Harmonic generation of interfacial waves at a submerged bathymetric ridge

Abstract

When two-layer, periodic, interfacial wave trains pass over a Gaussian ridge, waves of higher harmonic frequency can be excited at the ridge, which then propagate downstream independently of the incident wave. In laboratory experiments, the amount of energy transferred to higher harmonic frequencies increases with the nonlinearity of the main wave over the ridge crest. When the wave nonlinearity is increased to the point where breaking occurs over the ridge, harmonic generation can still occur. The length scale of the obstacle relative to the wavelength can also influence the energy transfer, which is consistent with analogous surface wave studies. The upper limit for which harmonic frequencies can be excited is set by the stratification. This wave-topography interaction provides a possible mechanism for transferring energy in the internal wavefield to smaller scales. Copyright 2010 by the American Geophysical Union.