Numerical simulation of anchored ship motions due to wave and wind forces for enhanced safety in offshore harbor refuge

It is essential to maintain the safety of ships that are anchored in offshore harbors to avoid the influence of storms. Recently, marine casualties have been reported on anchored ships stranded in coastal areas after their anchors dragged in stormy weather. However, there have been very few studies on anchored ship motions in waves with dynamic mooring forces. In this study, information on the safety of ships in offshore harbors during storms was gathered through a nationwide questionnaire. Because previous numerical models for reproducing reported situations of marine casualties appear flawed, this study considers the dynamic calculation of chain forces and compares the results with those obtained by the catenary method. A new algorithm is constructed to reproduce the dragging anchor and grounding in waves and winds. This study is expected to contribute to the improvement of port planning related to anchorage.

► Ship operators feel that waves makes ship anchoring very dangerous as well as winds.
► We model new simulation methods of anchored ship motions to evaluate offshore safety.
► Anchored ship motions are larger when the dynamic mooring method is used.
► The new model can simulate the stranded casualty in typhoon with practical accuracy.
► It is possible to predict the safety of offshore harbor refuges more accurately.