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
A combined Phase-Doppler Anemometry (PDA) and video imaging measurement technique for non-intrusive measurements in dispersed bubbly flows is presented. A one-component Phase-Doppler Velocimetry system has been employed to measure liquid seeding particle size and velocity as well as bubble size and velocity non-intrusively. Measurable flow quantities include: (1) mean velocities and RMS velocity fluctuations for bubbles and liquid; (2) local bubble diameter, and (3) local bubble passage frequency. Non-intrusive local measurement of seeding particle and bubble size is an advantage over techniques used previously (Laser-Doppler Velocimetry, Hot-Film Anemometry). Visual data collected simultaneously with the light-scattering measurements and analyzed with the aid of image processing are used to verify the trends portrayed by the light-scattering measurements. A multi-level phase discrimination technique based on velocity, diameter, and relative data rates between the carrier and dispersed phases is employed to minimize bias from bubble signals when measuring liquid phase data in dilute flows. An amplitude discrimination technique for the Phase-Doppler system is proposed for higher volume fraction flows. The proposed method enables local non-intrusive measurement of liquid phase velocity as well as local bubble size characteristics, velocity, and concentration.
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