trim can be correctly predicted by such calculations.


Sailing along irregular banks In addition to this approach, a more complete assessment of the navigational safety in inland waterways must include realistic scenarios, such as passing ships or sailing along irregular banks.


Figure 1: Captive model tests of an inland ship in shallow water


Indeed, the transition towards natural river banks in the Netherlands has resulted in irregularities in the bank slopes, due to non-homogeneous erosion. These irregu la ri- ties of the banks, especially when submerged, affect water flow in the waterway, placing unexpected and substantial manoeuvring loads on passing vessels. Ships therefore require additional lateral space in the waterway to correct for these effects.


A systematic, numerical study was conducted at MARIN to quantify the effect of a represen- tative bank irregularity on the sailing trajectory of a passing inland vessel (see Figure 2). This study combined complex CFD calculations evaluating the hydrodynamic loads induced by the irregularity (see Figure 3), with time-domain simulations determining the ship trajectory. The potential danger of bank irregularities can be assessed, which will help local authorities decide whether a river section should be dredged.


Our research improves the understanding of sailing in confined, shallow waters and will result in improved models for prediction of squat and manoeuvring performance in a variety of fairway configurations. We have subsequently concluded the tests and we are currently analysing the results. We look forward to outlining the full results in a next edition of Report magazine.


Figure 2: Track of a ship sailing along an irregular bank - time-domain simulations


Squat prediction Another part of the project focused on the squat of inland ships. In very confined waters, the already small under keel clearances are reduced even further due to squat. To start with, we made a summary of the available knowledge on this subject, based on an internal research project we performed earlier. An empirical method to obtain an estimation of the mid ship squat within approximately 10


centimetres is proposed. In some conditions, the dynamic trim due to squat can be substantial. More insight is required in the direction and the amount of dynamic trim. For this purpose model tests have recently been performed with a Class Va inland ship with various loading conditions, water depths and speeds. These model test results will be compared with the results from CFD calculations to check whether the dynamic


Figure 3: Asymmetric pressure field of a ship sailing along an irregular bank - CFD simulations


report 17


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