Third Australian Conference on Laser Diagnostics in Fluid Mechanics and Combustion December 2,3 2002 The University of Queensland, Brisbane

INVITED LECTURES

Research at the Laboratory for Turbulence Research in Aerospace and Combustion (LTRAC) is undertaken on a large variety of reacting and non-reacting turbulent flows. Our work includes the study of two and three dimensional shear layers, grid turbulence, jets (continuous and synthetic), hybrid rocket combustion, and novel propulsion systems. In the course of undertaking this, the Laboratory has developed several laser diagnostic techniques. Both quantitative and qualitative methods are heavily used, including PLIF, PIV (stereoscopic PIV, holographic PIV and holographic interferometry), and dye flow visualization.

Polarisation spectroscopy has recently been shown theoretically to be possible for orthogonal pump/probe beam intersection angles (Reppel and Alwahabi, 2001, Lavrinenko and Gancheryonok, 1999). Orthogonal Planar Laser Polarisation Spectroscopy (O-PLPS) images have been obtained experimentally for both linearly and circularly polarised pump beams (Reppel and Alwahabi, 2002a). In this paper, a historical review of Laser Polarisation Spectroscopy, with special attention to combustion diagnostics, is presented. The special orthogonal geometry for beam interaction is discussed in more details due to its importance in imaging application. The results, to date, have been summarised and discussed and the conditions required for optimum crossbeam quantitative imaging has been evaluated.

In the Shock Wave Research Center (SWRC) of the Institute of Fluid Science, Tohoku University, lasers have been applied to the diagnostics of shock wave phenomena in transparent media. We have utilized double exposure holographic interferometric method for the visualization of shock tube flows and recently it was used to visualize very strong shock waves accompanying intense real gas effects behind it. By using a 1,000 mm dia. spherical schlieren mirror a large field of view was visualized for shock Mach number ranging from 5 to 14 in air. This holographic interferometric method was extended with combination of digital phase shift technique to the quantitative visualization of weak shock waves. In order to emphasize usefulness of holographic interferometry applied to shock tube experiments, animated display from interferograms produced in a shock tube with higher degree of repeatability will be demonstrated.

Supersonic flows relevant to high-speed air-breathing propulsion systems present challenging environments for making laser-based measurements. This presentation will describe the Propulsion Directorate's interest in high-speed air-breathing propulsion, including the prevailing technical challenges and several key areas of on-going research. After a brief overview of our experimental facilities, several research efforts that utilize advanced diagnostics will be described. Methods of current interest include OH PLIF, Raman scattering, flame emission measurements, absorption spectroscopy, and simultaneous PIV/PLIF. Emphasis will be placed on both the application of the particular measurement technique and the results obtained from its use.