Effects of Gap Resonance on the Hydrodynamics and Dynamics of a Multi-Module Floating System with Narrow Gaps

Multi-module floating system has attracted much attention in recent years as ocean space utilization becomes more demanding. This type of structural system has potential applications in the design and construction of floating piers, floating airports and Mobile Offshore Bases (MOBs) generally consists of multiple modules with narrow gaps in which hydrodynamic interactions play a non-neglected role. This study considers a numerical model consisting of several rectangular modules to study the hydrodynamics and dynamics of the multi-module floating system subjected to the waves. Based on ANSYS-AQWA, both frequency-domain and time-domain simulations are performed to analyze the complex multi-body hydrodynamic interactions by introducing artificial damping on the gap surfaces. Parametric studies are carried out to investigate the effects of the gap width, shielding effects of the multi-body system, artificial damping ratio on the gap surface, and the dependency of the hydrodynamic interaction effect on wave headings is clarified. Based on the results, it is found that the numerical analysis based on the potential flow theory with artificial damping introduced can produce accurate results for the normal wave period range. In addition, the effects of artificial damping on the dynamics and connector loads are investigated by using a simplified RMFC model. For the case of adding an artificial damping ratio of 0.2, the relative heave and pitch motions are found to be reduced by 33% and 50%, respectively. In addition, the maximum cable and fender forces are found to be reduced by 50%, compared with the case without viscosity correction.

NEWMARK ALGORITHM FOR DYNAMIC ANALYSIS WITH MAXWELL CHAIN MODEL

This paper investigates a time-stepping procedure of the Newmark type for dynamic analyses of viscoelastic structures characterized by a generalized Maxwell model. We depart from a scheme developed for a three-parameter model by Hatada et al. [1], which we extend to a generic Maxwell chain and demonstrate that the resulting algorithm can be derived from a suitably discretized Hamilton variational principle. This variational structure manifests itself in an excellent stability and a low artificial damping of the integrator, as we confirm with a mass-spring-dashpot example. After a straightforward generalization to distributed systems, the integrator may find use in, e.g., fracture simulations of laminated glass units, once combined with variationally-based fracture models.

Modelling of Generalised Thermoelastic Wave Propagation of Multilayer Material under Thermal Shock Behaviour

This paper describes a time-discontinuous Galerkin finite element method (DGFEM-βc) for the generalised thermoelastic problem of multilayer materials subjected to a transient high-frequency heat source. The governing and constitutive relations are presented on the basis of the well-known Lord–Shulman (L–S) theory. A DGFEM-βc method is developed to allow the general temperature-displacement vector and its temporal gradient to be discontinuous at a fixed time t. A stiffness proportional artificial damping term is added to the final DG discretisation form to filter out the spurious numerical oscillations in the wave-after stage and at adjacent-layer interfaces. The numerical results show that the present DGFEM-βc provides much more accurate solutions for generalised thermoelastic coupled behaviour of multilayer structures. Compared with widely used traditional numerical methods (e.g., the Newmark method), the present DGFEM-βc can effectively capture the discontinuities behaviours of impulsive waves in space in the simulation of high modes and sharp gradients.

Introducing Entropy for the Statistical Energy Analysis of an Artificially Damped Oscillator

The purpose of this paper is to introduce the concept of entropy for a main resonator attached to a “fuzzy structure”. This structure is described explicitly using the Lagrangian method, and is treated as a layer of discrete resonators. A generic entropy formulation is then developed for the layer of resonators, which is used to determine the individual oscillator entropies. The combined entropy of the linear resonator system is then determined and compared numerically to the sum of the individual oscillator entropies. The entropy behavior of the system is then related to the energy behavior of the system and explained in regards to the the “artificial damping” of the main resonator.