New Aspects
Concerning Hydrodynamics of Turbidity Currents Based on Physical Experiments
Del Rey, Antonio Cosme1,
Rafael Manica2, Rogerio Maestri2, Ana Luiza de Oliveira
Borges2, Adriano Roessler Viana3 (1) Petrobras - Petroleo
Brasileiro S.A, Vitoria, Brazil (2) Universidade Federal do Rio Grande do Sul,
Porto Alegre, Brazil (3) PETROBRAS-Petroleo Brasileiro S.A, Rio de Janeiro,
Brazil
Over the last decades the turbidite study
has been subject of controversy and passionate discussions mainly due to the scarcity
of researches related to the mechanisms that involve flow initiation, transport
and its deposition. Thus, this work aims to evaluate the potential of physical
simulation of turbidity currents to comprehend the internal flow dynamics and
its implication on sedimentation process. In order to achieve this objective a
three-dimensional model with large dimensions (14m long x 5m wide x 1.20m
height) was constructed and a simplified geometry reproducing a channel-basin
was implanted inside. Then, a series of 12 simulations of turbidite currents
were performed with flows density ranged from 1002 kg/m3 to 1015 kg/m3. Mineral
coal sediment (density 1190 kg/m3) was used with grain size ranging between
0.125 and 0.297 mm. The experimental results show new geometrical and dynamical
aspects of turbidity currents and their influences on sedimentation process.
Essentially, a flow wavy layer was identified close the bottom being originated
by internal waves related to vortex detachment in the upper part of the current
(head and body). This dynamic process promotes cyclic changes in the current
velocity along the flow that are associated with variations on the frequency
and amplitude of these internal waves. This behavior also induces changes on
the rates of sedimentation/erosion. Hence, the results evidence the complexity
of turbidity currents flow evolution involving phases of acceleration and
deceleration with alternated erosion, transport and deposition process
interaction.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California