Ship handling simulation at the BAW
Practical investigation of waterways and manoeuvring in virtual space
Can the development of port entrances along the German North and Baltic Sea coasts keep up with the trend towards ever larger ships? And how, for instance, can lock structures along rivers and canals be made fit for use for the inland navigation of extra-long motorised freight ships? Is navigation safety impaired if waterways are navigated by vessels of ever increasing size? BAW's two ship handling simulators enable investigation measures for improving the safety and quality of waterways already in the planning stage and for analysing bottlenecks in their navigability.
The trend towards continuously larger ships increases the requirements for sea and inland waterways. In short: it's becoming narrower everywhere. For example, only a few decades ago, it was absolutely sufficient for shipping route planning in inland waterways to merely calculate the swept area width - i.e. the surface needed by a ship - from the curve radius to be driven, the ship dimensions, and the drift angle taken by the ship in curves. But already when the waterways to Berlin were enhanced in the early 1990s, the limits of this geometrical dimensioning method became obvious: The minimum radii of 600 m for 185 m long push-tow units and 110 m long large motorised freighters which had been aimed at so far would have triggered extensive modifications of the landscape within a protected area.
Towards a multi-dimensional model procedure for the dynamics of ship movement
"In 1995, we at the BAW developed the TRASSE programme in order to reduce the fairway width in inland waterways to the necessary minimum: We no longer applied a generalised calculation of the traffic area needs, but considered the construction of tractrices under dynamic ship movement aspects which illustrated the travel of a reference vessel" says Thorsten Dettmann who is dealing at the BAW's Karlsruhe office with simulation of the dynamics of inland vessels. In connection with the planning work for developing the middle River Weser in 2000, PeTra 1D was developed. This programme, which is based on TRASSE, enables fairway routing in streams as a function of water level, taking into account the influence of a river's flow velocity on the swept area width. However, only the two-dimensional model procedure for ship dynamics 'PeTra 2D' made it possible to also take into account the cross currents to which ships are exposed, for instance on the Rivers Rhine and Neckar.
"We then basically had everything at hand for being able to also simulate manoeuvre situations. But still missing was an interface between our calculation models and the acting human, the skipper - this means, what we needed was a simulator", Dettmann continues. And at the BAW's Hamburg office, the need for simulations was becoming more and more obvious too. So, in 2005, it was given the assignment by the coastal directorates to identify the model preciseness and state of the art of the simulators used in sea navigation, and afterwards to provide advice in all ship handling simulation matters relating to coastal areas. Then, in 2009, two commercially available ship handling simulators could be purchased for BAW's inland and coastal areas work. When interlinked, the bridges at the BAW offices may even participate in one common simulation with up to 4 manually handled vessels in one scenario.
Simulators serve above all for training purposes. With their high quality of simulating situations in the air, on the street and also on water, they have acquired such a high level of technical quality that the user gains the impression of being in real situations. Therefore, simulators are perfectly suitable for training borderline situations. "At the BAW, ship handling simulation serves, however, a somewhat different purpose", explains Dr. Carl-Uwe Böttner, simulation expert at BAW's Hamburg office: "Here in coastal regions, we focus on improving the economic use of sea navigation by optimising the fairway."
Simulation as a contribution to dimensioning sea waterways
For purposes of sea waterway dimensioning, a ship handling simulator needs to fulfil different requirements than when training nautical staff. During simulator training, it is perfectly sufficient for a simulator to behave in a "physically similar" way, i.e. that the reactions of the virtual vessel correspond to what would be felt in reality. For dimensioning sea waterways, however, quantitatively correct findings are required in addition to this qualitatively correct behaviour. For this purpose, models on ship dynamics are developed at BAW's Hamburg office. Their mathematical-physical description of ship behaviour is based on numerical flow simulations and on model tests carried out in the BAW's ship wave basin using freely manoeuvring model ships. This way, all aspects of ship dynamics are determined step by step (also by additional experiments in cooperation with external partners such as universities), are then transferred into models, and finally included in the simulator software.
Carl-Uwe Böttner: "Thanks to the ship handling simulation, it is now possible to check the planning of development measures of the German local Waterways and Shipping Offices along the North and Baltic Sea coasts, e.g. offshore from Emden, Wismar or, right now, Rostock for their suitability for practical use; and it has become possible to see what is necessary and what is feasible under the given boundary conditions and with consideration of certain ship sizes." In addition, BAW makes the developed models available to cooperation partners so that they can, for example, also be used for assessment journeys or for navigability analyses in the large sea navigation simulators equipped with complete navigational bridges (Full Mission Bridge).
Navigability analyses for enhanced safety
Whereas simulation activities in Hamburg focus mostly on economic aspects of dimensioning sea port access routes, in Karlsruhe the focus is on navigability analyses of existing inland waterways. Such analyses serve, for example, for detecting navigation bottlenecks or also for advising the German Federal Waterways and Shipping Administration (WSV) when deciding on awarding the approval for traffic on inland waterways to new ships.
Thorsten Dettmann states: "For simulating manoeuvre passages on inland waterways, we took an extra-long motorised cargo vessel (üGMS) as reference vessel because this ship class should, in the future, be able to also travel, for instance, on the River Neckar." In their simulations, BAW engineers can verify if, for example, the planned structural measures for extending the Neckar locks are sufficient. Because lengthening lock basins also means that their upper and lower layby basins need to be extended. "And this does, of course, have an impact on the discharge regime behaviour of the River Neckar", Dettmann confirms. It may, for example, be the case that the bow part of an extra-long motorised cargo vessel is already in the lock while the stern part is still exposed to the river flow. "We are now in a position to simulate the impact of such a situation on the behaviour in a realistic manner."
The virtual model - consisting of bits and bytes - has been created according to the real vessel VIGILIA navigating on the Rhine river - which is 135 m long and 11.45 m wide. First, the geometrical data of this ship and also measured data from exemplary manoeuvring were integrated into the simulation model at the BAW: in total, some 2,200 coefficients were parameterized. Subsequently, a module for the virtual navigation needed to be developed which would calculate the course paths based on ship dynamics. This needed to correspond to the course which a captain would choose given the respective discharge situation, the morphology of the waterbody, and based on the navigation police requirements.
Use of the simulator in Karlsruhe for the sake of inland navigation is not limited to analysing potential weaknesses of structural modifications, as e.g. along the River Neckar. It is also highly important to analyse shipping accidents, for instance, in order to be in a position to avoid such accidents later on. Thorsten Dettmann: "For this reason, we are currently modelling the travel of TMS WALDHOF." Early in the morning on January 13, 2011, this double hull tanker, made of stainless steel, capsized on the Rhine near St. Goarshausen for currently unclear reasons. The damaged ship was carrying a cargo of 2,377 tons of sulphuric acid. The salvage operations proved to be quite difficult and also raised great public awareness.
Contact: wasserbau@baw.de
