The transition towards natural river banks in the Netherlands has resulted in irregularities in shorelines and underwater banks. These irregularities and especially submerged banks affect water flow near the bank, placing unexpected and substantial manoeuvring loads on passing vessels. Ships therefore require additional lateral space in the fairway to correct for these effects.
The forces induced by an irregular bank on a typical 110-metre inland vessel are investigated by means of full-scale CFD1 calculations. The vessel is fitted with a single propeller and two spade rudders. Based on the results, a time-domain simulation model is developed, and the effect of the irregular bank on the ship motions is investigated through a large number of simulations. The irregular bank is modelled on the situation near Gennep on the Meuse river in the Netherlands, where unexpected behaviour of passing ships has been reported.
The vessel considered is a typical 110-metre inland ship, with a beam of 11.40 m and a draught at rest of 3.50 m. The water depth in the fairway is 5.20 m. The ship sails upstream at 3.5 m/s through the water, with and without current.
This investigation follows a study conducted in 2017, where MARIN and Rijkswaterstaat investigated the feasibility of a numerical approach by comparing model tests with CFD calculations.
Results of that study showed that the hydrodynamic forces are well captured by the CFD results. Surge and sway forces showed similar trends and order of magnitudes. Computed yaw moments evidenced a shift in time with respect to the model test results. (Exer 2015, Oud 2017).