Simulation-based investigation of ship response patterns in bi-chromatic following seas in support of model tests

• Numerical study supporting surf-riding model tests in bi-chromatic following waves. • Evaluation of the robustness of the existing theory as a research gap. • Bi-chromatic, being an irregular wave, differs qualitatively from monochromatic. • New characteristic motion patterns have been observed and classified. The aim of this qualitative study was to numerically investigate surging and surf-riding in bi-chromatic following waves in order to facilitate a model test. The demand to evaluate the robustness of the existing theory was identified as a research gap. The focus of this study is the ship’s instantaneous surge velocity under bi-chromatic following wave conditions, which is referred to herein as the ship’s response. The study, carried out in a bi-chromatic wave, reveals new phenomena in ship’s response that cannot be found in the monochromatic wave conditions and shows the qualitative difference between regular and irregular waves. Characteristic response patterns have been observed and classified with the intention to be investigated in the experimental study on the towing tank in the nearest future. The results obtained, represent progress toward a deeper understanding of the surf-riding phenomenon in bi-chromatic following waves. Future work will include developing the simple single-degree-of-freedom mathematical model used in this study. It will be based on the comparison of the results of towing tank experiment and the numerical study.