Use of computational fluid dynamics to investigate natural and mechanically induced flows in an aerated lagoon.Application: For installing new aerators and mixers or relocating those already in use, engineers can use computation fluid dynamics fluid dynamics n. (used with a sing. verb) The branch of applied science that is concerned with the movement of gases and liquids. to analyze flow behavior in an aeration aeration /aer·a·tion/ (ar-a´shun) 1. the exchange of carbon dioxide for oxygen by the blood in the lungs. 2. the charging of a liquid with air or gas. aer·a·tion n. lagoon lagoon Area of relatively shallow, quiet water with access to the sea but separated from it by sandbars, barrier islands, or coral reefs. Coastal lagoons have low to moderate tides and constitute about 13% of the world's coastline. . ********** Engineers at an Australian pulp and paper mill had the task of improving the wastewater treatment system. Their goal was to decrease the settling of solids in the aeration lagoon. An earlier study of the flow patterns in the lagoon had involved physical experiments with surface flotation devices. This time, to gain more insight, they used computational fluid dynamics Computational fluid dynamics The numerical approximation to the solution of mathematical models of fluid flow and heat transfer. Computational fluid dynamics is one of the tools (in addition to experimental and theoretical methods) available to solve (CFD CFD - Computational Fluid Dynamics ) to analyze both the natural water flow and the behavior of the flow that was mechanically induced. The natural flow patterns calculated with CFD matched the patterns of the earlier study. That told the engineers that the lagoon was modeled accurately and the CFD simulation was set up correctly. The idea was to simulate the flow patterns to determine if mixers could replace aerators to increase the turbulence. The engineers gathered the information needed and put the CFD software to work to calculate the detailed water velocity distributions for various combinations of aerators and mixers in different parts of the lagoon. The CFD results showed that the aerators and mixers produced complementary flow patterns and that alternating aerators and mixers should produce good vertical mixing between the surface and floor of the lagoon. This arrangement is expected to increase the overall water velocity in the lagoon, improve mixing, and minimize the accumulation of solids in the main treatment lagoon. S! de Kretser is with Kellogg Brown & Root Pty Ltd PTY LTD Propriety Limited (company structure in Australia) ., Matthews is with CFD Research Pty Ltd., and Williams is with Australian Paper Pty Ltd. Email de Kretser at dale.dekretser@halliburton.com. |
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