Laboratory investigation on internal solitary waves interacting with a uniform slope

摘要

Internal solitary waves (ISWs) propagating in a two layer stratified fluid system are studied by laboratory experiments through the standard lock-release method. We investigated the generation, propagation, and breaking phases of large amplitude internal solitary waves of depression, propagating horizontally in a wave tank. ISWs main features depend on the geometrical parameters that define the initial experimental setting. Relations between ISWs geometric and kinematic features and the initial setting parameters are analyzed and empirical relations are developed. The approach of the ISWs towards a uniform slope is investigated. Depending on both wave properties and slopes values, different physical processes characterize the shoaling phase, causing different breaker type. Following a qualitatively analysis of the different breaking mechanisms, collapsing-plunging breakers show the larger contribution in terms of mixing. The characteristics of the breaking events affecting internal wave packets propagating towards the North of the Messina Strait (Mediterranean Sea) are discussed. Additional laboratory experiments are performed to investigate how the pycnocline thickness is affected by the breaking of plunging ISWs. The consequent increase of the pycnocline thickness results to be nonlinearly related with the Iribarren number.