Focused and Cylindrical-Focused Laser Differential Interferometer Characterization of SBR-50 at Mach 2

摘要

Cylindrical and conventional focused laser differential interferometers (CFLDI vs FLDI) were employed to measure density disturbances in Mach 2 airflow in experimental facility SBR-50 at the University of Notre Dame. The data obtained by CFLDI and FLDI were compared to characterize the CFLDI authority. There was found that the power spectral density measured by CFLDI is similar to the FLDI power spectral density taken under same conditions in a core flow. The CFLDI was then used to measure density disturbances at varying streamwise and wall normal locations, including the boundary layer (which is not discoverable by means of FLDI due to a plane geometry). The level of disturbances increases with increasing streamwise position and increasing pressure (i.e. increasing Reynolds number). Along with obvious benefits delivered by CFLDI, there is determined that the spatial filtering of the CFLDI is not always sufficient to entirely mitigate the effect of turbulent boundary layers along the side walls.