Mixing in a water storage tank is important to ensure that pristine drinking water is delivered to end users. Insufficient mixing can cause microbial growth in water storage tanks which consequently becomes a concern for public health. Circular water storage tanks are a common geometry for water storage tanks in the United States. Experiment or numerical studies in the past have mainly focused on understanding the mixing capabilities of vertically oriented nozzles, however, when retrofitting existing water storage tanks, vertically oriented nozzles may not always be a practical option, and thus modifications to include horizontally oriented nozzles may be necessary. When considering horizontally oriental nozzles, the position, spacing, and outlet configurations may be important factors to consider. In this work, a 21.3m diameter circular water storage tank was retrofitted with two sets of symmetrical horizontal nozzles. The first set of nozzles is oriented radially to the center while two second set of nozzles were oriented to be tangential to the wall of the water storage tank. Three different nozzle spacings (18.3m, 15.2m and 12.2m) and outlet locations were systematically simulated using CFD. This study shows that nozzles spaced 15.2m apart provide optimal mixing performance. In addition, the outlet placed at the bottom center of the water storage tank has a strong influence on the vertical water movement and hence a more thorough mixing.
.jpg "Jie Zhang, PhD, PE photo")
