Experimental study of the wave propagation and decay in a channel through a rigid ice-sheet

Experiments are carried out in a wave flume, to study wave propagation in a narrow channel along a barge-like structure, attached to one of the side-walls. By geometric symmetry this is equivalent to a channel through a rigid ice-sheet, in a tank twice as wide. When both the draft and width of the channel are small, the wavelength increases dramatically as the waves enter into it. It is checked that this modification of the wavelength is in agreement with the theory given by Molin [J. Fluid Mech. 430 (2001) 27]. The slow decrease in amplitude of the waves, as they propagate along the channel, is related to losses of energy due to flow separation at the lower edges of the channel. These effects are expressed via some kind of drag force, involving a drag coefficient which is determined from amplitude measurements along the channel. Results are given for different values of the amplitude over width ratio. The present results have some relevance for the design of new offshore barge concepts, with large rectangular moonpools. (C) 2003 Elsevier Science Ltd. All rights reserved.