NONLINEAR GENERATION OF NARROW-BANDED WAVE TRAINS

摘要

Analytic method for nonlinear wave generation by a wavemaker that is somewhat different from the nonlinear theory of Schdffer is proposed. The method that is based on the Nonlinear Schroedinger (NLS) equation and the nonlinear boundary condition at the wavemaker is free of 2nd order limitation inherent to the existing wavemaker theories. Advantages offered by the NLS model allowed simplification of the expressions for determination of the wavemaker driving signal and thus made them easily applicable in practice. The nonlinear correction to the wavemaker driving signal is calculated from the complex surface elevation envelope obtained as a solution of the NLS equation at the prescribed location in the wave flume. The domain of applicability of the generation method was determined on the basis of numerous experiments in the wave flume. A veiy good generation of the required wave train shape was obtained for sufficiently narrow-banded wave trains.