Flow and liquid turbulence structure in developing two phase flow systems

气液两相流在许多工程应用中都很重要。例如，核能工业的安全分析规范要求蒸汽-液体界面传递项的闭合关系，而石油和天然气工业的管道系统设计需要精确的两相压降模型。在这些和其他应用中，在各种流动条件下，两相流可能发生在复杂的管道几何形状中，例如突然的面积变化、孔口、弯头和阀门。因此，了解不同管道组件对两相流的影响，特别是在这些组件下游的发展中地区，对于建立可靠的机理模型非常重要。本提案的总体目标是研究发展中的两相流的流动和液体湍流结构。特别是，将研究管道组件下游和入口区域的发展流动。两相流的流动和湍流结构将使用现有的直径1.5英寸的水平空气-水流动环和8英寸的垂直空气-水流动环进行研究。使用电容和光学探头测量局部空隙分布，使用热膜风速法测量液体速度和湍流度。一个四点光学探针将用于确定由于气泡合并/破裂而导致的气泡形状和大小的变化。采用高速粒子图像测速（PIV）系统测量气泡周围的液体湍流场。特别是对两相流发展区域的流动和湍流结构的研究很少。然而，这个区域在许多多相系统中是重要的，在许多工程应用中起着决定性的作用。这里将进行的测量将是独一无二的，并提供对这种复杂现象的物理见解，并为开发可纳入不同工程应用的机械模型提供输入。

Gas-liquid two-phase flows are important in a number of engineering applications. For example, the safety analysis codes for the nuclear energy industry require closure relations for the vapor-liquid interfacial transfer terms, while accurate two phase pressure drop models are necessary to design the piping systems in the oil and gas industry. In these and other applications, the two phase flow can occur in complex piping geometries such as sudden area changes, orifices, bends and valves under a variety of flow conditions. Thus, it is important to understand the effect of different piping components on the two phase flow, especially in the developing regions downstream of these components, to develop reliable mechanistic models. The overall objective of this proposal is to investigate the flow and liquid turbulence structure of developing two-phase flows. In particular, the developing flow downstream of piping components and in the entrance regions will be investigated. The flow and turbulence structure of the two phase flows will be investigated using an existing 1.5-inch diameter horizontal air-water flow loop and a 8-inch vertical air-water flow loop. The local void distribution will be measured using capacitance and optical probes, while the liquid velocity and turbulence will be measured using hot film anemometry. A four-point optical probe will be used to determine the change in the bubble shape and size due to bubble coalescence/break-up. A high speed Particle Image Velocimetry (PIV) system will be adapted to measure the liquid turbulence field around the bubbles. There are few studies, especially of the flow and turbulence structure in the developing region of two-phase flows. However, this region is important in many multiphase systems and plays a determining role in many engineering applications. The measurements that will be performed here will be unique and provide physical insight into this complex phenomena and provide input to develop mechanistic models that can be incorporated into different engineering applications.