Phase Discrimination Techniques for Phase Doppler Measurements in Dispersed, Bubbly Flows

Abstract

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.