Boundary between unsteady and overturning ship bow wave regimes

Measurements of the bow waves generated by a rectangular flat plate, immersed at a draught D = 0.2 in, towed at constant speed U = 1.75 m s(-1) in calin water and held at a heel angle 10 degrees and a series of nine yaw angles alpha = 10 degrees, 15 degrees, 20 degrees, 25 degrees, 30 degrees, 45 degrees, 60 degrees, 75 degrees and 90 degrees are reported. The measurements show that bow wave unsteadiness is significantly larger for the flat plate towed at yaw angles 30 degrees <=alpha <= 90 degrees than at 10 degrees <= alpha <= 20 degrees, which are associated with the unsteady and Overturning bow wave regimes, respectively, separated by the boundary U / root gD = 4.4 tance/cos alpha - 1 with g = acceleration of gravity. These measurements of bow wave unsteadiness provide preliminary experimental validation of the foregoing simple theoretical relation for the boundary between the unsteady and overturning bow wave regimes for non-bulbous wedge-shaped ship bows with insignificant rake and flare. Extension of this relation to more complicated ship bows, notably bows with rake and flare, is also considered.