Rudders

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Stephen R. Turnock - One of the best experts on this subject based on the ideXlab platform.

  • Energy efficiency of ship propulsive systems: rudder-propeller interaction
    Ship Propulsion Systems Conference, 2010
    Co-Authors: Stephen R. Turnock, A. G. Molland
    Abstract:

    The rudder of a ship is used to maintain its direction and for changing course. As such the goal of rudder design is to maximise sideforce for control of course while minimising resistive drag. Ship Rudders are typically mounted downstream of the propeller to take advantage of the higher speed flow in the propeller race. This flow also has a swirl component that results in a complex flow regime arriving at the rudder. Likewise, the presence of the rudder has an influence on the flow speed and direction passing through the propeller. It is therefore recommended that design of the propulsive system incorporates the rudder design. This will ensure that appropriate decisions are made that maximise the net propulsive thrust for a given engine power. We examine in this paper how the design of the combined propeller-rudder system can be best achieved for a goal of maximising propulsive efficiency without sacrificing the ability to manoeuvre. The design of the rudder requires careful thought as to its longitudinal, lateral and vertical position. The swirl component of propeller race results in a force distribution over the rudder that can give a net propulsive thrust by extracting energy from the flow rotation. Such effects can be used to compensate for the resistive drag of the form and surface area of the rudder itself. Design of Rudders are often based on evolutionary principles that will not capture the subtleties necessary to enhance propulsive efficiency. We discuss a hierarchy of computational analysis tools that includes unsteady solution of the Navier Stokes equations, their coupling with propeller blade element momentum analysis and use of surface panel and lifting line theories to understand rudder forces. Such techniques are suitable for design optimization. Conventionally it is the rudder structural strength and associated cost of construction that limits the types of Rudders that can be designed. Recent work on a variety of twisted Rudders has shown that there can be significant performance gains. For more radical shapes the use of suitable composite construction will give cost-effective performance while also reducing rudder mass as well. We show through three case studies related to: (1) twisted Rudders, (2) cathodic protection and (3) the influence of the rudder on kite assisted ship propulsion; that to achieve improved propulsive performance all that is required is greater care and attention to the rudder design process. Such design detail will more than cover its cost in fuel savings and the resultant reduced engine emissions

  • Marine Rudders and Control Surfaces
    Marine Rudders and Control Surfaces, 2007
    Co-Authors: A. G. Molland, Stephen R. Turnock
    Abstract:

    This book guides naval architects from the first principles of the physics of control surface operation, to the use of experimental and empirical data and applied computational fluid dynamic modelling of Rudders and control surfaces. The empirical and theoretical methods applied to control surface design are described in depth and their use explained through application to particular cases. The design procedures are complemented with a number of worked practical examples of rudder and control surface design. The online companion site contains an extensive modelling data library, plus software for theoretical control surface design, based on over 25 years of world-class research at the University of Southampton, an incredible resource for engineers in this field. • The only text dedicated to marine control surface design • Provides experimental, theoretical and applied design information valuable for practising engineers, designers and students • Accompanied by an online extensive experimental database together with software for theoretical predictions and design development

  • marine Rudders and control surfaces principles data design and applications
    2007
    Co-Authors: A. G. Molland, Stephen R. Turnock
    Abstract:

    • The only text dedicated to marine control surface design • Provides experimental, theoretical and applied design information valuable for practising engineers, designers and students • Accompanied by an online extensive experimental database together with software for theoretical predictions and design development This book guides naval architects from the first principles of the physics of control surface operation, to the use of experimental and empirical data and applied computational fluid dynamic modelling of Rudders and control surfaces. The empirical and theoretical methods applied to control surface design are described in depth and their use explained through application to particular cases. The design procedures are complemented with a number of worked practical examples of rudder and control surface design. The online companion site contains an extensive modelling data library, plus software for theoretical control surface design, based on over 25 years of world-class research at the University of Southampton, an incredible resource for engineers in this field.

  • Wind tunnel tests on the influence of propeller loading and the effect of a ship hull on skeg-rudder performance
    1995
    Co-Authors: A. G. Molland, Stephen R. Turnock, J.e.t. Smithwick
    Abstract:

    The results of wind tunnel tests on a rudder operating downstream of a propeller and hull combination are presented. The tests used the 3.5m x 2.5m low speed wind tunnel at the University of Southampton. This report presents the results for two Rudders, one all-movable the other a semi-balanced skeg-rudder. The Rudders both have a mean chord of 667mm and NACA 0020 sections, but with varying taper ratio. A four bladed, 800mm diameter, adjustable pitch propeller was used. This propeller is a modified version of the Wageningen B4.40 series. Open-water results for the modified design were validated against published data. The rudder propeller combinations were tested both in a freestream and in way of a representative Mariner stern hull form. The test consisted of a series of parametric studies into the effect of the longitudinal and lateral distance between the propeller and rudder, propeller thrust loading, presence of a hull, and presence of a hull at a yaw angle. A five-component strain-gauge dynamometer was used to measure lift, drag and three moments on the rudder. A rotating strain gauge dynamometer measured the developed thrust and torque of the propeller. In addition, both spanwise and chordwise pressure distributions were measured on the rudder and hull surface to provide a detailed knowledge of the distribution of forces over the hull and the rudder. A tunnel wind speed of 10m/s was used and propeller revolutions were varied between 0 and 2100 rpm. Results are presented in the form of non-dimensional coefficients of lift (C subscript L), drag (C subscript D), spanwise (CP subscript S) and chordwise (CP subscript C) position of the centre of pressure variation with incidence for the rudder. The influence of rudder on propeller performance is given in terms of non-dimensional thrust (K subscript T) coefficient variation with advance ratio (J). The surface pressure measurements on the rudder are presented as both a spanwise distribution of the local lift coefficient and as a surface pressure distribution. The surface pressure measurements on the hull are presented as spanwise and chordwise distritbutions together with integrated normal force coefficient over the range of rudder angles. The results provide data data for detailed rudder design, for numerical modelling of the rudder/propeller and hull interaction problem and for use in manoeuvring simulations.

  • Wind tunnel tests on the influence of propeller loading on ship rudder performance: four quadrant operation, low and zero speed operation
    1993
    Co-Authors: A. G. Molland, Stephen R. Turnock
    Abstract:

    The results of wind tunnel tests on a rudder operating downstream of a propeller are presented. The experiments simulated the condition of a rudder operating in the proximity of a propeller but without the influence of the hull. The tests were carried out in the 3.5m x 2.5m wind tunnel at the University of Southampton and form an extension to the basic rudder-propeller tests which have already been carried out and are reported on elsewhere. The Rudders tested were all movable, and the propeller used in the tests was modelled on a Wageningen B4.40. Tests were carried out with positive and negative wind speed and positive and negative propeller revolutions in order to simulate all the four quadrants of operation. These tests also included the case of zero and low wind speed. Results are presented as rudder lift, drag and moment coefficients and centre of pressure for selected angles of attack and changes in propeller thrust loading. Surface pressure distributions over the rudder were also obtained in selected cases in order to provide a detailed knowledge of the distribution of forces over the rudder. The results provide rudder force data for use in manoeuvring simulations and detailed data for the validation of numerical modelling of the interaction problem.

A. G. Molland - One of the best experts on this subject based on the ideXlab platform.

  • Energy efficiency of ship propulsive systems: rudder-propeller interaction
    Ship Propulsion Systems Conference, 2010
    Co-Authors: Stephen R. Turnock, A. G. Molland
    Abstract:

    The rudder of a ship is used to maintain its direction and for changing course. As such the goal of rudder design is to maximise sideforce for control of course while minimising resistive drag. Ship Rudders are typically mounted downstream of the propeller to take advantage of the higher speed flow in the propeller race. This flow also has a swirl component that results in a complex flow regime arriving at the rudder. Likewise, the presence of the rudder has an influence on the flow speed and direction passing through the propeller. It is therefore recommended that design of the propulsive system incorporates the rudder design. This will ensure that appropriate decisions are made that maximise the net propulsive thrust for a given engine power. We examine in this paper how the design of the combined propeller-rudder system can be best achieved for a goal of maximising propulsive efficiency without sacrificing the ability to manoeuvre. The design of the rudder requires careful thought as to its longitudinal, lateral and vertical position. The swirl component of propeller race results in a force distribution over the rudder that can give a net propulsive thrust by extracting energy from the flow rotation. Such effects can be used to compensate for the resistive drag of the form and surface area of the rudder itself. Design of Rudders are often based on evolutionary principles that will not capture the subtleties necessary to enhance propulsive efficiency. We discuss a hierarchy of computational analysis tools that includes unsteady solution of the Navier Stokes equations, their coupling with propeller blade element momentum analysis and use of surface panel and lifting line theories to understand rudder forces. Such techniques are suitable for design optimization. Conventionally it is the rudder structural strength and associated cost of construction that limits the types of Rudders that can be designed. Recent work on a variety of twisted Rudders has shown that there can be significant performance gains. For more radical shapes the use of suitable composite construction will give cost-effective performance while also reducing rudder mass as well. We show through three case studies related to: (1) twisted Rudders, (2) cathodic protection and (3) the influence of the rudder on kite assisted ship propulsion; that to achieve improved propulsive performance all that is required is greater care and attention to the rudder design process. Such design detail will more than cover its cost in fuel savings and the resultant reduced engine emissions

  • Marine Rudders and Control Surfaces
    Marine Rudders and Control Surfaces, 2007
    Co-Authors: A. G. Molland, Stephen R. Turnock
    Abstract:

    This book guides naval architects from the first principles of the physics of control surface operation, to the use of experimental and empirical data and applied computational fluid dynamic modelling of Rudders and control surfaces. The empirical and theoretical methods applied to control surface design are described in depth and their use explained through application to particular cases. The design procedures are complemented with a number of worked practical examples of rudder and control surface design. The online companion site contains an extensive modelling data library, plus software for theoretical control surface design, based on over 25 years of world-class research at the University of Southampton, an incredible resource for engineers in this field. • The only text dedicated to marine control surface design • Provides experimental, theoretical and applied design information valuable for practising engineers, designers and students • Accompanied by an online extensive experimental database together with software for theoretical predictions and design development

  • marine Rudders and control surfaces principles data design and applications
    2007
    Co-Authors: A. G. Molland, Stephen R. Turnock
    Abstract:

    • The only text dedicated to marine control surface design • Provides experimental, theoretical and applied design information valuable for practising engineers, designers and students • Accompanied by an online extensive experimental database together with software for theoretical predictions and design development This book guides naval architects from the first principles of the physics of control surface operation, to the use of experimental and empirical data and applied computational fluid dynamic modelling of Rudders and control surfaces. The empirical and theoretical methods applied to control surface design are described in depth and their use explained through application to particular cases. The design procedures are complemented with a number of worked practical examples of rudder and control surface design. The online companion site contains an extensive modelling data library, plus software for theoretical control surface design, based on over 25 years of world-class research at the University of Southampton, an incredible resource for engineers in this field.

  • Wind tunnel tests on the influence of propeller loading and the effect of a ship hull on skeg-rudder performance
    1995
    Co-Authors: A. G. Molland, Stephen R. Turnock, J.e.t. Smithwick
    Abstract:

    The results of wind tunnel tests on a rudder operating downstream of a propeller and hull combination are presented. The tests used the 3.5m x 2.5m low speed wind tunnel at the University of Southampton. This report presents the results for two Rudders, one all-movable the other a semi-balanced skeg-rudder. The Rudders both have a mean chord of 667mm and NACA 0020 sections, but with varying taper ratio. A four bladed, 800mm diameter, adjustable pitch propeller was used. This propeller is a modified version of the Wageningen B4.40 series. Open-water results for the modified design were validated against published data. The rudder propeller combinations were tested both in a freestream and in way of a representative Mariner stern hull form. The test consisted of a series of parametric studies into the effect of the longitudinal and lateral distance between the propeller and rudder, propeller thrust loading, presence of a hull, and presence of a hull at a yaw angle. A five-component strain-gauge dynamometer was used to measure lift, drag and three moments on the rudder. A rotating strain gauge dynamometer measured the developed thrust and torque of the propeller. In addition, both spanwise and chordwise pressure distributions were measured on the rudder and hull surface to provide a detailed knowledge of the distribution of forces over the hull and the rudder. A tunnel wind speed of 10m/s was used and propeller revolutions were varied between 0 and 2100 rpm. Results are presented in the form of non-dimensional coefficients of lift (C subscript L), drag (C subscript D), spanwise (CP subscript S) and chordwise (CP subscript C) position of the centre of pressure variation with incidence for the rudder. The influence of rudder on propeller performance is given in terms of non-dimensional thrust (K subscript T) coefficient variation with advance ratio (J). The surface pressure measurements on the rudder are presented as both a spanwise distribution of the local lift coefficient and as a surface pressure distribution. The surface pressure measurements on the hull are presented as spanwise and chordwise distritbutions together with integrated normal force coefficient over the range of rudder angles. The results provide data data for detailed rudder design, for numerical modelling of the rudder/propeller and hull interaction problem and for use in manoeuvring simulations.

  • Wind tunnel tests on the influence of propeller loading on ship rudder performance: four quadrant operation, low and zero speed operation
    1993
    Co-Authors: A. G. Molland, Stephen R. Turnock
    Abstract:

    The results of wind tunnel tests on a rudder operating downstream of a propeller are presented. The experiments simulated the condition of a rudder operating in the proximity of a propeller but without the influence of the hull. The tests were carried out in the 3.5m x 2.5m wind tunnel at the University of Southampton and form an extension to the basic rudder-propeller tests which have already been carried out and are reported on elsewhere. The Rudders tested were all movable, and the propeller used in the tests was modelled on a Wageningen B4.40. Tests were carried out with positive and negative wind speed and positive and negative propeller revolutions in order to simulate all the four quadrants of operation. These tests also included the case of zero and low wind speed. Results are presented as rudder lift, drag and moment coefficients and centre of pressure for selected angles of attack and changes in propeller thrust loading. Surface pressure distributions over the rudder were also obtained in selected cases in order to provide a detailed knowledge of the distribution of forces over the rudder. The results provide rudder force data for use in manoeuvring simulations and detailed data for the validation of numerical modelling of the interaction problem.

T.i. Fossen - One of the best experts on this subject based on the ideXlab platform.

  • Fuel-efficient rudder and propeller control allocation for marine craft: experiments with a model ship
    IEEE Transactions on Control Systems Technology, 2003
    Co-Authors: K.-p. Lindegaard, T.i. Fossen
    Abstract:

    We derived a control allocation algorithm for low-speed marine craft using propellers and Rudders. Active use of Rudders has advantages in a low-speed operation by decreasing the need for propeller power and fuel. However, at low speed, a rudder is effective only for positive thrust. This complicates the thrust allocation problem which can no longer be solved by convex quadratic programming. In fact, the existence of local minima introduces discontinuities in the commanded thruster signals even if the desired control force is continuous. Discontinuous signals cause excessive wear on the thruster system and must be avoided. This paper suggests an analytic, 2-norm optimal method that can ensure continuity of the solutions. Being analytic, however, its limitation is the capability of handling only configurations where one single thrust device is subject to sector constraints at a time. Experiments with a model ship illustrate the potential for fuel saving. For this particular vessel, the energy consumption was halved. An output feedback tracking control law with integral action was simultaneously derived and analyzed. Semiglobal ship controllers like this one rely on the yaw rate being bounded, and an admittedly conservative method for determining this upper bound was proposed.

Robert Hekkenberg - One of the best experts on this subject based on the ideXlab platform.

  • RANS Study on Hydrodynamic Characteristics of Flapped Rudders
    Volume 11B: Honoring Symposium for Professor Carlos Guedes Soares on Marine Technology and Ocean Engineering, 2018
    Co-Authors: Robert Hekkenberg, Bingqian Zhao
    Abstract:

    Ships that equipped with flapped Rudders have better manoeuvring performance than ships fitted with traditional spade Rudders. Moreover, this advantage is achieved without significantly affecting the ship’s resistance during normal cruising. Flapped Rudders are, therefore, favourable for ships that require high manoeuvring performance and sail long distance. Nowadays, there is a trend of using twin flapped Rudders on newly built inland vessels in the Yangtze River. To properly design these ships and analyse their manoeuvring performance, the hydrodynamic characteristics of the flapped Rudders are required. In this paper, a RANS study is performed to analyse the impacts of the three main properties of a flapped rudder on its hydrodynamic coefficients. The target properties are the rudder profile, the flap-linkage ratio (the flapped angle relative to the rudder chord line divided by the applied rudder angle), and the flap-area ratio (the sectional area of the flap divided by the total sectional area). The RANS simulations are carried out with commercial meshing tool ANSYS Meshing and CFD solver ANSYS Fluent.

  • Hydrodynamic characteristics of multiple-rudder configurations
    Ships and Offshore Structures, 2017
    Co-Authors: Robert Hekkenberg, Erik Rotteveel, J.j. Hopman
    Abstract:

    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.

  • Sixty years of research on ship Rudders: effects of design choices on rudder performance
    Ships and Offshore Structures, 2016
    Co-Authors: Robert Hekkenberg
    Abstract:

    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.

  • interaction effects on hydrodynamic characteristics of twin Rudders
    Proceedings 2016 International Conference on Maritime Technology, 2016
    Co-Authors: Robert Hekkenberg
    Abstract:

    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.

  • Impacts of rudder profiles on ship manoeuvrability
    2015
    Co-Authors: Frans Quadvlieg, Robert Hekkenberg
    Abstract:

    The performance of a ship’s rudder largely determines its manoeuvrability, which includes turning ability, initial turning ability, yaw-checking ability and course-keeping ability. However, existing empirical formulas for rudder forces do not concern the rudder profile. This paper discusses the impacts of various rudder profiles on ship manoeuvrability. Instead of empirical formulas for rudder characteristics, Computational Fluid Dynamic methods (CFD) are applied to obtain lift and drag coefficients of five profiles. Then, the normal force coefficient of each profile is calculated and corrected for the aspect ratio. Commercial packages Pointwise and ANSYS ICEM generate the unstructured and structured mesh, respectively. ANSYS Fluent solves the Navier-Stokes equations. 2D steady-state viscous simulations of Rudders in incompressible water are carried out with the k-w SST turbulence model. To test the impacts on manoeuvrability, a manoeuvring model is built in Python for the KVLCC2 tanker in deep water. Turning circle manoeuvres and zigzag manoeuvres are performed to compare the manoeuvring parameters. This paper concludes with insights into the impacts of rudder profiles on ship manoeuvrability.

K.-p. Lindegaard - One of the best experts on this subject based on the ideXlab platform.

  • Fuel-efficient rudder and propeller control allocation for marine craft: experiments with a model ship
    IEEE Transactions on Control Systems Technology, 2003
    Co-Authors: K.-p. Lindegaard, T.i. Fossen
    Abstract:

    We derived a control allocation algorithm for low-speed marine craft using propellers and Rudders. Active use of Rudders has advantages in a low-speed operation by decreasing the need for propeller power and fuel. However, at low speed, a rudder is effective only for positive thrust. This complicates the thrust allocation problem which can no longer be solved by convex quadratic programming. In fact, the existence of local minima introduces discontinuities in the commanded thruster signals even if the desired control force is continuous. Discontinuous signals cause excessive wear on the thruster system and must be avoided. This paper suggests an analytic, 2-norm optimal method that can ensure continuity of the solutions. Being analytic, however, its limitation is the capability of handling only configurations where one single thrust device is subject to sector constraints at a time. Experiments with a model ship illustrate the potential for fuel saving. For this particular vessel, the energy consumption was halved. An output feedback tracking control law with integral action was simultaneously derived and analyzed. Semiglobal ship controllers like this one rely on the yaw rate being bounded, and an admittedly conservative method for determining this upper bound was proposed.