Optical Diagnostics for High-Speed Flows

Abstract

Since the year 2000 there has been a revolution in diagnostics of high-speed air flows. The foundations for this revolution were laid over the previous few decades, but with the development of new short pulse and pulse burst laser technologies, higher laser powers and higher pulse energies, new high speed cameras, better laser control and improved detection and laser delivery methodologies, many very effective new capabilities have been developed. Newly developed methods for molecular tagging velocimetry provide high fidelity visualization of transport properties and may be extended to simultaneous temperature measurements. Rapid field imaging with frequency tunable pulse burst lasers show instantaneous flow structure and complex boundary and mixing interactions. Extending these pulse burst concepts to swept volumetric imaging is very promising for full volumetric data collection. Fast wavelength modulation spectroscopy follows real time flow variation, and three dimensional particle imaging extends particle imaging velocimetry to volumetric data acquisition.

A flexible master oscillator for a pulse-burst laser system

“…Arguably the first Nd:YAG pulse-burst laser system was reported by Knight and coauthors in 1980 [1]. Since then a range of pulse-burst laser capability has been developed at a variety of institutions, the predominant application being laser diagnostics for fluid dynamic measurements [2,3]. Recent development has emphasized high pulse energy at high pulse repetition rates for long burst durations [4,5].…”

Advanced Laser-Based Techniques for Gas-Phase Diagnostics in Combustion and Aerospace Engineering

“…Planar PIV can usually show two velocity components for a planar cross section of a flow. 212 Stereoscopic PIV 213 employs a pair of cameras to capture the motion of tracer particles from two different angles and it can reconstruct three velocity components in a planar cross-section. With the development of tomographic PIV, 214 it is possible to measure 3D velocity vectors in a volumetric flow.…”