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Ship manoeuvring in shallow and confined water

Knowledge centre

The Knowledge Centre Manoeuvring in Shallow and Confined Water aims to consolidate, extend and disseminate knowledge on the behaviour of ships in shallow and confined water. The Knowledge Centre is a collaboration between Flanders Hydraulics Research and the Maritime Technology Division at Ghent University.

Mashcon2019 The Knowledge Centre has a dedicated website, which gives an overview of the various projects that researchers associated with the Centre are involved in and of the experimental facilities that are used for these projects.

Every three years, the Knowledge Centre organizes the MASHCON conferences. After editions paying special attention to

  1. Bank effects (Antwerp, 2009)
  2. Ship - ship interaction (Trondheim, 2011)
  3. Lock effects (Ghent, 2013)
  4. Ship - bottom interaction (Hamburg, 2016)
  5. Manoeuvring in wind, waves and current (Ostend, 2019)
  6. Sixth conference will be held in Glasgow in 2022, paying special attention to ship operations

Every three months, the Knowledge Centre also sends out a newsletter that gives information about recent activities. Please click here to subscribe.

Estuary vessels

Explain

Examples

Mooring

With ships getting larger, the safety of (large) moored ships is becoming increasingly important. This concerns both mooring line and fender forces, as well as ship motions. PIANC has established two working groups working on 'safe mooring of large ships at quay walls' ( WG186) and 'update of WG24 - criteria for acceptable movement of ships at berths' ( WG212), both of which the department is involved in.

bunker

Moored vessels are subjected to external forces of various origins, which are always location dependant, leading to custom studies for each terminal. The external forces include environmental forces (wind, waves, current), as well as passing ship effects. Most services provided by Ghent University up to this day include berth areas which are sheltered from waves (e.g. estuary Scheldt - Antwerp), yet suffer from large wind forces and passing vessel effects. These dynamic mooring analyses (DMA) are performed using the in-house time-domain simulation software Vlugmoor.

Examples

The department's work focusses on providing expert services, which are often leading to (indirect) publications. These projects also identify gaps in existing knowledge, which are then subject of dedicated research work. Some examples of the work are given below, with references are included in case the work has been published.

  • For the Port of Antwerp area, several studies have been performed to evaluate the effect of passing ships on moored ships in restricted channels. The Port Authority also provided full scale motion measurements, which have been used for model validation. [Van Zwijnsvoorde, T.; Vantorre, M; Ides, S, 'Container ships moored at the port of Antwerp : Modelling response to passing vessels', PIANC World Congress Panama City, 2018]
  • Since ships (gas carriers, RoRo, container ships) are getting larger, passing events become increasingly critical for existing channel dimensions. Numerical predictions reach their limitations in these cases. In order to produce a mathematical model to cope with these conditions, a dedicated model test program has been performed at Flanders Hydraulics Research in spring 2019, called PESCA (Passing Effects in Shallow and Confined Areas). The regression model based on these systematic tests will aid the department in accurately predicting passing ship forces, in today's but also in future cases. STS towing tank moored
  • Incident cases where the moored ship's lines rendered and/or broke have been examined in detail, exposing the reasons for this unwanted event to occur. Rendering winches, as well as breaking lines were modelled in the software, as well as the tugs which were assisting in keeping the vessel moored.
  • Literature and informal discussions also reveal that issues with mooring operations and/or inadequate mooring equipment can lead to safety being compromised. Examples here are absence of pretension / slack in lines [Van Zwijnsvoorde, T; Vantorre, M, 'Safe mooring of large container ships at quay walls subject to passing ship effects', Trans RINA, vol 159, part A4, Intl Maritime Eng, Oct-Dec 2017] and use of very elastic lines [Van Zwijnsvoorde, T; Eloot, K; Vantorre, M; Lataire, E, 'A mooring arrangement optimisation study', 11th International Workshop on Ship and Marine Hydrodynamics, Hamburg, Germany, September 22-25, 2019] .
  • When dealing with passing ship effects, a standard well-balanced mooring configuration of a container ship at a quay wall can still be optimised, when it comes to mooring operation and ship design phase. moored
  • Air draught and wind area of both cargo as well as passenger ships keep on increasing, which makes them more susceptible to wind effects. Wind forces are usually calculated using simplified formula, concealing the expertise behind them. This has been addressed in [Van Zwijnsvoorde, T; Donatini, L; Van Hoydonck, W, Lataire, E, 'Wind modeling for large container vessels : a critical review of the calculation procedure', Maritime Transport, Italy, Rome, 2019] , revealing potentially large errors with improper use of coefficients, e.g. with differences in wind profile for wind coming from land/sea. windmoored
  • The effect of passing ships on bunkering ships moored next to large sea-going container ships has been evaluated. Results show that the phase difference in motion between both ships is an important factor contributing to line forces and motions of the bunker vessel.

Nautical bottom

The bottom of a harbour or access channel is mostly considered as solid. In reality this is not always the case. Due to the erosive effect of the current in rivers, particles are transported over a certain distance until they settle again. If those settlements are concentrated at a certain position the formation of a mud layer is possible, depending on the grain size. To avoid excessive formation of mud layers maintenance dredging works are needed so that a minimal under keel clearance can be guaranteed.

The question arises how much of the present mud layer has to be dredged. The mud layer consists of a material which characteristics change with the depth. In general the mud characteristics like viscosity or density increase with increasing depth. Therefore the upper part of the mud layer can rather be considered as black water. If the ship's keel touches this upper part it is unlikely that any damage can occur, on the other hand when a ship navigates above a mud layer an undulation of the water mud interface can be observed. This undulation can possibly have adverse effects on the manoeuvring behaviour of the vessel.

For these reasons PIANC has introduced the nautical bottom concept (1997, 2014):
The nautical bottom is the level where physical characteristics of the bottom reach a critical limit beyond which contact with a ship's keel causes either damage or unacceptable effects on controllability and manoeuvrability.

The nautical bottom concept can be applied to any bottom so that safety and manoeuvrability for the shipping traffic can be guaranteed.

Development of a CFD tool and associated experimental validation techniques for fluid mud bottoms disturbed by moving objects

In navigation areas with bottoms covered by a thick fluid mud layer, deep-drafted ships may be allowed to sail at a limited vertical distance above the mud-water separation , and sometimes ships even sail through the mud. This causes a very intense interaction between the water column, the mud layer and the ship. The purpose of this project (in collaboration with KU Leuven and Flanders Hydraulics Research) is to develop a numerical methodology to calculate the interaction between water, mud and a moving object, which will lead to a better understanding of the physical reality in such cases.

The project also comprises laboratory tests (at FHR) during which either objects are towed, or ship models are navigating in the vicinity of a mud-water interface. This will not only allow a validation of the numerical method, but will also lead to the development of general formulae for estimating forces on flat plates, geometric objects, hydrofoils and ship hulls moving in or close to fluid mud. Such formulations are mostly available for this type of bodies moving in water, but not in mud which has flow properties which are much more complex compared to water. Since classical measuring techniques for water cannot be applied in dense fluid mud layers, new validation techniques are proposed and will be evaluated. The results of the project will lead to a better understanding of the propulsion and manoeuvring of ship in muddy navigation areas, but will also stimulate the development and improvement of measurement techniques and dredging methods in such areas.

International cooperations

Jores

Development of an industry recognised benchmark for Ship Energy Efficiency Solutions to increase confidence in numerical methods and create a basis for further ship performance improvement and industry digitalisation

Windlass

Through this JIP we want to better understand 3D wind fields in exposed ports and waterways to develop a wind load prediction tool.

Ship as a wave buoy

Knowledge of the sea state is one key factor for safe ship operations, the most comprehensive description at least in the statistical sense is given by the directional wave spectrum. Current knowledge of the sea state comes from regular visual observations onboard, sometimes supported by hydrodynamical models based on wave buoys, satellite and weather data. Both data sources have limitations, the visual observation reduces the wave spectrum to a few characteristic numbers like the significant wave height and period and the mean wave direction. Hydrodynamical models can provide directional wave spectra, however, the quality of these spectra might deteriorate for vessels underway, far off the wave buoys which are usually located in coastal areas.

In order to establish an independent and autonomous data source, this project aims at estimating the directional wave spectrum from measured ship motions. A new algorithm is developed, basically the wave state is expanded into test functions which are localized in the frequency and angular domain. The well-known response amplitude operators (RAOs) are used to relate the expansion coefficients to measured cross and power spectra of ship motions. Additional conditions are required to generate a solvable set of equations, it assumed that the RAOs vary faster with frequency than the sea state. This set of equations is solved under non-negativity constraints.

In a first step the algorithm is tested in numerical simulations based on realistic seaway and RAOs for different existing ships. The numerical tests prove that the algorithm is working albeit currently high frequency parts of sea state are not detected properly. Full scale sea trials are undertaken on three different vessels, the ongoing data evaluation supports the results of the numerical simulations.

Simulator

Simulator studies for Inland Navigation:

To examine all possible bottlenecks, such as narrow areas, touching the bottom, effect of high current flows, the passage of bridges and quays and encountering other ships, the Maritime Technology Division of UGent execute and analyze real-time simulations to help both national and international companies in defining new traffic regulations, optimized design for infrastructures, optimized dredging... (ex: Grand Gabarit network of Nord-Pas-de-Calais , the Seine River...). These studies show the importance of research and development of manoeuvring models for inland vessels.

Track controller

Fast time ship manoeuvring simulation is a common technique for checking new navigation areas, for assessing channel safety, and for analyzing confined and shallow water effects on ships. The simulation offers a cost-effective and efficient approach for identifying potential risks when designing a fairway. In the fast time simulator, the human input is eliminated and replaced by a control algorithm, here named track-controller. Track-controller is preferred over autopilot in order to avoid confusion with the on-board device with the same name. The track-controller is a control model used in the fast time simulation system, which was initially developed for track-keeping (within restricted deviations) in a confined channel. This algorithm does not only provide new control actions (rudder deflection) at discrete time intervals with the help of a prediction model, which can deal with complex, highly non-linear ship behaviour, but also controls the engine speed thus setting the propeller rate.

The present track-controller, developed and in use at Flanders Hydraulics Research and Ghent University, is rather advanced, although the performance of this control system does not always lead to a satisfactory result. In order to optimize the present model, intelligent and advanced control strategies need to be taken into account. Apart from the classic PID control theory, fast time simulation track controllers can be based on fuzzy adaptive logic control, neural network control, and other more advanced or sophisticated tracking control algorithms.

The developed track-controller will be validated by means of the model tests in the Towing Tank for Manoeuvres in Shallow Water (FHR), and will be applied in the fast time simulator.The development of a more powerful controller for fast-time manoeuvring simulations, allowing the simulation of a total channel transit from pilot station to berth and vice versa, which can be applied in waterway design, assessment of safety of shipping traffic, voyage planning. Moreover, the developed control algorithms will also be applicable for control of unmanned vessels, development of automatic berthing procedures, etc.

Foiling

Foiling GoodallThe use of hydrofoils has been around for a long time but has recently experienced some kind of renaissance. This can for a large part be attributed to the introduction of hydrofoils in the America's Cup in 2013 but what are hydrofoils and what do they do? Hydrofoils are, similar to the wings of an airplane, structures which, when placed under a certain angle of attack in a fluid flow, generate lift. This lift can then partly or completely replace the buoyant force of a vessel, which is means as much as "the vessel starts flying". Some of the most notable advantages are the ensuing drag reduction and the decoupling of the vessel's movement from waves as the hull now flies above the water surface.

TyphoonAssessing the stability of a ship with and without hydrofoils are two very distinct practices. That is why we put out an effort to develop a framework to perform a dynamic stability analysis to be able to quantify dynamic characteristics and to be able to quickly compare the influence of design parameters on the stability behaviour. To support this framework we develop the easy to use software Typhoon based on the vortex lattice method.

SeaBubbles manoeuvring tests 2D video (1080p):

SeaBubbles tests 360 sample (4K):

Aquaculture

Edulis: Offshore mussel culture in wind farm

moored The Marine Spatial Plan (MSP) allows for commercial aquaculture activities in the Belgian part of the North Sea. Following this MSP, the Edulis project was initiated in 2017 to study the feasibility of growing mussel off the coast within the wind turbine parks of Belwind and C-power. Five private partners are involved in this project: Belwind, Brevisco, C-Power, Colruyt Group and DEME Group. Ghent University collaborated with the Institute for Agriculture, Fisheries and Food Research (ILVO) to conduct this research project. OD Natural Environment is also involved as a third research partner. The project is largely financed by private funding and facilitated by Flemish and European Funding. moored

Two full scale test setups were installed: Bio line and Force line. The Bio line was put into the water in May 2017 to study the growth of the mussels. In November 2017, the Force line was installed to measure the forces and positions of the system. In 2019, as planned, both lines were decommissioned. moored

The Maritime Technology Division has worked in the design process of the proposed array of mussel line system, namely park layout, for the deployment location of the Belgium part of the North Sea. The design process includes development of a numerical tool (Moordyn-UGent), validation with full scale test setup (Force Line), experiments carried out in a wind tunnel and extreme case simulations of the park layout.

Wier en Wind: Large scale seaweed culture in the North Sea

The interreg (Vlaanderen-Nederland) Wier en Wind project aims to provide a commercial benchmark for large scale seaweed cultivation in the offshore environment. Additionally, the seaweed farm will be located within a wind turbine park in order to contribute to the multi-use of the North Sea reducing the unused space in between wind turbines. Automation using machinery for the process of seeding and harvesting is going to be implemented in this project. This is done to achieve a lower production cost per kg of seaweed. The on-going project involves several private partners as well as public institutes: GEOxyz, Seaweed Harvest Holland, Murre Technologies, Noordzeeboerderij, Ghent University (UGent), HZ University of Applied Science and AtSeaNova as project coordinator.

The role of Maritime Technology Division is to calculate the mooring system used for the offshore seaweed farm layout designed by AtSeaNova. In order to perform the numerical simulation, MoorDyn-UGent will be developed and modified to cope with seaweed layout design under environmental load of waves and currents at the deployment location. Engineering requirement of the mooring system is the expected outcome of these numerical calculations.

Other floating devices

MPVAQUA: High-wave offshore solar panels.

The Belgium part of the North Sea is occupied by several largewind turbine parks. The large distance between two single wind turbines (up to 1km) has created large areas of unused space. In the past years, the Belgian Government has been encouraging the multi-use of the North Sea to obtain a more efficient use of the available space. Installing arrays of floating photovoltaic (PV) panels within offshore wind turbine parks will not only utilize the otherwise unused space, but also to have additional electricity generation. The idea is to use the available space in the most efficient way, along with aquaculture and existing offshore wind farms. mpvaqua

The project is under the framework of Flemish Blue Cluster and the consortium consists of Tractebel, Jan De Nul Group, DEME, Soltech and Ghent University (UGent) with the support of VLAIO. Maritime Technology Division of UGent takes the role in the calculation of the mooring system used for the floaters. Modifications to the MoorDyn-UGent software will be done to cope with floating large object subjected to environmental induced load of waves and currents.