Kelvin Wake

The Kelvin wake is the V-shaped wave pattern trailing a vessel moving through deep water, bounded by two cusp lines that, for any steady speed, make a half-angle of about 19.47 degrees with the track. Lord Kelvin derived it in 1887 from deep-water wave dispersion; the pattern combines transverse waves crossing the track and divergent waves angled outward, meeting at the cusps. The angle is independent of speed in deep water but the wavelength grows with speed. It is used in remote-sensing ship detection and is a wash hazard to small craft and moorings.