Flow Dynamics of Submarine Channels: The Influence of Scale, Slope and Channel Geometry
Keevil, G. M.1,
Jeff Peakall1, James Best1 (1)
Although much is known concerning the large-scale distribution of sediment within and surrounding submarine channels, there is little understanding of the fluid dynamic processes that control this sedimentation. Direct measurement of flow velocities and concentrations has proven to be extremely difficult within submarine channels, with the resultant paucity of direct observations making physical laboratory modelling critical for examining the processes that operate in, and control submarine channel development. Recent experimental and numerical studies have proposed a new model of secondary circulation within submarine channel bends, characterised by a reversal in the orientation of the secondary circulation cell relative to that found in meandering rivers. This new paradigm for submarine channels thus predicts flow from the inside to the outside of the bend towards the base of the flow, with an upper return flow directed towards the inner bend. The reversal in orientation of the secondary flow cell has been linked to the vertical profile of the downstream velocity. This paper assesses the applicability of this bend flow model against a range of key channel parameters, and assesses the relative importance of this mechanism in controlling secondary flow in submarine channels. This present work demonstrates that the vertical profile of downstream velocity is the principal mechanism that generates such secondary circulation, but that overbank shear may augment this. Secondary circulations with a reversed sense of orientation were present in all channels studied, and suggest that the deposits within submarine bends and in associated overbank deposits must be interpreted in the light of this new model of flow structure.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California