On the Generation of Spatially Periodic Breather in a Wave Tank

Spatially periodic modulational wave train was generated at the National Maritime Research Institute, Actual Sea Model Basin. The 76 m by 36 m basin of depth 4.5 m is surrounded by 382 paddle type wave generators with wave absorbing capacity. Taking advantage of this unique wave basin, we have compared two generation methods, first controlling the wave makers at both upwind and downwind sides and second controlling just the upwind side. The wave generator signal was computed a-priori by High-Order Spectral Method (HOSM hereafter). The HOSM provided temporally non-periodic time series of the unstable wave train as the wave-maker control signal. A number of wave wires located in the tank were used to compare the wave forms between two different generation methods. Our test result indicates that it is not necessary to provide signal at both ends, because the spatial evolution of the wave train remains periodic in space if the wave maker signal is appropriately controlled. The physical experiment and HOSM simulation seem to agree better with high order of nonlinearity.