Dynamic analysis on the interaction of two successive internal solitary waves with a ridge

Abstract

Internal solitary waves (ISWs) typically manifest as soliton or wave trains in the ocean. Previous studies have extensively explored the dynamic properties of individual ISWs over topography. However, when the distance between successive ISWs in a wave train is less than a certain threshold, the interaction of multiple ISWs with the topography introduces mutual interference, leading to a more complex dynamical process. Therefore, this study established a numerical model based on OpenFOAM and analyzed the dynamical processes of two successive ISWs interacting with Gaussian ridges at different intervals. The findings reveal that the velocity field induced by the second wave (Wb) can transport and deform the vortex generated by the first wave (Wa) when Rab < 5 (Rab=Dab/Lw, where Dab is the distance between two ISWs, and Lw is the half-amplitude width). Additionally, the background field variation induced by Wa affects the shoaling and breaking of Wb. Particularly, when Rab < 3, the energy radiated to both sides of the ridge varies markedly with changes of Rab. The reflected leading wave of Wa is strengthened, while the transmitted leading wave of Wb is weakened, transferring energy to the transmitted trailing wave of Wa(the peak occurs at Rab=2.52). The interaction between the two waves not only modifies the energy structure but also distinguishes the variation in the dynamics of the bottom boundary layer from that of a single ISW. Notably, the negative bottom shear stress extremes induced by Wb are significantly enhanced, with the maximum value increasing by about 60%.