In this paper, we present and test a discrete-event simulation approach for evaluating the inherent susceptibility to weather-induced delays during marine operations as a consequence of limitations in vessel response characteristics. The simulation routine replicates the execution of operations in a long-term perspective by applying weather data time series and vessel response-based operational criteria. Weather windows are taken as the basis for the operation start-up criterion. A case study is presented where we examine the capabilities of the simulation methodology towards reflecting the inherent weather challenges in operational scenarios and the ability to distinguish between alternative design concepts. Comparison is performed towards the percentage operability method and integrated operability factor to uncover advantages of the presented approach. Application of the simulation methodology is found to yield further knowledge of the inherent operational persistence and weather delay susceptibility of proposed vessel designs in the early phases of ship design.
In this paper, we present and evaluate three long-term wave models for application in simulation-based design of ships and marine structures. Designers and researchers often rely on historical weather data as a source for ocean area characteristics based on hindcast datasets or in-situ measurements. The limited access and size of historical datasets reduces repeatability of simulations and analyses, making it difficult to assess the sampling variability of performance and loads on marine vessels and structures.Markov, VAR and VARMA wave models, producing independent long-term time series of significant wave height (H s ) and spectral peak period (T p ), is presented as possible solutions to this problem. The models are tested and compared by addressing how the models affect interpretation of design concepts and the ability to replicate statistical and physical characteristics of the wave process. Our results show that the VAR and VARMA models perform sufficiently in describing design performance, but does not capture the physical process fully. The Markov model is found to perform worst of the tested models in the applied tests, especially for measures covering several consecutive sea states.
In this paper, a model for implementation of sea passage operational scenarios in the context of simulation-based design of ships is presented. To facilitate the transition towards more energy-efficient shipping, the ability to evaluate and understand ship and ship system behaviour in operational conditions is central. By introducing an optimization model in virtual testing frameworks, operational scenarios can be generated that enhances scenario relevance and testing abilities. The optimization for simulation approach provides speed and course commands based on an optimization framework which factors in the operational considerations and sea state conditions in the area of operation. Impact on the understanding of ship system performance using simulation is assessed in a case study where a sea passage over the North Pacific is replicated for varying operational scenarios and seasons. It is found that the variation of operational scenario, affecting the sea state and speed relation, causes significant differences in required power and fuel consumption estimates. Sea passage control is found to be an important dimension in virtual testing approaches.
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