TABLE OF CONTENTS In the "traditional" maneuvering and seakeeping analyses described in the preceding chapters, it is assumed that the geometry of the "wetted" hull surface is constant. For high-speed craft, dynamic lift is developed which results in a speed-dependent reduction in draft relative to the static condition, accompanied by a change of trim. Some of the consequences are:
All hydrodynamic (and "hydrostatic") coefficients are strongly dependent on speed, even when normalized using speed squared.
Longitudinal and lateral motions are coupled, since changes in trim and heave affect the underwater geometry, which in turn affects lateral as well as vertical and longitudinal forces.
In waves, the underwater geometry may change significantly during the passage of a single wave; in extreme cases the craft might even become airborne. Thus nonlinear seakeeping behavior is more significant compared with displacement ships.
Thus the methods presented in the previous chapters for prediction of hydrodynamic forces and moments should be applied with caution in the regime where dynamic lift is significant.
In this final chapter we will briefly summarize some of the available methods for prediction of the maneuvering and seakeeping behavior of high-speed monohulls. We will define "high speed" as that at which the effects of dynamic lift become significant; this generally occurs above a Froude number of about 0.7 0.8.
As we stated above, there is a high degree of coupling among the various motions of high-speed craft. Thus the surge-sway-yaw equations cannot be reliably used for trajectory predictions, as...
