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