Developments in Ultrasound Techniques for Multiphase Flow Measurements

Multiphase flows encompass a range of scales. Flows of solids in gas or liquid phases in fluidisation and pneumatic conveying. Liquid-liquid flows in the manufacturing of emulsions, in two-phase reactions and extractions used for the separation of metals in nuclear reprocessing or pharmaceuticals. To be able to understand and predict the physical behaviour of these systems, it is important to measure the spatial distributions of the phases, the development of the interfaces and the velocity profiles.

Often the test sections are opaque or the volume fractions of dispersed phases are high. These limit the application of optically based techniques such as high-speed imaging or laser-based approaches to study the multiphase systems. Therefore, Ultrasound based techniques are preferably used for opaque systems. In this project, we will contribute towards a novel measurement technique to probe complex multiphase flows, including liquid-liquid and solid-liquid flows in channels, stirred vessels and fluidised beds with a focus on turbulence near interfaces.

The above-mentioned technique will be based on the applications of Ultrasound Doppler Velocimetry (UDV), as shown in Figure1. In this technique, the velocity is measured by calculating the Doppler effect, resulting from the relative motion between the sound source and the particles or bubbles. We will use (UDV) to study the velocity and dispersed phase distribution characteristics of particle and bubble sizes in fluidised beds, in dispersed liquid-liquid flows and liquids-solid flows. The designed measurement technique will provide an insight into the performance of dispersions in multiphase flows through imaging.