Diffraction and Interaction of Interfacial Solitons in a Two-Layer Fluid of Great Depth

SIAM Journal on Applied Mathematics, Volume 84, Issue 4, Page 1385-1412, August 2024.
Abstract. This paper aims to present a novel isotropic bidirectional model for studying weakly dispersive and weakly nonlinear atmospheric internal waves in a three-dimensional system consisting of two superimposed, incompressible, and inviscid fluids. The newly developed equation is the Benjamin–Benney–Luke (BBL) equation, a generalization of the famous two-dimensional Benjamin–Ono (2DBO) equation and the Benney–Luke equation, derived using the nonlocal Ablowitz–Fokas–Musslimani formulation of water waves. The evolution results of the BBL and 2DBO equations, performed by implementing the classic fourth-order Runge–Kutta method, the pseudospectral scheme with the integrating factor method, and the windowing scheme, show that the anisotropic 2DBO equation agrees well with the isotropic BBL model for problems being investigated, namely the focus is the central part of the soliton evolution/interaction zone. By applying the Whitham modulation theory, modulation equations for the 2DBO equation are obtained in this paper for analyzing the soliton dynamics in five different initial-value problems (truncated line soliton, line soliton, bent-stem soliton, bent soliton, and reverse bent soliton). In addition, corresponding numerical results are obtained and shown to agree well with the theoretical predictions. Both theoretical and numerical results reveal the formation conditions of the Mach expansion, as well as the specific relationship between the amplitude of the Mach stem and the initial data.