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Numerical Simulation of Secondary Sedimentation Tanks to Increase the Efficiency

Lak, Behzad | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 48065 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Firoozabadi, Bahar; Afshin, Hossein
  7. Abstract:
  8. Sedimentation tanks are one of the important and costly stages of water treatment process in which remained particles from previous stages settle down due to gravity force. In this research, the hydrodynamics of secondary settling tanks without and in the presence of particles is numerically investigated using VOF method in order to simulate the interphase using RNG k-ε for turbulence modelling. The simulations are performed by means of open-source code OpenFoam, and the code is developed to model particles in the flow. The calculated velocity profiles using VOF method show a reasonable agreement with the experimental data. Comparing the concentration profiles with experiments shows the importance of size distribution and particle diameter deviation from the mean particle size, say D50. Effects of the inlet position as well as inlet Froude number on the volume of recirculation zones and mean concentration in the tank are studied for different conditions. The results show that the inlet position for maximum efficiency of the tank is close to the free surface. Also, the results of inlet Froude number investigation indicate that inlet Froude number decrease causes positive effect by reducing recirculation region volume and negative effect by increasing maximum. Therefore, an optimum Froude number can be obtaineded for each geometry and maximum efficiency
  9. Keywords:
  10. Numerical Simulation ; Volume of Fluid ; K-Epsilon Turbulence Model ; Efficiency Maximization ; Secondary Sedimentation Tanks

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