The Regional Municipality of Waterloo has four ground water well sites that require installation of disinfectant pipe contact chambers to achieve the required contact time. The approach proposed involves installing large diameter pipe sections in line with the supply pipeline at the site. Due to space limitations, the pipe contact chambers are to be as small as possible.
To optimize the design of these contact chambers, computational fluid dynamics (CFD) analysis has been applied to the most complicated of the four. The objectives of this CFD analysis are to:
- Model flow mixing in the proposed well site pipe contact chambers
- Suggest means to increase the baffling factors, or T10/T
- Predict the resulting baffling factor
A three-dimensional CFD model has been constructed to include a short section of the influent pipe, the pipe contact chamber and a short section of effluent pipe. Using a steady state solution of flow through the contact chamber as the initial condition, a separate fluid, with the same physical properties as the “old” water in the contact chamber, begins to enter the chamber through the influent pipe. As the time dependent solution progresses, the influent (“new”) water mixes with and displaces the “old” water. The degree of mixing is inferred by examining the influent concentration contour plots and by recording the influent concentration at the effluent pipe. The time dependent concentration can be used to estimate t10/T for various inlet flow conditioning approaches.