232 Estonian Journal of Engineering, 2008, 14, 3, 232–254 doi: 10.3176/eng.2008.3.04 Simulation of patterns of wakes from high-speed ferries in Tallinn Bay Tomas Torsvik a and Tarmo Soomere b a Bergen Centre for Computational Science, UNIFOB, University of Bergen, Thormøhlensgate 55, N-5008 Bergen, Norway; tomas.torsvik@bccs.uib.no b Centre for Nonlinear Studies, Institute of Cybernetics, Tallinn University of Technology, Akadeemia tee 21, 12618 Tallinn, Estonia; soomere@cs.ioc.ee Received 22 February 2008, in revised form 3 June 2008 Abstract. We analyse spatial patterns and far field properties of the long-wave part of wakes of fast ferries in Tallinn Bay with the use of the Boussinesq-type shallow-water model COULWAVE, forced by realistic ship motions. The calculated heights of ship waves exhibit substantial spatial variability. The largest waves were created when the ship, sailing to Tallinn, entered into super- critical regime when moving over the coastal slope. The maximum wave height eventually reached 3 m, whereas along other sections of the track the wave height was about 1 m. The highest waves hit the area of Pirita Beach that apparently has much larger ship wave loads than the adjacent sections of the Viimsi Peninsula. Key words: fast ferries, ship wakes, Boussinesq model, wave modelling. 1. INTRODUCTION Long and high waves from contemporary high-speed ships have become an important component of the local hydrodynamic activity in a number of inland waterways [ 1 ], small bays [ 2 ] and archipelago areas [ 3 ]. Intense high-speed ship traffic adds a new forcing factor into the local marine ecosystem also in certain semi-enclosed sea areas such as Tallinn Bay [ 4 ]. Ship waves usually are of modest height, but may have considerable larger periods than wind waves and swell. The ship wave heights typically do not exceed 1 m, but their periods are frequently about 10–15 s [ 5 ]. Such wind waves are very rare in the area in question [ 6 ]. The difference in periods, combined with the intensity of ship traffic, is the reason why the role of ship waves is impressive in terms of wave energy and power [ 7 ], and wave-induced near-bottom velocities [ 8 ]. Ship wakes