Shipping water events that propagate over the decks of marine structures can generate significant loads on them. As the configuration of the structure may affect the loading behaviour, investigation of shipping water loads in different structural conditions is required. This paper presents a numerical investigation of the effect of deck roughness and deck length on vertical and horizontal loads caused by shipping water on a fixed structure. Systematic analyses were carried out of isolated shipping water events generated with the wet dam-break method and simulated with OpenFoam Computational Fluid Dynamics toolbox. The numerical approach was validated and then the shipping water loads were examined. It was found that, as roughness increased, the maximum vertical and horizontal loads showed a delay. As the deck length reduced, the vertical backflow loads tended to increase. These results suggest it may be worthwhile examining the behaviour of shipping water as it propagates over rough surfaces caused by fouling, corrosion, or those with small structural elements distributed on them. Moreover, the effect of deck length is important in understanding the order of magnitude of loads on structures with variable deck lengths, and those which have forward and backflow loading stages.
The incorporation of new equations to extend the applicability of open-source computational fluid dynamics (CFD) software according to the user’s needs must be complemented with code verification and validation with a representative case. This paper presents the development and validation of an OpenFOAM®-based solver suitable for simulating multiphase fluid flow considering three fluid phases with different densities and temperatures, i.e., two miscible liquids and air. A benchmark “dam-break” experiment was performed to validate the solver. Ten thermistors measured temperature variations in different locations of the experimental model and the temperature time series were compared against those of numerical probes in analogous locations. The accuracy of the temperature field assessment considered three different turbulence models: (a) zero-equation, (b) k-omega (Reynolds averaged simulation; RAS), and (c) large eddy simulation (LES). The simulations exhibit a maximum time-average relative and absolute errors of 9.3% and 3.1 K, respectively; thus, the validation tests proved to achieve an adequate performance of the numerical model. The solver developed can be applied in the modeling of thermal discharges into water bodies.
Comprehensive knowledge of extreme values is required for designing offshore structures and ocean current turbines. However, data on the return levels of ocean currents are rarely available. This is the case for the Mexican Caribbean, where enormous energy potential in the ocean currents has recently been detected. In this study, long-term numerical data from the Hybrid Coordinate Ocean Model for a depth of 50m was adjusted via linear quantile regression to short-term empirical data for a depth of 49m. The error of the results was estimated using simplified extreme value analysis. Based on the numerical data, a comprehensive extreme value analysis was conducted using the peaks over threshold method and fitting a Generalized Pareto Distribution to the data. This method relies on filtering peaks with a moving time window and an automated threshold selection based on a reparameterised scale parameter of the Generalized Pareto Distribution. The adjusted numerical model is shown to underestimate the empirical data with the error converging to almost 22% for rare events (return period > 10years). The method showed consistent results in the domain, with some anomalies only at the boundaries of the underlying numerical model. The methodology is suitable for estimating the return levels of ocean currents provided by HYCOM, although further research is needed to reduce the error of the numerical model.
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