Bubbly Flow Experiment in Channel Using an Optical Probe and Tracking Algorithm

In this study, the phenomenon of two-phase flow was investigated in a square channel. The experiment was performed with stagnant liquid conditions. The gas and liquid dynamics of the bubbly flow were observed in two regions far from the inlet. Air was inserted through a porous media at three superficial gas velocities: 4.6 mm/s, 2.5 mm/s, and 1.4 mm/s.

Two techniques were applied in the experiment to measure the bubbly flow: an optical probe and an in-house developed tracking algorithm. Measurements of the bubble interface velocity, void fraction, bubble frequency, time of flight, and Sauter mean diameter were obtained by using the optical probe. The duration of the probe measurements for all three flow rates and both regions lasted approximately 33 hours. The tracking algorithm was used to analyze the experimental data for two visual methods: shadowgraphy and Particle Tracking Velocimetry (PTV). Shadowgraphy provided gas-phase measurements of the bubble centroid velocity and its fluctuations, void fraction, bubble size, and Reynolds stresses. Five data sets were acquired for each flow rate, resulting in a total of 327,540 shadowgraphy images. Liquid parameters such as the velocity, fluctuations in the velocity, and the Reynolds stresses were provided by PTV. Only one data set containing 10,918 images was obtained from liquid measurements for each flow rate. One data set was sufficient to provide reliable statistics since tracking two consecutive images lead to approximately 15,000 velocity vectors. The data obtained from this study was an effort to assist in the verification, validation, and improvement of two-phase flow simulations.