Projects per year
Abstract
The trend towards the installation of more offshore constructions for the production
and transmission of marine oil, gas and wind power is expected to
continue over the coming years. An important process in the offshore construction
design is the assessment of seabed soil stability exposed to dynamic
ocean waves. The goal of this research project is to develop numerical soil
models for computing realistic seabed response in the interacting offshore environment,
where ocean waves, seabed and offshore structure highly interact
with each other.
The seabed soil models developed are based on the ’modified’ Biot’s consolidation equations, in which the soilpore fluid coupling is extended to account for the various nonlinear soil stressstrain relations included. The Finite volume method (FVM) together with a segregated solution strategy has been used to numerically solve the governing equations. In the FVM segregated scheme, the conventional linear and uncoupled terms are discretized implicitly, whereas the nonlinear and coupled terms are discretized explicitly by using available values from previous time level or iteration step. The implicitexplicit discretisation approach leads to linearized and decoupled algebraic systems, which are solved using the fixedpoint iteration method. Upon the convergence of the iterative method, fully nonlinear coupled solutions are obtained. The developed nonlinear coupled soil models are capable of predicting the transient and gradual pore pressure variations as well as the developed nonlinear soil displacements and stresses under monotonic and cyclic loading.
With the FVM nonlinear coupled soil models as a basis, multiphysics modeling of waveseabedstructure interaction is carried out. The computations are done in an open source code environment, OpenFOAM, where FVM models of Computational Fluid Dynamics (CFD) and structural mechanics are available. The interaction in the system is modeled in a 1way manner: First detailed free surface CFD calculations are executed to obtain a realistic wave field around a given structure. Then the dynamic structural response, due to the motions in the surrounding water, are calculated using a linear elastic solver. Finally, the direct wave loads on the seabed and the indirect wave loads on the seabedstructure interface through the structure are provided as input for a dynamic soil response calculation. Simulation results in general demonstrate that, the interaction modeling provides improved wave loading environments for geotechnical assessment of the seabed soil.
The seabed soil models developed are based on the ’modified’ Biot’s consolidation equations, in which the soilpore fluid coupling is extended to account for the various nonlinear soil stressstrain relations included. The Finite volume method (FVM) together with a segregated solution strategy has been used to numerically solve the governing equations. In the FVM segregated scheme, the conventional linear and uncoupled terms are discretized implicitly, whereas the nonlinear and coupled terms are discretized explicitly by using available values from previous time level or iteration step. The implicitexplicit discretisation approach leads to linearized and decoupled algebraic systems, which are solved using the fixedpoint iteration method. Upon the convergence of the iterative method, fully nonlinear coupled solutions are obtained. The developed nonlinear coupled soil models are capable of predicting the transient and gradual pore pressure variations as well as the developed nonlinear soil displacements and stresses under monotonic and cyclic loading.
With the FVM nonlinear coupled soil models as a basis, multiphysics modeling of waveseabedstructure interaction is carried out. The computations are done in an open source code environment, OpenFOAM, where FVM models of Computational Fluid Dynamics (CFD) and structural mechanics are available. The interaction in the system is modeled in a 1way manner: First detailed free surface CFD calculations are executed to obtain a realistic wave field around a given structure. Then the dynamic structural response, due to the motions in the surrounding water, are calculated using a linear elastic solver. Finally, the direct wave loads on the seabed and the indirect wave loads on the seabedstructure interface through the structure are provided as input for a dynamic soil response calculation. Simulation results in general demonstrate that, the interaction modeling provides improved wave loading environments for geotechnical assessment of the seabed soil.
Original language  English 

Place of Publication  Kgs. Lyngby 

Publisher  Technical University of Denmark 
Number of pages  286 
ISBN (Print)  9788778773579 
Publication status  Published  2014 
Projects
 1 Finished

Modeling of SoilStructureWater Interaction
Tang, T., Johannesson, B., Pedersen, J. R., Fabricius, I. L., Jasak, H. & Vabbersgaard Andersen, L.
15/11/2011 → 23/02/2015
Project: PhD