Extension of a coupled mooring–viscous flow solver to account for mooring–joint–multibody interaction in waves

Abstract

To account for nonlinear wave–structure interaction, mooring dynamics and the associated viscous flow effects, a coupled mooring–viscous flow solver was formerly developed and validated (Jiang et al. in Mar Struct 72:783, 2020a, Validation of a dynamic mooring model coupled with a RANS solver). This paper presents an extension of the coupled mooring–viscous flow solver to solve mooring dynamics interacting with an articulated multibody offshore system. The presently extended solver is verified by comparing the predicted motions of and loads on a moored floating box to those obtained from the formerly validated solver, which was aimed for solving mooring dynamics interacting with a single floating body. The almost identical results obtained from both solvers verify the presently developed multi-module coupling technique for solving the mooring dynamics and articulated multibody dynamics in a coupled manner. Apart from the code comparison and verification, the numerical predictions are also validated against experimental tank measurements both for a single body and an articulated multibody. The good agreements between the numerical predictions and the experimental measurements validate the presently extended solver, where wave-induced body motions together with loads acting on mooring lines and joint connections were examined. Developed as an open-source tool, the extended solver shows a potential of the coupled methodology for analyzing an articulated multibody offshore system, moored with various mooring configurations in extreme sea states, which goes beyond the state of the art.

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.…”

“…Nevertheless, to capture the nonlinearities of viscous and/or complex free-surface flows, high-fidelity viscous-flow solvers are the preferred choice (Jiang, 2021).Computational fluid dynamics (CFD) has been commonly applied in wave-structure interaction (WSI) problems based on generally two approaches: Eulerian (meshbased) and Lagrangian (mesh-free) methods. In terms of the applications of mesh-based methods for multibody hydrodynamics, see Seithe and el Moctar (2019); Jiang et al (2022c); Jiang et al (2022d); Jiang and el Moctar (2023), where wave-induced motions and loads on articulated multibody offshore platforms were numerically analyzed. Regarding mesh-free approaches, Moreno et al (2020) analyzed the response of a multi-float wave energy converter M4 in focused waves via a smoothed particle hydrodynamics (SPH) solver, where complex multi-floats were coupled with mechanical constraint and mooring.…”

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

“…This section gives a brief overview of used numerical methods, including the Navier-Stokes equations governing fluid dynamics, a lumped-mass model addressing mooring line dynamics, and a forward algorithm simulating the nonlinear rigid body motions of the MFSs. For a more comprehensive description, refer to Jiang [13]; Jiang and el Moctar [11].…”

“…In previous work, we developed and validated a mooring-viscous flow solver to consider viscous-flow effects, nonlinear wave-structure interaction as well as mooring dynamics, focusing on a single body [10]. Subsequently, we extended our investigation to include two different connections, namely rigid joints and flexible joints, between two modular floating structures to study the motions and loads of an articulated and moored floating platform consisting of multiple bodies in waves [11,12]. In this paper, we introduce a novel aspect by presenting an analysis of a rotational damper integrated into an articulated and moored floating multibody platform subjected to waves.…”

High-fidelity modelling of moored marine structures: multi-component simulations and fluid-mooring coupling

“…Multibody simulations are available in the OpenFOAM CFD framework (Weller et al 1998;OpenCFD Ltd 2022), within the rigidBodyDynamics library. It was used in a recent study to model a hinged wave energy device with four catenary moorings modelled in MoorDyn (Jiang and el Moctar 2022). However, to fully resolve a hybrid mooring system in CFD means that the CFD-mooring coupling must support multi-body simulations with inter-mooring capabilities, i.e.…”