Free-surface and rigid-lid MCC models for internal waves generated by a bottom disturbance

Bottom disturbances in density-stratified oceans can generate both internal and surface waves. In this paper, the strongly non-linear free-surface Miyata-Choi-Camassa model (MCC-FS) is applied to investigate the internal and surface waves generated by a moving bottom body in a two-layer fluid system, and a comparison with its rigid-lid counterpart (MCC-RL) is conducted to clarify the influence of the free surface on the generated internal waves. The waves generated by a moving bottom body are simulated and compared with computational fluid dynamics results, showing good agreement in both internal- and surface-wave profiles. A systematic comparison between the MCC-FS and MCC-RL models shows that the MCC-FS model predicts fewer internal waves within the same time interval, a shorter propagation distance of the leading wave, and a slightly lower critical speed, while the wave amplitude is only weakly affected. Moreover, the leading-wave location difference increases non-linearly with body speed when the moving-body speed is lower than the critical speed, but the free-surface effect becomes insignificant when the moving-body speed exceeds the critical speed.