Fast and safe navigation in shallow waters Safety standards for twin-hull ferry transportation have limited high speed ferries from navigating through shallow waters to considerably reduced speeds. This limitation results in delays, extended travelling times and higher operational costs. The results of the Safe Passage And Navigation (SPAN) project establish a clear basis for planning a safe navigation system allowing high speed in shallow waterways for fast twin hulled vessels. Industrial Technologies © PhotoDisc The main objectives of the SPAN project were to aid the safe passing of fast ferries at high speeds in shallow water and the real time navigation for fast twin hulled vessels. There are three means for achieving these objectives. Firstly, new proven data software application tools have been developed that improve waterjet design and enable shallow water jet performance to be within 48% of deep water, compared with the present 10-20%. Secondly, a computer model has been produced which ensures safer passage by realistic examination of operational limits in shallow water. Thirdly, an on board model-based predictive system has been built that aids in avoiding collision/grounding in shallow waters and therefore, maintains safe navigation. SPAN can provide safe passage for ferries that range from 150 - 180 tonnes laden displacement carrying 350 - 500 passengers running at 25-30 knots in only 2 - 5m of water at drafts of 1.2 - 1.5m restricting wash to 30 cm. This achievement has been documented in a set of sub-results concerning; hull design, including Computational Fluid Dynamics (CDF) modelling, water tank testing and sea trials; water jet design, taking into consideration the effects of water intake interaction with the hull; an intelligent software system, that encodes the results of the modelling into guidelines on safe operating requirements, and is implemented using a combination of modern and conventional techniques focusing on squat behaviour, the effects of wave action and safe manoeuvrability; wash limits, environmental and safety circumstances on permissible wash height, and assistance to navigation as a pilot advisor with conventional navigational instruments (e.g. radar) incorporating the safe operating criteria. Within the framework of these studies, a low wash hull form has been developed that is more efficient than those currently used. Additionally, for special wash conditions an ultra low wash form of hull has also been designed for use. The newly designed waterjets permit lowering craft weights and better manoeuvrability. Compared to full-scale trials the first quality CFD results ease further optimisation of the inlets for shallow water effects. It is worth mentioning that the advanced fully functioning navigational aid developed is comparable to those currently used in the military aerospace industry. The exploitation of the highly sophisticated SPAN results will have a significant impact on nautical transportation. Twin hulled water jet propelled ferries, which now offer superior performance will benefit from the reliable and verified hydrodynamic data to predict their behaviour, particularly in shallow waters by the development of an enhanced control system that can provide safe manoeuvring in busy waterways. Hence, fast high-speed commuter ferry services will appreciate the safe passage capabilities and the fully functioning navigation aid developed. A Portugeuse company currently employing this technology, Transtejo Transportes Tejo, which operates a ferry service across the Tagus River in Lisbon, has a daily carrying capacity of 100,000 to 150,000 commuters and has increased needs in safe craft manoeuvrability at high speeds in narrow channels where excessive wash is also a problem. Simultaneously, SPAN can affect a wide range of maritime industries, from shipbuilders to manufacturers of marine propulsion and control systems. Moreover, Regulatory Authorities will be able to issue their marine licenses based on sound data upon which they will now be able to interpret the IMO Code of Practice for High Speed Craft.
