圆形水跃的实验与数值研究
An experimental and numerical study of the circular hydraulic jump
AI总结：
本文通过实验和数值模拟研究圆形水跃，测量液膜厚度并估算韦伯数、弗劳德数和雷诺数，发现厨房水槽尺度下表面张力控制水跃，并定义了重力起作用的临界射流流量。
AI中文摘要：
本文描述了圆形液体射流垂直冲击水平表面的实验和数值模拟，例如水龙头流出的水冲击厨房水槽底部的情形。在这种情况下，冲击表面的液体以快速流动的薄膜形式铺展，在距冲击点一定距离处，流动厚度突然增加，流速降低。在本文研究的实验中，流动关于射流轴线呈轴对称，深度的突变发生在给定半径处，称为圆形水跃（CHJ）。我们开展了新的实验，测量了水跃内部及外部的液膜厚度，并利用这些测量值来估算控制参数，即分别决定表面张力、重力和粘性影响的韦伯数、弗劳德数和雷诺数。我们还进行了流动的数值模拟，模拟结果与实验高度一致，并为这些无量纲参数提供了独立的估算值。我们发现，在厨房水槽的尺度下，对于高雷诺数和低邦德数的水，在水跃处韦伯数约为1，而弗劳德数较大，这意味着水跃受表面张力控制。我们还定义了一个临界无量纲射流流量，超过该流量，这种控制不再成立，重力将发挥重要作用。
英文摘要：
This paper describes experiments and numerical simulations on the normal impact of a round liquid jet onto a horizontal surface, such as when water from a tap hits the bottom of a kitchen sink. In this case the liquid impacting on the surface spreads as a fast-flowing thin film and, at some distance from the point of impact, the thickness of the flow abruptly increases and the speed of the flow is reduced. In the experiments studied here the flow is axisymmetric about the axis of the jet, and the abrupt change in depth occurs at a given radius and is known as a circular hydraulic jump (CHJ). We present new experiments in which we measure the thickness of the liquid film inside and beyond the jump and use these measurements to estimate the governing parameters, the Weber, Froude and Reynolds numbers that determine the influence of surface tension, gravity and viscosity, respectively. We also carry out numerical simulations of the flow that show excellent agreement with the experiments and provide independent estimates of these dimensionless parameters. We find that, on the scale of a kitchen sink, and for water at high Reynolds number and low Bond number, at the jump the Weber number is of order unity while the Froude number is large, implying that the jump is controlled by surface tension. We also define a critical dimensionless jet flow rate at which this control no longer holds and gravity plays a significant role.
