Bubbly pipe flow study via refractive index matching

Abstract

A phase-Doppler light-scattering method is used to measure, nonintrusively, liquid and bubble velocities and bubble size in vertical-upwards, dispersed, bubbly pipe¯ow. Bubble size measurements are also obtained with a video imaging technique. Optical distortion is eliminated, by using pipe material with index of refraction equal to that of water at room temperature, in combination with an index-of-refraction-matching box. Pure-liquid velocity and turbulence intensity test-measurements performed with the incorporation of this technique compare very well with existing data in pipe¯ow. Measurements of bubble velocity and size at two locations along the pipe are presented with emphasis on the near wall region. The experiments have been carried out at a Reynolds number of 12086 and a volumetric¯ow ratio of 2.7%. Bubble velocity¯uctuation properties were found to be almost uniform in the core region. Bubble mean velocity was constant within one average bubble diameter from the wall and axial velocity¯uctuations peaked at approximately half that distance. Velocity distributions near the wall were non-Gaussian and skewed towards lower values. The average bubble size was found to be in the range between 1200 mm and 1400 mm with standard