CFD modeling of stagnation reduction in drinking water storage tanks through internal piping

Poor mixing is considered to be the main reason for stagnation in water tanks. This can pose threats to public health. Internal tank piping with sprinklers (distributed outlets) has been previously proposed to avoid flow stagnation. This study is the first to use Computational Fluid Dynamics (CFD) modeling to investigate more cases and come up with design suggestions. The CFD modeling results using a realizable k-ϵ model were verified with experimental results for a limited number of cases involving the sprinkler system. The CFD model was used to investigate various tank aspect ratios and spherical tanks. Results showed the superior mixing of an angled-nozzle sprinkler system for spherical tanks. The effect of height-to-diameter ratio (H/D) on cylindrical tanks employing a sprinkler system as their inlet and outlet were investigated and two equations were suggested for prediction of mixing. These showed that for H/D less than 0.75 there was faster mixing