This paper gives results of an experimental study of incident and reflected waves of the bore type in the neighborhood of a sharp change in the channel bed level. It is shown that under conditions typical of accidents at ship locks, the wave height can reach 8 m.Introduction. The term breaking waves is used for downstream waves produced by dam break [1]. In the initial stage, as a rule, a breaking wave has the shape of a classical moving hydraulic jump and then becomes an undular jump. A moving hydraulic jump is termed a bore [2]. Similar waves are caused by breakdown if lock gates. In this case, the wave pattern is significantly affected by the presence of a sudden lowering of the downstream bottom level at the lock site. In particular, under certain conditions, two hydraulic jumps moving one after another are formed behind the drop [3][4][5]. Breaking waves are also generated by a tsunami or a tidal wave entering a river, by landslides of reservoir shores, falls of meteorites or rock fragments, an abrupt stop of a tanker or an inclined boat lift, wave impingement on a ship deck, etc.Breaking waves are calculated using the first shallow-water approximation [2-4, 6], Saint-Venant's equations [1,7,8] and the finite control volume method [9]. The calculation method based on the mathematical model of [10], which takes into account turbulent mixing in a hydraulic jump, is also promising. This method describes the real shape of a hydraulic jump, whereas in other methods all five possible shapes of the jump are modelled by a free-surface discontinuity. Among experimental studies, [11][12][13] worth noting.Investigation of the transformation of breaking waves on bottom irregularities is an urgent problem. In the dam-break problem, this information is necessary for accounting for the effect of local hydraulic resistances. In the problem of breakdown of a lock gate, of interest is the accident in which there is breakdown of the gate between the approach channel and the upper chamber with the second gate open (from above) and the third gate closed. This situation is especially dangerous for a ship that sails from the downstream side and is in the lower chamber at the moment of the accident.In the present paper, we give results from experimental studies of the transformation of breaking waves on a bottom irregularity in the form of a drop that can be used to check various calculation methods. Such calculations have not yet been performed since the above-mentioned methods require a rather complex adaptation to this problem.Experimental Technique. Figure 1 shows a diagram of the experiment and the coordinate system used. The experiments were performed in a rectangular channel of width 0.2 m. A drop of height b = 0.072 m was at a distance l = 2.4 m from the right closed end of the channel. The left open end of the channel was attached to a tank of width 1 m. This simulated the boundary conditions typical of a ship lock ahead of which there is a outside harbor with a large free-surface area. The initial difference between the f...
