FLUCTUATING FLOWFIELD VELOCITY MEASUREMENTS USING FREQUENCY MODULATED - FILTERED RAYLEIGH SCATTERING

The Arnold Engineering Development Center (AEDC) has identified a need for a time-mean, and rapidly fluctuating velocity measurements in support of turbine aircraft engine ground testing. We propose to employ a new non-intrusive optical diagnostic, which combines the inherent sensitivity of Frequency Modulated (FM) spectroscopy, with the high spectral specificity afforded by molecular vapor filter technology. We have termed this new approach Frequency Modulated - Filtered Rayleigh Scattering (FM-FRS). It is anticipated that this method will provide velocity measurement capability with accuracy on the order of 1 m/sec, without recourse to seeding of any kind, and with essentialy no Mach number limit. In this Phase I effort we propose a specific set of laboratory proof-of-concept experimental measurements, as well as a feasibility study for implementation in targeted AEDC engine test facilities. Extension to flow density and temperature will also be explored.