We report experimental results on the injection of a heavy fluid into a light one in a closed-end pipe, inclined at intermediate angles. The injection of the heavy fluid is made using an inner duct with a smaller diameter than that of the pipe in which the light fluid is placed. The fluids used are miscible and Newtonian, and they have the same viscosity. Our observation shows that, during the removal/replacement of the light fluid by the heavy fluid, at least four distinct flow stages can be identified: (i) initial buoyant jet of the heavy fluid, (ii) development of a mixing region, (iii) slumping flow of the heavy fluid, and (iv) heavy fluid front reaching the pipe end and returning toward the mixing region. Using high-speed camera images along with the ultrasound Doppler velocimetry and laser induced fluorescence data, the flow characteristics in these flow stages are quantified, and they are described in detail vs the dimensionless groups that govern the flow dynamics, namely, the Froude number (Fr), the Reynolds number (Re), the Archimedes number (Ar), and the pipe inclination angle (β). While our findings are of fundamental importance, they can also be used to provide a fluid mechanics understanding of the dump bailing method in the plug and abandonment (P&A) of oil and gas wells.

中文翻译：

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将重流体注入封闭端管中的轻流体

我们报告了在以中间角度倾斜的封闭端管中将重流体注入轻流体的实验结果。使用直径小于放置轻流体的管道直径的内部管道进行重流体的注入。使用的流体是可混溶的和牛顿流体，它们具有相同的粘度。我们的观察表明，在重流体去除/替换轻流体的过程中，至少可以确定四个不同的流动阶段：（i）重流体的初始浮力射流，（ii）混合区域的发展，（ iii) 重流体的坍落流，以及 (iv) 重流体前端到达管端并返回混合区域。使用高速摄像机图像以及超声多普勒测速和激光诱导荧光数据，这些流动阶段中的流动特性被量化，并详细描述了它们与控制流动动力学的无量纲群，即弗劳德数 (Fr)、雷诺数 (Re)、阿基米德数 (Ar) 和管道倾斜角 (β)。虽然我们的发现具有根本重要性，但它们也可用于提供对石油和天然气井堵塞和废弃 (P&A) 中倾倒倾倒方法的流体力学理解。