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Updated: May 10, 2026

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Ship wakes: Kelvin or Mach angle?
1Laboratoire FAST, Université Paris-Sud, UPMC Université Paris 6, CNRS, Bâtiment 502, Campus Universitaire, 91405 Orsay, France.
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.
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