Centre for Computational Fluid Dynamics

FACULTY OF ENGINEERING

 

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The numerical definition of a sinuous channel designed with Gambit.
The numerical definition of a sinuous channel designed with Gambit.
The sinuous channel meshed with rectangular cells
The sinuous channel meshed with rectangular cells
Isocontours of concentration of a  current in a sinuous channel

Isocontours of concentration of a steady state saline density current in a sinuous channel. The tilt of the isocontours of concentration at the bends seem to be a first approximation of the complex secondary flow of  sinuous submarine channels.

NUMERICAL MODELLING OF GRAVITY AND TURBIDITY


 

 

Francesco Giorgio-Serchi CFD PhD Student

Francesco Giorgio-Serchi pmfgs@leeds.ac.uk

Project Title: CFD Modelling of Sinuous Submarine Channels
Supervisors: Jeff Peakall (Earth Sciences), Derek Ingham (SPEME), Alan Burns (Earth Sciences)

 

Submarine channels are present in all of the world’s ocean basins, and can be kilometres to tens of kilometres wide, have channel banks hundreds of metres high, and be thousands of kilometres long. They are probably the least understood landform on planet Earth, and this despite being important conduits for the transport of fluids, sediment and pollutants across the shelf and into the deep-ocean. The flows that are responsible for these fluxes are typically large magnitude, have high flow velocities and are highly destructive. These flows pose a significant hazard for sub-sea engineering structures such as pipelines, cables and sea-bed hydrocarbon production facilities. Furthermore, the sediment deposited in and at the termini of these channels forms important reservoirs for oil and gas. Understanding the nature and distribution of these sediments is therefore critical for optimising the extraction efficiency of these hydrocarbon reservoirs. However, despite their importance remarkably little is known about the fluid dynamics and sedimentary deposits of submarine channels.

In the last few years, physical and analytical modelling undertaken at the University of Leeds have shown that the three-dimensional flow field is of critical importance and very different from that in other sinuous channels such as meandering rivers, In particular, it has been demonstrated that there is reversal in the orientation of secondary flows in submarine channels, relative to rivers (Corney et al., 2006; Keevil et al., 2006, in review); and that these differences in the fluid dynamics have significant impact on sedimentation within submarine bends (Peakall et al., 2007).

The aim of the project is to model, using CFD, the three-dimensional fluid dynamics and deposits of sinuous submarine channels, and to validate them using the physical modelling methodologies proven in previous works. Our numerical modelling uses FLUENT and CFX as the primary solvers. Considerable work has been undertaken at Leeds on gravity current modelling using FLUENT, mainly focusing on the attempt to numerically reproduce the lock-release experiment, where a fixed amount of dense fluid is let to flow in a less dense fluid, giving rise to a typical density current. The present project aims at building upon this existing platform. The FLUENT based model will be extended and modified to allow improved modelling of flow and sedimentation in complex sinuous geometries, and the incorporation of ‘continuous’ currents (rather than lock-release). Further development of the project is foreseen in extending the model in order to handle erosion and deposition, and the resultant changes in bed elevation with time. This would be made possible by introducing a sediment erosion algorithm and the implementation of adaptive meshing. Development of the CFD model should allow broad-scale prediction of flow processes in submarine canyons and channels for the first time, and might enable existing models of secondary flows and overbank flow dynamics to be tested. The model developed will be of great practical importance for engineering and geological applications for the oil industry.