Ship interaction is a phenomenon that occurs when two ships encounter (opposite direction of motion) or overtake (same direction of motion). One of these ships may be stationary and the ships may or may not have different speeds. This interaction phenomenon manifests as time-dependent force and moment trends (6 degrees of freedom) that depend on relative position, speeds, draughts, water depths and drift angles, among others.

To account for this phenomenon during simulations with a real-time ship simulator, Flanders Hydraulics (FH) developed a regression model based on a model test program from 2000. However, this model has some significant drawbacks:

• A separate set of regression coefficients is necessary for each ship combination, for each degree of freedom and for each manoeuvre.
• The number of extrema, and the shape of trend line, is fixed in advance, which is not always the case when ships differ in length.
• The modelling is closely related to the examined ship combinations from the towing tank and is not always realistically applicable to different ship combinations or ships with different shape from the simulator fleet..

Ship combinations that were not included in the original test programme are determined by the simulator via an interpolation of the regression coefficients. This and the above limitations became increasingly apparent in recent years, so this doctoral research was initiated to improve the real-time modelling in the simulator at FH. The main goal is to extend the formulation to arbitrary ship shapes and to ship combinations with widely varying dimensions.

To achieve this goal, model tests carried out after the original test programme can be used. Numerical tools such as potential codes and computational fluid dynamics (CFD) can also be used to increase the understanding of the phenomenon. The structure of the new model is open for research (regression model, potential code...). The aim of this PhD research is to develop a new model that truthfully estimates the interaction trend in real-time for arbitrary combinations of vessels.