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DIRECTED ENERGY PROFESSIONAL SOCIETY

Abstract: 24-Symp-010

UNCLASSIFIED, PUBLIC RELEASE

Numerical Simulation of Aero-Optical Distortion for Supersonic Mixing Layers

At high flight Mach numbers, aero-thermodynamic heating can damage optical windows. Cooling films that protect the windows potentially degrade light beams.
A multi-tiered approach of experiments and theory at Notre Dame University (ND) as well as wall-modeled large-eddy simulations (WMLES) at New Mexico State University (NMSU) is taken to understand and model the aero-optics of turbulent mixing layer flows over optical windows with film cooling.
The WMLES are modeled after Mach 2 experiments in the SBR-50 Supersonic Wind Tunnel at ND. The approach boundary layer is turbulent. A two-dimensional nozzle issues a wall-tangential subsonic jet over an optical window that is recessed into a cavity. Air, Helium and CO2 cooling film are considered. The freestream total temperature is 300K. For the air-cooling film, total temperatures of 450K and 650K are considered as well.
The root-mean-square optical path distortion over the optical window is computed directly from the WMLES data and compared with the experiment. A proper orthogonal decomposition with a density-based kernel reveals that spanwise coherent density fluctuations are chiefly responsible for the optical distortions.

UNCLASSIFIED, PUBLIC RELEASE