Hydrodynamic Sensitivity of Moored and Articulated Multibody Offshore Structures in Waves

Abstract

Within the framework of Space@Sea project, an articulated modular floating structurewas developed to serve as building blocks for artificial islands. The modularity was one of the keyelements, 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.

Seakeeping criteria of a moored and articulated multibody floating platform in head seas

“…This is because the properties of the floating module, as well as its superstructures may be different from one to another. Combining our previous studies (Jiang, 2021;Jiang et al, 2021;Jiang et al, 2022a;Jiang et al, 2022b;Jiang and el Moctar, 2023), the procedure of defining the limiting criteria of a module floating concept may be summarized as follows: I. Prepare the geometry and the structural properties of the design module, including mass, center of gravity, moments of inertia, connectors, mooring system, etc.…”

“…Determine the optimal number of modules and configurations. One can reference to Jiang et al (2021), which studies the hydrodynamic sensitivity of multimodule structures. III.…”

Effect of a rotational damper on a moored and articulated multibody offshore system in waves

“…Based on our review of research on MFSs, it becomes evident that the potential flow theory approach has been widely utilized. In these studies, connections are conventionally modeled as independent linear springs with six degrees of freedom [8]. For instance, Jiang et al [9] assessed the potential flow theory solver's ability to simulate an articulated and moored floating system consisting of multiple bodies.…”

Hydrodynamic Analysis of a Novel Modular Floating Structure System Integrated with Floating Artificial Reefs and Wave Energy Converters

“…Based on this background, a number of studies on the MFS have been developed [9,10]. Among these, Jiang et al [11] investigated the effect of module arrangement on the hydrodynamic sensitivity of the MFS. Results revealed that the hydrodynamic responses were similar in chain-type and parallel-type, and the motion responses of the first up-wave module were the largest.…”

“…The proposed novel MFS system is initially designed for a representative sea zone with the well-shielded effect of the natural surrounding islands in the South China Sea. Compared with the current general MFS [11,13], the integration of floating artificial reefs can provide habitats for marine species, thereby improving the marine ecological environment around the MFS system. The outermost floating artificial reef modules coupled with WECs can attenuate the wave loads, as well as producing considerable wave energy.…”