Australian Research Council Centre of Excellence Geotechnical Science and Engineering

Mr Henning Mohr

Supervisors

  • Professor David White
  • Winthrop Professor Mark Randolph
  • Winthrop Professor Liang Cheng

Research Interests

  • Pipelines soil fluid interaction
  • Pipelines
  • Soil behaviour

Research Topic

Computational fluid dynamics modelling and experimental simulations of pipe-soil interaction in current

Research Abstract

In the proposed research project, Computational Fluid Dynamics (CFD) modelling and experimental simulations will be used to examine the effects of hydrodynamic loading on pipelines and the resulting seabed erosion, scour and liquefaction response in non-cohesive soils. The first part of the project involves numerical analysis with the open source CFD software package Openfoam to investigate lateral stability of pipeline due to current loading. This work will include simulations of the hydrodynamic loading of pipelines, but will focus particularly on how to extend this modelling into the seabed, via simulations of scour and liquefaction processes, that are driven by the hydrodynamic action. The second part of the project involves experimental simulations using the University of Western Australia’s novel O-tube flume facilities. These large and small O-tube flumes provide the physical modelling environment to reproduce wave and current-induced water velocities at full and small scale, allowing simulation of the complete pipe-soil-fluid interaction response. The experimental results will then be analysed in the context of the numerical results, providing validation of new pipe-soil-fluid interaction modelling techniques and insight into potential methods to control pipeline stability.

The main outcome of the study is to provide an improved understanding of on-bottom stability design issues for offshore pipelines. It is anticipated that this will be of considerable financial value to the offshore energy industry by reducing capital expenditures for offshore pipeline construction.

Why my research is important

The number of major offshore hydrocarbon resource developments offshore Australia has increased over the past decade, with subsea pipelines being a vital component that provides a reliable, cost-effective solution for resource transportation, often extending for several hundred kilometres from field to shore. In shallow water, these pipelines are subjected to wave and current loading over their lifetimes, particularly during Australia’s severe cyclones, that can result in pipeline instability, leading to stresses and strains in the walls of the pipe. Conventional theories of on-bottom pipeline stability often consider idealised hydraulic and geotechnical interactions in isolation, but in reality these interactions are related. The ocean interacts with the seabed as well as the ocean loading the pipe and the pipe being supported by the seabed. As a consequence, existing design solutions may involve cost inefficiency, or they may be unconservative. A more complex design approach is necessary that considers the physical processes of the pipe-soil-fluid interaction together.

Funding

Centre for Offshore Foundation Systems (COFS)