In article ,
Stephen Baker wrote:

"THe energy associated with the transverse wave system travels at the "group
velocity" of the waves, which equals one-half of the phase velocity in deep
water. The propulsion system of the ship must therefore put additional energy
into the wave syste, to replace that which "falls behind". A nominal
relationship between ship speed and the length of the corresponding transverse
wave may be found by equating the ship velocity with the _celerity_ (phase
velocity) of a small-amplitude gravity wave in deep water,

Vship = Cwave = sqrt( g.Lw/(2.pi)) = 2.26 sqrt(Lw)

Yes, this is the formula. But what I'm interested in is the theory
it's based on - the general theory of waves in fluids, of which
small-amplitude deep-water surface waves are one particular case.



Thank you,
Sakari Aaltonen