| Research Abstract |
Pumping the hypolimnion water to the free surface is available for the eutrophication protection of the reservoir, de-freezing the harbor, and promoting the marine products. Among various pumping systems, the usage of the air bullet to push up the water through a shroud, hydraulic gun systems is expected to be an efficient system. Here, the system was improved to release the pumped water near the free surface to expect the high entrainment rate at the falling stage.
Various experiments, in a homogeneous water and in the stratification, one air-bullet release and the periodical release, were performed to get both bulk and detailed flow structures. Based on these, a physical model was developed for the system both in a homogeneous water and in stratified environments. Then, the following quantities were calculated : pumping rate and velocity as a function of the air flux rate and the length of the shroud, the ambient stratification change with time, etc.. These results were compared with both laboratory and field experiments.
Together with the analysis just for this system, compatible systems such as bubble plumes were also studied. At first, experiments were performed both in linearly stratified and in two-layered environments. Then, several important features for the mixing and the pumping rate efficiencies were obtained. In addition, the physical model was developed to analyze the environmental density distribution change. Using these results, the comparison of the bubble plume system and the hydraulic gun system were made in various points. Briefly, the hydraulic gun system becomes better with smaller depth and in case that reliability is important.
Finally, as an application of this system, de-eutrophication mechanism by pumping was analyzed. Then, it is proposed that by controlling the thermocline depth with respect to the euphotic layer, the production of photoplankton can be suppressed.
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