For navigation locks, the forces on moored ships during the lockage are a most relevant design criterion, as they are a measure for the safety of the ships during the locking process. In most cases, these forces are controlled by the choice of the filling system and by the valve schedules. For locks at the boundary between fresh and saltwater regions, the situation differs significantly from locks with the same water density at both sides. While filling systems with distribution systems (longitudinal culverts, pressure chamber under the lock chamber etc.) are rather robust in terms of the impact of density differences, through-the-head systems show a significant impact of the density induced currents on the vessel.
In this presentation, the impact of the density induced currents on the vessels for different through-the-head filling systems will be shown on the basis of three-dimensional numerical model tests. A special focus will be put on the question whether a better mixing in the area of the upper head will be a viable solution to mitigate the density induced currents and thus the forces on the vessel. This mixing process can be induced by the shape of the filling system and is very effective for systems with freshwater only (or saltwater only). In these cases, the mixing distributes the momentum of the flow over a larger area of the chamber and thus reduces the forces on the vessel. Here, the effectivity of this process will be evaluated for situations were additionally density currents occur.