Inland ship stern optimization in shallow water

Inland ships continuously operate in restricted waters, where the depth and width are regularly less than twice the ship's draft and four times ship breadth, respectively. In restricted water, the flow around the hull changes compared to that in unrestricted water due to presence of the fairway bottom and sides, that lead to increased return flow, stronger squat effects and changes in the wave pattern produced by the ship. If these changes to the flow are significant, it is worthwhile to optimize the hull form for shallow or confined water rather than for unrestricted water. This paper specifically focuses on the effects of water depth on inland ship stern optimization. It presents the optimization of propulsion power for various water depths using a parametric inland ship stern shape, CFD and surrogate modeling. The change of parameter influence in different water depths is analyzed and explained by means of flow visualization. Using Pareto fronts, a trade-off is shown: propulsion power in shallow water can be decreased at the cost of increased propulsion power in deep water and vice versa.