Preliminary 3D CFD Simulations of a Single Baffle Hydraulic Flocculation Tank
Abstract
Extend the current 2D CFD models of flocculation tank in to 3D, will greatly enhance our understanding of the fluid dynamics of flow inside the flocculation tank. In this report, 4 sets of preliminary 3D computational simulations were presented and discussed: first investigated the difficulty of 3D models in converging to satisfactory residual; and then compared the assumption and validity of 2D and 3D models by imposing 2D assumption onto 3D model.
Introduction
Compared with 2D models, CFD simulations in 3D provide closer numerical approximation to the real fluid flows in hydraulic flocculators, which enable better quantitatively investigation of performance parameters of flocculation and thus lead to well-studied guidelines for the design, construction and operation of hydraulic flocculators of AguaClara treatment plants.
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Case 4: Periodic boundary condition was defined at the walls along the x-y plane, 1st order solver with convergence criteria of 10^-6 2nd order solver with convergence criteria of 10^-6 (solution obtained from the 1st order solver was used as an initial guess for the 2nd order solver).
Click here for detailed procedure of mesh generation in Gambit and problem definition in FLUENT.
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Possible future simulation experiments and research topics are:
To build a stable and reliable computational model:
- To create refined mesh with proper boundary conditions, and run simulations on SGI server, check grid convergence;
- To investigate the fluctuating tail of residual plots;
- Design numerical experiments to observe the fluctuation of extremely small numbers;
- Use difference turbulence models and compare the shape of the tails;
- Simulation with periodic boundary conditions with various period length
- Use backstep experimental data to validate 3D models with periodic boundary conditions