On the simulation of amplified bow waves induced by motion in head seas

The prediction of bow wave amplification for a ship navigating in head seas is achieved by means of the 2D + t nonlinear slender-body theory. High-res olution numerical simulations show the development of spray sheets along th e hull. For conditions of navigation severe enough, the thick jets rise and top the deck level, leading to the possibility of deck wetness. The overal l capabilities of the method of calculation are demonstrated through a syst ematic study for a frigate. Continuous time domain pictures of the flow as the bow enters the incoming waves are presented. The relationship between t he incoming wave parameters and the sequence of probable events (deck wetne ss, slamming,...) that occurs in the bow region is studied, leading to pred ictions of both the onset and strength of probable deck wetness, as well as forefoot emergence and possible slamming events. The probability of deck w etness in the numerical simulation is confirmed by model experiments. Resul ts are summarized in charts that allow critical evaluation of a given desig n (see Figs. 8 and 9), including the nonlinear dynamic rise of the water el evation, experienced as a spray sheet along the hull-of critical importance for predicting the probable onset of deck wetness. These charts would seem extremely useful in the design phase, and it is our major purpose here to bring the possibility of computing them with the 2D + t method to the atten tion of naval architects.