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Accurate estimation of ship motions is inevitable for safe, economical, and environmentally friendly ship routing. Onboard measurements have been conducted for a bulk carrier in 2010–2016, including eight rough seas in the Northern and Southern Hemispheres. Rough sea conditions were reproduced using a wave model, WaveWATCH III, with wind inputs from meteorological organizations. Ship performances were evaluated using traditional seakeeping theories, with the main focus being on transverse motion. The 3D frequency-domain Rankine Panel Method (RPM), New Strip Method (NSM), and Enhanced Unified Theory (EUT) were compared. First, roll decay tests and simplified Ikeda's methods of roll damping were applied in each method. Second, the results of the model tests in oblique seas in regular waves were additionally considered for the accurate estimation of ship motions in actual seas. These were validated with measured ship motions in eight rough sea voyages. It was found that errors are smaller in the RPM than those in the EUT and NSM for measured roll and pitch motions in actual seas. The favorable results obtained using the proposed methods may provide a new alternative for optimal ship routing to predict ship roll and pitch motions in rough seas with reliable accuracy and computational efficiency. • Ship motions in actual seas are analyzed for 28,000DWT bulk carrier. • Frequency-domain Rankine panel method is used to estimate ship motions. • New strip method and enhanced unified theory are used for comparison. • Roll damping is estimated by decay tests and simplified Ikeda's methods. • Ship motion computations are validated by model tests and actual seas. [ABSTRACT FROM AUTHOR]

In recent years, the number of waiting ships in offshore anchorage has increased owing to several reasons, such as the port lockdown and increased cargo volumes in maritime transportations. Moreover, port terminals have ordered ships to stay outside the harbor to prevent mooring accidents when rough waves are forecasted. Anchored ships have been exposed to dangers owing to dragging anchors under rough sea conditions, especially those facing the open seas. In this study, we perform a numerical simulation of anchored ship motions to reproduce the dragging anchor. Additionally, we further evaluated the anchored ship motions based on underestimated wave conditions. Lastly, we constructed a novel risk assessment technique for anchored ships to assess the stranding risk, damage to marine structures, and risk of collision. The stranding risk was evaluated based on the relationship between the vertical displacement and Under Keel Clearance (UKC). Damaging risk can be identified from the information of harbor charts. The risk of collision was quantitatively assessed considering the main influential factors such as Closest Point of Approach (CPA), and the Ship Domain Overlapping Index (SDOI). Results showed that the proposed methodology can contribute to port safety and ship operation in terms of optimal ship routing. • Anchored ship motions are simulated for 28,000-DWT bulk carrier. • Drifted distance of anchored ship can be estimated with underestimated waves. • Risk of stranding is assessed by the UKC and vertical displacements. • Risk of collision can be quantitatively estimated with relative ship's positions. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

Restrictions on greenhouse gas emissions and the existence of developing countries has diversified ship routes and ship types, making the ship operation more complex. Many types of simulation methods have come up in the last decade due to the enforcement of the energy efficiency design index. However, few studies that validated their simulations with actual data. This study performs the optimal ship routing of a 28,000-DWT-class bulk carrier to evaluate the optimal ship route with the speed loss analysis. The simulation results are compared with the measurement data of the bulk carrier in conditions including rough sea voyage in the Pacific Ocean. For comparison, a modified version of the speed loss analysis algorithm is developed. These algorithms are combined with the isochrone method. The differences in the simulation results with the American and European weather databases without higher wave avoidance and deliberate speed reduction are obvious. The simulated routes are closer to the measured ship trajectory if higher wave avoidance is considered. There are a couple of remarkable speed drops in the measured result, and the deliberate speed reduction is considered. Finally, some factors to control the reproducibility of ship routing including in rough sea voyages are summarized. • The analytical model with time-domain speed loss evaluation is constructed. • Optimal route is simulated for 28,000-DWT bulk carrier with measured data. • Differences of simulations are clarified in each condition with actual voyage. • Speed loss is evaluated by introducing precise seakeeping and propulsion theories. [ABSTRACT FROM AUTHOR]

In addition to other studies focused on the WRF performance of rainfall, temperature, and precipitation, the present study provides practical suggestions for ship operators on choosing grid point value (GPV) datasets and WRF modeling approaches to help make better decisions on weather routing by estimating strong wind with a higher accuracy. Two different GPV datasets, the NCEP-FNL and ERA-Interim, are used for WRF modeling. Various modeling approaches, which include applying different physics options and choosing whether to adopt the four-dimensional-data-assimilation, are employed for numerical simulation. Then, on-board measurements of a bulk carrier has been used to validate the calculated wind of eight rough-sea navigational cases. This occurs over a wide spatial range, covering ocean regions such as the Northwest Pacific Ocean, South of Australia, Tasman Sea, Southeast of Africa, and Southeast of America, as well as a wide temporal range of four years. Results of 64 WRF simulations show that ERA-Interim is suitable for longer periods, while NCEP-FNL can analyze extremely high winds. Additionally, grid nudging can also reduce the wind strength due to its smoothing effect. Finally, selections of these different GPV datasets and modeling approaches for ship weather routing are discussed, particularly for rough-sea navigations. • Ocean surface wind over rough seas of several seasons and ocean regions have been generated. • GPV datasets including both the NCEP-FNL and ERA-Interim have been utilized for wind simulation. • On-board observations of weather and ship motion has been done for a long term. • Modelling approaches can add significant value to optimum ship routing. [ABSTRACT FROM AUTHOR]

Abstract: Sea states, such as waves, tidal currents, and wind are important factors for safe and economic ship navigation. In previous papers of Xia et al. (2006a, 2006b) single factor generated by low pressure was studied independently. The objective of this paper is to study how ship navigation is affected by the combined effects of these factors. For clarification, simulations of two representative typhoons were conducted, and the results were compared. Numerical simulations of tidal currents, waves, and wind were applied to provide high-resolution information, which was then used to simulate ship navigation. Estimation of ship position was found effectively by comparing the results from these two cases and using the proposed numerical navigation simulation method. [Copyright &y& Elsevier]