低气压环境中的挑流水舌动水压强实验研究

随着我国高坝建设的发展,西部高海拔地区低气压环境下的高速水流特性对高原建坝提出了新的挑战。本文采用实验的方法来研究环境气压变化对水舌挑距和水垫塘内动水压力特性的影响,为高海拔地区建坝提供技术指导。研究发现减压使水垫塘中的动水压强增大,气压降低10 kPa,时均压强最大可达3.9%,脉动压强最大可达5.5%;同时在低气压环境中水舌的挑距受到水舌在空中掺气扩散的影响,由于模型和原型相似律的原因,空气阻力对水舌挑距的影响在模型和原型中有所不同,但环境气压降低,空气密度和空气阻力减小,水舌在空中的掺气也会减少,即水舌扩散程度降低,低气压下水舌更加集中。

Experimental study on influence of low atmospheric pressure on dynamic pressure of water jet plunging

As high dams are built on the high-altitude plateau of Western China, the issue of high-speed jet nappes under low atmospheric pressure emerges as a new challenge to dam construction. In this study, an experiment is conducted to examine the influence of ambient air pressure on the trajectory distance of water jets and their dynamic pressure produced at the plunge pool bottom. The study shows that a drop in atmospheric pressure increases the dynamic pressure of the plunging jet. An air pressure drop of 10 kPa causes a dynamic pressure rise of up to 3.9% and a pulsating pressure rise of up to 5.5%. In low-pressure air, the trajectory distance of a jet nappe is affected by the aeration and diffusion of the nappe flow in the air. By the similarity of model and prototype, the influence of air resistance on the trajectory distance of a jet is different between model and prototype. With air pressure dropping, air density and air resistance are decreased and the air volume entrained by a jet nappe in the air will also be reduced. This means that the diffusivity of the nappe will be reduced, and a low-pressure jet nappe will be more concentrated.