Local Measurements in Air-water Two-phase Turbulent Flows

摘要

Experimental data of both gas- and liquid-phase parameters with high resolution are essential for understanding and modeling two-phase flow behavior and validating computational codes. In the current study, local gas- and liquid-phase measurements in air-water two-phase turbulent flows with high void fractions are performed. The gas-phase measurements are performed using four-sensor conductivity probes, which provide radial distributions of the gas-phase (bubble) velocity, void fraction, interfacial area concentration, and bubble number frequency. The liquid-phase measurements, including the velocity and its fluctuations, are carried out using a particle image velocimetry (P1V) system with fluorescent particles. An optical phase separation method, which uses an optical filtration technique, was adopted to extract the velocity information of the liquid-phase only. A newly developed image processing scheme was imposed on the raw P1V images to remove noise due to bubble residuals, optically distorted particles, etc. The test section used in the experiments is an acrylic vertical pipe with an ID of 50 mm and height of3.2'm. Both the gas- and liquid-phase measurements are conducted at a local measurement port of z/D = 32, downstream from the inlet for flow development investigation. The flow conditions with the void fraction up to 43% are carried out in the current work and the results are discussed. In addition, multiple elemental error sources that affect the PIV measurement uncertainty in two-phase flows are qualitatively discussed.