Offshore Technology Research Center

 

OTRC Project Summary

Project Title:

Wake II Model for Hydrodynamic Forces on Marine Pipelines for the Wave Plus Current Case

Prinicipal Investigators:

Billy Edge

Sponsor:

National Science Foundation

Completion Date:

June, 1999

Final Report ID#

A100(Click to view final report abstract)

One of the major tasks in the design of submarine pipelines is the analysis of the hydrodynamic stability of the pipeline.  This analysis is important to ensure that, during the construction and operation stages, the pipeline will remain stable under the action of the hydrodynamic forces produced by the waves and the currents.  In order to reach this stability the horizontal and lift forces are balanced against the minimum submerged weight of the pipeline.  The gravitational and friction forces act together to resist the hydrodynamic forces of the waves and currents.

One of the difficulties in the calculation of the hydrodynamic forces is the determination of drag, inertia and lift coefficients.  Extensive measurements have been made in order to define the coefficients as a function of Reynolds number, pipe roughness and Keulegan-Carpenter number.  One of the main sources used for the coefficients is the Norwegian rules Det Norske Veritas (1981).

In general, currents may be present, and must be added to the wave induced velocity in the computation of the forces.  Methods for doing this are overly simplified and subject to potential for error.

The objective of this research is to extend the concept of the wake velocity correction proposed by Soedigdo (1997) in the Wake II Force Model to include the case of regular waves plus steady currents.  The results will be in a form useful for both researchers and engineers involved in design of pipeline projects.

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