On the surface and internal gravitational waves in a three-layer immiscible liquid

A capillary–gravitational periodic wave motion in a laminated three-layer liquid is theoretically studied in terms of a linear mathematical model. Two upper layers are of a finite thickness, whereas the bottom layer is indefinitely deep. A dispersion relation is derived. Two analytical expressions for the internal-to-internal and internal-to-surface wave amplitude ratios are found. It is shown that the internal-to-surface wave amplitude ratio may be large if the densities of the respective liquids are close to each other.