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The parametric resonance, found in a single floating body, discloses that the kinetic energy could be transferred from heave mode to roll mode and causes motion instability if there is an integer multiple relationship between the two mode natural frequencies. For multi-module floating structures, the event of parametric resonance has not been investigated, but important for the stability and safety design of the floating platforms. In this paper, an experimental test is carried out using five box-type floating modules in a wave flume and observes the existence of the parametric resonance between the heave mode and roll mode. A mathematical model, validated by the experiment data, is built up for the theoretical analysis of the influential factors of the parametric resonance. The effects on the motion instability of wave condition, connector stiffness and number of modules are analyzed. It reveals that an appropriate stiffness setting of the connectors could eliminate the parametric resonance of multi-module floating structures. This theoretical finding is confirmed in a further experiment test on a five-module floating structure in the wave flume.

The development of floating photovoltaic systems (FPV) for coastal and offshore locations requires a solid understanding of a design’s hydrodynamic performance through reliable methods. This study aims to extend insights into the hydrodynamic behavior of a superficial multi-body FPV system in mild and harsh wave conditions through basin tests at scale 1:10, with specific interest in the performance of hinges that interconnect the PV panels. Particular effort is put into correctly scaling the elasticity of the flexible hinges that interconnect the PV modules. Tests of a 5 × 3 FPV matrix are performed, with and without shelter, by external floating breakwater (FBW). The results show that the PV modules move horizontally in the same phase when the wave length exceeds the length of the FPV system, but shorter waves result in relative motions between modules and, for harsh seas, in hinge buckling. Relative motions suggest that axial loads are highest for the hinges that connect the center modules in the system and for normal wave incidence, while shear loads are highest on the outward hinges and for oblique incidence. The FBW reduces hinge loads as it attenuates the high-frequency wave energy that largely drives relative motions between PV modules.

The use of floating photovoltaic panels (FPVs) on lakes and reservoirs is expanding globally. However, their impacts on water column motion, mixing, and thermal stratification remain poorly understood, often characterized by overly simplistic modeling approaches. Here, three‐dimensional simulations, supported by analytical calculations, are used to understand the internal transport processes and mixing dynamics of an idealized lake with anchored floating structures under a range of conditions. The effects of FPVs on lake physics include: (a) increased thermal inertia with greater areal coverage, delaying and attenuating seasonal oscillations; (b) perturbations in surface equilibrium temperatures; (c) altered surface heat fluxes in uncovered areas due to lateral heat redistribution, resulting in either increased (conductive FPVs) or decreased (insulating FPVs) near‐surface temperatures; (d) reduced vertical mixing rates and mixed layer depths, depending on areal coverage and spatial arrangement of the FPVs in relation to the boundaries; (e) changes in the internal dynamics and velocity fields of the lake in response to the spatial arrangement of the devices; (f) higher rates of mechanical energy exchange across the air‐water interface and greater horizontal transport between covered and uncovered regions for lower areal coverages; and (g) a greater fraction of the mechanical energy flux into the lake being used to enhance lateral transport rather than vertical mixing.

A numerical hydrodynamic model for a moored interconnected floating large structure under the action of regular waves is presented to analyze the effect of current and wind. The floating structure consists of 20 hinged plates that are linked together and secured with mooring lines along its edges. A brief discussion is provided on the multi-body hydrodynamics equations related to the numerical model definitions in both the frequency and time domains. Conversely, a concise overview of the experiment is given. The numerical model outcomes of vertical displacements and wave quantities are compared against the results obtained from model test data sets and numerical and analytical models in a recent publication. A high degree of accuracy has been noted in reflection and transmission coefficients with a certain value of current velocity. The numerical model simulating interconnected structures of 10 and 16 hinged plates is analyzed, and the resulting vertical displacements under the influence of current are compared to those of a 20-hinged structure. The impact of currents and winds on the hydrodynamic response of the structure is examined by studying various results, using stiffness values for both mooring and hinges. Further, the effect of wavelengths on the wave transmission on every side of the interconnected structure through contour diagrams, hydrodynamic diffraction for different incident angles, and wave quantities on current speed are analyzed. It is observed that as the current speed rises, the structural displacement also escalates; meanwhile, no impact of the wind on the floating interconnected structure is noted. It has been observed that as the wave direction shifts from 0° to 60°, the interconnected floating structure experiences a slight reduction in wave motion throughout the entire system.

Photovoltaic (PV) power generation is a form of clean, renewable, and distributed energy that has become a hot topic in the global energy field. Compared to terrestrial solar PV systems, floating photovoltaic (FPV) systems have gained great interest due to their advantages in conserving land resources, optimizing light utilization, and slowing water evaporation. This paper provides a comprehensive overview of recent advancements in the research and application of FPV systems. First, the main components of FPV systems and their advantages as well as disadvantages are analyzed in detail. Furthermore, the research and practical applications of offshore FPV systems, including rigid floating structures and flexible floating structures, are discussed. Finally, the challenges of offshore FPV systems are analyzed in terms of their stability and economic performance. By summarizing current research on FPV systems, this overview aims to serve as a valuable resource for the development of offshore FPV systems.

Park, S.H. and Cho, Y.J., 2023. Wave overtopping control effect of AWOC equipped with self-adaptive floating concrete structure: A numerical study. In: Lee, J.L.; Lee, H.; Min, B.I.; Chang, J.-I.; Cho, G.T.; Yoon, J.-S., and Lee, J. (eds.), Multidisciplinary Approaches to Coastal and Marine Management. Journal of Coastal Research, Special Issue No. 116, pp. 1-5. Charlotte (North Carolina), ISSN 0749-0208. In this study, the Active Wave Overtopping Controller (AWOC) was presented as an effective measure to mitigate flooding in the wake of storm surges or harsh waves. Numerical simulations to verify the wave overtopping control effect of AWOC were carried out against waves of various characteristics as well. In doing so, the intensity of standing waves appearing in front of a breakwater can affect wave overtopping was also tested. To the best of the author's knowledge, the impact of standing waves on wave overtopping has not been explored in the current literature, which might explain the poor performance of existing overtopping models. In AWOC, a simple box type floating concrete structure that acts as a wave overtopping controller is submerged in a mild sea. On the other hand, when a storm surge or harsh waves strike the AWOC, the floating structure constituting AWOC rises along with fluctuating sea level due to the presence of a storm surge or harsh waves, and as a result, could effectively control wave overtopping. The numerical results showed that the floating structure of the AWOC effectively controls wave overtopping, not just against long waves, but also against solitary waves, without any changes to its shape.

Within the framework of Space@Sea project, an articulated modular floating structure was developed to serve as building blocks for artificial islands. The modularity was one of the key elements, intended to provide the desired flexibility of additional deck space at sea. Consequently, the layout of a modular floating concept may change, depending on its functionality and environmental condition. Employing a potential-flow-based numerical model (i.e., weakly nonlinear Green function solver AQWA), this paper studied the hydrodynamic sensitivity of such multibody structures to the number of modules, to the arrangement of these modules, and to the incident wave angle. Results showed that for most wave frequencies, their hydrodynamic characteristics were similar although the floating platforms consisted of a different number of modules. Only translational horizontal motions, i.e., surge and sway, were sensitive to the incident wave angle. The most critical phenomenon occurred at head seas, where waves traveled perpendicularly to the rotation axes of hinged joints, and the hinge forces were largest. Hydrodynamic characteristics of modules attached behind the forth module hardly changed. The highest mooring line tensions arose at low wave frequencies, and they were caused by second-order mean drift forces. First-order forces acting on the mooring lines were relatively small. Apart from the motion responses and mooring tensions, forces acting on the hinge joints governed the system’s design. The associated results contribute to design of optimal configurations of moored and articulated multibody floating islands.

Due to the dense construction of underground projects in urban areas, nearby activities like foundation pit excavation can cause subsidence in the shield tunnel, posing a safety risk to subway operations. This paper proposes an optimization method using combination weighting and grey correlation degree for the Xi’an under highway tunnel project. It conducts numerical simulations of the original scheme using ABAQUS and selects calculation parameters, then optimizes anti-floating structure parameters through orthogonal experiments. The optimized operating conditions were compared with the original ones to validate the optimization results. These findings serve as valuable references for tackling real-world engineering challenges.

This review comprehensively overviews of theoretical and numerical methods used to assess the sensitivity and uncertainty in the hydrodynamic and hydroelastic behavior of floating offshore structures. The different methodologies associated with basic governing equations for floating offshore structure systems on the sensitivity and uncertainty assessments are discussed. Then, a brief overview of a comparative analysis of the methodologies, highlighting their key features, applications, and findings are provided in a table form. In addition, a technical comparative analysis of different numerical models and a comparative analysis of the sensitivity of different mooring parameters are also provided in a table form. Further, the uncertainty and sensitivity analysis for floating structure systems are presented by providing detailed discussions. In conclusion, this review highlights the revisions arising from the present analysis and outlines future research directions.

A novel modular floating structure (MFS) system moored by tension legs was proposed, which is composed of hexagonal floating modules, floating artificial reefs and wave energy converters (WECs). The integration of floating artificial reefs and WECs into the MFS can improve the marine environment and produce considerable electricity. The effects of both wave characteristics and the module quantity on the hydrodynamic responses of the MFS system were studied in depth, based on a time-domain numerical model. Both the modules’ hydrodynamic interaction effect and the connectors’ mechanical coupling effect were considered. The results indicate that floating artificial reefs combined with WECs can effectively reduce wave loads and convert wave energy into electricity for the MFS system. More modules involved in the MFS system could significantly reduce motion response and produced more wave energy output, which indicates that the MFS system is suitable for large-scale expansion. The effect of different power take-off (PTO) damping coefficients on the WECs’ performance was further investigated, and the optimal damping coefficient was recommended for the MFS system. Finally, the main extreme responses of the MFS system were further investigated, and its safety was checked thoroughly. One survival strategy was proposed, which could efficiently reduce extreme connector loads by more than 50%.