Performance parameters analysis in 2D - preliminary simulation experiments
Objective
The effort began in Fall 2008 to try to characterize flocculation tank performance using parameters calculated from numerical solutions from CFD simulations containing all values at each node of the mesh. The following sets of experiments are carried out to confirm the previous results and provide an exploratory basis for further investigation of the relationship between the performance parameters and geometry of the flocculation tank.
Methods and Procedures
h/b ratios of 5, 10 and 20 were tested with 5 baffles. The completed test are summarized in the following table:
...
Summary of completed tests
...
The series of geometries and meshes were created using the journal file vary_flocculator_height, by varying the flocculator height. The boundary conditions and all the other FLUENT settings can be found in the report summary
Results
...
and Discussion
Click here for a complete results of the preliminary simulations, summarized in an Excel Workbook. Only parts of the graphical results are given below.
Shown below are contours of energy dissipation rate for h/b of 5 and 10, with symmetry boundary condition at the water air interface and one case with no slip(i.e. wall) boundary conditions.
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...)
Residual 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