Chapter 13 - Laser doppler anemometry: Applications in multiphase flow systems

Abstract

This chapter discusses Laser Doppler Anemometry (LDA). It is a non-invasive optical technique, which can be used to conduct the in situ measurements of velocity, fluctuating velocity, size and concentration, high spatial resolution, fast dynamic response and the ability to detect reversal flows for particles, bubbles, and droplets in single and multiphase flow systems. The chapter focuses on LDA theory and techniques for measuring: (a) velocity and fluctuating velocity, including the Doppler Model, the Fringe Model, and large particle LDA techniques; (b) particle or bubble size, including visibility and pedestal techniques, the phase Doppler technique, the shape discrimination technique, and the flight time technique for large particles; (c) particle concentration, including the Time Ratio Technique and the Data Rate Technique; (d) the Threshold Technique for discriminating signals for multiphase flow systems; and (e) the Matched Refractive Index Method for multiphase flow measurement with very high particle concentration. It also presents the two examples of particle flow parameter measurement in dilute gas-cohesive particle systems and bubble flow parameter measurement in a three-phase circulating fluidized bed that were conducted at Illinois Institute of Technology (IIT).