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Flocculation is direct process of particle collision. Past research has shown that fluid shear plays important role in causing the collision. Hence using CFD, the process in the flocculation tank is simulated. The ultimate result of this research is to find the strain rate in the flow that causes the shearing process which influencing the particle collision. The CFD tools that were used in the modeling process were Gambit and FLUENT. Gambit was used to create the geometry of the flocculation tank and flocculator, set up boundary conditions and creating mesh while FLUENT was used to plug in the data and initial conditions to obtain resultssolution.
Modeling Approach
The real life flocculation tank designed by Aguaclara involved a 180 deg turn over few dozens baffles. For validating result and modeling purpose, a simple 180 deg turn over two baffles was modeled. The first step was to set up the geometry of the of the simple flocculator. For future comparison with the experimental data, the design parameters for the pilot plant test flocculator was modified and used.
Figure 1: Geometry of flocculator
The design parameters used are:
Height: 1m
Clearance: 0.15m
Baffle width: 0.1m
With the geometry, we can then set up the boundary condition of our model.
Figure 3: Boundary condition for modeling
Figure 3 shows the boundary condition that was used for modeling. For a flocculator, there is an in flow and out flow of the fluids. Since we know the inlet velocity, the inlet was set to the Velocity Inlet type boundary condition. And since we know the outlet pressure is known, the outlet is set to Pressure Outlet boundary condition type.
Figure 1. Mesh of the Flocculation Tank
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