Assessment of intermittent two-phase flow using a high-speed visualization technique

The intermittent two-phase horizontal flow is recognized by many authors to be one of the most highly complex inherently unsteady flow pattern. Great efforts have been made in recent years to develop theoretical models to predict the intermittent flow interfacial parameters. However, as far as the flow structure itself is concerned, these models are not capable to predicting them yet. The liquid slug and gas bubble velocity, length and evolution along the flow are examples of structural parameters that require experimental specialised work to their evaluation. In this paper, we describe the application of a visualization technique to assess the intermittent two-phase air-water horizontal flow. The technique consists in employing a high-speed digital camera to take a series of pictures of the bubbles moving in the upper side of a horizontal pipe, where a gas-liquid mixture flows. From the images obtained the bubbles can be tracked along. Analyzing frame by frame it is possible to extract the gas bubbles lengths and velocities. This investigation is restricted to liquid superficial velocities ranging from 0.3 to 2.0 m/s and to gas superficial velocities ranging from 0.1 to 1.6 m/s. (author)