--> Abstract: High Resolution Numerical Simulations of Bidisperse Particle-Driven Gravity Currents; #90063 (2007)

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High Resolution Numerical Simulations of Bidisperse Particle-Driven Gravity Currents

 

Hoyes, James R.1, Lionel Elliot1, Derek B. Ingham1, William D. McCaffrey1, Jeff Peakall1, Mohammed Pourkashanian1 (1) University of Leeds, Leeds, United Kingdom

 

High resolution, three-dimensional Direct Numerical Simulations (DNS) have been performed to investigate the internal dynamics of bidisperse particle-driven gravity currents. Particular interest is given to the manner in which fine and course particles segregate within the flow leading to particle size stratification in the resultant deposits. Differences between the flow characteristics of mono and bidisperse currents are analysed three-dimensionally and it is shown that the bidisperse case cannot be approximated by a monodisperse current. Results are rigorously compared with predictions from shallow water theory and experimental data and shown to be in good agreement. The validity of one-dimensional box and shallow water models, which assume no vertical stratification in the flow, are discussed in light of the fully resolved DNS results.

 

The simulations were performed using second order numerical algorithms within the commercial software package FLUENT and run on a large parallel computing cluster. The density difference between particle-laden and ambient fluids was assumed to be small (< 5%) allowing use of the Boussinesq approximation. Low volumetric particulate concentrations meant that particle-particle interactions such as hindered settling could be neglected. Particles had low Reynolds number and were therefore assumed to be convected by the buoyancy induced fluid motion, and settle vertically with a constant settling velocity. Simulations were performed at Reynolds number of the order of 1000, gravity currents propagating at this Reynolds number have been shown to be ‘similar' to those propagating at higher Reynolds numbers.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California