||Equipped with advanced field instruments in the past few decades, oceanographers have been able to comprehend some characteristics of the internal waves(IWs), such as the generation, propagation and energy dissipation, as well as to promote understanding in oceanography and marine ecology affected by IWs in the world ocean. Although surface gravity wave and internal wave are two of the most common natural phenomena in the ocean, the interaction between them has not been fully investigated, despite limited theoretical derivations in the literature, nor using laboratory experiments to verify the theory.|
A series of laboratory experiments were conducted at the National Sun Yen-sen University to study the waveform evolution of continuous IWs propagation on the flat bottom and across a trapezoidal obstacle. Surface waves were generated on a density stratified fluid system in a wave flume, from which IWs were induced indirectly to investigate their wave properties associated with their propagation . The experimental results are then used to determine the maximum depth which could be affected by surface waves in different wave conditions(wave height and period), as well as the amplitude of the IWs induced. The relationship between them are then presented in graphic form. Experiments were also conducted in uniform density and stratified fluid system with a trapezoidal obstacle. The results reveal that (1)long-period surface waves were susceptible to the interaction with the IWs in a stratified system, thus rendering wave height reduction, and (2)short-period surface waves interactions with their IWs counterparts was insignificant, hence yielded wave height similar to that in uniform density fluid system.
Moreover, experiments were also conducted to study for long and short period IW propagated over pseudo slope-shelf(using trapezoidal obstacle). The results show that the variation in the IWs significantly affected the strength of internal hydraulic jump and vortices on the front slope and subsequent waveform inversion on the horizontal plateau. For IWs with short period, the horizontal distance on the plateau affected by the IWs was shirter and the total time of wave-topography interaction decreased.