AIS data analysis tool
Flanders Hydraulics (FH) has developed a tool to analyze AIS data in a flexible and effective way. AIS data contain useful information that can for example be used to analyze shipping traffic for operational purposes or to analyze specific manoeuvres at particular locations. However, the mere size of the data files are a real challenge to work with.
The AIS data analysis tool therefore sorts vessel data based on the passing times of predefined entry lines. The data can then be filtered based on different parameters, such as ship characteristics (dimensions, type) or voyage characteristics (destination, in- or outbound sailing, draught, time). For visualisation purposes the tool also provides export options in different formats, which can be opened with GIS-viewers.
On behalf of the Common Nautical Authority, the Knowledge Centre used the tool to analyze historic ship speeds for different ship types and destinations on the Western Scheldt. AIS data of 2012 and 2013 were supplied by the Scheldt Radar Chain. In order to reduce the dataset, the study was limited to vessels longer than 200 m and wider than 30 m. The study provided insight in the influence of ship type, draught, tidal conditions and operational boundary conditions on actual ship speed for inbound and outbound manoeuvres to Flushing Sloehaven and Antwerp.
The AIS analysis tool was also applied for several other projects. One example is the analysis of passing distances and vessel speeds close to a wave gauge on the Western Scheldt in order to correlate water level changes with ship waves. Another example is a replay function of ship trajectories between two entry lines in the port of Zeebrugge in order to evaluate realistic manoeuvring speeds and rate of turn for a selection of vessels.
Computational Fluid Dynamics (CFD)
CFD offers the opportunity to study specific hydrodynamic problems which are difficult or impossible to study by experimental means. In addition, due to the relative short computing times, CFD can be used as a practical and cost-effective alternative for one-off experimental research. With decreasing costs of computing facilities and improvements in numerical algorithms, more complicated configurations can be tackled by CFD.
However , shallow water conditions and confined environments are still a challenge. The interaction with a nearby bottom or wall leads to a highly complex flow, which requires a much finer mesh in certain critical areas and thus longer computing times.
The software package FINETM/Marine, which is developed by NUMECA, computes the turbulent air-water flow around a vessel with the Reynolds-Averaged Navier-Stokes equations. Initial research focused on recreating experimental cases that were investigated in the Towing Tank for Manoeuvres in Confined Water, such as ship-bank interaction and ship-ship interaction. Currently, research focuses on the behaviour in shallow water of ships with a drift angle of 30 degrees. The figure at the right shows the mass fraction on the hull and streamlines to visualize the massive separation region that originates at the bow in this condition.
OpenFOAM is also used by researchers associated with the Knowledge Centre.
Hydrostatics
DELFTship
- DELFTship is a complete design package for application in the marine industry. It is characterised by its ability to create any kind of hullform, high flexibility, low learning curve and visual approach. It can be used for almost any kind of floating object. The basic hullform program is free for all users.
- A professional DELFTShip License is in use
Rhino, Orca3D
- Orca3D is an extension of the 3D software package "Rhino3D"
- This program calculates the hydrostatics and stability of a ship. A wide range of input and output file types can be handled.
- A professional Orca3D License is in use
ArchimedesMB
- Archimedes is a low cost, benchmarked, software utility for generating hydrostatics and cross curves for arbitrary floating bodies.
HeelMe
- HeelMe is a tool that allows calculating heel angles or displacement volumes of specific configurations. It either calculates the displacement volume of a vessel rotated around a position (y,z) at a specified heel angle or the heel angle at which the critical point becomes, for a specified displacement volume, submerged. Two versions of the program are available: an applet and a stand-alone application.
Wolfson Unit
- Network license (50 users) of the Windows version of the package HST
Hydrodynamics
Probabilistic Access Policy: ProToel
Seakeeping: Octopus Office - Seaway
Effects of passing ships on moored ships: ROPES
- a lumped-mass mooring line model for simulating the dynamics of moorings connected to floating offshore structures.
- accounts for internal axial stiffness and damping forces, weight and buoyancy forces, hydrodynamic forces from Morison's equation (assuming quiescent water so far), and vertical spring-damper forces from contact with the seabed.
Resistance and propulsion
PSP Wageningen Propeller Series
Ship construction
VLUGMOOR: Simulating the behaviour of moored vessels
Vlugmoor is used to calculate the behaviour of the moored vessel, under specific external loads. The software can handle input time series of wind, wave and current forces. Passing vessel forces are also modelled, using input from the commercial package RoPES [1]. The response of the moored vessel to these external influences is calculated in the time domain, in order to capture the non-linear nature of the vessel's response. Mooring lines and fenders are modelled, as are the ship's hydrodynamics. Both mooring at a quay and a jetty can be modelled.
[1] J.A.,Pinkster; H.J.M., Pinkster, 'A fast, user friendly, 3D potential flow program for the prediction of passing vessel effects', PIANC World Congress San Fransisco, 2014
Code specification
The code is at the moment exclusively used by the department, to perform mooring studies and research. The software is written in MATLAB language, using object oriented programming to make the code easy to rewrite in other computer languages. The advantage of this using this self-developed package is that it can be easily operated and modified, making it possible to include new modules to the code. The code is at the moment being fully overhauled as part of a PhD thesis.
Validation
The software has been validated successfully for passing ship effects, based on full-scale measurements performed at the port of Antwerp. Some of the results have been published at the PIANC World Conference 2018 in Panama [2]. The figures are taken from the referred paper, with on the left passing event at the North Sea Terminal in the port of Antwerp and on the right the surge motion of the moored vessel during the passing event, with a comparison between measured (GPS) and modelled motions. With the further development of the code, more validation work is planned in the near future.
Specific features
The code is not limited to only calculating time series of line forces and motions, it also allows post-processing, which can be finetuned to match project needs. For forces and motions due to cyclic wave action for example, the time series are converted to the frequency domain, to allow the calculation of significant and most probable maximum forces and motions, as well to identify possible resonance in the mooring system.
RIVSEA : Risk analysis estuary vessel at sea
Inland vessels are a key component in the connection between a (coastal) port and the hinterland. A good inland connection is not always available. In these cases, it might be opportunistic to perform a limited sea journey, under strict conditions, with well-equipped inland vessels. In Belgium, such traffic exists between the port of Zeebrugge and the mouth of the river Scheldt, allowing these so-called estuary vessels to reach Antwerp and travel further to neighboring countries. This is regulated by the Royal Decree for sea-going inland vessels [3]. According to this regulation, all inland vessels who want to perform estuary studies need to undergo a probabilistic sea-keeping analysis. Rivsea allows to calculate the response in waves of vessels, based on which a operational significant wave height is defined, by imposed risk limitations imposed by the Royal Decree.
Description
The Rivsea code is used to evaluate the risk of a inland vessel performing a sea journey. This is done according to the procedure outlined in [3] In a first step, the response of the vessel to incoming waves is calculated, based on the wave climate specification and the ship's response function (RAO). This is done for a representative period (e.g. 1 year measurement, with wave data every 2h), based on which the total number of exceedances of a given threshold response is calculated. Based on this risk assessment, the significant wave height up to which the vessel can operate is determined [4]. The figures show a spectral distribution of wave energy (left) and the ship response (RAO) to a unity wave height (center). The right figure shows the result of the risk analysis, giving a significant wave height up to which the vessel can operate. In this publication, a review of the sea-keeping analysis in the current legislation is given.[5] [3] FOD, 'Koninklijk besluit betreffende binnenschepen die ook voor niet-internationale zeereizen kunnen worden gebruikt', Staatsblad 2013 [Dutch] [4] Vantorre, M.; Eloot, K.; Delefortrie, G., 'Probabilistic regulation for inland vessels operating at Sea as an alternative hinterland connection for coastal harbours', EJTIR, 2012 [5] Donatini, L. et al.,'Belgian Royal Decree for sea-going inland vessels, a review for container and bulk cargo vessels', Pianc World Congress Panama City, 2018
Code specification
The calculation of ship responses for large data sets is performed using MATLAB, which is very efficient to handle large data matrices, performing calculations based on matrix manipulations. The code is written in a flexible way, where the core calculation core is written separately from the in- and output generation modules. This means that wave data can be imported from various locations, being either numerical hindcast results or measured wave data, and converted to the required input format. The software is suited to calculate the response for different variables (bending moment, relative motion) at different locations in a fast and efficient way, allowing to perform risk studies for a design vessel within acceptable time.
Specific features
The main advantages of the code are that it can handle different input wave sources and that it allows flexibility in the calculation. Next to the default calculation where the significant wave height is calculated up to which a vessel can operate, the need strength/freeboard can also be calculated for a target significant wave height, allowing to give valuable input to ship design.