Simultaneous Measurements of Size and Velocity of Bubbles in an Opaque Tube Using X-ray PTV Technique

An X-ray PTV (particle tracking velocimetry) technique was developed to measure size and velocity of bubbles simultaneously without any optical aberrations. This advanced experimental technique is based on the combination of the in-line X-ray holography and 2-frame PTV method. The X-ray PTV is simple to adopt and its configuration is similar to conventional optical imaging techniques. The bubbles made by air explosion were used as tracer particles. The size and velocity information of bubbles (10∼60μm) moving upward in an opaque tube (φ=2.7mm) were measured simultaneously using the X-ray PTV technique. Due to different refractive indices of water and air, phase contrast X-ray images show clearly the exact shape of overlapped bubbles. For several working fluids of DI water and NaCl electrolyte solutions, the measured up-rising terminal velocity of bubbles is proportional to the square of bubble diameter. This advanced technique can be applied to get useful information of two-phase fluid flows for which conventional optical methods have difficulties to analyze