An investigation of hydrodynamic forcing on a semi-planing monohull in following and stern quartering seas

Artikel i vetenskaplig tidskrift, 2006

Navigating a ship in following and stern quartering seas is well known to seafarers for the possible troublesome situations that may arise. The issue has also been addressed by many researchers during the last 50 years. In 1964 Du Cane and Goodrich presented one of the first systematic studies on ships in following seas together with a compilation of accounts on real occurrences of dangerous situations for ships in following and stern quartering seas. Later research has confirmed the possibility for occurrence of several types of allegedly capricious behaviour for a ship travelling at a course within one third of the compass card, i.e. between −60° and 60° relative to the waves. The research included in the references is covering many different types of ships from fishing boats to fast naval vessels and merchant ships. Despite the 51 years of research in the tradition pointed out by Du Cane and Goodrich’s work, there is still a lack of effective methodology within many of the areas connected to following and stern quartering seas. The present paper is mainly focusing on manoeuvring in following seas. Nevertheless, results included in the current paper, among others, show that ship motion in the horizontal plane has a major impact on the magnitude and timing of wave excitation in all degrees of freedom. Therefore the presented results are of importance for most of the seakeeping and safety issues related to navigation in following and stern quartering seas. The most significant results presented in the current paper come from semi-captive tests with a semi-planing ship model At these tests the surge force, sway force, roll moment and yaw moment were measured, while the ship model was free to heave and pitch. The test data are compared to computational data obtained by a strongly simplified hydrodynamic modelling. This comparison shows very encouraging results. The paper does also address criteria for safe manoeuvring in following and stern quartering seas, methodologies for full-scale tests and experiments with a free-running scale model.