Optimal Short-Range Routing of Vessels in a Seaway

Abstract

An investigation of the optimal short-range routing of a vessel in a stationary random seaway is presented. The calculations are performed not only in head seas but also in oblique waves. The evaluation of the added drag is performed by computing the time average wave force acting on the vessel in the longitudinal direction. Subsequently, the added drag is superimposed on the steady drag experienced by the ship as it advances in calm water. In this manner, the fastest path between the origin point A and the destination point B can be evaluated, taking into account operational constraints. To obtain the fastest path between two points, the underlying structure and properties of the maximum mean attainable speed are analyzed. This detailed analysis allows us to demonstrate the fastest path for the problem without any operational constraints to be a straight line. Subsequently, the solution is reevaluated for scenarios where the original optimal path violates at least one of the operability criteria considered. For that case, a fastest path is found to be a path consisting of one waypoint, that is, a two line segment path. In addition to providing a closed-form fastest-path solution for the case of no operational constraints, a bound is provided for travel time error for more general speed functions in the case where a straight line path is followed.