while ensuring profitable ship operations. A practical bi-objective speed optimization (BSO) algorithm for container ships is developed based on the variable weight idea, the discrete optimization idea, and the ideal point method to meet the urgent needs of shipping companies to improve operating profits and reduce emissions. By constructing two BSO models of ship main engine fuel consumption-ship sailing time and ship operating costs (SOC)-ship CO2 emissions (SCE), the effectiveness of the BSO algorithm is confirmed through extensive optimization experiments. The results show that compared to the historical sailing results, the BSO reduces the SOC by 4.43 % without causing a significant increase in the SCE, and reduces the SCE by 0.25 %. Moreover, the results demonstrate the effectiveness and feasibility of the BSO in reducing the cost of ship operations while reducing the impact on the environment. The results provide valuable references for shipping companies in the trade-off analysis between economic and environmental benefits and optimization decision-making.

Consequences of the Improved Wave Statistics on a Hull Girder Reliability of Double Hull Oil Tankers

This paper investigates the change in hull girder failure probabilities and partial safety factors caused by the implementation of the new procedure for direct computation of wave loads recommended by the International Association of Classification Societies (IACS). Differences between new and previous procedures are primarily related to the different associated scatter diagrams, and secondarily due to the assumptions on wave spectrum, wave energy spreading, and ship speed. This study performs a comparative structural reliability analysis of the global longitudinal bending of five oil tankers of different sizes between two procedures for wave load computation. Firstly, failure probabilities are compared, and secondly, modified partial safety factors are proposed, resulting in similar failure probabilities according to two separate procedures. It is found that implementation of the new revision of the IACS procedure for direct computation of wave loads results in a reduction of the minimum required ultimate vertical bending capacity of a ship hull by 10%. In addition to the novel investigation of the safety of oil tankers using a revised wave scatter diagram, this study offers a new rapid method for calculation of extreme vertical wave bending moments based on the regression of the parameters of the Weibull function, used for the long-term probability distribution of wave-induced loads.

Investigation of the efficiency of wind-assisted systems using model-based design approach

To achieve the goal of a 50% reduction of CO2 emission in the maritime industry by 2050, different systems and solutions were proposed by researchers. Rigid wind sails, rotor sails, suction wings, and kites were developed to contribute to cleaner and environment-friendly transportation by reducing total fuel and energy consumption. In the present study, a ship dynamics model of KVLCC2 consisting of hull, rudder, propeller, and sailing system was built considering the effects of wind and wave. Firstly, the amount of energy consumption reduction of both systems was examined under different wind directions and wind speeds. It was found that a single sailing system can reduce total energy consumption by up to 10%. Then, the effects of the ship speed, the position of the sailing system, and the number of sails on the reduction of energy consumption were examined. It was found that the amount of overall energy reduction reaches around 23% and 16% when the number of sails was increased to 10 rigid wind sails and 10 rotor sails, respectively. The effects of waves were also investigated, and it was revealed that wave forces decrease the percent energy reduction more when environmental conditions become more severe, starting from the Beaufort scale of 7.

A Framework for Structural Analysis of Icebreakers during Ramming of First-Year Ice Ridges

This paper presents a framework for structural analysis of icebreakers during ramming of first-year ice ridges. The framework links the ice-ridge load and the structural analysis based on the physical characteristics of ship–ice-ridge interactions. A ship–ice-ridge interaction study was conducted to demonstrate the feasibility of the proposed framework. A PC-2 icebreaker was chosen for the ship–ice interaction study, and the geometrical and physical properties of the ice ridge were determined based on empirical data. The ice ridge was modeled by solid elements equipped with the continuous surface cap model (CSCM). To validate the approach, the simulated ice resistance was computed using the Lindqvist solution and in situ tests of R/V Xuelong 2. First, the local ice-induced pressure on the hull shell was determined based on numerical simulations. Subsequently, the local ice pressure was applied to local deformable sub-structural models of the PC-2 icebreaker hull by means of triangular impulse loads. Finally, the structural response of sub-structural models with refined meshes was computed. This case study demonstrates that the proposed framework is suitable for structural analysis of ice-induced stresses in local hull components. The results show that the ice load and the structural response obtained based on the four first-year ice-ridge models show obvious differences. Furthermore, the ice load and corresponding structural response increases with the width of the ridge and with increasing ship speed.

Experimental Analysis of the Influence of the Cross-Section Coefficient on the Ship Squat While the Ship Exits the Shiplift Chamber

Due to the small cross-section coefficient of a shiplift chamber, the hydraulics problem becomes a complex water flow problem in ship operation. To prevent the ship from touching the bottom and ensure the safety of ship navigation and the docking of the chamber, a generalized physical model was used to study the ship squat of a 1000 t ship leaving the chamber. Throughout the experiment, the law of variation law in the ship squat under different chamber widths, water depths, chamber lengths, ship speeds and ship starting acceleration was obtained. In this study, the flow pattern of the ship leaving the chamber was divided into two parts: backflow and bottom flow. According to sensitivity analysis, when the shipping speed was less than 0.9 m/s, the influence of the width of the chamber on the squat was greater than that of the depth of the chamber; when the speed is greater than 0.9 m/s, the influence of the depth of the chamber on the squat was slightly greater than that of the width of the chamber. Based on our theoretical analysis, the basic expression of a ship squat was established.

Identification and detection of high NO x emitting inland ships using multi-source shore-based monitoring data

In urban areas situated along busy waterways like the Yangtze River, the diesel engines of inland navigation ships emerge as significant contributors to air pollution. Among these vessels, certain high-emission ships exhibit considerably higher levels of nitrogen oxides (NOx) emissions compared to others. To effectively identify such ships, this study employed a cost-effective ship emission monitoring sensor platform, comprising high-precision gas sensors, automatic identification system receiver, and sensitive meteorological sensors, along the Yangtze River in Wuhan City. By combining multi-source shore-based monitoring data, we identified ship emission signals and proposed a high-emission ship detection method using inverse modeling. Using this method, we successfully detected inland high-emission ships based on two months of monitoring data. Furthermore, the relationship between different ship types, sizes, speeds, and ship NO x emission rates were investigated. The results of this study are beneficial for strengthening the regulation of high-emission vessels in inland waterways, thereby reducing the adverse impact of ship emissions on the environment and climate. It also encourages the inland shipping industry to adopt more environmentally friendly technologies and fuels, as advocated by the International Maritime Organization.

The analysis of operation and failures of a power plant on high-speed vessels with semi-submersible propellers

Over the past century, shipbuilding has been closely linked to solving the most acute problem of increasing the speed of ships. Builders of high-speed vessels habitually justify this struggle for speed in connection with the requirements of the modern market. In Russia, as well as all over the world, there is a need for modern, high-speed, maneuverable and economical vessels. To meet this need, Almaz Central Design Bureau has developed, the Rybinsk Vimpel Plant has launched a high-speed vessel with semi-submersible propellers of project 12150 "Mongoose". Currently, about 75 ships have been launched [1]. This article analyzes the work of foreign and domestic engines accumulated during the operation of high-speed engines MTU 10V2000M93 (manufactured in Germany), ZVEZDA M470MK-M3 (manufactured in Russia) installed on high-speed vessels of project 12150. In particular, information on the most characteristic failures of the components of the main power plants and the propulsion system as a whole, as well as on the possible causes of the occurrence and development of typical engine failures installed on these high-speed vessels, which allow us to assess the advantages and disadvantages of the power plant used.

A Study on the Ice Resistance Characteristics of Ships in Rafted Ice Based on the Circumferential Crack Method

In previous studies of ship–ice interactions, most studies focused on ship–level ice interactions, overlooking potential rafted ice conditions in extreme ice conditions. The purpose of this study is to develop a numerical model for predicting ship resistance in rafted ice regions. Numerical modeling of rafted ice was carried out using preset grid cells. By comparing the model test results, the accuracy and reliability of the numerical model are verified. On this basis, we undertook the analysis of the impacts of different ice thicknesses, ship speeds, bending strengths, and crushing strengths on the ice resistance of ships under level and rafted ice conditions. The results show that the ice resistance of ships is significantly higher than that of rafted ice under the condition of level ice; however, level ice and rafted ice have different effects on ship ice resistance. Compared with level ice, the ice resistance of ships navigating in rafted ice is more concentrated. The findings of the present research can serve as a technical reference for studies focused on predicting ship resistance in rafted ice regions.

On the data-driven investigation of factors affecting the need for icebreaker assistance in ice-covered waters

Merchant vessels often require icebreaker (IB) assistance to create safe pathways and improve efficiency when navigating in the Baltic Sea. Since IB resources are limited, an accurate estimation on the need for IB assistance is important. Whether IB assistance is needed depends on multiple factors. While practical experience from captains is naturally a source of valuable information for the decision on the need for IB assistance, systematic analysis of the reasoning is limited. The primary aim of this paper is to holistically investigate the influencing factors and their effect on estimating the need for IB assistance through data-driven techniques. Based on a comprehensive list of potential factors, different of data such as traffic history, environmental conditions, and ship specifications are gathered to present complex navigational scenarios. Each scenario is labeled by different navigation modes (independent navigation or IB assistance), laying the foundation for influencing factor identification and effect quantification. Logistic regression is applied to evaluate the effect of the factors on the need for IB assistance. The results show that the impact of the factors is diverse, and ridged ice concentration has the most significant impact. The effectiveness of identified factors is measured by comparing it to that of the factors that have been implemented by the existing studies (e.g., the combination of ice concentration, thickness, and ship ice class, or only ship speed). By considering the factors in this study, the classification performance can be improved by at least 5.6%. The findings in this paper can provide insights for predicting IB workloads and optimizing IB resources and have the potential to support the development of an intelligent decision-support system for winter navigation.

The control method for ship tracking when navigating through narrow and curved sections

A track control method is proposed to solve the problem of manual steering difficulties in narrow and curved sections. The performance of a ship heading controller is affected by various factors, such as delay of the ship steering gear, external environmental disturbances, and variations in ship's speed. Firstly, a Smith optimal PID heading controller is designed. Then, a speed control method based on dichotomous method is proposed to accurately control ship speed and improve the rudder efficiency. Finally, a track control method based on model prediction and feedback compensation is proposed, considering the coupling relationship between course control and speed control. The Lantang Channel is selected as the experimental water area, and comparative simulation experiments are carried out under static water and environmental disturbance. The pre-planned route information is taken as input, and the target course at the current moment is calculated by the guidance method. The target course is used as the input of the course controller to calculate the rudder angle to control the ship's motion, and the new ship position is compared with the planned route information. The above steps are repeated to track the planned route. In order to make the ship pass the curve smoothly, the target speed of the control point is preset according to the sailing convention of decelerating first and accelerating later, and the variable speed time point and variable telegraph are solved by the dichotomy. The results are as follows: (1) The maximum track deviation and speed deviation of the Smith-OP PID are 2 m and 0.21 kn, respectively, without considering environmental interference. The maximum track deviation of the traditional PID is 8 m. (2) The maximum track deviation and speed deviation of the Smith-OP PID are 25 m and 0.27 kn, respectively, under the set environmental interference. The maximum track deviation of the traditional PID is 49 m. (3) The track control method is consistent with the practical practices of "deceleration before acceleration" and "hanging high and taking low". In summary, the track control method can be well applied to narrow and curved sections, and provide a theoretical basis for subsequent research on autonomous navigation and intelligent ships.

Dynamic risk analysis of allision in port areas using DBN based on HFACS-PV

The increased number, speed, and size of ships leads to an increased risk of accidents in ports with restricted navigational areas. A comprehensive risk assessment is required to understand the causal mechanisms involved in accidents. This study investigated the factors causing allision accidents that occurred during ship manoeuvres in the port areas. Nonconformities obtained from 112 allision accident reports were classified qualitatively with the Human Factors Analysis and Classification System for Passenger Vessel Accidents (HFACS-PV) method. Then, temporal and causal relationships between nonconformities were evaluated quantitatively with the DBN method. As a result, the probability of an allision accident and the risk identifying factors (RIFs) affecting allision during port manoeuvres were calculated. Familiarity with the vessel, using the bridge navigation equipment and features of structures in the port area are the riskiest factors leading to allision accidents. The study is thought to contribute at a practical and strategic level to ship owners, ship personnel, pilotage services, port authorities and all relevant stakeholders in understanding the risk of allision accidents occurring in ports and developing preventive regulations.

Ship Speed Optimization Method in Canal Environments Considering Waiting Times for Crossing Locks

The shipping industry faces a pressing challenge with carbon emissions, prompting a focus on speed optimization for energy conservation and emission reduction. While much research has centered on optimizing speeds in oceans and rivers, canals have received less attention, despite their unique challenges of narrow waterways and busy locks. This study fills this gap by establishing a fuel consumption prediction model integrating key environmental factors such as water depth, width, and flow velocity. Drawing upon established methodologies in speed optimization, this study augments these models with waiting time limits for each canal segment. To validate the efficacy of the model, three representative ships are selected as case studies. The findings reveal a high predictive capability of the fuel consumption model, as evidenced by R2 values exceeding 0.97 across all cases. Notably, the optimization approach yields a fuel consumption reduction ranging from 4% to 5% for short waiting times. Furthermore, compared to conventional methods, the proposed optimization strategy achieves an 8.19% enhancement in fuel consumption and carbon emission reduction for long waiting times, culminating in an overall optimization rate of 11.54%. These results underscore the significance of employing the proposed speed optimization methodology, particularly during peak periods of canal congestion.

Propeller and Engine Performance of Commercial Windships: Benefits and Trade-Offs

_ Wind propulsion systems (WPS) for commercial ships can be a key ingredient to achieving the IMO green targets. Most WPS installations will operate in conjunction with propellers and marine engines in a hybrid mode, which will affect their performance. The present paper presents the development of a generic, fast, and easy tool to predict the propeller and engine performance variation, along with the cost, as a function of the wind power installed in two operation conditions: fixed ship speed and constant shaft speed. Specific focus is directed toward showing generic trends and trade-offs that inform economic decision-making. To this end, a key feature of the presented work is the ability to assess the cost–benefit of both controllable pitch propellers and fixed pitch propellers (CPPs and FPPs). This provides advice on when, in terms of WPS installation size, it is worthwhile to install which kind of propeller. CPPs are found to be more suitable for newly built wind-powered ships (>70% wind power), while a conventional FPP is satisfactory for wind-assisted ships (<70% wind power) and retrofitted installations. The results for a 91,373 GT bulk carrier showed that a WPS unloads the propeller and the engine, which leads to an increase in the propulsive efficiency and a detrimental rise of the engine specific fuel oil consumption. However, propeller gains are found to be greater than engine losses, which result in extra savings. Thus, not only does a WPS save fuel and corresponding pollutant emissions, but it also increases the entire propulsive efficiency. Keywords Windship; sailing ship; wind propulsion technologies; propulsion; performance prediction; marine engines; decarbonization; alternative propulsion