Ignacio LASALA, Lucas FORD, Eric BACH, Guillermo PANIAGUA, Etienne CHOQUET, Thierry ANDRE
DOI Number: N/A
Conference number: HiSST-2025-279
A probe nacelle is designed to deliver a laser sheet for planar laser diagnostics in high-temperature supersonic flows subjected to flow-induced vibrations. The nacelle houses sheet–forming optics and submerges them directly into the flow field, improving modularity in facilities with limited external access. Placing the optics within the flow shortens the focal length of the optics and increases irradiance in the laser sheet, enhancing diagnostic capability. To withstand harsh operating conditions, the probe is equipped with an actively cooled jacket, enabling its use in high-temperature, high-pressure environments. A key challenge in these environments is vibration, which can disrupt optical alignment and focal positioning. This study demonstrates the ability of the probe to perform planar laser diagnostics under vibration by testing it in the Facility for Instrumentation and Open-Jet Research (FIOR) at PETAL laboratories. The probe was exposed to an 80-mm turbulent free jet operated at underexpanded supersonic conditions (Mach 1.15). The flow through FIOR was seeded with micron-sized oil droplets and illuminated with the laser sheet for planar Mie scattering delivered by the probe. A high-speed camera, recording at 5–20 kHz, captured particle motion. Probe vibrations were measured with piezoelectric accelerometers sampled at 30 kHz and with high-speed optical imaging at 20 kHz, processed using Proper Orthogonal Decomposition (POD). It was found that the vibration amplitude of the probe increased linearly with jet momentum flux, reaching a maximum amplitude of 0.2 mm at Mach 1.15. Frequency analysis showed that accelerations were dominated by a 1600 Hz mode, while displacements were governed by a lower-frequency 45 Hz mode. Planar Mie scattering was successfully conducted at the highest vibration levels, enabling visualization of flow structures within the particle-laden jet plume. An uninterrupted laser sheet
was maintained under all test conditions. These results advance the development of actively cooled probe nacelles toward feasible laser sheet delivery withing supersonic environments, advancing diagnostic capabilities for high-Mach facilities.