Mini-Tsunami Made by Ship Moving Across a Depth Change

Abstract

A ship moving across a shallow depth change, in water in a small or narrow space, may create a small tsunami, 0.5–1 km long, observed as a harbor wave on shore, where a wave height up to 1.4 m has been measured. The paper gives an interpretation of the generation process of this new phenomenon. At a depth change, the ship-induced fluid velocity produces a reaction velocity of equal magnitude and opposite direction, orthogonal to the bottom. This velocity appears as a vertical velocity at the water surface, making the waves. The waves propagate with the shallow water speed upstream of a ship moving at subcritical speed. Theory and numerical calculations for a real ship geometry are compared with a moving pressure distribution. Computations compare favorably with a few available wave height measurements.