Crest-trough asymmetry of waves generated by high-speed ferries; pp. 182–195
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doi: 10.3176/eng.2009.3.03Authors
Dmitry Kurennoy, Ira Didenkulova, Tarmo Soomere
Abstract
The shape of waves from high-speed ferries in Tallinn Bay, the Baltic Sea, is analysed from the viewpoint of the potential asymmetry of the crest heights and trough depths. Only the waves from the first group of the wake (that usually contains the highest and longest waves) are analysed. On average, wave crests deviate from still water level 1.4 times more than the wave troughs. In extreme cases, the crest height exceeds the trough depth by up to a factor of 3. It is shown that asymmetry is an important parameter of the wakes, the values of which do not necessarily correlate with the maximum wave height in the wakes, a quantity that otherwise characterizes the basic properties of the wakes well. The results for the ratio of the crest height over the trough depth coincide with estimates made using classical cnoidal wave theory. Distribution functions of the wave asymmetry for vessels, operating in Tallinn Bay, show that the most frequent values for the ratio of the crest height over the trough depth lie between 1 and 1.6.
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