Study On Water Flow Characteristics Of Aeration Facilities In Spillway Tunnel

For hydraulic engineering discharge release structures, including the spillway, spillway tunnel, etc., when the discharge flow speed reaches a certain level, the so-called high-speed flow, due to the high water head, water pressure will decreases, and when the water pressure is reduced to a certain extent, cavitation bubbles will be formed in the water flow. When cavitation bubbles in the water flow from the low pressure area to high pressure area along the chute, vacuoles will develop and collapse. If the bubble collapse occurs in the vicinity of the flow channel solid boundary, the micro-jet resulted in bubble collapse and its role in the shock wave radiation may cause cavitation damage to the solid walls and bottom plate of discharge works.Aeration facilities could reduce cavitation damage to flow discharge structures. Sudden lateral enlargement and sudden drop facilities will form the bottom cavity and the side cavities, to obtain better aeration effect, and to protect floor and side walls of the building from cavitation erosion. Based on the sudden lateral enlargement and sudden drop facilities of hydraulic models with different widths, drop heights in different test conditions, many important factors such as sudden expansion width, drop heights, bottom and lateral cavity lengths can initially determined.In this paper, based on the model chute with the sudden lateral enlargement and sudden drop facilities and by changing different sudden expansion and drop size, forming different combinations of sudden expansion ratio with different sudden drops in different flow conditions, hydraulic characteristics of aerated flow were analyzed. The aerator flow pattern, flow pressure, flow cavitation number, air concentration distribution and other characteristic feature elements were obtained. The empirical formulas for calculating bottom and lateral cavity length of this aeration facility were obtained according to experimental data and they can provide some reference for similar projects.In this paper, the numerical simulation method using calculation software such as Fluent, Eulerian two-fluid3D models were implored to simulate some factors of aerated flow. Comparison shows that the simulation results of turbulent models are believable checked by model experiments.Model experiment together with numerical simulation reveals the different mechanism of forming side cavity and bottom cavity after the sudden lateral enlargement and sudden drop facility and reveals their mutual influences and common action law. The research results are useful to improve the effects of cavitation control by the aeration facility of sudden lateral enlargement with sudden bottom drop, and may provide some theoretical basis for cavitation control by aeration facilities on utilization in engineering projects.