We report on the structure of the scalar index-of-refraction field generated by turbulent, gas-phase, incompressible and compressible shear layers and incompressible jets, and on associated beam-propagation aero-optical phenomena. Using simultaneous imaging of the optical-beam distortion and the turbulent-flow index-ofrefraction field, wavefront-phase functions were computed for optical beams emerging from the turbulent region in these free-shear flows, in an aero-optical regime producing weak wavefront distortions. Spatial wavefront-phase behaviour is found to be dominated by the large-scale structure of these flows. A simple level-set representation of the index-of-refraction field in high-Reynolds-number, incompressible shear layers is found to provide a good representation of observed wavefront-phase behaviour, indicating that the structure of the unsteady outer boundaries of the turbulent region provides the dominant contributions. † Present address: Mech. & Aerospace Eng.,

We used a two-laser two-detector experiment to investigate the temporal evolution of the mixing layer of a pressure matched supersonic jet at an exit Mach number of 1.5. discharging into still air, resulting in a convective Mach number of 0.7. The convective speed of the structures present in the flow was measured and compared with previous findings. Additional views of the mixing layer provided information on the three dimensionality of the mixing layer. We found that the structures travel with a velocity higher than the predicted velocity and they rotate as they progress downstream.

Recent progress in the development of a miniature Laser Doppler Anemometer (LDA) and a micro optical shear stress sensor is described. Miniaturization of these sensors has been achieved with the use of integrated optics and micro fabrication techniques. This paper describes the fabrication of the two sensors and presents an experiment for the evaluation of the sensors. The results show perfect agreement between the boundary layer velocity gradient performed with the LDA, and the measurements obtained with the shear stress sensor. The range of experimental conditions suitable for the wall shear sensor is reported. Finally, we describe the application of the sensors in a series of tests performed at the William B. Morgan Large Cavitation Channel of the Navy's Carderock Division, in Memphis, Tennessee.

The first reported instantaneous two-dimensional map of the fuel-gas concentration in a turbulent diffusion flame using quantitative Ramanography is described. Details of the experimental configuration are presented, along with data obtained in both cold flows and turbulent reacting flows.

No abstract