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Abstract

A model for internal interfacial waves between two layers of fluid in the presence of current and variable bottom is studied in the flat-surface approximation. Fluids are assumed to be incompressible and inviscid. Another assumption is that the upper layer is considerably deeper with a lower density than the lower layer. The fluid dynamics is presented in Hamiltonian form with appropriate Dirichlet–Neumann operators for the two fluid domains, and the depth-dependent current is taken into account. The well known integrable Intermediate Long Wave Equation (ILWE) is derived as an asymptotic internal waves model in the case of flat bottom. For a non-flat bottom the ILWE is with variable coefficients. Two limits of the ILWE lead to the integrable Benjamin–Ono and Korteweg-de Vries equations. Higher-order ILWE is obtained as well.

Keywords

Dirichlet–Neumann operator, Intermediate long-wave equation, Internal waves, Shear current

Publication Date

2026-01-01

Publication Title

Nonlinear Analysis: Real World Applications

Volume

87

ISSN

1468-1218

Deposit Date

2026-01-27

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.


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