Residence time and local mean age of fluid are important parameters of the fluid flow, with which we are able to detect the functioning and non-functioning zones. It is a novel approach to estimate the effect of dead-zones on chemical and biological processes. In this paper, we introduce a numerical tracer study, which is calibrated by field measurements and which is applied in different cases such as settling tank and aeration tank of wastewater treatment. Using an advective-diffusive passive scalar transport equation, the age of the fluid can be calculated. It also shows the short-circuits and dead-zones of the fluid and this corresponds with our observations. This method helps eliminate potential hydraulic problems at the early stage of design.
CFD, dead-zone, local mean age, tracer study
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