Preliminary Study on the Contribution of External Forces to Ship Behavior (original) (raw)

An analysis methodology for the passing ship problem considering real-time simulations and moored ship dynamics: Application to the Port of Santos, in Brazil

Applied Ocean Research, 2018

An analysis methodology for the passing ship problem in ports combining a potential flow model, a dynamic simulator for moored ships and a real-time simulator is presented. Traditionally, the passing ship problem is approached by defining a criteria based on safe distances and maximum velocities, neglecting manoeuvring aspects that are crucial to verify whether the ship can meet such requirements or not. In order to overcome this limitation, the proposed methodology extends the standard one by including results of pilot guided real-time simulations into the analysis process. The method is applied to evaluate the manoeuvring feasibility of a 366 m long container ship in the Port of Santos, Brazil, taking into account the hydrodynamic effects that might be caused on small capesize vessels moored at different berths of the port. Results are discussed in terms of moored ship motions and mooring loads for different manoeuvring cases, including also possible improvements on the mooring arrangements in order to increase the port operational limits.

Towards generalized ship's manoeuvre models based on real time simulation results in port approach areas

Ocean Engineering, 2020

This paper presents an attempts towards creation of generalized models of ships manoeuvring area determination and ship performance created on the base of real simulation results. Those models are needed for better understanding of the safe navigation process in ports areas and its approaches and for risk analysis when no full information about the ships behaviour is available. The data coming from real time ship simulations that are conducted by experienced pilots and captains are applied in the study. In the first step, general regression models are created to determine manoeuvring areas and major correlations between basic parameters affecting the safe area needed for ships to navigate in restricted areas of ports and its approaches. In the second step, the ship performance models are created to describe the behaviour of the ship including human factors. The ship performance for long-term prediction of the navigation risk regarding the possibility of ships exceeding the channel limits, assumed as grounding or collision with a fixed structure are created by the method which consists of two developed models: (1) an ARMAX (Auto Regressive and Moving Average eXogenous) model is adopted to identify the ship steering dynamic system. With the help of this model, the outputs of the system (course, position, etc.) can be estimated based on the system input conditions (rudder, engine, etc.); (2) the stochastic sequences of the inputs for the first model used are generated using a semi-Markov model. In the paper the implementation of the semi-Markov model for rudder actions has been described. The study used input/output measurements from a ship-handling simulator to estimate the model parameters, so the human factor has been included in the models. The method allows us to extend the results obtained from the simulator to predict future conditions of the system outputs. Since the predicted results and using probabilistic approach, possible ship manoeuvring area margins will be identified and long-term assessment of the navigation risk can be realized.

Evaluation of Mathematical Models for Tankers' Maneuvering Motions

Journal of ETA Maritime Science, 2017

In this study, the maneuvering performance of two tanker ships, KVLCC1 and KVLCC2 which have different stern forms are predicted using a system-based method. Two different 3 DOF (degrees of freedom) mathematical models based on the MMG(Maneuvering Modeling Group) concept areappliedwith the difference in representing lateral force and yawing moment by second and third order polynomials respectively. Hydrodynamic coefficients and related parameters used in the mathematical models of the same scale models of KVLCC1 and KVLCC2 ships are estimated by using experimental data of NMRI (National Maritime Research Institute). The simulations of turning circle with rudder angle ±35 o , zigzag(±10 o /±10 o) and zigzag (±20 o /±20 o) maneuvers are carried out and compared with free running model test data of MARIN (Maritime Research Institute Netherlands) in this study. As a result of the analysis, it can be summarised that MMG model based on the third order polynomial is superior to the one based on the second order polynomial in view of estimation accuracy of lateral hull force and yawing moment.

Mathematical modelling of forces acting on ships during lightering operations

Ocean Engineering, 2012

The transfer of liquid cargo (crude oil and LNG) from a larger ship (the ship to be lightered, STBL) to a smaller vessel (service ship) when both ships are moored to each other and sail at a (slow) constant forward speed is known as lightering. These ship to ship operations are expected to increase in the near future and are expected to take place in harsher environmental conditions (polar regions). In order to better understand the hydrodynamic phenomena involved in this specific manoeuvre, a knowledgebuilding project with user involvement entitled ''Investigating Hydrodynamic Aspects and Control Strategies for Ship-to-Ship Operations'' was carried out in 2007-2011. As a part of this project, more than two thousand captive model tests were carried out at the towing tank for manoeuvres in shallow water (co-operation Flanders Hydraulics Research-Ghent University) in Antwerp, Belgium. A model of a very large crude oil carrier (VLCC) was attached to the main frame of the towing carriage and a model of an Aframax tanker was attached to the computer controlled planar motion carriage. Forces, moments and vertical positions were measured on both models. This paper covers the analysis of the extensive model test data reported by Lataire et al. (2009a) and the influence of different parameters on the manoeuvre. Particular attention is paid to the forces and moments induced on the service ship by the proximity of the ship to be lightered. A mathematical model of lightering manoeuvres for both the service ship and the ship to be lightered is derived. This model can be implemented in a ship manoeuvring simulator for training purposes.

Numerical simulation of large commercial ship navigation on Paraná river, Argentina

MARINE VII : proceedings of the VII International Conference on Computational Methods in Marine Engineering, 2017

In recent years, the large commercial ships (Post-Panamax) started sailing the Argentinean waterway of the Paraná River. So that, the research project of the FICH-UNL called "Analysis of Hydro-Sedimentological Effects Caused by River Navigation on Argentinean Waterways" decided to use the computational simulation as one of tools research to study the hydraulic and sedimentological effects caused by the navigation of these ships on the morphology of the rivers of the Argentine waterway. One of the premises of this work was to explore the capabilities of the Adapco STAR CCM + CFD code to simulate the ship navigation in calm water in order to measure the heights of waves generated (among others), validating its results with the experimental one (physical model of large ships navigation carried out at the Hydraulics Laboratory of FICH-UNL). Navigation situation simulated: JAPAN Bulk Carrier (JBC; Lpp: 280 m, Bwl: 45 m and D: 25 m) with a service speed of 22 knots (11,3m/s) navigating against a flow stream with velocity of 2m/s (habitual situation of JBC navigation on Paraná River). The numerical modeling reproduced the navigation ship in scale (1/36.7), using a Computational Fluid Dynamics code (CFD) by finite-volume method (VOF). A study of mesh dependence was performed to analyze the convergence model. A mesh of hexahedral cells was used in the Volume of Fluid (VOF) Multiphase Model for waves and dumping waves. The turbulence was modeled by a k-Epsilon model from Reynolds Average. Wave damping was used in the lateral walls of the domain.

Numerical and Experimental Studies on Ship Motions Induced by Passing Ship

Volume 7A: Ocean Engineering, 2018

To investigate the ability of numerical models to simulate the behavior of moored ships subjected by ship-wake waves, use is made of scale model tests where a ship model sails with constant speed along a straight path at a constant distance from an otherwise motionless ship. The tests were carried out at one of the wave tanks of the Portuguese Civil Engineering Laboratory (LNEC). The moving ship is a self-propelled scale model of the "Aurora" chemical ship whereas the otherwise motionless ship is a scale model of the "Esso Osaka" tanker. The free-surface elevation was measured with a set of resistive wave gauges and ADVs. The tanker's movements, induced by the wake waves, were measured along the six degrees of freedom with a gyroscope deployed inside the ship. The numerical model WAMIT provides, in the frequency domain, the quantities required to estimate the hydrodynamic forces associated to the interaction of a free-floating ship with waves. The BAS model uses those hydrodynamic forces to study in the time domain the ship interaction with any sea-waves acting on it. Wind and current actions can also be accounted for. The results of these numerical models are compared to the measurements made in the several repeats of one of those scalemodel tests, in terms of the response amplitude to several wave components. These comparisons enabled the evaluation and

A Mathematical Model for Analysis on Ships Collision Avoidance

This study develops a mathematical model for analysis on collision avoidance of ships. The obtained model provides information on the quantitative effect of the ship’s engine’s response and the applied reversing force on separation distance and stopping abilities of the ships. Appropriate evasive maneuvers require the engine’s ability to quickly reverse and an appropriate increment in the reversing force as proposed by the mathematical model. Numerical simulations were performed to demonstrate the validity of the mathematical model along with quantitative and qualitative analyses of the collision avoidance. It was found that the longer it takes the engine to move from forward to full astern, the longer the stopping distance and stopping time; and the closer the ships move, therefore increasing the risk of collision. However, the higher the amount of force applied in the opposite direction to the forward movement of the ships, the faster they will stop, reducing considerably risk of collision. This leads to the conclusion that for two encountering ships navigating in an area where alteration of course is not possible (confine water or no sufficient sea room) the increment in the ship resistance followed by an appropriate engine response are vital for imminent collision avoidance. Key words: Collision Avoidance, Mathematical Model, Numerical Simulations.

Calibration of a Lagrangian Transport Model Using Drifting Buoys Deployed during the Prestige Oil Spill

Journal of Coastal Research, 2009

ABASCAL, A.J.; CASTANEDO, S.; MENDEZ F.J.; MEDINA, R., and LOSADA, I.J., 2009. Calibration of a Lagrangian transport model using drifting buoys deployed during the Prestige oil spill. Journal of Coastal Research, 25(1), 80-90. West Palm Beach (Florida), ISSN 0749-0208.

Development of a tabular manoeuvring model for hull forces applied to full and slender ships in shallow water

2003

Most formulations of mathematical modelling of ship manoeuvres in shallow water discussed in literature are based on expressions for the deep water case. Several usual and unusual phenomena occurring during manoeuvres at limited under keel clearance (10% to 50%) are not considered. A tabular model for the hull forces is proposed, taking the shallow water condition as starting point, with the intention to cover wide ranges of kinematical parameters so that a great variety of manoeuvres can be simulated. The implementation of the mathematical model is based on captive model tests with 4 m models of the tanker Esso Osaka and a fourth generation container carrier. The experimental program consists of well-known, classical PMM test types combined with alternative tests. Preliminary guidelines are formulated for the selection of test parameters, taking account of their influence on the hydrodynamic coefficients.