title: Ship wakes: Kelvin or Mach angle?
abstract: From the analysis of a set of airborne images of ship wakes, we show that the wake angles decrease as U(-1) at large velocities, in a way similar to the Mach cone for supersonic airplanes. This previously unnoticed Mach-like regime is in contradiction with the celebrated Kelvin prediction of a constant angle of 19.47° independent of the ship's speed. We propose here a model, confirmed by numerical simulations, in which the finite size of the disturbance explains this transition between the Kelvin and Mach regimes at a Froude number Fr=U/√[gL]~/=0.5, where L is the hull ship length.
authors.affiliation: Laboratoire FAST, Université Paris-Sud, UPMC Université Paris 6, CNRS, Bâtiment 502, Campus Universitaire, 91405 Orsay, France.
authors.forename: Marc
authors.initials: M
authors.lastname: Rabaud
authors.forename: Frédéric
authors.initials: F
authors.lastname: Moisy