Laboratory Generation of Waves of Constant Form

The paper reports measurements of waves generated by a piston type wave generator. The experiments show that for 0.10 < h/L < 0.65 the waves produced by a sinusoidal piston motion can be described as a second order Stokes wave superimposed by a free second harmonic wave. Results are presented for the height and phase velocity of the free second harmonic wave and compared with theories by Fontanet (1961) and others. Finally, the height of the free second harmonic wave is successfully reduced by a non-sinusoidal time variation of the piston motion, whereas addition of a rotation to the flap motion appears to yield only minor improvements.