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Hydrodynamics of two-dimensional, laminar turbid density currents

Author(s): B. Firoozabadi; B. Farhanieh; M. Rad

Linked Author(s): Bahar Firoozabadi, Bahar Firoozabadi, Bahar Firoozabadi

Keywords: Particle-laden flows; turbidity currents; turbid density currents

Abstract: Motion of turbid density currents laden fine solid particles, released on sloping bed and under still bodies of clear water, are numerically investigated. The equations of mass, momentum and diffusion for unsteady, laminar flow are solved at the same time in the fixed Cartesian directions, on a non-staggered grid using finite volume scheme. The velocity-pressure coupling is handled by SIMPLEC method. Turbidity currents with uniform velocity and concentration enter the channel via a sluice gate into a lighter ambient fluid and move forward down-slope. At the front of this flow, a vortex forms and grows while moving downstream. Comparison of the computed height of turbidity current with the experimental data shows a good agreement. In this paper, the deposition of particles and the effects of their fall velocity on concentration distribution are also investigated. The results show that the coarse particles settle rapidly and create maximum concentration on the bed. However, medium size particles, 50 microns, encountered with vertical velocity component due to up-lift flow, during deposition, form a spongy layer near the bed. This layer, which could be seen also in experiments, shows the interaction of particles and velocity components of fluid, especially near the bed. Fine particles of around and less than 10 microns, are distributed in the main parts of the fluid concentration profiles are similar to salt-water density currents. Also, in this work, the structures of two grain sizes in the flow are investigated and results show that fine particles with the highest share of concentration in the main body of the flow, have the most effect in the total concentration distributions. However, the presence of coarse particles could affect the solid accumulation near the bed.

DOI: https://doi.org/10.1080/00221680309506894

Year: 2003

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