An optical deflectometer for the quantitative analysis of turbulent structures

The optical deflectometer is proposed to make turbulence measurements. The instrument, which is based on the schlieren principle, is nonintrusive and has a practically unlimited frequency response. Its novelty also lies in the fact that it produces a real image of the flowfield under study, in which optical probes may be positioned precisely. This instrument has been successfully applied in studying the turbulent mixing layers of both a low-speed CO₂ jet and highly compressible Mach 3 airjet. The results are shown to be consistent over a broad range of knife-edge cutoff settings, and are comparable to turbulence data obtained by other more standard turbulence instruments. The major limitation of the optical deflectometer, in its present embodiment, is the fact that it integrates fluctuations across the flow