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Based on our understanding of flocculation model, we use Pi-cell, G-theta and epsilon-theta as important design parameters that characterize the performance of hydraulic flocculation tanks. By comparing the performance parameters that derived from or assumed according physical understanding or intuition with the values that are calculated from the discrete numerical solutions from CFD simulation, we want to verify the validity of the flocculation model and draw more insights of how to design hydraulic flocculators.
Methods and Procedures
The mesh of 2D models is swept in the z-direction with a width of 0.1m (lengthxheightxwidth(x*y*z) = 0.2*1*0.1), and a mesh interval size of 0.002m (#intervals=50), which is in the same order of magnitude as that of x and y directions.
Preliminary Observations and Discussion (on-going simulation)
Since the finer mesh contains 1,500,000 cells, which is 50 times as many as that of the 2D mesh and 70 times as big as the 2D mesh in terms of the file size, the iteration takes about 30 seconds per step. After about 3000 iterations for 30 hours, the residual plots showed a promising tend to fall below a satisfactory level. (The simulations is still running at this moment)
(Still waiting for the more converged results for the energy dissipation contour...)
preliminary simulation experiments
- To investigate the appropriate boundary condition settings and the convergence level
Simulations with various h over b ratios
According to the results of the preliminary simulation experiments, the simulation are design in following ways:
- Mesh generation
- The mesh files for various h over b ratios are generated using the journal file
- Define the problem in FLUENT
- Click here for a report summary of all parameters of FLUENT model
- Formulations of the performance parameters
Wiki Markup Click !here^CFD tasks.ppt! for a summary of the derivation and formulation of the performance parameters
Results and Discussion
Click here for a summary of the calculated parametersResidual plot at 3096th iteration with maximum scaled residual of about e-5
Energy dissipation contour at 3096th iteration with maximum scaled residual of about e-5, for the plane at mid-width