Author(s): Haoran Liang; Wangru Wei; Yuxuan Qiu; Ju Deng; Mingjiang Liu; Yubo Ran; Qiang Long

Linked Author(s): Wangru Wei

Keywords: High-speed flow; Air-water flow; Atmospheric pressure; Aerated water flow; Physical model test

Abstract: The aeration dynamics of high -speed open channel flow are critically influenced by atmospheric pressure, a factor of critical importance for the hydraulic design of hydropower projects in high -altitude regions. To elucidate these effects, comparative experiments were conducted by leveraging the natural pressure difference between a high altitude location (low atmospheric pressure, local pressure 70.91kPa) and a normal altitude location (normal atmospheric pressure, local pressure 95.39kPa), across a flow rate range of 0.071 to 0.189 m³ s-1. This study systematically analyses cavity features, aeration rates, and concentration development. Results indicate that the lower air density at high altitude substantially suppresses the total air entrainment rate. Conversely, key parameters such as aeration cavity length exhibited minim al sensitivity to atmospheric pressure compared to the dominant influence of flow rate. A counterintuitive result is that the average air concentration below the clear-water zone, nearly the impingement point (x/L = 1-1.5), becomes higher at the low atmospheric pressure site. Further downstream, the concentration distributions for both pressure conditions converge within the region of x/L = 1.5 to 2.5. Additionally, the development of the lower air-water interface is retarded at low atmospheric pressure, resulting in a longer clear-water region. These findings provide a theoretical basis for the hydraulic design of plateau regions.

DOI: https://doi.org/10.64697/iahr.proc.ise2026.abs.155

Year: 2026