Development of Prediction Methods Required for Stability Assessment of River-Sea Ships

The natural roll frequency and the effective wave slope coefficient are two essential parameters for dynamic ship stability assessment. While these parameters may be calculated based on first principles, or even experimentally, simplified semi-empirical methods still represent a more practical approach for everyday use. However, there is a lack of adequate methods for river-sea ships. Therefore, the paper presents regression formulae for added inertia, for use in the prediction of natural roll frequency, and for effective wave slope coefficient at the natural roll frequency. The performance of the developed formulae is assessed with respect to the original data they were derived from, as well as with respect to a test dataset. Furthermore, for the prediction of natural roll frequency, a comparison is carried with an existing semi-empirical method specifically intended for inland vessels and river-sea ships, showing that the formulae proposed in the paper could lead to significant improvements in prediction capabilities.