Numerical analysis of the ship propulsion control system effect on manoeuvring characteristics in model and full scale (original) (raw)
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SIMULATION OF THE PROPULSION SYSTEM BEHAVIOUR DURING SHIP STANDARD MANOEUVRES
The paper presents a comprehensive approach to simulate the propulsion system behaviour during ship manoeuvres. The behaviour of the ship systems is simulated by means of a dynamic simulation model that was already validated for the performance prediction of ship propulsion plants with the ship travelling in straight line. Now the dynamic model has been extended to consider the ship manoeuvrability in the horizontal plane. In order to analyse the different manoeuvres of a ship, the simulation model has been applied to a propulsion system consisting of a twin shaft arrangement with controllable pitch propellers, driven, through reduction gears, by turbocharged medium speed diesel engines. The accuracy of the simulation procedure is illustrated in the paper through comparison with full scale results for different manoeuvres such as turning circle, zig zag and spiral.
Marine Propulsion System Dynamics During Ship Manoeuvres
… Conference On High- …, 2008
Marine propulsion plants can experience large power fluctuations during tight manoeuvres. During these critical situations, dramatic increases of shaft torque are possible, up to and over 100% of the steady values in straight course. In the case of a twin-screw ship turning circle, the two shaft lines dynamics can be completely different in terms of required power and torque. This phenomenon, if not correctly considered, is potentially dangerous, especially for propulsion plants with two shaft lines powered via a unique reduction gear, which can be subject to significant unbalances. The paper presents a simulation approach able to represent the dynamics of a twin-screw ship propulsion plant in these critical working conditions. The numerical model includes the ship manoeuvrability and the dynamic behaviour of prime movers, shaft lines, propellers and propulsion control system. Numerical results obtained have been compared to fullscale measurements in order to validate the proposed simulation approach.
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The accurate characterization of ship motions in different seaways is a basic requirement in the design of an effective ship motion control system. Traditionally, ship motion characteristics are obtained either by conducting model tests or by using numerical simulation based on simplified theories. However, model tests are typically expensive and time-consuming, and simplified theories may not be suitable for advanced hull forms such as wave piercers or multi-hulls and for ships operating at high speeds. More advanced numerical simulation tools are needed. In this paper, an advanced numerical simulation method is described that incorporates nonlinear, time-domain wave-body hydrodynamics and control system models for the design and assessment of motion control systems. Sample results using these control systems are shown to demonstrate the efficacy of these systems.
Twin screw vessels' propulsion system experiences strong off design conditions during tight manoeuvres due to the propellers inflow asymmetry arising from the coupled yaw-drift motion. Unfortunately, simplified mathematical models based upon statistical data or ad hoc executed captive model test (PMM or CMT) do not provide such a detailed information. Indeed, free running model tests are the best mean in order to get ship's trajectory and kinematics parameters data and propulsion behaviour by recording the loads (thrust and torque) on the shafts. More insight into this complex aspect is desired in order to improve and generalize the application of existing manoeuvring mathematical models for the preliminary design of unconventional propulsive configuration control system.
Mathematical model of the ship manoeuvring
Analele Universităţii "Dunărea de Jos" din Galaţi. Fascicula XI, Construcţii navale/ Annals of "Dunărea de Jos" of Galati, Fascicle XI, Shipbuilding
Starting with the initial design phase, the knowledge of the ship manoeuvring performance is an important problem. One of the methods to evaluate the manoeuvring characteristics is based on the time domain simulation of the standard manoeuvring tests. A typical mathematical model that may be used to determine the manoeuvring characteristics of the ships is presented in this paper.
Four Quadrant Thrust Generation Model for Ship Manoeuvring Simulation
2016
The environment where ship operates defines its hydrodynamic characteristic. Interaction between the ship and boundaries around the regions particularly characterised the ship steer-ability and manoeuvrability. Despite the fact that ships are inherently designed to navigate in forward direction in open sea, however inevitably ships have to sometimes navigate backward or manoeuvre in restricted waterways. A thrust generation model was developed by fully utilising continuous function of the propeller across four quadrants. The model is fruitful for ship manoeuvring simulation in all round working operations. The practicability of the model was examined via real time simulation for crash stopping condition. The result exhibits successful performance to model the propeller and ship characteristics dynamically in four quadrant operations.
Systematic modelling, verification, calibration and validation of a ship propulsion simulation model
Proceedings of the Institute of Marine Engineering, Science, and Technology. Part A, Journal of marine engineering and technology
The need for ship propulsion simulation models is widely acknowledged. However, a ship propulsion simulation model can only rightfully be used after its validity has been assessed. The importance of high quality validation increases when the simulation model is intended to be used to design working equipment. This paper proposes a systematic approach towards the modelling, verification, calibration and validation of a ship propulsion simulation model. Both the validity of static operating points and of the dynamic system behaviour are quantified, enabling objective quality assessment. The model that is validated here has successfully been used to develop and test a propulsion control system, aiming at increased cavitation free time in operational conditions. This is the topic of a further paper.
Numerical analysis of the container vessel's self-propulsion at different rudder deflection angles
2019
Nowadays, CFD becomes one of the most commonly used research method in ship hydrodynamics, limited to the analyses of hull resistance in calm water. With continuously improving computing power and increasingly more accurate numerical methods it is possible to simulate more complex cases. State of the art CFD tools also enable development of new ways of assessing ship maneuvering performance. This paper presents an attempt on using CFD for evaluation of the coefficients used in the formulation of rudder forces applied in the ship manoeuvring model. These coefficient are normally evaluated in captive tests of the hull with working propeller and rudder deflected at different angles; the paper presents the results of CFD simulation of this kind of experiment. The test case used in the analyses is the well known the KRISO Container Ship (KCS). The computations were carried out at model scale 1:50, for which the reference model test results are available. Comparison of CFD and experimenta...
Journal of Marine Science and Engineering
The purpose of this study is to assess the quality of the manoeuvre prediction of a twin-shaft naval vessel by means of a time-domain simulator based on Computational Fluid Dynamics (CFD) hydrodynamic coefficients. The simulator uses a modular approach in which the hull, rudders, appendices and propellers are based on different mathematical models. The hydrodynamic coefficients of the hull in the bare and appended configurations are computed using virtual captive tests performed with an open-source CFD code: OpenFoam. This paper demonstrates that the application of the CFD hydrodynamic coefficients led to a good estimate of the macroscopic characteristics of the main IMO manoeuvres with respect to the experimental measures. The adopted test case is the DTMB 5415M frigate both with and without appendages. This test case has been investigated in several research studies and international benchmark workshops, such as SIMMAN 2008, SIMMAN 2014 and many CFD workgroups.