Abstract
Flow aeration is an effective way to protect the chute structure from cavitation erosion damage, and various chute aerators are applied for high-velocity and large discharge flows. The aeration protection for the chute floor and sidewall is mainly affected by aerator designs and air diffusion properties. However, detailed comparisons of air concentration distributions generated by different chute aerator types are limited. In this paper, physical model tests are conducted to measure and compare the air diffusions generated by different chute aerators, including the bottom aerator, the lateral aerator, and the full-section aerator. A clear-water zone in the middle of the water flow easily appears for the bottom aerator, and the air concentration in the zone near the bottom plate decays faster downstream. The lateral aerators can effectively improve the aeration protection of the sidewall in the middle of the water flow, but due to the influence of water fins, a prominent clear-water zone appears near the bottom plate of the sidewall, which cannot be eliminated downstream. The full-section aerator composed of the bottom aerator and lateral aerator can generate a fully aerated flow and eliminate clear-water effects. In addition, the air diffusion generated by the full-section aerator near the chute bottom and sidewalls increases and stably develops downstream. Test results indicate that compared to isolated bottom and lateral aerators, the full-section chute aerator can obtain acceptable air concentration distributions and near-wall air diffusions for cavitation erosion protection of high-velocity chute flows.
Highlights
This paper systematically describes the aeration forms of highspeed water flow under different aeration forms
By comparing the air concentration of the aerated water flow, the characteristics of the aerated water flow under different aerated forms are analyzed, and the following conclusions are obtained: (1) It can be seen from the experiment that the water fin and the clear-water in the lateral aerated water fin start to develop from the front of the attachment section, and the relative height of the water fins and the clear-water in the lateral aerated water fins gradually increases downstream and increases with the increase of the water discharge
Lateral aeration effectively avoids the clear-water zone in the middle of the water flow, there is a clear-water zone near the bottom plate, and it is difficult to eliminate downstream
Summary
Many researchers have concluded that setting aerators in the spillway to aerate high-speed flow can effectively reduce cavitation damage. A combination of bottom and lateral aerators provides good aeration protection performance, entraining sufficient air bubbles and eliminating the bottom and lateral clear water layers near the chute wall. The “clear-water core” is a region without air located in the middle of the jet It puts the side wall at risk because the bottom aerator does not provide sufficient protection, while for lateral aerator effects, water fins close to sidewalls are unfavorable. Based on experimental tests, this paper systematically studies the air entrainment and its downstream development generated by bottom deflector aerators, lateral aerators, and full-sectional aerators
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