Session: 08-06-01 non-presentations

Paper Number: 126878

126878 - Parametric Study of a Mitigation Device for Pipelines on Free Span Based on 2d Fsi Analysis With Verification Assessment. 

Offshore pipelines are frequently laid down in an uneven marine bed. It is known that geophysical and geotechnical surveys must be performed in a seabed to avoid free spans, that is when the contact between the pipeline and seabed is lost over an appreciable distance on a rough seabed. It is also possible that the flow around these structures may create an erosion and pipeline spanning may occur. This may result in failure of pipelines due to excessive yielding and fatigue.

The flow around the pipeline, in these free span regions, may generate Vortex Induced Vibrations (VIV) that are known to be one of the major sources of dynamic loads, worsen the scenario and decreasing the lifetime of the structure. Given that these free span erosions may appear anytime and anywhere on seabed, it is impossible to design it previously the installation for a mitigation of VIV phenomenon. Therefore, the mitigation devices must be installed only when the damage is already initiated.

This paper presents a possible design solution that may be installed on a pipeline in a free span region. Similar to the ribbon fairings mitigation device, the solution presented is based on the geometry of an octopus and its tentacle.

Numerical analysis based on Computational Fluid Dynamics are carried out in ANSYS Fluent for this device under different configuration. A two-way Fluid-Structure Interaction (FSI) on a two-dimensional (2D) geometry is done in order to analyze the interaction of the tentacles and the flow. The results of this parametric study considering variation of the material, quantity, coverage factor and lengths provides data for discussion on the feasibility and effectiveness of the purposed design. These CFD results are verified using Richardson Extrapolation for error quantification.

Presenting Author: Antonio Fernandes Federal University of Rio de Janeiro

Presenting Author Biography: Professor of Hydrodynamics in the Naval Architecture, Marine and Ocean Engineering Program, UFRJ (Federal University of Rio de Janeiro). He got his Ph.D. at MIT (Massachusetts Institute of Technology). He is member of the Executive Committee of ITTC (International Towing Tank Conference) as representative of the Americas. He is also ex-member of the Executive Committee of the OOAE (Ocean, Offshore and Arctic Engineering) of ASME (American Society of Mechanical Engineers) that is responsible to organize the yearly conference OMAE (Offshore Mechanics and Arctic Engineering). He runs an academic laboratory called LOC at COPPE/UFRJ where fundamental research has been addressed and reviewed. He is also one of the Directors of LabOceano, the deepest wave basin of the world.

Authors:

Lucas Machado Federal University of Rio de Janeiro
Thomaz Benatti Federal University of Rio de Janeiro
Antonio Fernandes Federal University of Rio de Janeiro
Joel Junior Federal University of Rio de Janeiro
Cassiano Neves CRN Engenharia