Particle image velocimetry (PIV) is a well established measurement technique to measure velocity in a variety of different fluids. Using PIV to measure single-phase flow is well established, but recently PIV has been used to measure two-phase flows as well. Most two-phase PIV measurements have been for dispersed or bubbly flows, often utilizing the bubbles or droplets as PIV seed particles. However, there are other types of two-phase flow situations, such as stratified or slug flow, in which PIV measurement techniques are not yet well established. Situations such as these require both liquid and gas phases to be seeded separately with particles that can distinguish each phase. A particle injection method is presented for the air phase of a two-phase system using fluorescent tracer particles. Information about the system, including details of the fluorescent particles and injection device are given. The device injects micron sized fluorescent particles at a uniform rate into the flow of interest. A cut-off lens filter on the PIV camera is used to distinguish the fluorescent particles used for the air phase from non-fluorescent particles used in the liquid phase. Results using the technique with a two-phase air/water system in a thin rectangular channel for stratified/wavy flow are given. The channel is enclosed in a clear acrylic plastic tank and the dimensions of the channel are 600 mm long, 40 mm high, and 15 mm wide. The results demonstrate the ability to use PIV to measure the gas phase of a two-phase system for stratified/wavy flow and the method could be extended to other two-phase flow regimes as well.
Draft tube discharge fluctuation during self-sustained pressure surge: fluorescent particle image velocimetry in two-phase flow
