National Transport Library Research Database

Stora och snabba fartygs interaktion med omgivningen i skärgårdstrafik (The interaction of large and high-speed vessels with the environment in archipelagos)

Sponsors, duration, budget: Vinnova ; 2000-05-01 -- 2002-05-01 Registration number:
  • Vinnova
Subject(s): Online resources: Abstract: Detta projekt undersöker vilka delar av vågor och andra vattenrörelser, som uppstår genom att stora och snabba fartyg trafikerar skärgården, som är viktiga för säkerheten och stranserosion och att visa hur datorsimuleringsverktyg kan användas för att beskriva hur de oilka rörelserna genereras, sprids och förändras samt den stranderosion som de förorsakar. De metoder som används är litteraturstudier, datorsimuleringar, fältundersökningar och -mätningar, fartygsmodelltest och laboratorieexperiment. Tre olika beståndsdelar av svallvågorna analyseras i projektet. Olika typer av vågor har olika effekter på strandlinjerna. S.k. Bernoulli- och Kelvin- vågor är viktiga för säkerhet och stranderosion i skärgårdar och påverkar även vattenståndet i smala sund eller kanaler, medan enstaka vågor förmodligen inte är det. De olika effekterna beskrivs med hänsyn tagen till vågornas beskaffenhet, skärgårdens utseende och strändernas form. Rapporten är skriven på engelska. Abstract: The purpose of this research project is to investigate which components of the wake wash, i.e. which waves or other water motions, generated by large and high-speed vessels operated in archipelagos that are important for safety and shoreline erosion, and to show how computer modelling tools can be used in order to describe the generation, propagation, and transformation of such components, and the resulting shoreline erosion caused by them. The methods used in the project are literature studies, computer simulations, field investigations and measurements, ship model tests, and laboratory experiments. Three different wake wash components are analysed in the project. • The formation of the water surface around the vessel hull due to the pressure distribution in the water around it, i.e. the Bernoulli wave. • The Kelvin wave pattern consisting of divergent and transverse waves, and corresponding pattern at shallow water, called Kelvin waves in the present report. • The single wave that might occur and that travels ahead of the vessel, called solitary wave. It is concluded that Bernoulli and Kelvin waves are important for safety and shoreline erosion in archipelagos, while solitary waves probably are not. That the Bernoulli wave can cause a large lowering of the water level along the banks when the vessel is operating in a canal, a so-called drawdown, is a well-known phenomenon. In the present project, it is found that the Bernoulli wave also can cause significant drawdown in bays and other seemingly sheltered areas along the fairway, when a large vessel is passing outside them. This drawdown can be a direct result of the vessel’s passage but it might also be a result of the Bernoulli wave being scattered by for example an island outside the bay. There are also possibilities for a seiche to be generated in the bay, i.e. a periodic variation of the water level. Shoreline effects of the drawdown are different depending on if the shore has a mild or a steep slope. Shoreline erosion on mildly sloping shores will be negligible. On steep shores (banks), the temporarily lowered water level during drawdown causes outward hydraulic pressure gradients, which decrease the structural stability of the bank resulting in erosion.
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