Fluid flow analysis software uses computational fluid dynamics (CFD) to help operators of water and wastewater systems predict the performance of new designs, study flow characteristics of existing designs, and troubleshoot design alternatives.
Fluent Inc. is one company offering such software. Its package includes a set of CFD tools and technical support. Its software has a graphical user interface and is highly interactive. It can be used to analyze such systems as aerators, combined sewer overflows, clarifiers, contact tanks, diffusers, filters, incinerators, sedimentation basins, sludge processing, wastewater transportation and weirs.
Municipalities can also use CFD simulation to investigate the performance and possible design of various water treatment processes. With the software, operators can check design performance, troubleshoot, and improve existing designs.
The simulation programs can work with dynamics such as the flow of water in pipes/channels, combined air/water flows, wind-driven water flow, solids sedimentation, non-Newtonian fluid flows, heat transfer, mixing, chemical coagulation, and disinfection.
Geometries in water and wastewater treatment can range from simple rectangular tanks to complex baffle/plate/pipe arrangements and detailed nozzle designs. The CFD program can be used for better understanding of these processes.
Contact Tank Modeling
In one study, engineers from Hazen and Sawyer used Fluents UNS software package to create a CFD model of a chlorine contact tank used in an existing drinking water treatment plant.
Contact Tank Modeling
Flow hydraulics and detention time within a contact tank are critical to the effectiveness of the disinfection process. The engineers computed the residence time for chlorine contact and the results from the CFD model were compared to the results of a tracer study performed on the existing tank. The CFD model came within 5 percent of the tracer study results.
Contact Tank Modeling
Based on the positive results of the study, CFD modeling was used in the design of a new chlorine contact tank for the facility.
Contact Tank Modeling
Thames Water in England has been using CFD simulation to investigate the performance and possible design of various water treatment processes since 1992. Projects there have included the simulation of a dissolved air floatation unit, with air/water volume fraction depicted; velocity vectors and contours in a contact tank, and the effect of water level changes in a service reservoir.
