The method of dissolving oxygen in water (liquid), which is one of the methods for improving the water quality environment for closed water bodies, is through using air bubbles. As a result of using water flow generated by gravity as means for supplying air bubbles into water without using pores, negative pressure is generated and bubbles are taken into the running water. Experiments and flow analysis were carried out in order to establish a method of charging in water as a mixture of water and air bubbles.
Closed waters represented by Osaka Bay and Lake Biwa accumulate sewage flowing as sludge. For this reason, in closed waters, eutrophication and red tides etc. are occurring. And the catch volume tends to decrease. The method of dissolving oxygen in water (liquid), which is one of the methods for improving the water quality environment for closed water bodies, is through using air bubbles. The use of bubbles is a method of increasing the amount of oxygen transfer from the gas side to the liquid side.
As previous studies, methods using microbubbles, nanobubbles, fine bubbles and etc. have been proposed in reference Michioku et al (2001) and Tsuge (2010). In these methods, pressurized air is sent to tubular, plate-like, spherical instruments with pores, and air bubbles are injected from the pores into the water. Apparently, with the method using pores, there is a problem that clogging occurs in pores due to dust or the like as time elapses, so that the effect of the apparatus is deteriorated.
Therefore, we began developing a method that does not use pores. As using water flow generated by gravity as means for supplying air bubbles into water without using pores, negative pressure is generated and bubbles are taken into the running water.
In order to overcome the above problems, the authors introduce the density function method in reference Asai et al (2006), which is one of the effective interface capturing method. The density function method can solve the gas-liquid two-phase flow at the same time, and it can also be applied to a flow field slip. The water tank is a gas-liquid two-phase flow is difficult to measure the velocity. Therefore, it is necessary to predict the flow field by numerical calculation.
