Laboratory Studies of Internal Solitary Waves Propagating and Breaking over Submarine Canyons

This paper carried out laboratory experiments to study evolution of internal solitary waves (ISWs) over submarine canyons with a combination of PIV (particle image velocimetry) and PLIF (planar laser-induced fluorescence) techniques. Taking canyon angle theta and collapse height increment (H) as variables, Froude number F-r, head position, energy loss, vorticity field and turbulence intensity when ISWs propagate to the canyon were analyzed. According to the Froude number F-r values, the study cases can be divided into three types: F-r > 1.7 means complete internal hydraulic jump (IHJ); 1 < F-r < 1.7 denotes wavy IHJ and F-r < 1 represents no IHJ. The greater canyon angle, collapse depth and amplitude of the incident wave more easily generate IHJs, which can lead to more energy loss, greater vorticity and turbulence intensity in the canyon area. Among all canyon cases, vorticity and turbulence intensity of the no IHJ case showing an obvious bimodal distribution are smaller than IHJ cases. For wavy IHJ, the energy dissipation is not obvious, and the average turbulent intensity performs a "sharp unimodal distribution". Complete IHJ cases last for a long time and cause violent mixing, the average turbulent intensity is the largest and its distribution presents a "gentle single peak" pattern. For the 180 degrees conditions (no canyon cases), less energy is delivered to the reflected wave and more energy is dissipated near the terrain, so the energy loss is the largest in comparison to other conditions. These findings will deepen our understanding of the evolution mechanisms of ISWs propagating over submarine canyons.