A Coupled Eulerian Lagrangian method for modelling coupled hydro-geomechanical moored systems

Abstract

Understanding the response of floating structures to harsh waves and current loads is essential for the safe design and operation of coastal and marine anchors and foundations. A Coupled Eulerian Lagrangian large deformation technique is presented for simulating the complex fluid-structure interactions of semi-submerged moored floating structures, with the objective of developing coupled hydro-geotechnical models involving wave and current conditions, flexible moorings and embedded anchors. As a result of the hydro-geomechanical coupling, the impacts of environmental conditions on floating structures and foundation performance can be assessed. Furthermore, the role of anchor displacement in the motion of moored, floating structures can be considered. A semi-submerged floating box similar to a floating pontoon under wave loads is first considered, providing a strong agreement with laboratory tests. Thereafter, the method is extended to encompass combined wave and current loading regimes. The response of a moored floating buoy connected to an embedded anchor under wave and current loading is considered, providing a mechanism for assessing both the fluid and geotechnical behaviour of moored flexible floating offshore systems in a single monolithic simulation. As a result of the two-way hydro-geomechanical coupling, several mechanisms of anchor displacement can be observed, notably anchor heave, rotation and pivoting. Key features of the fully coupled model are the development of plastic strains surrounding anchor shaft in the direction of loading, as well as dynamic wave and current-driven soil deformation which are not readily considered in conventional static analyses.