| Experiments using nonintrusive optical diagnostics have been carried out to study the large-scale structure of high-Reynolds-number axisymmetric mixing layers. Coflowing mixing layers with convective Mach numbers, M;A key objective of this research is to develop a new turbulence measurement technique to characterize large-scale turbulent mixing layer structures. This technique is applicable to the high-Reynolds-number compressible flow regime, where more conventional forms of turbulence measurement may be difficult to implement. The instrument developed to accomplish this objective is based on the schlieren principle, and is called an "optical deflectometer." It is relatively simple, inexpensive, and nonintrusive to the flowfield. The technique is novel in that it produces a real image of the flow field in which optical "probes" may be positioned precisely. The frequency response of this instrument is limited only by the size of area sensed in the schlieren image.;The optical deflectometry technique was successfully applied to the mixing layer of a "baseline" incompressible (M;Optical deflectometry was then carried out for a moderately-compressible (M;Finally, average convective velocity measurements via optical deflectometry differ from those obtained by photographically-based methods. The latter measurements overestimate the convective velocity of the largest-scale structures in the mixing layer of the highly-compressible (M... |
