A quantitative investigation on the visualization experiment of the intermittent flow in a helically coiled tube

Visualization experiments were often used to observe the flow patterns of gas-liquid two-phase flow. The development of high-speed camera technology in recent years induces an increase of the tendency for quantitative measurements of flow characteristics through visual observations. In this work the characteristics of intermittent flow in a helically coiled tube (HCT) are extracted quantitatively by introducing the gray intensity of the images. The variations of the flow patterns at several typical points of the tube are monitored to explore a series of unique intermittent flow phenomena in the HCT. It is found that the gas-liquid interface would vary from long wavelength fluctuations to the short wavelength and large wave number fluctuations by increasing the liquid flow rate. In addition, a new approach to calculate the transient translational velocity of the elongated bubble is proposed by using the distributions of the gray intensity. The research design in this work may supply a frame to extract the flow structures of multiphase flows quantitatively from a visualization experiment.