Mujal i Colilles, Anna; Bateman Pinzón, Allen;.Medina Iglesias, Vicente

Phenomenon of mixing in drinking water storage tanks and reservoirs has a direct effect on the quality of water due to creation of poor mixing zones and volume stratification, which can produce negative effects in public health. The design of a storage tank must consider the conditions of the inlet and outlets, and also their orientation (vertical or horizontal) to prevent the formation of these zones. Experiments done in a reduced scaled-model with a rectangular base and
three different inlets (a pipe, and two waterfalls) had the objective to decide which of these inlets achieved the best mixing efficiency. Moreover the effects of columns that support the roof of the tank were studied by running the three entrances with and without columns in the four situations. Using a digital treating image technique the results are found in a qualitative way. Results showed that the pipe entrance gets better results in model and prototype than waterfalls because of the
horizontal momentum. As waterfalls are made of four different inlets, the friction between inlets and the ambient fluid increase because the specific surface increases. It is important to say that time taken to mix the volume stored depends on the distance between the inlet and the opposite wall as though as its orientation In terms of columns, neglecting the viscous scale effects and taking into account the whole tank columns have a negative effect on mixing efficiency although they divide the
flux and create local zones of turbulence around them, increasing local mixing

Download: 2008-IAHR-02