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Comparison of Meso Scale Subsea gas Release With Multiphase Eulerian-Lagrangian CFD Model

Comparison of Meso Scale Subsea gas Release With Multiphase Eulerian-Lagrangian CFD Model

Category
Part of a book/report
Abstract
We compare the observed dynamics of subsea starting plumes with multiphase computational fluid dynamics (CFD) simulations. In the event of subsea loss of containment of either natural gas or carbon dioxide it is important to understand how the gas disperses in the ocean column and acends to the surface where it can pose a risk to installations, vessels and on-board personnel. Risks factors include; fire and explosion hazards, sudden and persistant hydrodynamic loads, in case of carbon dioxide the hazard of asphyxiation, and in case of a gas rich in hydrogen sulfide toxic effects. Thus, it is routine to conduct atmospheric dispersion simulations to estimate size of exclusion zones on rigs and safe stand-off distances for vessels in case of loss of containment. Atmospheric dispersion is today in some respects seen as a routine and mature exsersize. Howerver, subsea dispersion of gas and surfacing of this gas is still an area with limited data and large uncertainties with respect to a number of factors (Olsen & Skjetne(2016-A)); transient release rates, depth, mass transfer to ocean, degassing at ocean surface. A key obstacle to obtaining good data has been the challenge of subsea imaging and characterization of large transient bubble plumes structures. Here we utilize recent developments in 3D temporal sonar imaging obtained for starting plumes from 30 meters depth with predictions obtained using computational fluid dynamics. We investigate the effects of release rate on overall plume dynamics such as rise time and plume angle and compare CFD simulations with experimental observations. We find that progress in sonar imaging now allows subsea gas plumes to be visualized in detail and may prove a very useful tool in field situations. The CFD model captures all the main features observed in the experiments.
Language
English
Affiliation
  • SINTEF Industry / Process Technology
  • SINTEF Ocean / Miljø og nye ressurser
Year
2017
Publisher
CRC Press
Book
Safety and Reliability – Theory and Applications
ISBN
9781138629370