Application of laser-induced thermal acoustics to a high-lift configuration

Laser-Induced Thermal Acoustics (LITA) has been used to measure the flow field in the slat region of a two-dimensional, high-lift system in the NASA Langley Basic Aerodynamics Research Tunnel (BART). Unlike other point-wise, non-intrusive measurement techniques, LITA does not require the addition of molecular or particulate seed to the flow. This provides an opportunity to obtain additional insight and detailed flow-field information in complex flows where seeding may be insufficient or detection is problematic. Based on the successful use of LITA to measure the flow over a backward-facing step, the goal of this study was to further evaluate the technique by applying it to a more relevant and challenging flow field such as the slat wake on a high-lift system. Streamwise velocities were measured in the slat wake and over the main element at 11.3 degrees angle of attack and a freestream Mach Number of 0.17. The single-component LITA system is described and velocity profiles obtained using LITA are compared to profiles obtained using two-dimensional, Digital Particle Image Velocimetry (DPIV) and a steady, Reynolds-Averaged Navier-Stokes (RANS) flow solver for the same configuration. The normalized data show good agreement where the number of measurement locations had sufficient density to capture the pertinent flow phenomena.