Acquisition of void fraction of pulsatile gas-liquid two-phase flow in rectangular channel

Abstract

Experiment on two-phase pulsatile flow in a narrow rectangular visualization channel was carried out and photographed. Every frame was treated and restored as a black-white binary picture with the threshold of both gray-scale and gray-scale gradient. The gas-liquid interface in the binary pictures can be recognized well, including some very obvious interface, which either cannot be distinguished, or introduce big wrong-recognized area with the gray-scale threshold only. Then after such as ‘dilate’, ‘erode’, ‘fill’, ‘filter’ and so on operating, the binary pictures can reflect the twophase distinction situation in the experimental channel well; The instantaneous average void frictions at the length that the camera covered were calculated by counting the black and white pixels from the pictures. The average void fractions in the whole length of the test section were calculated with an iteration method. The average void fractions in the special length covered by camera and the ones in the whole length of the test section are different. The former shows that the void frictions dramatically frequently change, while the later at steady flow almost stay peace, at pulsatile flow change smoothly.