Reducing Turbulent Flow Aero-Optical Distortion

High-speed endo-atmospheric interceptors need cooling to protect the body and homing sensors from hot external flow. The windows for infrared seekers are cooled with some form of wall jet(s), but turbulence generated in the mixing layer between the cooling jet(s) and the external flow distorts the image the seeker receives. Large eddy simulation (LES), in which time-accurate numerical solutions of the 3D Navier-Stokes equations are used to compute the mean flow and large scales of turbulence, will be validated for predictions of aero-optical distortion; used to obtain information about turbulence which will guide development of turbulence control methods; and used to demonstrate the feasibility of these methods. Based on the present understanding of turbulence in high speed shear layers, several control methods may be effective. Successful completion of Phase I and II work will yield: methods of controlling aero-optical distortion for specific configurations; verification of these methods' effectiveness; and softwate for predicting the turbulent distortion and evaluating control methods in general configurations.