Simultaneous measurements of two phases using an optical probe

For a detailed characterisation of multiphase flows, a local measurement technique that is capable of quantifying both continuous and dispersed phases has to be employed. In the present study, a new optical probe was tested for its ability to provide simultaneous local measurements of gas and liquid/solid in a three-phase system. The new probe can measure the intensity of light reflection due to the presence of gas or liquid medium surrounding the probe tip in conjunction with the Doppler frequency caused by the approach of a solid particle. The experiments were carried out in a pseudo-2D rectangular column by passing gas bubbles through a stationary liquid with suspended seeding particles. In these experiments, measurements were carried out by using three techniques namely optical probe, particle image velocimetry (PIV), and high-speed imaging (HSI). PIV measurements were used to validate seeding particle velocity obtained using the optical probe, whereas HSI technique was used to validate bubble chord length data from optical probe. The difference between the particle velocity from the probe and PIV was in a range of 13%–20%, while the difference between chord length measured by the probe and HSI was within ±8%.