Optical Methods for Data Processing in Heat and Fluid Flow

12

Development of an Optical Measuring Technique for the Study of Acoustical Phenomena

J M Buick, J A Cosgrove, D M Campbell, and C A Greated

Abstract

We consider the application of optical methods to the measurement of acoustical phenomena. In particular we consider the suitability of applying measuring techniques that rely on the flow being seeded with small particles. This is a common practice when acoustic fields are not present, however, interactions between the seeding particles and the sound waves can change both the motion of the particles and any acoustically generated flow. The novel measuring technique of fluorescent dye velocimetry (FDV) is proposed which does not require the flow to be seeded. The accuracy and applicability of the new technique is then assessed using simulated images.

12.1 Introduction

Optical measuring techniques are now widely applied to flow measurement in a range of applications in fluid mechanics. One significant advantage that optical measuring techniques have compared to other methods is that they are considered to be non-intrusive; that is, there is no probe or measuring device inserted in the fluid and so the procedure of making a measurement does not alter the system in any way. However, many techniques, such as particle image velocimetry (PIV) and laser Doppler anemometry (LDA), rely on small seeding particles being present in the fluid. Provided these particles follow the flow in a reliable manner they are not considered to influence the ...