Abstract
The inside structure of an seismic water storage tank is extremely spacious compared to the size of the inlet pipe, therefore the flow velocity of water in the aseismatic water storage tank becomes slow and the occurrence of stagnation is a concern. Since storage tanks are often installed at the ends of water distribution networks, it is also important to manage the residual chlorine concentration as well as the flow field inside such tanks.
In this study, the flow condition of aseismatic water storage tank when the inflow velocity has changed was examined using computational fluid dynamics. We first analyzed the flow field in a storage tank of typical shape to identify the locations of the stagnation regions as well as the residual chlorine concentration changes in the inflow and outflow of strage tank. Then, validity of the analysis results were confirmed by comparing with the measured value of the residual chlorine concentration at the inlets and outlets of the storage tank in service. By this analytical method, the flow field in storage tank with a capacity of 100 m3 was simulated with four inflow rate scenarios, and it revealed that the residual chlorine concentration in the storing and outflow water decreased considerably against the inflow water, providing a potential to cause degradation of water quality when the rate of inflow dropped below 10 m3/day.
