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Numerical simulation of manoeuvring vessels by means of system identification

Vessels distinguish themselves from land vehicles by their huge mass and the lack of any rigid coupling to their surrounding. Consequently, their maneuvring motions are much more difficult to predict and to control. This yields a demand to calculate them. Oppositely to the analysis of ship designs, existing ships do not necessarily require expensive and complicated CFD software to predict their reactions to rudder executes - the more maneuvers an existing ship sails, the more secrets about herself she reveals. To exploit this never exhausting source of data, one can register the manoeuvring motions, save them and process them to obtain the coefficients of an empirical mathematical model. After that, a possibility is available to simulate any other maneuvre numerically in future by means of data obtained from maneuvres in the past. The development of such numerical methods and their implememtation as software is my main professional activity at present. I managed to launch a first version that works, and I'm working on an improvement of its reliability and precision. In future, a practical application will be to display the predicted vessel motion on the electronic nautical map (ECDIS) on board, so that it can be deflected into the desired form by the helmsman. This will also provide a reliable and comfortable alternative to the years of nautical experience required to estimate the probability of collision or ground contact in critical situations. Another possible application could be to supply a more realistic motion simulation in nautical simulators for education and training. Additionally, these numerical methods allow to evaluate model tests in the towing tank and to simulate those maneuvres numerically that don't fit into this narrow water surface.
If you are interested in a practical application, you can contact me at HSVA , the Potsdam Model Basin.

Dynamic analysis of submerged towed systems

Submerged towed sensor carriers, camera carriers or ROVs are required for miscellaneous applications in maritime environmental survey, geosciences and offshore technology. The oscillations of the towing vessel in waves are transferred to the cable and the towed body. On the other hand, for most applications it is necessary that the towed body moves without any oscillations with a constant velocity in a constant depth. The research projects aims to develop a numerical modelling of the system and to contribute solutions to the problem by means of recommended parameter combinations (cable length, towing speed, depressor inclination) and countermeasures (dynamic winch control). It focusses on the dynamic behaviour of submerged cables.

Structural dynamic analysis of offshore pipelines during laying in waves

Offshore oil and gas fields are exploited by means of a pipeline infrastructure whose technological limitations are determined by strength criteria. Within several research projects I developed algorithms to calculate the motions and stresses of the pipe span that oscillates between the laying vehicle and the soil when such a pipeline is installed in waves. In that situation, the pipe experiences loads far above those during operation.

27 Mar 2002 home  Henning Weede