Eine Methode zum Aufmessen des Wellenfeldes schneller Fähren
Prof. Dr.-Ing. G.J. Grigoropoulos
Dipl.-Ing. D. Chalkias
Kurzfassung nur in englischer Sprache:
Waves generated by ships operating in restricted waters affect the erosion of shoreline as well as swimmers and passengers of small boats sailing nearby. The problem evolves to a serious one in the case of modern fast ferries operating in routes neighboring habitant areas at very high speeds accompanied by large generated waves. Although naval ships generate similar waves, they usually sail at maximum speed far away from coastline.
Three years ago, in the framework of the national program “PYTHAGORAS”, the authors initiated an effort to predict and record the effect of the waves generated by high-speed ferries. In this work three methodologies were investigated. At first, the waves generated by various fast ferry types were predicted using linear and non-linear potential flow panel codes (Chalkias and Grigoropoulos, 2005). This methodology, however, predicts the generated waves at lateral distances comparable with ship length athwarships, due to computer power limitations and divergence of numerical results. This shortcoming is only partly remedied by applying various propagation laws and techniques. Secondly, two large manned models were constructed and tested at sheltered conditions at sea (Chalkias and Grigoropoulos, 2007). Although this methodology has some potential and it is complementary to the numerical predictions, it is not free of difficulties and inaccuracies, due to the small size of the waves there are recorded, especially far away from the model track.
In this paper the third methodology which was used is presented. It consists of measuring the actual waves generated by passing by ferries. Since the route of the ferries under investigation is a few miles away of the coast, a chase boat was used to approach their track. In order to achieve accurate recordings, the precise knowledge of the speed of the vessel as well as the lateral distance between the track of the vessel and the measuring point is essential. In this respect the Automatic Identification System (AIS), required by SOLAS for all passenger vessels, was used. In order to record the time histories of the free surface elevation, a wave rider buoy was employed. The recordings of a high speed catamaran, a fast displacement mono-hull and three high-speed semi-displacement mono-hulls are presented and compared with numerical predictions.
A Methodology for Recording the Wash Waves of Fast Ferries
Waves generated by ships operating in restricted waters affect the erosion of shoreline as well as swimmers and passengers of small boats sailing nearby. The problem evolves to a serious one in the case of modern fast ferries operating in routes neighboring habitant areas at very high speeds accompanied by large generated waves. Although naval ships generate similar waves, they usually sail at maximum speed far away from coastline.
Three years ago, in the framework of the national program “PYTHAGORAS”, the authors initiated an effort to predict and record the effect of the waves generated by high-speed ferries. In this work three methodologies were investigated. At first, the waves generated by various fast ferry types were predicted using linear and non-linear potential flow panel codes (Chalkias and Grigoropoulos, 2005). This methodology, however, predicts the generated waves at lateral distances comparable with ship length athwarships, due to computer power limitations and divergence of numerical results. This shortcoming is only partly remedied by applying various propagation laws and techniques. Secondly, two large manned models were constructed and tested at sheltered conditions at sea (Chalkias and Grigoropoulos, 2007). Although this methodology has some potential and it is complementary to the numerical predictions, it is not free of difficulties and inaccuracies, due to the small size of the waves there are recorded, especially far away from the model track.
In this paper the third methodology which was used is presented. It consists of measuring the actual waves generated by passing by ferries. Since the route of the ferries under investigation is a few miles away of the coast, a chase boat was used to approach their track. In order to achieve accurate recordings, the precise knowledge of the speed of the vessel as well as the lateral distance between the track of the vessel and the measuring point is essential. In this respect the Automatic Identification System (AIS), required by SOLAS for all passenger vessels, was used. In order to record the time histories of the free surface elevation, a wave rider buoy was employed. The recordings of a high speed catamaran, a fast displacement mono-hull and three high-speed semi-displacement mono-hulls are presented and compared with numerical predictions.
