Spatial variations of waves propagating over a submerged rectangular obstacle

Experiments are performed in a wave flume to examine the generation of harmonics by non-breaking surface waves travelling over a submerged obstacle. Spatial wave profiles are recorded using an optical measurement system, similar to the approach used by Perlin [Perlin, M., Lin, H., Ting, C.L., 1993. On parasitic capillary waves generated by steep gravity waves: an experimental investigation with spatial and temporal measurements. J. Fluid Mech., 255, 597-620]. Moreover, an extended Boussinesq equation developed by Nwogu [Nwogu, O., 1993. An alternative form of the Boussinesq equations for modelling the propagation of waves from deep to shallow water. J. of Waterway, Port, Coastal and Ocean Eng. ASCE, 119(6), 618-638] is used to numerically simulate the wave field. The experimental results demonstrate that non-linear wave effects generate super harmonics, and the amplitude of those harmonics grows as waves travel above the models. The order of super harmonics increases with wave non-linearity. Numerical results are also found to over-estimate the amplitudes of super harmonics and the total averaged energy flux.