Correctly predicting the track of a ship when impacted by incident waves is one of the most important tasks in accurately simulating seakeeping performance. This is especially difficult during a storm surge in coastal regions, where the bottom topography rapidly changes. In fact accurately predicting a ship track in calm water has not been completely solved. Most recently, Lin et al. integrated the total forces and moments over an actual ship hull and rudders in a fully nonlinear ship motion model named the Digital, Self-consistent Ship Experimental Laboratory (DiSSEL) by using finite element/finite difference in calm water (Lin et al. 2005 [1], Lin and Kuang, 2006 [2], 2008 [3], 2009 [4]; Lin et al., 2009 [5]). The new method is not only accurate, but also computationally efficient. As part of a continuing effort, in this study, the incident wave impact is now included. The incident wave impact on the ship hull and rudders is integrated over the actual wetted surfaces at each time step, based on the ship position. First, the numerical simulations are benchmarked using existing experimental data for an experimental hull form. The DiSSEL simulations agree well with the experimental data. Based on the simulations, we explore the physics to gain an understanding into the possible factors that cause changes to the ship tracks. For example, why will the turning circle of a ship with constant rudder angle and ship speed, in the presence of waves, sometimes be a spiral while other times remain a circle? Finally DiSSEL will be coupled with the coastal wave model by Lin and Perrie (1997, 1999) [6], [7], to predict the ship track in a coastal region impacted by a storm surge. Future improvements to DiSSEL will include the incorporation of a propeller model. Since a model for the propellers has not yet been implemented, the influence of the propeller slipstream on the rudder is currently handled by empirically modifying the effective inflow velocity into the rudder to account for the acceleration of the flow by the propeller.

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