A Time Domain Solution to the Motions of a Steered Ship in Waves.
CALIFORNIA UNIV BERKELEY DEPT OF NAVAL ARCHITECTURE
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The problem of ship motions in waves is formulated in the time domain by means of a convolution integral which relates the ship motion response to arbitrary exciting forces, under assumption that the response is linear. The convolution integral is evaluated numerically to obtain the ship motions at discrete intervals of time. Frequency independent nonlinearities of arbitrary form are incorporated into the model by considering them as part of the arbitrary exciting forces. Nonlinearities with time lag, such as those arising from rudder motions, are particularly amenable to this treatment. Nonlinearities that are functions of the instantaneous motions of the ship are approximated by continuously extrapolating the ship motions. Thus one is able to include frequency-dependent linear force terms in what amounts to a stepwise solution of the nonlinear equation of motion, a capability not available in the conventional direct numerical integration techniques exemplified by, e.g., Runge-Kutta. Author
- Physical and Dynamic Oceanography
- Marine Engineering