Nonlinear Time Domain Simulation Technology for Seakeeping and Wave-Load Analysis for Modern Ship Design

This paper describes recent developments and new applications in the field of numerical simulation for nonlinear ship motions using the Large Amplitude Motion Program (LAMP), following up on our 1997 paper (Shin, et al. 1997). The objective of LAMP’s development is to develop an analysis tool for highly realistic prediction of wave loads and behavior for a ship in severe seas. This approach is based on physics and does not rely on statistical information gathered from model tests or existing ships, so it is expected to be especially useful for new ship types. The kernel of LAMP is panel-based potential flow solution of the ship-wave hydrodynamic problem with many numerical options, including a recently-added Rankine singularity model with a damping beach and an option to rapidly compute the perturbation potential using pre-computed Impulse Response Function (IRF) potentials. The paper describes important implementation details for these and other computational options added since 1997. The LAMP System is structured so that numerical or empirical models of other systems or effects can be directly incorporated into the time domain ship motions and load calculations using a series of optional features. One such feature is a multi-level green-water-on-deck model including a finite-volume solution of 3-D shallow water flow over the deck. This model can be used for analyzing ship behavior with water on deck and loads caused by green-water-on-deck. Numerical results illustrate the effect of green-water-on-deck on the pitch motion and vertical bending moment of a cruiser in head seas and on the roll behavior of a fishing vessel. Another feature involves anti-roll fin and tank systems, including an integrated anti-roll tank model that solves for fluid motion in a U-tube tank concurrently with the wave-body hydrodynamics. The paper evaluates the use of passive anti-roll tanks to mitigate parametric roll resonance. Recent development has focused on applying LAMP to unconventional ships, multi-hull high-speed displacement ships, and non-ship-like configurations. Results are presented from studies for an advanced Naval hull form, a trimaran, and a semi-submersible platform.