Focused Laser Differential Interferometric Investigation of Turbulent Jet Spectra

Abstract

In this work, a model of focused laser differential interferometry (FLDI) is derived by incorporating the local intensity of each beam in an FLDI beam pair. We rederive some known transfer functions to reduce FLDI data. Additional transfer functions are also derived, intended to model increasingly complex disturbance fields, namely, isotropic turbulence. The new transfer functions account for disturbances not only in the streamwise direction but also in the two spanwise directions. Additionally, it is shown that strategically selecting the integration limits for the idealized FLDI in the denominator of the transfer functions () can simplify the FLDI data-reduction procedure. This is done for disturbance fields in a finite boundary (e.g., a wind tunnel of scale ), by removing the need to characterize the FLDI probe-volume length scale. Finally, results are presented from experiments performed with a turbulent jet probed by an FLDI that indicate that increasing the complexity of the transfer function has merit with some qualifications.