Author(s): G. La Forgia; T. Tokyay; C. Adduce; G. Constantinescu

Linked Author(s): Claudia Adduce, George Constantinescu

Keywords: Internal solitary waves; Large eddy simulation; Wave breaking; Sloping boundary; Mixing efficiency

Abstract: By Large Eddy Simulations (LES), we investigate the effects of internal solitary waves (ISW) breaking over a sloping boundary. We analyse how the different breaking mechanisms affect the entrainment, the mixing efficiency and the bed shear stress. ISWs interacting with the continental shelf/slope can shoal and then differently break, depending both on the bathymetry and on the waves geometric and kinematic features. Three ISWs breaking mechanisms are commonly identified in literature: plunging (P), collapsing (C) and surging (S) breakers. The Iribarren number is used to define the breaking domains. It is defined as the ratio between the topographic slope and the square root of the wave slope (i.e. the ratio between the wave amplitude and the wavelength). The steepening of the trailing edge and its quick overturning characterize the plunging breakers. When the downward and offshore motion of the dense fluid confined between the wave and the incline induces boundary layer separation, a collapsing breaker occurs. A surging breaker shows, instead, a large gravity current flowing up the slope. We reproduced three laboratory experiments on ISWs by fully 3-D LES, focusing on quantities that cannot be obtained by laboratory experiments. We qualitatively and quantitatively described the different breaking mechanism, relating their dynamics with the effect they induce within the fluid and over the inclined surface. For three different breaking types, we investigated the fluid entrainment into the pycnocline region, and the instantaneous mixing efficiency. Moreover, we analyzed the spatial and temporal distribution of the bed shear stress velocities on the incline during the interaction with the wave.

DOI: https://doi.org/10.3850/978-981-11-2731-1_064-cd

Year: 2018