JL
J. Liu
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1
Over the past two decades, a number of methods have been proposed for solving maritime collision avoidance problems. Most of these works take a single ship's perspective and focus on one-to-one or one-to-many situations. To more complicated many-to-many situations, less attention has been paid. To deal with the many-to-many collision avoidance problem, this paper proposes a distributed coordination strategy which consists of two phases: firstly, predictions of ship trajectories are made based on ship dynamics, giving different candidate rudder angles, and potential collision risks that may be caused by each rudder angle selection are evaluated based on calculations of collision risk parameters; secondly, an optimization strategy is adopted to find the most efficient collision avoidance plan for the ships, namely, the rudder angles that each ship should take, and the corresponding operation time for rudder steering, with the overall objective to minimize the sum of time that each ship spends in avoiding collisions with the other ships. Simulation experiments are carried out to evaluate the effectiveness of the proposed method, as well as the corresponding communication and computation costs.
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Over the past two decades, a number of methods have been proposed for solving maritime collision avoidance problems. Most of these works take a single ship's perspective and focus on one-to-one or one-to-many situations. To more complicated many-to-many situations, less attention has been paid. To deal with the many-to-many collision avoidance problem, this paper proposes a distributed coordination strategy which consists of two phases: firstly, predictions of ship trajectories are made based on ship dynamics, giving different candidate rudder angles, and potential collision risks that may be caused by each rudder angle selection are evaluated based on calculations of collision risk parameters; secondly, an optimization strategy is adopted to find the most efficient collision avoidance plan for the ships, namely, the rudder angles that each ship should take, and the corresponding operation time for rudder steering, with the overall objective to minimize the sum of time that each ship spends in avoiding collisions with the other ships. Simulation experiments are carried out to evaluate the effectiveness of the proposed method, as well as the corresponding communication and computation costs.
With the trend towards less-polluting and sustainable transport solutions, the European Commission aims to strengthen the competitive position of inland waterway transport, and to facilitate its integration into synchromodal logistic chains. To stimulate inland waterway transport, it is essential to ensure smooth containers transshipments from seaports to hinterland and vice versa. Currently, inland vessels usually spend unnecessary long times in the port area due to insufficient terminal and quay planning with respect to the sailing schedules of the vessels. Coordination among multiple vessel operators and multiple terminal operators is required in order to improve the efficiency and reliability of inland waterway transport within the port. For this, four recently proposed classes of coordination strategies from our earlier work are reviewed. Two levels of cooperativeness, including partially-cooperative and fully-cooperative, as well as two types of interaction, including single-level and multi-levels are considered. The proposed coordination strategies are compared and evaluated from a methodological perspective and from an information needs perspective. Our results provide insights for vessel and terminal operators in the ways in which they can cooperate with each other: vessel operators can decide to what extent they would like to coordinate their actions based on the information requirements of each coordination strategy; terminal operators can estimate information that should be made available during different coordination phases. Moreover, our results also provide insights for policy makers or practitioners to determine the most suitable coordination strategy under different circumstances.
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With the trend towards less-polluting and sustainable transport solutions, the European Commission aims to strengthen the competitive position of inland waterway transport, and to facilitate its integration into synchromodal logistic chains. To stimulate inland waterway transport, it is essential to ensure smooth containers transshipments from seaports to hinterland and vice versa. Currently, inland vessels usually spend unnecessary long times in the port area due to insufficient terminal and quay planning with respect to the sailing schedules of the vessels. Coordination among multiple vessel operators and multiple terminal operators is required in order to improve the efficiency and reliability of inland waterway transport within the port. For this, four recently proposed classes of coordination strategies from our earlier work are reviewed. Two levels of cooperativeness, including partially-cooperative and fully-cooperative, as well as two types of interaction, including single-level and multi-levels are considered. The proposed coordination strategies are compared and evaluated from a methodological perspective and from an information needs perspective. Our results provide insights for vessel and terminal operators in the ways in which they can cooperate with each other: vessel operators can decide to what extent they would like to coordinate their actions based on the information requirements of each coordination strategy; terminal operators can estimate information that should be made available during different coordination phases. Moreover, our results also provide insights for policy makers or practitioners to determine the most suitable coordination strategy under different circumstances.
Sixty years of research on ship rudders
Effects of design choices on rudder performance
Rudders are primary steering devices for merchant ships. The main purpose of using rudders is to generate forces for course keeping and manoeuvring. In exceptional cases, rudders are also used for emergency stopping and roll stabilisation. Furthermore, rudders affect propeller thrust efficiency and total ship resistance. Therefore, rudders are important to navigation safety and transport efficiency. The performance of rudders depends on the rudder hydrodynamic characteristics, which are affected by the design choices. Scholarly articles concerning the design of rudders date back more than 60 years. Moreover, a lot of knowledge fragments of rudders exist in literature where ship manoeuvrability and fuel consumption are discussed. It is worthwhile to gather this information not only for researchers to advance the state-of-the-art development but also for designers to make proper choices. To have a contemporary vision of the rudders, this paper presents a consolidated review of design impacts on rudder performance in ship manoeuvrability, fuel consumption, and cavitation. The discussed design choices are rudder working conditions (Reynolds numbers and angles of attack), profiles (sectional shapes), properties (area, thickness, span, chord, and rudder aspect ratios), types (the position of the stock and the structural rudder–hull connection), and interactions (among the hull, the propeller, and the rudder). Further research is suggested on high-lift rudder profiles, multiple-rudder configurations and interactions among the hull, the propeller, and the rudder. Recommendations for industry practices in the selection of the rudder design choices are also given.
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Rudders are primary steering devices for merchant ships. The main purpose of using rudders is to generate forces for course keeping and manoeuvring. In exceptional cases, rudders are also used for emergency stopping and roll stabilisation. Furthermore, rudders affect propeller thrust efficiency and total ship resistance. Therefore, rudders are important to navigation safety and transport efficiency. The performance of rudders depends on the rudder hydrodynamic characteristics, which are affected by the design choices. Scholarly articles concerning the design of rudders date back more than 60 years. Moreover, a lot of knowledge fragments of rudders exist in literature where ship manoeuvrability and fuel consumption are discussed. It is worthwhile to gather this information not only for researchers to advance the state-of-the-art development but also for designers to make proper choices. To have a contemporary vision of the rudders, this paper presents a consolidated review of design impacts on rudder performance in ship manoeuvrability, fuel consumption, and cavitation. The discussed design choices are rudder working conditions (Reynolds numbers and angles of attack), profiles (sectional shapes), properties (area, thickness, span, chord, and rudder aspect ratios), types (the position of the stock and the structural rudder–hull connection), and interactions (among the hull, the propeller, and the rudder). Further research is suggested on high-lift rudder profiles, multiple-rudder configurations and interactions among the hull, the propeller, and the rudder. Recommendations for industry practices in the selection of the rudder design choices are also given.
Ship manoeuvrability is fundamental for the navigation safety of ships. Furthermore, through the equipment used for manoeuvring, it also affects investment, operation, and maintenance cost of these ships. Ships are primarily designed from an economic point of view. To ensure and improve the maritime efficiency, research on inland vessel manoeuvrability deserves more attention than the present situation. Most of the research on manoeuvrability has been performed for seagoing ships. Since sailing conditions and ship particulars between seagoing ships and inland vessels are different, the impacts of these differences on manoeuvring prediction and evaluation should be carefully considered.
Inland vessels should be designed in such a way that they should always be capable of manoeuvring without significantly harming the cost-effectiveness of operations. One of the biggest differences between seagoing ships and inland vessels is the rudder configuration. Conventionally, seagoing ships have similar single-rudder configurations while inland vessels have more complex multiple-rudder configurations. Although multiple-rudder configurations can have a positive effect on manoeuvrability, they often have a negative effect on resistance and, therefore, also a negative effect on the fuel consumption.
Quantitative impacts of the rudder configuration on ship manoeuvrability have not been fully understood, especially for multiple-rudder configurations with complex rudder profiles. These differences in the rudder configuration may significantly change the ship manoeuvring behaviours and, therefore, should require further research. Moreover, to compare and evaluate the manoeuvring performance of inland vessels with different configurations, the existing manoeuvring tests and standards for inland vessels are less elaborate than those for seagoing ships. The above-mentioned considerations formulate the following main research question: What are the proper rudder configurations to achieve well manoeuvrable inland vessels without significant loss of navigation efficiency?
The main research question of this thesis can be answered through resolving four key research questions as follows:
Q1. What are the practical manoeuvres to evaluate and compare the manoeuvring performance of inland vessels?
Q2. How does the rudder configuration affect the rudder hydrodynamic characteristics?
Q3. How do changes in the rudder configuration affect the ship manoeuvrability in specific manoeuvres?
Q4. How to choose a proper rudder configuration according to the required manoeuvring performance?
An accurate estimation of rudder forces and moments is needed to quantify the impacts of the rudder configurations on ship manoeuvring performance. This thesis applied Reynolds-Averaged Navier-Stokes (RANS) simulations to obtain rudder hydrodynamic characteristics and integrated the RANS results into manoeuvring models. Additionally, new manoeuvres and criteria have been proposed for prediction and evaluation of inland vessel manoeuvrability. Simulations of ships with various rudder configurations were conducted to analyse the impacts of rudder configurations on ship manoeuvrability in different classic and proposed test manoeuvres. Accordingly, guidance on rudders for inland vessel manoeuvrability has been summarised for practical engineers to make proper design choices.
Through the research presented in this thesis, it is clear that different rudder configurations have different hydrodynamic characteristics, which are influenced by the profile, the parameters, and the type of a specific configuration. New regression formulas have been proposed for naval architects to quickly estimate the rudder induced forces and moments in manoeuvring. Furthermore, an integrated manoeuvring model has been proposed and validated for both seagoing ships and inland vessels. Using the proposed regression formulas and manoeuvring model, the impacts of rudder configurations on inland vessel manoeuvrability have been studied.
The manoeuvring performance of a typical inland vessel can be improved by 5% to 30% by changing the rudder configuration. The rudder configuration should be capable of providing sufficient manoeuvring forces and then optimised to reduce the rudder induced resistance. In general, well-streamlined profiles are good for efficiency but not as good as high-lift profiles for effectiveness. As a summary, the ship manoeuvring performance can be improved by using effective profiles, enlarging the total rudder area, accelerating the rudder inflow velocity, increasing the effective rudder aspect ratios, and enlarging the spacing among multiple rudders.
...
Ship manoeuvrability is fundamental for the navigation safety of ships. Furthermore, through the equipment used for manoeuvring, it also affects investment, operation, and maintenance cost of these ships. Ships are primarily designed from an economic point of view. To ensure and improve the maritime efficiency, research on inland vessel manoeuvrability deserves more attention than the present situation. Most of the research on manoeuvrability has been performed for seagoing ships. Since sailing conditions and ship particulars between seagoing ships and inland vessels are different, the impacts of these differences on manoeuvring prediction and evaluation should be carefully considered.
Inland vessels should be designed in such a way that they should always be capable of manoeuvring without significantly harming the cost-effectiveness of operations. One of the biggest differences between seagoing ships and inland vessels is the rudder configuration. Conventionally, seagoing ships have similar single-rudder configurations while inland vessels have more complex multiple-rudder configurations. Although multiple-rudder configurations can have a positive effect on manoeuvrability, they often have a negative effect on resistance and, therefore, also a negative effect on the fuel consumption.
Quantitative impacts of the rudder configuration on ship manoeuvrability have not been fully understood, especially for multiple-rudder configurations with complex rudder profiles. These differences in the rudder configuration may significantly change the ship manoeuvring behaviours and, therefore, should require further research. Moreover, to compare and evaluate the manoeuvring performance of inland vessels with different configurations, the existing manoeuvring tests and standards for inland vessels are less elaborate than those for seagoing ships. The above-mentioned considerations formulate the following main research question: What are the proper rudder configurations to achieve well manoeuvrable inland vessels without significant loss of navigation efficiency?
The main research question of this thesis can be answered through resolving four key research questions as follows:
Q1. What are the practical manoeuvres to evaluate and compare the manoeuvring performance of inland vessels?
Q2. How does the rudder configuration affect the rudder hydrodynamic characteristics?
Q3. How do changes in the rudder configuration affect the ship manoeuvrability in specific manoeuvres?
Q4. How to choose a proper rudder configuration according to the required manoeuvring performance?
An accurate estimation of rudder forces and moments is needed to quantify the impacts of the rudder configurations on ship manoeuvring performance. This thesis applied Reynolds-Averaged Navier-Stokes (RANS) simulations to obtain rudder hydrodynamic characteristics and integrated the RANS results into manoeuvring models. Additionally, new manoeuvres and criteria have been proposed for prediction and evaluation of inland vessel manoeuvrability. Simulations of ships with various rudder configurations were conducted to analyse the impacts of rudder configurations on ship manoeuvrability in different classic and proposed test manoeuvres. Accordingly, guidance on rudders for inland vessel manoeuvrability has been summarised for practical engineers to make proper design choices.
Through the research presented in this thesis, it is clear that different rudder configurations have different hydrodynamic characteristics, which are influenced by the profile, the parameters, and the type of a specific configuration. New regression formulas have been proposed for naval architects to quickly estimate the rudder induced forces and moments in manoeuvring. Furthermore, an integrated manoeuvring model has been proposed and validated for both seagoing ships and inland vessels. Using the proposed regression formulas and manoeuvring model, the impacts of rudder configurations on inland vessel manoeuvrability have been studied.
The manoeuvring performance of a typical inland vessel can be improved by 5% to 30% by changing the rudder configuration. The rudder configuration should be capable of providing sufficient manoeuvring forces and then optimised to reduce the rudder induced resistance. In general, well-streamlined profiles are good for efficiency but not as good as high-lift profiles for effectiveness. As a summary, the ship manoeuvring performance can be improved by using effective profiles, enlarging the total rudder area, accelerating the rudder inflow velocity, increasing the effective rudder aspect ratios, and enlarging the spacing among multiple rudders.
A good mesh is a prerequisite to achieving reliable results from Computational Fluid Dynamics (CFD) calculations. Relevant mesh properties include mesh types, computation domain shapes and sizes, element sizing, and cell growth rate. However, in literature, no clear consensus about what these properties should be was found. In this article, we strive to determine what the suitable mesh properties are for the analysis of aerofoil-shaped ship rudders as rudder profiles are commonly adapted from aerofoils, for instance, the NACA series. This paper presents a step-by-step study of mesh properties and their impacts on the accuracy of solutions of rudder hydrodynamic coefficients. A classic NACA0012 profile is chosen as an example. Commercial packages ANSYS ICEM and Pointwise are applied for meshing. ANSYS Fluent is used as the numerical solver. Suitable mesh properties are summarised.
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A good mesh is a prerequisite to achieving reliable results from Computational Fluid Dynamics (CFD) calculations. Relevant mesh properties include mesh types, computation domain shapes and sizes, element sizing, and cell growth rate. However, in literature, no clear consensus about what these properties should be was found. In this article, we strive to determine what the suitable mesh properties are for the analysis of aerofoil-shaped ship rudders as rudder profiles are commonly adapted from aerofoils, for instance, the NACA series. This paper presents a step-by-step study of mesh properties and their impacts on the accuracy of solutions of rudder hydrodynamic coefficients. A classic NACA0012 profile is chosen as an example. Commercial packages ANSYS ICEM and Pointwise are applied for meshing. ANSYS Fluent is used as the numerical solver. Suitable mesh properties are summarised.
The manoeuvring performance of inland vessels is even more crucial than that of seagoing ships due to more complex navigation environment. One of the most effective possibilities to improve ship manoeuvrability is to change the rudder configuration. Twin or even quadruple rudders and high-lift profiles are widely applied to inland vessels. When inland vessels equip with multiple rudders, the interaction effects between the rudders affect the hydrodynamic characteristics of each rudder. This paper presents a study on these interaction effects using two-dimensional Reynolds-averaged Navier–Stokes (RANS) methods. Various twin-rudder and quadruple-rudder configurations with different profiles and spacing among the multiple rudders were studied. RANS simulations were performed with a k−ω SST turbulence model and a pressure-based coupled algorithm. Series of NACA, IFS and wedge-tail profiles were tested. Regression formulas have been proposed for the twin-rudder lift and drag coefficients. Finally, interaction effects on multiple rudder hydrodynamics have been summarised.
...
The manoeuvring performance of inland vessels is even more crucial than that of seagoing ships due to more complex navigation environment. One of the most effective possibilities to improve ship manoeuvrability is to change the rudder configuration. Twin or even quadruple rudders and high-lift profiles are widely applied to inland vessels. When inland vessels equip with multiple rudders, the interaction effects between the rudders affect the hydrodynamic characteristics of each rudder. This paper presents a study on these interaction effects using two-dimensional Reynolds-averaged Navier–Stokes (RANS) methods. Various twin-rudder and quadruple-rudder configurations with different profiles and spacing among the multiple rudders were studied. RANS simulations were performed with a k−ω SST turbulence model and a pressure-based coupled algorithm. Series of NACA, IFS and wedge-tail profiles were tested. Regression formulas have been proposed for the twin-rudder lift and drag coefficients. Finally, interaction effects on multiple rudder hydrodynamics have been summarised.
Ship manoeuvrability is important for navigation safety. However, few studies have been specifically carried out for inland vessels. Since most of the empirical methods were generated based on databases of seagoing ships, the usability of these methods for inland vessels is doubtful. The objective of the present work is to assess the existing manoeuvrability models and find the most suitable ones for inland vessels. Furthermore, these models are integrated into a single new model that can predict the manoeuvring behaviour of benchmark inland vessels without extensive experimental tests. The method aims at inland ships of typical dimensions in the Yangtze River (inland ships on European waterways have different dimensions), which is characterised by a large water depth. After preselecting the most promising methods through reviewing literature, a selection of the empirical methods for hull forces and moments is performed by comparing simulation results to model-scale free-running experiments of various turning and zigzag manoeuvres. Considering the large variety of rudder configurations for inland vessels, this paper describes a procedure of using 2D open-water RANS results to calculate the rudder forces and moments. Accordingly, hydrodynamic coefficients of benchmark rudder profiles are provided to apply the proposed procedure for different rudder configurations.
...
Ship manoeuvrability is important for navigation safety. However, few studies have been specifically carried out for inland vessels. Since most of the empirical methods were generated based on databases of seagoing ships, the usability of these methods for inland vessels is doubtful. The objective of the present work is to assess the existing manoeuvrability models and find the most suitable ones for inland vessels. Furthermore, these models are integrated into a single new model that can predict the manoeuvring behaviour of benchmark inland vessels without extensive experimental tests. The method aims at inland ships of typical dimensions in the Yangtze River (inland ships on European waterways have different dimensions), which is characterised by a large water depth. After preselecting the most promising methods through reviewing literature, a selection of the empirical methods for hull forces and moments is performed by comparing simulation results to model-scale free-running experiments of various turning and zigzag manoeuvres. Considering the large variety of rudder configurations for inland vessels, this paper describes a procedure of using 2D open-water RANS results to calculate the rudder forces and moments. Accordingly, hydrodynamic coefficients of benchmark rudder profiles are provided to apply the proposed procedure for different rudder configurations.
The profile of a ship rudder influences the forces it generates, which in turn influence the manoeuvring performance of a ship. Thus, rudder forces and moments should be calculated considering the profile. Instead of an empirical estimation of the rudder normal force coefficient, this paper applies a RANS method to determine the hydrodynamic characteristics of various profiles, i.e. lift and drag coefficients. The RANS method is validated with a classic NACA 0012 profile and applied to 9 profiles from the NACA series, the wedge-tail series, and the IFS series. Furthermore, the 2D open-water RANS results are corrected for the effects of the propeller slipstream and the rudder aspect ratio. New regression formulas of the normal force coefficients are proposed for the tested profiles. These formulas are then integrated into a standard MMG model. Taking the KVLCC2 tanker as a reference ship, the manoeuvring model is validated with free-running tests executed by MARIN. Finally, the manoeuvring performance of the reference ship with various rudder profiles are quantified with turning and zigzag manoeuvres. The simulation results confirm that the wedge-tail series is most effective (largest manoeuvring forces) while the NACA series is most efficient (highest lift to drag ratio) among the tested profiles. The IFS series achieves a balance of effectiveness and efficiency.
...
The profile of a ship rudder influences the forces it generates, which in turn influence the manoeuvring performance of a ship. Thus, rudder forces and moments should be calculated considering the profile. Instead of an empirical estimation of the rudder normal force coefficient, this paper applies a RANS method to determine the hydrodynamic characteristics of various profiles, i.e. lift and drag coefficients. The RANS method is validated with a classic NACA 0012 profile and applied to 9 profiles from the NACA series, the wedge-tail series, and the IFS series. Furthermore, the 2D open-water RANS results are corrected for the effects of the propeller slipstream and the rudder aspect ratio. New regression formulas of the normal force coefficients are proposed for the tested profiles. These formulas are then integrated into a standard MMG model. Taking the KVLCC2 tanker as a reference ship, the manoeuvring model is validated with free-running tests executed by MARIN. Finally, the manoeuvring performance of the reference ship with various rudder profiles are quantified with turning and zigzag manoeuvres. The simulation results confirm that the wedge-tail series is most effective (largest manoeuvring forces) while the NACA series is most efficient (highest lift to drag ratio) among the tested profiles. The IFS series achieves a balance of effectiveness and efficiency.
An accurate estimation of the rudder forces and moments is essential for manoeuvrability prediction. Previous research has shown that ships have different manoeuvring performance in deep and shallow water. Before considering the rudder’s contribution to shallow water manoeuvring, it is meaningful to analyse the shallow water effects on the rudder itself. In shallow water, the rudder gets close to the channel bottom. Therefore, mirror effects are expected, which may greatly affect the rudder effective aspect ratio and the generated rudder forces. Instead of high-cost model tests and time consuming full ship CFD simulations, this paper applies 3D RANS methods to analyse the shallow water effects on rudder hydrodynamic characteristics. 3D RANS simulations are carried out with a pressure-based coupled algorithm through ANSYS Fluent 16.2. The turbulence is simulated by a realisable k-e turbulence model. Based on a NACA 0020 profile, the method is validated through a comparison of the CFD results with the wind tunnel tests. Then, NACA 0020 spade rudders with geometric aspect ratios of 1.2 and 1.5 are tested with different tip clearance. Rudder lift and drag coefficients are generated to calculate the normal force coefficient for manoeuvring simulations. Finally, shallow water effects on rudder hydrodynamics are summarised.
...
An accurate estimation of the rudder forces and moments is essential for manoeuvrability prediction. Previous research has shown that ships have different manoeuvring performance in deep and shallow water. Before considering the rudder’s contribution to shallow water manoeuvring, it is meaningful to analyse the shallow water effects on the rudder itself. In shallow water, the rudder gets close to the channel bottom. Therefore, mirror effects are expected, which may greatly affect the rudder effective aspect ratio and the generated rudder forces. Instead of high-cost model tests and time consuming full ship CFD simulations, this paper applies 3D RANS methods to analyse the shallow water effects on rudder hydrodynamic characteristics. 3D RANS simulations are carried out with a pressure-based coupled algorithm through ANSYS Fluent 16.2. The turbulence is simulated by a realisable k-e turbulence model. Based on a NACA 0020 profile, the method is validated through a comparison of the CFD results with the wind tunnel tests. Then, NACA 0020 spade rudders with geometric aspect ratios of 1.2 and 1.5 are tested with different tip clearance. Rudder lift and drag coefficients are generated to calculate the normal force coefficient for manoeuvring simulations. Finally, shallow water effects on rudder hydrodynamics are summarised.
In order to reach the required manoeuvrability, inland vessels often use twin rudders, but the interaction effects are poorly understood. To achieve a proper configuration, this paper applies 2D RANS simulations to analyse the interaction effects on the twin-rudder hydrodynamics. Various twin-rudder configurations with different profiles and spacing of the rudders are studied. RANS simulations are carried out with a k-w SST turbulence model and a pressure-based coupled algorithm. Commercial CFD package ANSYS Meshing and ANYSYS Fluent are applied as the mesh generator and the numerical solver. Series of NACA, IFS, and Wedge-tail profiles are tested and compared in various configurations. Finally, the interaction effects on twin-rudder hydrodynamic characteristics are summarised.
...
In order to reach the required manoeuvrability, inland vessels often use twin rudders, but the interaction effects are poorly understood. To achieve a proper configuration, this paper applies 2D RANS simulations to analyse the interaction effects on the twin-rudder hydrodynamics. Various twin-rudder configurations with different profiles and spacing of the rudders are studied. RANS simulations are carried out with a k-w SST turbulence model and a pressure-based coupled algorithm. Commercial CFD package ANSYS Meshing and ANYSYS Fluent are applied as the mesh generator and the numerical solver. Series of NACA, IFS, and Wedge-tail profiles are tested and compared in various configurations. Finally, the interaction effects on twin-rudder hydrodynamic characteristics are summarised.