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Hydrodynamics of two-dimensional laminar turbid density currents

Firoozabadi, B ; Sharif University of Technology | 2003

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  1. Type of Document: Article
  2. Publisher: Sharif University of Technology , 2003
  3. Abstract:
  4. In this paper, the motion of turbid density currents, laden with fine solid particles, released on sloping beds and under still bodies of clear water, has been 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 a finite volume scheme. The velocity-pressure coupling is handled by using the 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 the 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 of 50 microns, encountered during deposition, with a vertical velocity component due to up-lift flow, form a spongy layer near the bed. This layer, which could also be seen in experiments, shows the interaction of particles and the 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, which are similar to that of salt-water density currents. Also, in this work, the structures of two grain sizes in the flow are investigated and the 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
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  7. Source: Scientia Iranica ; Volume 10, Issue 1 , 2003 , Pages 122-130 ; 10263098 (ISSN)
  8. URL: http://scientiairanica.sharif.edu/article_2675.html